I have 2.055 /1.57 valves on my new heads and was checking P2V clearance earlier today.

Looks like I have adequate space from valve bottom to piston top ~.10" However, the edge of the valve comes to close <.025" to the inner edge of the cut relief in my stock piston.

This is only a problem with the intake vale - the exhaust side is fine.

Is there a cutter or other method of enlarging reliefs (dremel?)

The block is in the car - I am looking for an option to address the issue in place.

 

You have to remember that you won't be at FULL LIFT when the piston is at TDC, if you clear it at TDC then you will never have problems. Hope this helps.

 

I did the play doh test this morning and measures space after turning the crank over a couple of times by hand - i only checkded one cylinder but the clearance was minimal and in one spot it must have rubbed as there was a tear in the putty.

I assume that means it's too close

 

Ummmm No you only want to be at the lift the valve is at when you are at TDC.

This comes along with the myth that more lift will hurt piston to valve clearance. Actually duration and LSA (& advance and retard) will effect the piston to valve clearance, lift has zero impact on the piston to valve clearance.

If you went by your rule you would have to have a .800 valve relief in a dirt motor that limits you to xx castings and flat top pistons, you could easily loose 1 point of compression in a situation like that. When you are fighting for every last HP that's a big loss because you would need about .700 more piston to valve clearance than what you actually needed in the motor.

BPS,

Are you saying that the outside edge of your valve is too close, not the depth? So if your valve was a 2.08 valve then it would touch the valve relief? If so then you are fine .025 is pleanty for the side clearance on the valves, it's the piston to valve depth and clearance there that is the critical dimension.

If you need to cut the pistons more a shop with a piston vice and a mill can help you or Isky has a tool that will help you if you have the time to do it yourself (as long as you are very clean!)

Bret

 

That's exactly it -

I read an old post

http://web.camaross.com/forums/showt...t=valve+relief
where oldsstroker seemed to suggest that 0.5 clearance to the edge was required.

But if I can get away with .025 then all is well -

I check the rest of them to be on the safe side

Thanks.

 

Nah I think my old man missed a 0 in there someplace because .5 is a ton of room!

I wouldn't be too scared to get it closer than that, in a motor where compression is only limited by how much you can mill the heads, flat top pistons and valve relievs then the closer you can get it the beter.

Sounds like you are ok though.

Bret

 

great - thanks