valve to piston?

[mustangfury86]

i am wondering how do u know when ur buying heads and a cam and pistons how big of valve releaf u need . got a block and wanted 2 build it up with trick flow heat head combo and need help with pistons!

thank you ,
Justin

[Intmdtr]

best advice i can give is...no valve clearance is ever the same, before you buy a cam contact the company that makes it and talk to a sales associate, some of the guys on here know a few names....and talk over your needs and wants. they will help you pick the best cam profile for your combination. you will still need to check P2V clearance once you have it together to make sure. when i built my 351 i already had the pistons and heads, just called Comp Cams and asked what would be best for what i had...they punch it in there pc and it gives them a list of cams for your combination, ie what pistons and stroke you are running and what heads, valves and springs you are running. hope thats a start....

[mustangfury86]

u think that i could call summit or should i call trick flow because the cam is already in the heat kit ???

[Intmdtr]

i would call Trick flow, they may be able to tell you your max dish size for your pistons for clearance.

[johnisbubba]

Its all about lift baby.

[lafinrat]

Actually, duration and lobe center play a bigger role in P-V clearance than does max lift. The valves are closest to the pistons near TDC. Most cams have 0.100 to 0.200" lift at TDC. Other contributing factors are valve and angle and spacing and deck clearance.

As stated, you need to "clay check" the motor for P-V clearance before anything is final assembled. I use Play-Doh. Most cams under 250 duration at 0.050" will have tons of room. Wide lobe center cams (112+) also have more room due to lower overlap. You need 0.080" intake clearance, 0.100" ex and 0.060" radial clearance everywhere. You can get away with less if absolutely necessary.

[91gt347]

If that still has the stage 1 cam in the kit,you could run stock forged pistons from like a 90 5.0. I ran that setup for a long time.

[mezapu]

Trick flow heads can get away with a lot more p-v clearance than other brands because of their design. My buddy had a set on his stock (true) flattop piston 1986 shortblock, running a TFS stg1 cam and 1.72 rockers with good p-v clearance. Went 12.1's with a 125 shot.