How big of a cam(duration) and how much can you mill the heads before you start having piston-to-valve clearance problem? Any advice and input is appreciated. Thanks BTW, on a stock short block.

 

My cam has 58X lift and my heads have 50CC chambers. Using the .026 gaskets I had to do some minior filling to the reliefs in the pistons. I imagine it all depends on what pistons you use. When I did my short block I never intended on milling the heads as much as I have now! Any builder should be able to help with piston, head, and cam combo's. It's still always a good idea to check you clearance when assembling the engine!

 

There is no magical formula to determine piston to valve clearance. The only sure-fire way to determine is to mock up the engine using clay and check.

Additionally, lift is not the important number when it comes to p/v clearance. Duration is MUCH more important, as the maximum lift of the valve is nowhere near TDC.

 

100% agreed

too many variables to even attempt to say,so the best way is to check during assembly chances are you wll be fine but research is best

 

Not even really a duration issue is a valve timing issue. The piston chases the exhaust valve closed, if the exhaust lobe is opened and therefore closed late that will put it closer to the piston than just using more duration on the same centerline.

I have heard of VERY few cases of guys have PTV issues on a stock shortblock, one case I suspect was actually a decked block, no longer truely stock, another supposedly the heads were HEAVILY milled. Both used the same head shop but the shop switched cam grinders between incidents so there are a good number of variables involved.

If in doubt put down some clay and measure it. Much cheaper and easier than finding out too late.

 

Thanks alot guys for your input. I have a new top end set up and just wanna make sure it will run and not blow up. Thanks again.