Ok, I have a hard core engine question here...

[Jstas]

...hopefully someone here can give me some help.

I have a future uncle-in-law who picked up a 1965 Ford Thunderbird. I have not seen it yet but I'm told that its in solid shape but it's rough. I'm told it doesn't run right but I haven't seen, heard or smelled it running to be able to accuratly figure out what is wrong. I'm guessing that it needs a carb rebuild.

So anyway, it has a 390 under the hood. They were good for about 300 horses and 425 pound feet of torque if I remember correctly. He was complaining that it felt quite sluggish. I mentioned to him that it may be due to the fact that it doesn't run properly and that it weighs more than my truck. I'll bet it will have alot more go if it gets to be running properly.

However, I did some research and noticed that the car came with a pretty tall 3.00:1 gear ratio. Kinda weak. I think that would be the first to change if he wants more go. 3.55's would be a massive improvement but 3.73's would get it moving even better I bet.

Back to the original question! The 390, what engine family from Ford is it? Is it an FE or is it a bigger version of like a Y-block? I'm trying to figure it out because I think that if he wants to make more power, his best bet is a better carb, new intake and a set of headers and exhaust. But if I can find a cheap set of heads or the current ones are good to port then maybe that will help out too. It will certainly push the power peaks up the RPM range a little but "pep" would be an understatment I am sure!

If someone can give me some history on the 390, I would greatly appreciate it. I also do not want to hear or need to hear any personal opinions or about how much of a pile of junk it is. He doesn't have a whole lot of cash to throw at it so this is about all he has to work with. If I can, I'll head up to the Swap Meet at Englishtown in the spring and see if I can't find a decent set of hotter heads, headers and an intake for it.

[03 Topless]

You were right, it's an FE. 352, 360,390,406,427,428, all the same family. You can make it run, but parts won't be cheap, and the T-Bird is probably no light weight car either. :D

[Jstas]

I don't want to make it run. I was just trying to figure out how to get more power out of it. It helps to know what engine family it is associated with so I know what kind of parts interchangability there is. It's already making enough power but it would nice to see it run a little better than the factory rated 17.XX second 1/4 mile.

[Elapidae]

I wouldn't go too high on the gear either. My guess is that the red line is pretty low on that engine.

[rkwahl]

The 390 is in the FE family and is a good durable torque monster of a v-8 and is great for highway cruising! They are VERY heavy engines and respond well to aluminum intakes, head porting, and headers. There are many cams to choose for the street that wake them up. Depending on how much you want to spend, Dove makes alum heads for the FE's that REALLY wake them up! Rear gears in the 3.50 range will help off the line and still return acceptable mileage, of course none of these cars returned very good mileage, with most in the 12-16 mpg range.:spinem:

[Jstas]

I don't think mileage is a concern, it's not a daily driver. I just wanted to see what was out there for them and at what cost. I think a new intake and carb, a set of headers and sending the heads out to be ported would be good for enough power to make him happy.

The gears would be a good idea too. The redline was mentioned earlier but gears have less of an impact on redline than a torque converter or clutch has. Besides, gears are there to multiply or reduce torque. If redline was an issue, going from a 3.00:1 ratio to say a 2.08:1 ratio would cause a problem with the redline because the engine would run out of steam and hit it's redline long before the car was able to get moving. A lower gear like a 3.55 or 3.73 would give much more grunt down low and keep the engine in its power band.

I realize this is going to sound retarded but for those of you with a Sony Playstation, try messing with the gear ratios on a car in the Gran Turismo series of games. That will give you a good idea of how gear ratios affect redline, acceleration and top speed. I'm really no good at explaining and I will just end up saying something that is wrong, that I know is wrong and wasn't really what I meant because it came out wrong.

[Elapidae]

Originally posted by Jstas
<snipped>The gears would be a good idea too. The redline was mentioned earlier but gears have less of an impact on redline than a torque converter or clutch has. Besides, gears are there to multiply or reduce torque. If redline was an issue, going from a 3.00:1 ratio to say a 2.08:1 ratio would cause a problem with the redline because the engine would run out of steam and hit it's redline long before the car was able to get moving. A lower gear like a 3.55 or 3.73 would give much more grunt down low and keep the engine in its power band.<snipped>


My statement above was a little brief and you're absolutely right that rear end gears have nothing to do with engine redline but I'd have to say that I disagree with your statement
If redline was an issue, going from a 3.00:1 ratio to say a 2.08:1 ratio would cause a problem with the redline because the engine would run out of steam and hit it's redline long before the car was able to get moving.
I think the opposite is true. Example A If you've got a high torque engine with a flat torque curve that redlines at low rpms, putting in a taller gear and keeping you near the top of the rev limit isn't going to get you down the 1/4 faster. Example B If, on the other hand, you have an engine with a steep torque curve and a higher rev limit it would make sense to put in a taller gear to keep you on the upper end of the powerband.
We still agree on the gear choice though. I think 3.55 or 3.73 would be a good choice (leaning toward 3.55).

I don't own a Nintendo though so maybe I need to get one of those to do a better analysis ;)

[Jstas]

Gears, final drive or transmission, are not meant to keep you in a powerband. They are meant to multiply and transfer torque. You choose your gear ratio that best suits your power band.

The higher numerically the gear is, the shorter it is. It will reach redline faster but there will be alot more work done in that short time and distance than if you had a numerically lower but taller gear ratio. The closer to 1:1 you get in gearing, the more work the engine has to do with less results. If you have a higher gear ratio, the engine will work at the same level as the lower gear ratio but it will DO much more work, about 1.5 times more work than the lower ratio. Consequetly you will have have much better results. That's why so many people will change to 3.73:1 or 4.10: ratios for drag racing. They help acceleration yet still keep a reasonable amount of economy. Gears can be worth a couple tenths in the 1/4 mile.

Basically, given an engine with 300 pound feet of torque, a tall gear ratio (numerically lower) will allow you to do a certain amount of work over a certain distance and time. A shorter gear ratio (numerically higher) will allow you to do the same amount of work over a shorter distance and time compared to the taller ratio thereby increasing your accleration rate. Gears allow a engine making 300 pound feet of torque to do the same amount of work every time time but with varying results.

Transmissions have very low gears for reverse, first and sometimes second. This is the case because it takes alot of power to move a vehicle from a standing start so the gearing has to be low. The low ratio (high number) of the 1st gear combined with low ratio of the final drive gives a very low gear ratio. Your 3rd and 4th gears are often times closer to a 1:1 ratio because once the car is moving, it takes alot less power to keep it moving. So much so that over drive gears are a ratio of .80:1 or so. Which means that for every revolution the engine makes, the wheels make only 80% of a full revolution.

But, like I said before, gears have little to do with keeping an engine at any given RPM. The torque converter or clutch do that with pre-determined shift points that are chosen with your powerband as a guide. Your gears are dictated by your power band but if your torque converter or clutch and shifting linkage didn't change gears for you, you would never leave a gear and always be stuck at a high RPM. You are giving gears way too much credit. Your shift pattern in a manual or the stall speed of your torque converter determine when your gear changes happen, at what RPM they shift at and at what RPM they drop to when they enter the next gear.

[03 Topless]

Geeeeeez John,
Betcha can't repeat that backwards......;) :D ;)

[Elapidae]

Originally posted by Jstas
Gears, final drive or transmission, are not meant to keep you in a powerband. They are meant to multiply and transfer torque. You choose your gear ratio that best suits your power band.

The higher numerically the gear is, the shorter it is. It will reach redline faster but there will be alot more work done in that short time and distance than if you had a numerically lower but taller gear ratio. The closer to 1:1 you get in gearing, the more work the engine has to do with less results. If you have a higher gear ratio, the engine will work at the same level as the lower gear ratio but it will DO much more work, about 1.5 times more work than the lower ratio. Consequetly you will have have much better results. That's why so many people will change to 3.73:1 or 4.10: ratios for drag racing. They help acceleration yet still keep a reasonable amount of economy. Gears can be worth a couple tenths in the 1/4 mile.

Basically, given an engine with 300 pound feet of torque, a tall gear ratio (numerically lower) will allow you to do a certain amount of work over a certain distance and time. A shorter gear ratio (numerically higher) will allow you to do the same amount of work over a shorter distance and time compared to the taller ratio thereby increasing your accleration rate. Gears allow a engine making 300 pound feet of torque to do the same amount of work every time time but with varying results.

Transmissions have very low gears for reverse, first and sometimes second. This is the case because it takes alot of power to move a vehicle from a standing start so the gearing has to be low. The low ratio (high number) of the 1st gear combined with low ratio of the final drive gives a very low gear ratio. Your 3rd and 4th gears are often times closer to a 1:1 ratio because once the car is moving, it takes alot less power to keep it moving. So much so that over drive gears are a ratio of .80:1 or so. Which means that for every revolution the engine makes, the wheels make only 80% of a full revolution.

But, like I said before, gears have little to do with keeping an engine at any given RPM. The torque converter or clutch do that with pre-determined shift points that are chosen with your powerband as a guide. Your gears are dictated by your power band but if your torque converter or clutch and shifting linkage didn't change gears for you, you would never leave a gear and always be stuck at a high RPM. You are giving gears way too much credit. Your shift pattern in a manual or the stall speed of your torque converter determine when your gear changes happen, at what RPM they shift at and at what RPM they drop to when they enter the next gear.

I agree and yet somehow I still stick to my analysis that a low revving, high torque engine should have smaller rear end gears and a high revving, lower torque engine should have larger rear end gears. (for racing)

[Jstas]

But why? If you are revving high then you have a pretty broad power band up high in most cases. High revving engines have to run at high RPM's for a long time at the top of the gear. They have to breathe. Keeping thier gearing short and low cuts them off half way through the power band. It's great for street driving because the car gets to its power band quicker and gets moving quicker. In a race, dead stop acceleration, unless it is a drag race, is like almost non-existant. Short gearing would be of no use and hurt more than help.

If you have a high torque low rev motor and tall gears, you are going to spend more time out of your power band. Say your power band peaks at 2,000 RPM and your power band is effective from about 800 RPM to 3200 RPM. Your gears are tall so it spends alot of time in each gear. It's gonna burn through that first 3000 RPM in a matter of seconds and then spend about 60% of it's time in the gear wheezing at the top end cause a low rev motor can't breathe at high RPM. Shorter gearing with more gears keeps that low revving engine in it's sweet spot of the power band longer by shifting back into it.

If your power band starts to drop off after 3500 RPM and you redline somewhere just north of 5 grand then a tall gear is going to run right into that redline where your low-rev engine's valvetrain can't flow enough air to support the RPM level. If your stall speed is too high on your converter then you won't shift out of the gear soon enough and spend too much time in the gear. You can obviously control this better with a manual but you will be short shifting before the engine runs through the whole power band. As long as the engine is in its power band, it is going to accelerate the car the fastest. Short shifting cuts the amount of time that you can accelerate, lowers your MPH and raises your E.T. and if you are road racing, the guy who makes one shift less is going to beat you to the corner by a car length or two.

[MKeller1]

:wtf:

Everybody. Repeat after me. "The engine's airflow capacity (including cam timing) and its valvetrain's resistance to valve float determine the absolute maximum engine RPM." Of course this is not taking into account the mechanical limitations of the short block.

You gear the vehicle based on intended use, weight and engine torque/HP curves. Typically, for ideal acceleration, you try to gear the car so that the RPM level (when shifted just above the HP peak) falls just before on the peak of the torque curve. This minimizes time spend between gears, maximizes acceleration and keeps the motor buzzing where IT wants to.

JSTAS - Your confused on several principles and some terminology. If you'd like more information or find out where to get it, please E-mail me direct.

In regard to your 390 equipped T-Bird question.

The car is heavy. You'll need a properly geared torquey motor with more power if you plan on making any serious stabs at improving 1/4 miles times. 390s can be built up to anything from a low RPM torque monster to an 8000RPM high horse power beast. For applications in a heavier car use the Edelbrock Performer RPM intake and 600CFM carb. If you can find/afford an orginal 428 police interceptor intake use that. Stick to a mild cam regardless of what you do. The Performer cam (not the RPM) or some other stick with mild lift and duration numbers will work fine. Somthing resembling a 390GT/428CJ cam would work real nice too. Keep the lift at the valve under .500" and the compression up to 9.5 to 10:1. The heads you have are probably hurt and need to be rebuilt. Head porting is not cheap. Neither is (correctly) rebuilding a set of 390 heads. 16 valves, 16 guides, 8 hardeded seats, a deck clean up, 3 angle valve job and misc machine work easily puts the head rebuild tab at around 600 dollars. Add in the minimum 750 dollars to port the heads and its easy to see that the smart way to go on FE heads is to replace them with aftermarket ones (Edelbrock). If you go with the aluminum heads keep the compression up to around 10:1.

You'll need more gearing. 3.50:1 is a good compromise. 3.55 and 3.73 are typical 8.8" rearend ratios. 3.50, 3.70, 3.89. 3.91 are typical streetable 9" ratios. Many late model guys get this confused sometimes.

-Mike

[Jstas]

OK, you tell me I am wrong but won't tell me why I am wrong and tell me to email you to find out. Meanwhile, you deprive everyone else here of the "proper" information. I will not email you. Post it here where everyone can see it. If I am wrong, I am wrong but I do not believe I am. I did not explain myself clearly I suppose but explaining gears and thier effect on things is not easy.

Also, I never said the Thunderbird was going to be a drag car. My uncle was complaining that the car was a slug. I was just trying to find out the info on the engine so I could figure out what his options are for getting some more "pep" from the car.

Oh yeah, the gears. I can check the Summit catalog too.




1.) FMS-M-4209-A310 Ring Gear And Pinion Set Oval Track 3.10 Ford 9 Inch $499.95 B/O
2.) FMS-M-4209-A356 Ring Gear And Pinion Oval Track 3.56 Ford 9 Inch $499.95 B/O
3.) FMS-M-4209-A370 Ring Gear And Pinion Oval Track 3.70 Ford 9 Inch $499.95 B/O
4.) FMS-M-4209-A389 Ring Gear And Pinion Oval Track 3.89 Ford 9 Inch $499.95 B/O
5.) FMS-M-4209-A391 Ring Gear And Pinion Oval Track 3.91 Ford 9 Inch $499.95 B/O
6.) FMS-M-4209-B411 Ring Gear And Pinion Oval Track 4.11 Ford 9 Inch $495.39 B/O
7.) FMS-M-4209-B430 Ring Gear And Pinion Oval Track 4.30 Ford 9 Inch $499.95 B/O
8.) FMS-M-4209-B444 Ring Gear And Pinion Oval Track 4.44 Ford 9 Inch $499.95 B/O
9.) FMS-M-4209-B471 Ring Gear And Pinion Oval Track 4.71 Ford 9 Inch $499.95 B/O
10.) FMS-M-4209-B486 Ring Gear And Pinion Oval Track 4.86 Ford 9 Inch $499.95 B/O
11.) FMS-M-4209-H373 Ring Gear And Pinion Oval Track 3.73 Ford 9 Inch $189.95
12.) FMS-M4209A350 Ring Gear & Pinion Sets 9 inch Ford 3.50 Ratio $499.95 B/O
13.) FMS-M4209C514 Ring Gear & Pinion Sets 9 inch Ford 5.14 Ratio $499.95 B/O
14.) FMS-M4209C550 Ring Gear & Pinion Sets 9 Inch Ford 5.50 Ratio $499.95 B/O
15.) FMS-M4209C557 Ring & Pinion Gear Set 9 inch Ford 5.57 Ratio $499.95 B/O

Take special note of gear set number 2, number 6 and gear set number 11. These gear sets are for a Ford 9 inch and these units are from Ford Racing Performance Parts. In addition, there are several other manufacturers that offer gear sets just like these for the Ford 9 inch. My numbers were one hundreth off for 2 sets and there are 3.73's for the Ford 9 inch.

I would find more examples but I am currently at work and can't really waste the time. I am skeptical about the size of the differential in the 65 Thunderbird too. I have a book of specifications at home and I will check.

The other information you provided is useful and I thank you.

[Elapidae]

Originally posted by Jstas
But why? If you are revving high then you have a pretty broad power band up high in most cases. High revving engines have to run at high RPM's for a long time at the top of the gear. They have to breathe. Keeping thier gearing short and low cuts them off half way through the power band. It's great for street driving because the car gets to its power band quicker and gets moving quicker. In a race, dead stop acceleration, unless it is a drag race, is like almost non-existant. Short gearing would be of no use and hurt more than help.
I'm making some assumptions that may not be correct, but I'll try to explain why I'm "sticking to my story" ;)
I'm assuming that this is a high torque low rev monster with a flat torque curve and torque that comes on almost immediately. I'm also assuming that the goal is 1/4mi or drag performance as apposed to fuel economy. Understanding that HP is just a function of torque, I'm really only talking about torque but it generally applies to HP. Now, that having been said:

In the above paragraph you seem to be saying that a high revving engine needs taller gears. I agree completely. The torque curve is not flat and comes on in the higher rpms to gearing that keeps the engine in it's "sweet spot" is ideal.


Originally posted by Jstas
If you have a high torque low rev motor and tall gears, you are going to spend more time out of your power band. Say your power band peaks at 2,000 RPM and your power band is effective from about 800 RPM to 3200 RPM. Your gears are tall so it spends alot of time in each gear. It's gonna burn through that first 3000 RPM in a matter of seconds and then spend about 60% of it's time in the gear wheezing at the top end cause a low rev motor can't breathe at high RPM. Shorter gearing with more gears keeps that low revving engine in it's sweet spot of the power band longer by shifting back into it.

Here we go our separate ways... (this is not meant to flame you by the way. I'm not an expert, I just wanted you to see where I was coming from in my analysis whether it be right or wrong).
If you have a high torque, low rev motor, your power band is almost immediate off idle and though it may peak at 3200 rpm, the difference between the torque at 800rpm and 3200rpm isn't significant and trying to rev the engine higher simply "costs" too much time to be effective (for the reasons you mention) when the upshift will put you in a high torque RPM in the next gear. This is different in a high revving engine that has a steep torque cuve and high torque at high rpms because with the high revving engine, you would want to upshift into the next gear and maintain high rpms to get you closer to the "sweet spot". Or in other words, with a high revving engine that has a steep torque curve and produces peak torque at high rpms, the "sweet spot" is small and you want your gearing to keep you close to it. In a high torque low revving engine with a flat torque curve, the "sweet spot" is large and primarily drops of on the upper end so your gearing should take advantage of the broad torque.


Originally posted by Jstas
If your power band starts to drop off after 3500 RPM and you redline somewhere just north of 5 grand then a tall gear is going to run right into that redline where your low-rev engine's valvetrain can't flow enough air to support the RPM level. If your stall speed is too high on your converter then you won't shift out of the gear soon enough and spend too much time in the gear. You can obviously control this better with a manual but you will be short shifting before the engine runs through the whole power band. As long as the engine is in its power band, it is going to accelerate the car the fastest. Short shifting cuts the amount of time that you can accelerate, lowers your MPH and raises your E.T. and if you are road racing, the guy who makes one shift less is going to beat you to the corner by a car length or two.

I'm only talking about rear end gears. There are some mechanics at work here that have to be viewed on a dyno chart. I, again, am comparing high revving, steep torque curve engines with low revving flat torque curve engines. On a high revving engine, you might carry the rpms past the sweet spot a bit because of the benefit of the "power" placement on the upshift. You really have to analyze the graphs to know how to do this for your specific engine. Again, the taller gearing get's you closer to the sweet spot on the upshift so you would need to rev past the sweet spot less (theoretically). The low rev, flat torque curve, high torque engine is doing the most work at lower rpms and there would be no reason to try to rev it beyond it's broad "sweet spot". Yes, shifting will slow you down depending on how well you do it, but if you compare the 1/4 mi time of a stock 99 Cobra with 3.27 gears and a stock (except for gears) 99 Cobra with 4.10 or 4.30 gears, you will see that the tall gear got the 99 Cobra down the 1/4 faster despite the extra shift.

This is just my explanation for my thinking on the rear end gears. Like I said, it's not a flame and I'm not an expert nor am I saying that my opinion on this matter is right. I just wanted you to see my thinking on the subject. :tmb:

[Jstas]

I don't think we are talking about the same thing. Everything you referenced concerning shifts and shift points occurs in the transmission. The gears allow you to choose your shift points by letting you stay in a gear longer and use your power more efficiently. Shifting into and out of an RPM range are determined by shift points. That RPM range is what you need to know so that you can choose your gearing so that it will allow you to utilize that RPM range that the engine makes the most power.

The differences in power at each RPM are very significant because you have to choose gearing and shift points that will fully exploit that RPM range and power band. I do not know what the power curves for this Thunderbird look like so saying that they aren't significant is, not to be a jerk but, dumb. The difference can be 150 pound feet or it can be 5 pound feet, I don't know. All I know is that the car is lacking performance through out the entire RPM range and does not live up to the 300 horses, 427 pound feet of power it is rated at. Gears, a new intake and bigger carb and an exhaust system will solve that problem.

What I was saying, where we "go our seperate ways" is that if you have a torque peak of 2,000 RPM and a power peak at 4,000 RPM, you do not want to select a gearing that lets you shift at 6,000 RPM. If you want to drag race and accelerate fast then you need short gears. If you want to road race and acceleration from a dead stop is not important than you want tall gears. I am looking for quicker acceleration and not so much a top speed so I need short gears. Remember, short gears have a numerically higher ratio. Tall gears have a numerically lower ratio.

And finally, for the last time in this thread, this is not a race car. The only reason I asked about the engine was because I wanted to know what my options were for a couple of bolt on, go-fast goodies.

[Elapidae]

I respect your position on the subject :tmb:

It ought to be a really sweet ride no matter which rear end gear you choose. ;)

[MKeller1]

Jstas,

Please follow along.....


[QUOTE]Originally posted by Jstas
[B]OK, you tell me I am wrong but won't tell me why I am wrong and tell me to email you to find out. Meanwhile, you deprive everyone else here of the "proper" information. I will not email you. Post it here where everyone can see it. If I am wrong, I am wrong but I do not believe I am. I did not explain myself clearly I suppose but explaining gears and thier effect on things is not easy.

-----

I wasn't going to bore the rest of the folks with the basics and I wasn't going to point out every little item out here in front of everybody. However, it seems that since your initial post and your later ones that you've got a few things straightened out on your own in regard to rearend gearing. (that, or your explaining it better) Your assumtions on high reving motors having broad power bands and needing to rev longer are not entirely correct. Most high reving motors have narrow peaky HP and torque curves. You need the gearing to keep them in the desired RPM range. We'll go over the picky stuff anyway since you.
-----

Also, I never said the Thunderbird was going to be a drag car. My uncle was complaining that the car was a slug. I was just trying to find out the info on the engine so I could figure out what his options are for getting some more "pep" from the car.

----

Both drag racing and not being a 'slug' are in regards to acceleration. The same things that allows the car to run the 1/4 mile better will also make the car less of a 'slug'. YOU mentioned improving on the 17 something second factory stated 1/4 mile times.

-----


Oh yeah, the gears. I can check the Summit catalog too.


Take special note of gear set number 2, number 6 and gear set number 11. These gear sets are for a Ford 9 inch and these units are from Ford Racing Performance Parts. In addition, there are several other manufacturers that offer gear sets just like these for the Ford 9 inch. My numbers were one hundreth off for 2 sets and there are 3.73's for the Ford 9 inch.

I would find more examples but I am currently at work and can't really waste the time. I am skeptical about the size of the differential in the 65 Thunderbird too. I have a book of specifications at home and I will check.

----

You'll note that you were looking at *oval* track gears. They'll work in most 9"Ford rearends but there is a difference in metallurgy and design that would kill them on the street. If you read my post you'll not that I mention common STREET gears, as in those commonly found from the factory and found on the street. Anybody well versed in FOMOCO knows that 3.50, 3.70, 3.89, 3.91, 4.30 are VERY common street gears offered by Ford as OEM offerings in the 9" rear. Same is true for the 3.55 and 3.73 gearsets for the 8.8" rearend. Now you know too.

-----


Originally posted by Jstas
But why? If you are revving high then you have a pretty broad power band up high in most cases. High revving engines have to run at high RPM's for a long time at the top of the gear. They have to breathe. Keeping thier gearing short and low cuts them off half way through the power band. It's great for street driving because the car gets to its power band quicker and gets moving quicker. In a race, dead stop acceleration, unless it is a drag race, is like almost non-existant. Short gearing would be of no use and hurt more than help.

------

Could you explain your paragraph better?

Because my drag motors spend very little time at 8500RPM and do not need to be there a long time. My open track (road race) motors spend plenty of time at 7000+ RPM once in top gear, however, they too do not take long to get to 7000 rpm between shifts and it doesn't matter how long they stay there either. How does keeping the gearing "short and low" cut these motors off halfway through their powerband?

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Originally posted by Jstas
I don't think we are talking about the same thing. Everything you referenced concerning shifts and shift points occurs in the transmission. The gears allow you to choose your shift points by letting you stay in a gear longer and use your power more efficiently. Shifting into and out of an RPM range are determined by shift points. That RPM range is what you need to know so that you can choose your gearing so that it will allow you to utilize that RPM range that the engine makes the most power.

------

I think what your trying to say is that the engine has fixed torque and HP curves. The gearing is chosen so that the motor stays in its sweet spot while doing work. The final drive ratio ultimately determines the efficiency (fuel use/engine RPM vs distance the car was moved A.K.A. WORK). The shorter the gearing the LESS efficient the machine is, however. The short gearing may allow part throttle operation (therefore less fuel use) through mechanical advantage that probably outweighs the loss in pure mechanical efficiency. Ultimately the engine's power curves dictate the RPM (operating) range of the engine , not the gears. The gears allow the motor to maintain efficient use of power while doing work.

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Originally posted by Jstas
If your power band starts to drop off after 3500 RPM and you redline somewhere just north of 5 grand then a tall gear is going to run right into that redline where your low-rev engine's valvetrain can't flow enough air to support the RPM level.

HUH? If your powerband drops off at 3500RPM you'll probably never see 5000RPM. How does "tall" gearing "run you right into that redline"? It doesn't. SHORT gearing allows the engine to rev quicker. Gearing has NOTHING to do with the engine's redline folks.

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Originally posted by Jstas
If your stall speed is too high on your converter then you won't shift out of the gear soon enough and spend too much time in the gear. You can obviously control this better with a manual but you will be short shifting before the engine runs through the whole power band.

HUH? Converter stall speed has nothing to do with shift points. IT effects launch RPM but not shift points. With a manual trans you simply hold the trans in gear until you get to and through the powerband. If its taking you THAT long to get into the engine's powerband the gearing is too tall, the motor is too weak, and the car is too heavy.

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Originally posted by Jstas
As long as the engine is in its power band, it is going to accelerate the car the fastest. Short shifting cuts the amount of time that you can accelerate, lowers your MPH and raises your E.T. and if you are road racing, the guy who makes one shift less is going to beat you to the corner by a car length or two.


Partially correct. The first sentence is correct. The second is also correct but WHY would you short shift the car? You don't NEED to be in high gear at the end of the 1/4. Run the car out in 3d or 4th gear if you don't have enough gearing but ALWAYS run the car in its powerband.....even if it means running the car in only two gears. In reference to the road racing and short shifts....thats true ONLY if the car has a strong and broad enough torque curve to pull the car around. A good example of short shifting is my 428CJ equipped Mach I (strong and broad torque curve) that I'd run in 3d and 4th gear all around Watkins Glen. My SVT Focus on the other hand (slightly under powered for some parts of the course) needed to be shifted all the way around the course to stay in its power band.

-Mike

[Jstas]

Yes, I said the 17 second 1/4 mile sucks which is why I was looking at a gear set. It would improve the 1/4 mile time and drop a few tenths off of the time. That means better acceleration and more "pep". I'm not looking to change the appearance or comfort level of the car at all. I was just looking to give my future uncle in law the performance level he was looking for. It's not a race car and worth alot more to him both nostagically(Is that even a word?) and financially to leave it in a restored, as close to stock as he can get it, condition.


As far as the gears go, Ford Racing Performance Parts are not the only vendors to offer gears. Richmond, Auburn and a few others have had listings for "street" gears and many other kinds of gears in all the sizes listed in Summit. Summit also does not list full lines of gear sets. I know this first hand. I used to work a parts couunter and had access to distributer and jobber books for parts and parts interchangability.



Because my drag motors spend very little time at 8500RPM and do not need to be there a long time. My open track (road race) motors spend plenty of time at 7000+ RPM once in top gear, however, they too do not take long to get to 7000 rpm between shifts and it doesn't matter how long they stay there either. How does keeping the gearing "short and low" cut these motors off halfway through their powerband?



You might want to revist the threads that came before that post. The discussion was about race cars in general and it addressed a different scenario than drag racing.



HUH? If your powerband drops off at 3500RPM you'll probably never see 5000RPM. How does "tall" gearing "run you right into that redline"? It doesn't. SHORT gearing allows the engine to rev quicker. Gearing has NOTHING to do with the engine's redline folks.


How many times have I stated that in this post? Engine RPM has nothing do with any gearing at all. Your gearing choice is dictated by engine RPM and your power curves. In reference to the powerband, a powerband does include your torque curve and if your torque curve drops off at 3500 RPM but the power curve doesn't stop climbing until 4500 RPM then you redline of 5,000 RPM is much more believable now. Having a gear ratio that is too tall will cause the engine to run at high revs too long. If the car is an automatic that is. mainly because if the engine runs out of breath at 5,0000 RPM and you gear set and stall speed are causing you to shift in that range where the engine is running out of breath, shifting is not occuring at an optimal time. Maybe I left out some things that I thought more people would have been able to fill in without forcing me to type it all out.

Stall speed does affect shift points because if your shift point is not set to your stall speed, the car will hang in a gear until there is enough pressure built up to shift the gears. I know because I did it. As soon as I had the shift kit put in and had the trans guy change the shift point to suit the stall speed, the car shifted hard and ran like a bat out of hell without hanging in 1st and 2nd because it wasn't getting anywhere close to the shift point.



Your approach to this whole topic sucked. Take the chip off your should and try discussing things instead of "trying not bore everyone" or save me from some kind of percieved embarrasment. So far you have only corrected minor mistakes and agreed with me on a whole. I am happy to discuss things. I like to do it and I think things with Elapidae went well until you posted with your rather condenscending and rude post. We are all on the same team here bro. Like my mother used to tell me, you get alot more bees with honey than you do with vinegar.

[Chuck G.]

Having owned an FE, a 30. over 428.I can tell you the weak point of the FE series is the valve train,Bent and broken push rods.broken rocker shafts.broken grade 8 rocker arm bolts.I would contact FORD POWER PARTS I beleive they are in California if they are still in existance.They should be able to solve all your 390 problems. For value sake most people would want the engine as close to original as possible. 2 cents Chuck

[MKeller1]

Yes, I said the 17 second 1/4 mile sucks which is why I was looking at a gear set. It would improve the 1/4 mile time and drop a few tenths off of the time. That means better acceleration and more "pep". I'm not looking to change the appearance or comfort level of the car at all. I was just looking to give my future uncle in law the performance level he was looking for. It's not a race car and worth alot more to him both nostagically(Is that even a word?) and financially to leave it in a restored, as close to stock as he can get it, condition.

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Understood. If your uncle ever wants to put a hurt'n on the local kids with his T-Bird barge give me an E-mail. There's alot that can be done with that engine family without raising any red flags in regard to its potential. That ship on wheels could be built to put a hurt'n on many unsuspecting 5.0 cars without even a hick-up.

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As far as the gears go, Ford Racing Performance Parts are not the only vendors to offer gears. Richmond, Auburn and a few others have had listings for "street" gears and many other kinds of gears in all the sizes listed in Summit. Summit also does not list full lines of gear sets. I know this first hand. I used to work a parts couunter and had access to distributer and jobber books for parts and parts interchangability.

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True. But you'll note that the gears for street use offered by the aftermarket, for the most part, also stick to the factory available ratios. Circle track and drag gear sets are available in almost any imaginable ratio.

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Because my drag motors spend very little time at 8500RPM and do not need to be there a long time. My open track (road race) motors spend plenty of time at 7000+ RPM once in top gear, however, they too do not take long to get to 7000 rpm between shifts and it doesn't matter how long they stay there either. How does keeping the gearing "short and low" cut these motors off halfway through their powerband?


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You might want to revist the threads that came before that post. The discussion was about race cars in general and it addressed a different scenario than drag racing.

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The quote above also mentions road racing. In almost any racing venue acceleration is one of the primary conscerns. All of the priciples for acceleration are the same regardless.

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HUH? If your powerband drops off at 3500RPM you'll probably never see 5000RPM. How does "tall" gearing "run you right into that redline"? It doesn't. SHORT gearing allows the engine to rev quicker. Gearing has NOTHING to do with the engine's redline folks.

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How many times have I stated that in this post? Engine RPM has nothing do with any gearing at all. Your gearing choice is dictated by engine RPM and your power curves. In reference to the powerband, a powerband does include your torque curve and if your torque curve drops off at 3500 RPM but the power curve doesn't stop climbing until 4500 RPM then you redline of 5,000 RPM is much more believable now. Having a gear ratio that is too tall will cause the engine to run at high revs too long. If the car is an automatic that is. mainly because if the engine runs out of breath at 5,0000 RPM and you gear set and stall speed are causing you to shift in that range where the engine is running out of breath, shifting is not occuring at an optimal time. Maybe I left out some things that I thought more people would have been able to fill in without forcing me to type it all out.

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The torque and horsepower curves could be considered parts of the "power curve" if thats how you'd like to think of it. Folks tuning/optimizing engine/driveline packages don't think 'power curve' they use torque and hp curves. If you go back through your posts you intermix the terms here and there. Maximum acceleration (the mainstay of almost every racing venue this side of an absolute top speed event or car show) is accomplished by shifting the vehicle (manually or automatically) at a point *just* past the peak horsepower RPM point. If your gearing is optimized to your particular engines 'power curve', each upshift will allow the engine RPM to drop just below the peak of the torque curve. Drag cars tend to want the drop to be on the torque peak. Circle track and road race cars tend to need to use a little of the torque gain to pull the car out of the corners and want the drop to hit just below the torque peak....but the differences are minor (a few hundred RPM). Thats it in a nut shell.


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Stall speed does affect shift points because if your shift point is not set to your stall speed, the car will hang in a gear until there is enough pressure built up to shift the gears. I know because I did it. As soon as I had the shift kit put in and had the trans guy change the shift point to suit the stall speed, the car shifted hard and ran like a bat out of hell without hanging in 1st and 2nd because it wasn't getting anywhere close to the shift point.

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My automatic trans experience is limited, however, it sounds like your hanging in gear problem was a part throttle drivabilty issue rather than a WOT acceleration one? Is that so? At WOT you should definitely hit the RPM point at which the converter stalls. IF you didn't it almost sounds like you have a converter with too much stall speed for application. It sounds like they reprogrammed for higher line pressure and firmer shifts......or did they play with the govenor or electronics (if equipped) to actually raise the shift point RPM?

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Your approach to this whole topic sucked. Take the chip off your should and try discussing things instead of "trying not bore everyone" or save me from some kind of percieved embarrasment. So far you have only corrected minor mistakes and agreed with me on a whole. I am happy to discuss things. I like to do it and I think things with Elapidae went well until you posted with your rather condenscending and rude post. We are all on the same team here bro. Like my mother used to tell me, you get alot more bees with honey than you do with vinegar.

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I agree that I was kind of a prick on that first post and came on a little strong. E-mailing directly would have saved everybody here from alot of jibberish. I'm a long time newsgroup and message board user and having to dig through pages of snippy BS to get to the good information is usually a bore...... I was trying to avoid a flame war.....hard to do if I'm the one with the gas can and cigarette, eh?

-Mike

[MKeller1]

Originally posted by Chuck G.
Having owned an FE, a 30. over 428.I can tell you the weak point of the FE series is the valve train,Bent and broken push rods.broken rocker shafts.broken grade 8 rocker arm bolts.I would contact FORD POWER PARTS I beleive they are in California if they are still in existance.They should be able to solve all your 390 problems. For value sake most people would want the engine as close to original as possible. 2 cents Chuck

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FE's are very sensitive to valvetrain geometry. Incorrect geometry on the FE's is usually caused by running a cam thats too large to use without an adjustable valvetrain and/or geometry changes caused by milling the head or block deck surfaces.

Ford ran non-adjustable rockers on engines with less than .500" lift (at the valve). Anything over .500" lift used the 427 type adjustable rocker arms (regardless of if the cam was solid or hydraulic).

I suspect that your 428 needed to have adjustable valvetrain components (rockers and push rods from a 406-427) to eliminate the breakage problems. Once sorted out and corrected a relatively stock FE valvetrain is quite reliable to 7000RPM. If you add solid spacers between the rockers, use steel rocker stands and install HD shafts for the stockers, the sky is the limit.

-Mike.

[Jstas]

My automatic trans experience is limited, however, it sounds like your hanging in gear problem was a part throttle drivabilty issue rather than a WOT acceleration one? Is that so? At WOT you should definitely hit the RPM point at which the converter stalls. IF you didn't it almost sounds like you have a converter with too much stall speed for application. It sounds like they reprogrammed for higher line pressure and firmer shifts......or did they play with the govenor or electronics (if equipped) to actually raise the shift point RPM?



It was hanging in all gears at all speeds and throttle applications. The reason was, when my friend had had the trans rebuilt, he did not tell the trans shop what stall speed or size converter he was planning on using. They rebuilt the trans to stock specs. The bigger converter with the higher stall speed was barely getting to lock-up and the trans wouldn't shift. When the guy rebuilt the trans he put a shift kit in and changed the line pressure. He also did a tweak to the governor that I don't quite remember, something about a new spring or something. It wasn't my trans so I'm not 100% sure about all the details. All I know is that the trans guy told me what was wrong, what he did to fix it and gave me a box with used parts.

Oh, it was a Chevy TH350 trans. No electronic control.

[Chuck G.]

Put 3.90 gears in it and forget about unless you want to limit your cruising speed to 55mph. then go with 4.10s(My ole 428 had a high lift H/M cam .lo riser heads, alumn PI intake,hardened steel rocker shafts. what it needed was a girdle that held down the ends of the rocker shafts.)Sorry if we are on a different page!I just like 60's Fords:I'm out of here! :p