piston to valve cl. check
 

any difference in measurement between using a checking sping and using a race spring? stocker bbc engine.

Re: piston to valve cl. check
 

There sure is. I check mine with a race spring and a fixture that uses the rocker arm to open the valve with a 1/2" drive pull handle, using a dial indicator on the valve spring retainer. I check every 5 degrees of crankshaft rotation from
25 degrees BTDC to 25 degrees ABDC for intake opening and exhaust closing. You will find valve train deflection in a big block Chevy Stock Eliminator engine to be impressive, to say the least.

Re: piston to valve cl. check
 

Alan is right. There is a huge difference between actual spring pressure, and using checking springs. We've seen as much as .050. But that being said, if you get a min. one way, don't assume that min. applies when using actual spring pressure. In other words my min. is .035 intake, .080 exhaust with checker springs. I wouldn't use those numbers on actual spring pressure. At those settings I have seen the shadow of the exhaust valve in the piston. Other guys may have a very different take on this.

Re: piston to valve cl. check
 

If it is a rectangle port big block Chevy Stock Eliminator engine that makes enough power to be competitive, I'd be real surprised if you could not see the "shadow" of the valves on the piston.

Re: piston to valve cl. check
 

Check the valve lift at retainer with both
springs and see the difference

Re: piston to valve cl. check
 

thank you.....exhaust im getting .105'' w/checking spring & dial indicator, .155'' w/race spring and clay method. The .028'' valve lash has been set while testing both ways...

Re: piston to valve cl. check
 

thanks everyone....we are going with what we have measured w/the race spring installed. its well safe. The answer to the question therefore is "using the intended valve spring to measure p2v clearance gives appx. +.050'' more than what the checking spring method shows". sp.

Re: piston to valve cl. check
 

THAT's impressive

!

Re: piston to valve cl. check
 

Guys I wanted to ask a question about checking P/V clearance with a HYD/Shubeck set up? Do you put in a solid lifter and a longer push rod to make up for the overall length? Or do you use the shubecks and check as usual and figure in the approx .015 lifter slack? I would like to hear what you guys do to check the P/V on a SBC stocker set up.

Thanks

Re: piston to valve cl. check
 

I use a solid lifter with the push rod I race with. You wouldn't
use a longer one it would be shorter and that .015 I
don't think would make a difference.:)