Engine Problem - Page 2

392cobra · #21 (**permalink**) 02-28-2007, 04:40 PM

392 stroker Ford crate engine

http://www.clubcobra.com/forums/show...9&postcount=15

re: cast piston failures

olddog · #22 (**permalink**) 02-28-2007, 08:17 PM

From what I could see in the pictures, it looks to me like the piston land broke and the pieces that came off the piston did all the damage. I'm not at all certain, but I do not think the valve hit the piston. Rather the chunks off of the piston hit the valve.

I have seen pistons break like this when the cylinder leaned out. The lean condition overheats the piston. The piston expands and become larger than the bore. This sticks the piston to the bore, and then the piston land breaks off.

Look on the cylinder walls and see if there is aluminum rubbed off or hard scuff marks or both. When the piston is out, look closely at the lands on the sides of the piston.

Rick Parker · #23 (**permalink**) 02-28-2007, 11:03 PM

I agree with Olddog, the valve shows no evidence of being struck by the piston, except it looks like the piston may have been cracked for some time, waiting to break loose. The fractured area looks to be quite dark, it may have already been cracked, it is not not bright like you would expect freshly exposed aluminum to be. one more thing, in picture #2 the manifold is discolored or stained for about 2" near the head mating surfaces. Is this from the coolant you spilled or has there been standing moisture on the manifold in the past?
Unfortunately it would appear you are in for a major rebuild. After it is done you will have a bullitproof ride. This is an unfortunate initiation to the Cobra world but in reality it was nothing anyone knew was going to happen other than Ford. Based on past performance it looks like a poor piston design. The heads appear to be GT-40X "Turbo Swirl" heads.

kinglenario · #24 (**permalink**) 03-01-2007, 06:53 AM

Thanks for the Input guys. the car is at the experts now...

i did not spill coolant on the mani as i just got the car, but yeah that was the first thing i thought. how did all this coolant pool up in there.

it looks like the whole area where the piston broke is black, not like a fresh break. could this piston land have already been partially broken? the piston does not at all look like it was running too lean does it? none of that white coloration that lean pistons get.

392cobra · #25 (**permalink**) 03-01-2007, 07:23 AM

Sorry this happened so very soon after getting it.
The timing of this could have been worse though.Now you will have it better with a long driving season still in front of you.

Now would be the time to go with better heads ! It would be very easy to end up in the 525 hp range with the swap.

Your crank is cast as well.

Go to 408 with a forged crank and pistons,better heads ???

olddog · #26 (**permalink**) 03-01-2007, 07:22 PM

I have to agree that the coloration of the piston didn't look like it was burning lean. I wasn't thinking about that.

Still could have been too tight a fit. It might be worth checking the piston to cylinder clearance. If it is too tight you just might get the manufacturer to step up a little. I wouldn't count on it, but it's always worth a try (assuming there was a real problem).

kinglenario · #27 (**permalink**) 03-02-2007, 06:58 AM

Thanks again for your input guys.

i don't think it just ran like that for nearly 10,000 miles then magically the day i drive it, in the first 20 miles it expires. something was up here. i have been told a couple of times about the discoloration of the where the piston broke being dark, unlike a fresh break. i think this had something to do with it as well.

olddog · #28 (**permalink**) 03-03-2007, 09:39 AM

I didn't realize the engine had 10K miles. I doubt it had anything to do with assembly fit.

The piston could have been leaned out long ago and caused a crack. Many other possibilities, as well (bad piston as others have said).

I do not think an over rev or any other driving issue would cause this. I doubt the previous owner new anything was wrong. A failure like this goes un-noticed until a chunck comes loose.

Sorry about your luck. Hope you end up happier with a better engine when your done. You will get a lot of personal satifaction from helping to design what goes into it and knowing what is in it.

kinglenario · #29 (**permalink**) 03-15-2007, 09:23 AM

I got the engine diagnosed at Southern Automotive by Bill Parham. He said the broken piston was caused by detonation which was caused by a ballast being removed from the distributor. This caused the distributor to run at the wrong voltage causing a break in a forged piston. he said there is no question in his mind this is what happened. Since i bought this car used the seller did not disclose this pre existing engine problem and very dangerous modification. The repair cost is going to be $3,500. i'm trying to get the previous owner to cover the expense but they are saying that they wont. i think i am going to have to sue the previous owner and the dealer i bough the car on consignment from. any input?

thanks

392cobra · #30 (**permalink**) 03-15-2007, 09:41 AM

Sure is a sorry way to start your Cobra experience.

Did you have a mechanic check it out and did you drive it before buying it ?

Unless you got a written warranty I believe it would be "as is".

Proving the seller knew of this damage before selling could be pretty tough going.

Hope it all works out the way you want.

Excaliber · #31 (**permalink**) 03-15-2007, 10:02 AM

Removing the BALLAST RESISTOR will allow max battery voltage to the PRIMARY coil windings and depending on WHICH coil your using could burn out the coil.

I fail to see ANY connection between a high or low voltage coil being the cause of preignition or detonation. While the coil is running on max primary voltage the SECONDARY high voltage it may (or may not) provide to the plug is not a 'bad thing'.

Back to square one for me, I doubt the coil is the culprit.

Typical battery voltage is 14 volts. Typical primary coil voltage required is 7 to 9 volts. SOME kind of ballast resistor is needed to reduce primary voltage. Could be INTERNAL to the coil (can't be removed) or EXTERNAL (could be removed). Secondary voltage fires the plug, this could be as little as 20,000 volts or as high as a 100,000 volts (as most modern cars utilize).

kinglenario · #32 (**permalink**) 03-15-2007, 07:21 PM

i'm not sure of the exact details but these guys are experts. pretty much the foremost 427 guys in the country. i will get more exact information, but he specifically said that the forged piston broke due to detonation and was caused by the distributor being tampered with and the Ballast resistor removed.

Excaliber · #33 (**permalink**) 03-15-2007, 07:28 PM

Timing could well have been to advanced (dist tampered with), THAT would certainly cause it! Question now becomes, who and when set the timing last?

...and they also found the ballast resistor was incorrect while they were at it.

Ernie (an expert at just about, well, everything)!

olddog · #34 (**permalink**) 03-15-2007, 08:18 PM

Quote:

Originally Posted by Excaliber

Removing the BALLAST RESISTOR will allow max battery voltage to the PRIMARY coil windings and depending on WHICH coil your using could burn out the coil.

I fail to see ANY connection between a high or low voltage coil being the cause of preignition or detonation. While the coil is running on max primary voltage the SECONDARY high voltage it may (or may not) provide to the plug is not a 'bad thing'.

I have to agree 100%.

Pre-ignition is when the fuel ignites before the plug fires. The ignition system has nothing to do with this.

Detonation is more difficult to explain. Under normal combustion, the spark plug lights off the fuel. The fuel burns in a controlled mannor from the spark plug across the combustion chamber in all directions until all fuel is burned. During the controlled burn, as the flame front travels across the combustion chamber, an uncontrolled explosion of the remaining fuel charge is called detonation. This can be caused by timing too far advanced, fuel mixture too lean, too much compression for the octain of the gasoline, and other things as well. Again coil voltage has nothing to do with this.

I hope what you thought you heard was not what the expert meant. Otherwise they are not the experts you think they are. The ballast resistor had nothing to do with it. Yes, I 100% agree that detonation was the likely cause. Detonation can take an engine out in seconds.

When it happened is unknown. Unless you have a warrenty in writing, I doubt you have a leg to stand on.

The easiest defense against you would be to claim you put too low of octain fuel in the car. The next thing is claim that the timing was moved by you. It doesn't have to be true, just create some doubt.

Excaliber · #35 (**permalink**) 03-15-2007, 08:25 PM

To bad the coil didn't burn out from over voltage before the piston burned out, it was a race to the finish.

kinglenario · #36 (**permalink**) 03-16-2007, 06:51 AM

i drove the car for 20 minutes and less than 20 miles. i paid good money for the car. at least they could offer to pay $1500 or something. anything just to be reasonable. but they will not.

for me it's just a matter of principle now. i will sue them and it will cost them more to defend when they have to hire a lawyer.

it's just rediculous how many people are totally unreasonable.

Gotalbots · #37 (**permalink**) 04-11-2007, 10:10 PM

Similar thing just happened to me, if it makes you feel any better. FRPP 392 Stroker circa 2002. Less than 7k miles. Same experience, gentle drive, suddenly implosion. Spark plug mangled. Head off shows cylinder #4 piston hole, head has valve wedged sideways in its seat. Expert says not detonation though. FRPP has it for assessment.