I've been noticing a lot people talking about blown headgaskets on there built motor trucks latelly..............

Anyone have any input on this? What's causing it; what could be done to prevent it? Just seems a little strange trucks with headstuds are blowing gaskets.

 

ported heads and cams are letting the engines breath a lot better so when it goes into detonation now.....it makes a big bang

Seriously tho....the more power the engine makes the more damaging the detonation and the quicker it does its damage. Its also harder to detect and hear. Feel lucky the the heads are lifting....its like a safety valve. If we didn't have that....something else probably more expensive would be damaged instead.
Dale

 

Alright; so it's a detonation problem...........not a figurative boost number correct?

 

I think anything from 24 psi and up is going to lift a head at some point. Even with studs and the best gaskets available the Modular motor doesn't have the ideal head bolt arangement around the cylinders for a boosted engine.

Jody

 

Jody
I think you have to look at what is being done with a mod motor in racing today. What are they up to ?? some 2200 hp now with the same head gaskets and studs that we run. I won't put a boost number on anything, not when I know there are guys running 35/40 lbs with nearly twice the head flow numbers that a 2V motor has and its staying together.
Dale

 

But, why are us 2v guys having trouble and Cobra 4v guys arn't? Do the 4v heads "hold down" better? Or, is they are flow/cooling and preventing detonation better?

 

I always understood it was the 4 bolts around each cylinder instead of five. I know the LSX engines have the same issue, other than this new aftermarket block/head package that Dart just came out with. Doesn't mean they don't make huge boost and power; Wheel 2 Wheel has one going 6's but they also have a blow-off on the cooling system as they pressurize it on every pass since the bolt arrangement can't hold things in place. Maybe that's what the mod guys are doing too.

As far as our trucks I've had a couple well-respected engine builders give me those specs. They're obviously not written in stone, but it sure seems that every one who runs more than that amount does pull their trucks apart to fix the gaskets on a semi-regular basis. That is fine in a race environment as you'll be pulling the engine for freshening on a regular basis, but would suck for a street truck.

Jody

 

ive seen a few trucks left the heads at the track. i have also seen those same trucks drive home and run again at the track with no work preformed on them.

one of the trucks i have seen do this, has put down over 800rwhp after the heads lifted.

detonation is no doubt lifting these heads, i wonder if a turbo would be alittle more forgiving when detonation occurs?


rick

 

Well....if the 24lb number is the magic number then it would be related to the breathing dynamics of the head IMHO. (That is if spark plug inserts and valve springs have been ruled out) I have pulled my engine apart and seen evidence of heavy wash on one side of the cylinder bore directly in front of were the intake valve would be discharging its air/fuel. Smashing the air/fuel mixture into the side of the cylinder wall would lead to detonation caused by fuel fall out. The 2V cylinder head is supposed to be a high swirl or tumble type design but if the ports aren't aimed just right and you turn the boost up it could be doing evil things to the mixture ???? Just an educated guess I guess
Dale

PS...I'm sure the heads are lifting because of detonation.....but not exactly sure what is causing the detonation but I have some clues.

 

I really don't know for sure, just quoting what I've heard from builders that I think know what they're doing.

If it's detonation it isn't an octane issue as these guys run the best gas available. But there are a lot more things than octane that can cause detonation, so you may be onto something. I will say I have not heard of anyone running 25+ psi for a length of time without freshening the engine, lifting a head, etc.

Jody

 

I think some of this "head lifting" is actually the block twisting under crankshaft torque, which flexes the decks, breaking the seal.

 

I just lifted mine for the second time yesterday. I didn't send it to a machine shop to check the decks the last time cause I thought it was just an erroor on my part only running 100 octane gas, but yesterday I was running 116 and was seeing 21#'s of boost with my LM-1 saying 11.2-1 AF. I'm hoping when I pullit out this time I find a deck problem to explain why this keeps happening. If they are straight I don't know what I'm gonna do.

 

when i first read your post i thought, naaaw!!!!

but after thinking about it alittle, you might be right? that would defenitly explain why the 4.6 litter doesnt lift heads as often


rick

 

Well I know for sure that at 600+ hp the cylinder walls in a 5.4L are flopping around like a towel in the wind (so to speak) so maybe he is on to something.

 

whats your opinion on the aluminum block