How much P to V clearance do you guys run at the MINIMUM.. thanks

I have run as little as .058 on the intake and .076 on the exhaust with a solid roller. I ran just a little more with a solid flat tappet twisting the engine 8500 in the water, shifted at 8000. Both steel rod engines. I guess it really depends on the cam, valve springs and such. I was told by an engine builder that I could have got by with less clearance but he wouldn't say how much less.

I got away with .039 on the intakes and .060 on the exhaust accidently on my old 415 HP M.W., it had .100 plus when I first put it together with the stock 1963 heads with 86.? CC, NHRA blueprint specs called for 81.5 CC so I ended up later removing the heads and had them cut without thinking about the P to V clearance change
I ended up changing the intake valves to 440 style that flowed better than the stock 1963 intake valves did after that and ended up having to grind a little around in the combustion chambers in the intake valve reliefs to get the legal CC back after that valve change
On roller cam race motors I shoot for .060 on the intakes and .080 on the exhaust with light checking springs

Good to know guys.. thanks for that info.. I forgot to check that when I milled the pistons down..
looks like I can get away with .020 more.. that will give me a total gasket thickness of .065.
Since I have to order a custom thickness who would you go with.. thanks again

Cometic.

Yeah thats who I'm looking at now.. those things sure are pricey at over $100 each.. I guess
its been a lot of years since I had to buy any.. I still have a stock pile of them about 25 or so
but none the thickness I need

Mike, I got by with a LOT less than that 20 years ago when building a 14.5:1 W5 engine. The tech that put my heads together had stamped the cylinder number on the face of each valve. I thought I was being anal about specifics when getting the thing together but boy was I wrong. The insides were 6.4 MGP rods and JE 1.22 CD pistons. Anyway I would have bet money that I had the correct amount of valve to piston clearance. I would usually wind it to 74 to 7600 rpm. My surprise was the next time I tore it down every piston had the number imprinted on the piston from the stamping. I still don't know what I did wrong but I was ultra careful from then on.

Thanks.. I know one time I had .030 clearance and ran the season.. when I tore down for
a inspection I seen the exhaust valve was just touching the edge of the head and a
very slight bit of grinding on the edge of all of the piston it cleared fine I turned it to 8200
I know I wont be turning this engine that high since its a back up for mu street rod

.031"/.069"

I can tell you on a R3/W9 engine that .045 is ALMOST, enough.

It survived seven or so dyno pulls and several runs down the track.

Biggest lesson learned don't believe everything you read on the Internet.

Good call, research who is giving you advise to determine if they actually build racing engines, or are regurgitating suspect info from others.

I have been measuring the clearance.. started at zero clearance to find where the exhaust valve
will open all the way with zero clearance.. but it still a guess on how much P to V clearance
is truely needed.. since these pistons were milled temp changes are a unknown and
I dont want to lower the compression to much.. I dont want to mill the valve relief is it
doesnt need it but looks like I might have to (I dont want to make these pistons to thin)
I thing I will have to check the relief area with my sonic tester