Head gaskets and piston/valve clearance

[SpinMonster]

What is the max lift you can run from cam/rocker arm ratio changes without hitting a piston? Does cometic gasket make varying thicknesses for viper head gaskets?

Anyone running a higher comression ratio?

 

[Cris]

what or who is cometic?

If you check the archives you will find info on shaved heads and compression ratio increases.

Regarding rocker ratio related piston-valve clearance I do not believe valve clearance is the limiting factor. If you couple it with a longer duration, higher lift cam profile than you may get into problems.

 

[SpinMonster]

cometic gasket makes after market multi-layer steel gaskets for just about any vehicle you can think of in varying thicknesses to increase compression without shaving heads.

What is the max lift you can run without a valve kissing a piston on a stock set-up.....(requires you to know the stock clearance for a stock engine- piston to valve)?

 

[Cris]

It is not the max lift that causes valve to piston interference. It is how quickly the valve opens. Most valve interference occurs somewhere near TDC. You can make a plot of piston height versus valve position and determine the theoretical clearance (it is all just geometry) or you can check the current clearance with clay or other medium. Either way works. But it is impossible for anyone to state how much lift it can handle when they do not know the intake opening and exhaust closing points or the acceleration rates.

Unfortunately I cannot tell you the current clearance. Maybe one of the tuners can. Have you called any of them?

 

[utahviper]

I know there are alot of tuners that run 600 lift cams and shave 60 thousandths off the heads without any pistons hitting. I don't think you can do much more than that.

 

[Martin D]

I am running over 725 lift. I did have to notch the pistons. The unexpected situation was the base circle size..... Go to big on the cam, and you will see what I mean! My compression is 10.8

Regards,

 

[SpinMonster]

The base circle was smaller and you needed shorted pushrods or adjustable rockers?

 

[Martin D]

Nope, the lifters fall down below the retainers..... Now that was a real problem/challenge!

 

[SpinMonster]

that is a solid roller cam?.....what do you rev to for shifting?

 

[Martin D]

It is a solid. It is all done making power by 6k - even though it should make power well past 7k. We think it is a limitation of the heads and or intake.

Regards,