DOHC failures...

[SVTOA Boston]

I'm getting really tired of blowing up these 4.6 motors. First one failed from a seized cam. Second DOHC was factory fresh with less than 15k on it when this happens.BTW- This was only my 2nd day of OT on this motor.

http://www.svtoa.org/interactive/videos/96dohcfailure.wmv

Not sure what went this time but from the video you can see how sudden and catastrophic it was. I'm guessing oil pump gears but won't know for sure until teardown. Definitely seized, car will not crank @ all.

I spent some time on the phone today with Modmax. www.modmaxracing.com They mentioned a # of the cobra open trackers are switching over to an external oiling system. The billet gears seem to help but they do not appear to be a final solution. Dry sump sounds great but I really don't have 2-3k to spend on that kind of oiling system.

I'm just so pissed that these "technologically superior" motors can't take any kind of abuse IMHO. I can thrash my 5.0 ALL day long without so much as a hickup yet the 4.6 DOHC seems to have a glass jaw. So now question is do I dare stay with the 4.6 going all forged/balanced/blueprinted or do I throw in a stroked 351 and call it a day? To be honest I love the power delivery and rpm of the 4.6 but I really worry about its longterm reliability.

[gcassidy]

I watched the video, and since I'm taking my car on track next weekend, all I can say is "YIKES". I can only imagine what went through you mind when that happened. Most of us aren't professional racers with a garage full of mechanics to fix things. And I know you must love your car as much as I love mine (maybe a little less after that). I would have a whole range of emotions if that happened to me, from fear of cost to repair, to how will I get it home, etc. Have you done a teardown, yet? Please let us know what happened. I've heard of other people changing their oiling systems, but wouldn't Ford or SVT run these engines enough on test tracks to find these problems?
By the way, based on your video, I'm puting a fire bottle in my car before next weekend, just to be safe. Good luck.
Greg Cassidy

[SVTOA Boston]

I would have a whole range of emotions if that happened to me, from fear of cost to repair, to how will I get it home, etc. Have you done a teardown, yet? Please let us know what happened. I've heard of other people changing their oiling systems, but wouldn't Ford or SVT run these engines enough on test tracks to find these problems?

Yeah it's disappointing really. I love the cobra but the reliability of the motor leaves something to be desired IMHO. There's been a ton of people that have lost DOHC's due to the cast oem oil pump gears. It's one of the well known weaknesses of this motor. I know Ford performs simulated WOT durability tests but my guess is the beancounters would have nixed billet gears. +$20 or $30 x 40,000-50,000 units = a lot of $$$

I won't know for sure if that's what happened to mine until teardown but it seems likely. I'm probably going to go with an external wet sump oil pump on the next motor...sigh

[sibs4972]

What kind of mods did you have done to your motor? Hell, all I was doing was pulling away from a toll booth when my motor took a dump.

[SVTOA Boston]

What kind of mods did you have done to your motor?

Typical bolt-on stuff. Exhaust, cold air induction, pullies, maf, gears etc. I had just put LT headers on the last motor, was prob making around 315rwhp N/A.

[Poisoned Pony]

ouch :eek: Man, so far I've been lucky with my Cobra's stock motor. I have 110k on it and I'm more than likely going to stay N/A. These motors sure like to suck the oil too.

[SNAKEYE]

Originally posted by Poisoned Pony
ouch :eek: Man, so far I've been lucky with my Cobra's stock motor. I have 110k on it and I'm more than likely going to stay N/A. These motors sure like to suck the oil too.

So, at 110K miles, what type of driving are you doing, what is your oil consumption, and what type and viscosity oil are you running?

[Sharppony]

I've read on several posts about heavy oil consumption in the mod motors. My 96 Cobra has 41K and uses no oil between changes every 3K. My wife's 5.4 Expedition uses a quart every 1000 miles! My neighbor is a Ford Certified Mechanic at a major regional dealership and says Ford considers a quart every 700 miles as normal consumption in the mod motors. This seems excessive to me, especially when the daily beater with over 186K and a lowly 200 6 only consumes a quart every 2500 miles. :huh:

[Snakeman69]

what brand were yours?
i have heard that welding slag from the longtubes can get sucked into the EGR system and right into the intake...

i vote for forged internals

[sibs4972]

Snakeman what brands were having the problems with slag?

[Snakeman69]

but try a search over at the corral (http://www.corral.net) messageboards for further info...

[U TINK]

Originally posted by Snakeman69
what brand were yours?
i have heard that welding slag from the longtubes can get sucked into the EGR system and right into the intake...

i vote for forged internals If you`re thinking of buying Longtubes for your Cobra,spend the money and go with Hooker or BBK. Stay away from Mac if you want motor to stay running.Check the Corral and Stangnet for feedback on Mac long tubes and hurt motors caused by them.

[Rocket]

Just my $.02,
Sorry to see that happen to anyone.
Now that I read your post, I vaigley
remember when I had my 96 Mystic
having some oiling problems to the heads
i.e. valves, maybe totally non-related
but my dealer back then said many cars had
some failures due to the loss of oil and compounded
with some actual oil problems they had within
some of their stock i.e. oil barrels "supply". Seems
some of the valves were actually locking up, eventually
causing head and or lower end damage. Good luck.

[Poisoned Pony]

Originally posted by SNAKEYE
So, at 110K miles, what type of driving are you doing, what is your oil consumption, and what type and viscosity oil are you running?

Agressive driving :D It's my only car, so it's still daily driven, I hit the 1/4 mile once a month and she sees redline about 3 times a week. I consume about a quart every 2500-3000 miles. I run Amsoil 5w30 with a Motorcraft filter

[SNAKEYE]

Originally posted by Poisoned Pony
Agressive driving :D It's my only car, so it's still daily driven, I hit the 1/4 mile once a month and she sees redline about 3 times a week. I consume about a quart every 2500-3000 miles. I run Amsoil 5w30 with a Motorcraft filter
2500-3000 miles per quart on an engine with 110K on it doesn't sound out of line for a daily driver with a few red lines a week.
At 34K miles running 5W50 Syntech I'm using about 1/2 quart in 3K miles. At 110K miles I'll be happy at a quart/3K. Just change it regular at 3K. Maybe step up to 40 weight to see if there's any improvement.

[CobraCommander]

I am new to this, but did it look to anybody that this guy was in first gear the whole time???

[SVTOA Boston]

I am new to this, but did it look to anybody that this guy was in first gear the whole time???

If it were first gear I'm sure it would have self-destructed after the first lap. :D Limerock is a very short track and with 4.30's in the rear the only time I really need to shift to 4th is going down the front straight.
I actually prefer longer tracks with a mix of striaghts and hairpins so I can work on my heel & toeing...