Piston to valve clearance??
Safety Car
Joined: Sep 2003
Posts: 3,558
Likes: 2
From: Cape Coral FL
It's not the lift of the cam, it's the duration, ICL and ECL. When the valves are open all the way the piston is pretty far away from them. As the piston moves towards TDC the valves begin to close. If one hasn't closed enough due to excessive duration or centerline too close you will hit. A lot of big cams do this due to overlap. And it gets worse as the duration gets larger and the lsa gets smaller. Also every engine has slightly different tolerances like deck height variances that affect the actual distance between the bottom of the valve and the top of the piston. One deck can have the piston out of the hole .010" and the other .004". The .004" will obviously have .006" more clearance. I'm pretty sure the spec for deck height variance is .025".
I think one could make a general assumption that with this or that cam you won't hit the head and have adequate p/v but I have read here and other places that as long as you are recamming the engine you really should check. It's not that hard when the time comes and you will rest easy knowing that you won't turn your motor into mush.
I think one could make a general assumption that with this or that cam you won't hit the head and have adequate p/v but I have read here and other places that as long as you are recamming the engine you really should check. It's not that hard when the time comes and you will rest easy knowing that you won't turn your motor into mush.
Instructor
Joined: May 2003
Posts: 154
Likes: 0
From: Kansas City Kansas
As a point of reference, I have the Trex cam from Thunder Racing in my 2002 Z06.
That with 242/248, 608/612, 110lsa specs.
It's on the ragged edge as far as P-to-V clearances, so much so that you need stock heads and gaskets to maintain clearances.
As stated above, "It's not the lift of the cam, it's the duration, ICL and ECL."
Hope this helps!
Steve
That with 242/248, 608/612, 110lsa specs.
It's on the ragged edge as far as P-to-V clearances, so much so that you need stock heads and gaskets to maintain clearances.
As stated above, "It's not the lift of the cam, it's the duration, ICL and ECL."
Hope this helps!
Steve
Pro
Joined: Mar 2002
Posts: 712
Likes: 0
From: Santa Clarita Ca
Originally Posted by Fastbasser
Thanks for the info guys. What is the minimum clearance you should have when you turn the motor over with all in place?
.100 exhaust valve to piston
