[Joecool]

I have recently built a stroker motor from a 351W with a Scat rotating assembly for a 408(actually a 414 because it is .060 over). The kit came with Keith Black forged IC750 pistons.
I assembled the engine using ProComp CNC Aluminum heads with 2.02 intake and 1.60 exhaust valves.
The valves are hitting the pistons at the top of the valve reliefs. I would have thought that the pistons would have had big enough valve reliefs - since they are designed for a stroker engine.
I contacted the piston company, and they said it had enough material to cut the required opening - but not to get to close to the sides of the pistons(because it could get into the top ring).
I will clay it again - because I am concerned about the side clearence also.
Has anyone had a similar experience?
Thanks
Joe

 

[dennis112]

If only one set of valves, such as the intake are hitting, you could experiment with adjusting the cam timing to compensate. If both intakes and exhaust are hitting, then you might have the wrong pistons. If you think that your only out is to notch the pistons, then I would like to suggest the following tech article which shows a simple way to do it:

http://www.fordmuscleforums.com/engine-articles/484906-another-technique-piston-notching.html

 

[PSIG]

Agreed that cam timing is the primary factor for if and where the P-V interference occurs, but there are other factors as mentioned and more. Do a clay print and post the results with a few different good photo angles for us. Measured minimum actual clearances, and where, would also be helpful.

David

 

[mustangboy]

Wow what are your cam specs?..I am running a pretty healthy solid roller cam and slightly larger valves and I have tons of clearance using the same pistons..I am also running edelbrock vic jr heads which I understand the pro comps were designed after..

 

[Joecool]

Ok guys thanks for the replies. I reclayed the pistons, and it is ok - not sure what I saw the other day - maybe a senior moment or my arthritis meds kicking in -haha
I had purchased to long of push rods - they were on the valves tips ok =but making the valves hit the pistons. Remeasured push rods, and installed new ones - everything is good.
Valves opening and closing with .150 to .180 clearence.
With the long push rods it was locking the motor up.
Again thanks for the help.
Joe

 

[mustangboy]

Glad it was an easy fix..