Boost vs. Cylinder Temps vs. Gaskets & Internals

[laser92awd]

I am trying to figure out the approximate limit a stock engine can be pushed to without having a "problem". (Problem defined as: blown head gasket / broken fasteners / bent or busted rods / etc.).

Say you've got a pretty well modded car - but a bone stock engine. Assume everything is in perfect working condition and compression is perfect, low miles, everything is working well. Figure you've done all the supporting hardware - fuel pump, fuel computer, injectors, huge intercooler, exhaust, tuning with an O2 / EGT / logger, etc.

Now say you have a good turbo capable of putting out as much airflow as you can use that can easily run 20 to 30psi boost pressure (for example).

My question is - is it the cylinder temperatures or the boost pressure that is going to cause the engine to hurt itself?

Say you are running race gas, and flowing so much fuel that your EGT's are still low after a 1/4 mile run. Would this mean the boost can continue to go up safely on a stock engine? Where does the stock engine start showing weakness?

It seems to me that regardless of how well tuned your engine is, and how low your cylinder temps are, that there must be a realistic limit as to how much air you can try to force through the stock system.

Before you exceed those limits, what should get upgraded? For instance, do people always wait until after they blow their head gasket to put a steel head gasket in? Do some people actually do this in advance or can it be avoided?

Your thoughts on this appreciated!

 

[TwoLiterV8Eater]

i dont have any solid facts of my own, but my friends talon runs 120 trap speeds on a bone stock engine and he tells me that at 25 psi the stock head bolts stretch and he pushes some coolant out through the headgasket, so i would say that is defintely one of the things to upgrade..i have a set of ARP's waiting to go in my car.

 

[laser92awd]

Originally posted by TwoLiterV8Eater
i dont have any solid facts of my own, but my friends talon runs 120 trap speeds on a bone stock engine and he tells me that at 25 psi the stock head bolts stretch and he pushes some coolant out through the headgasket, so i would say that is defintely one of the things to upgrade..i have a set of ARP's waiting to go in my car.

So would you say I should upgrade the head bolts but leave the stock head gasket in there? Or do both together? That's impressive that he's running 120's on a bone stock engine. I wonder if anybody out there has figured out the farthest a bone stock engine can be pushed. In fact, if he replaced those bolts before they let the head gasket go, IMO the engine would still be bone stock - I wonder how much farther he could go from there?

 

[TwoLiterV8Eater]

Im not sure of the limits of a stock engine, but other than the headbolts/headgasket problem he is having now he hasnt had anything else internal break yet. i bought a 4 layer mitsu gasket along with my ARPs, but as far as i know my friend plans of sticking with the stock gasket. the 4 layer gasket is a good idea if you've ever had your head shaved. my head is a rebuilt one so im sure it has probably been shaved in the past.