[Tom McQueen]

Originally Posted by steve25

Next time you are at a national event at the race track, ask one of the big time pro stock engine buliders what they run for piston to valve clarance.

----------------------------------------------------------------------------------------
I dont work with Pro Stock engines. Im mostly involved with street/strip stuff. And unlike the Pro guys, I dont have sponsors throwing parts at me. I have to write personal checks for my parts. I look at this differently. Risk vs reward. I dont see any reward for the risk involved with squeezing the piston to valve clearance down to the bare bones. Maybe Im just stuck in the past. Oh well. It works for me.

[Half-Inch Stud]

Thanks to Chris (Blaktopr) he advised me to "Roll the valves into clay, then pull head and see what impression I get". [I knew that about 20 years ago.] Befuddled to figure it out in 2010.

.080 space for Alum rods is gonna be fine for my junk.

[John Langer]

I have ran .050 on the intake but you better bet your a$$ that you have a very good valve spring in there. When you have less then .045 with an aluminum rod, the valve will kiss the piston.

[Cliff R]

When I build engines here with "big" solid roller cams, I like to put both heads on the engine with no head gaskets, run the lash at zero, and turn them thru. If they don't hit, then I'll run the lash about .020" down on each valve and turn it thru, and continue to do this till I hit.

I like to see .080/.100" clearance at a minimum, but prefer the method described above to find it, rather than trying to use clay or furnace putty, etc, on top of the pistons.....Cliff

[PONTIAC DUDE]

Originally Posted by Gach

I was thinking of throwing in the bigger roller, when I was putting the motor together I put it in to check piston to valve. I'll have to check my notes but from what I remember
I had .65 and wanted to check if it would take the same push rod lenght, to make sure I
could just make the change while on the dyno. Which there was no problem. We did dyno the motor with the bigger cam and it made 805 hp. But the PV made me
nervous, thinking about going out for the first time with the car. So I wanted to play it
safe.

But I think I'll just leave it along because the converter is perfect for
the cam that's in they. Don't want to touché it. Although I don't think
it would be much different converter wise. I'll have to check but it think
it mover the torque peak up to 6200 where as the cam that's in it now
made peak torque at 5200.

The plain is get the cage in, car certifed by the
end of May and go for my lic when the track opens
in April.

Bump

[cfmcnc]

If you use checking springs plan on adding for pushrod flex ,rocker bend etc ,the more spring the more load on bending ,deflecting parts .We like to use the Loaded valve train when checking piston to valve,have seen way to many pistons flycut that didnt have to be.have seen the difference from checking springs to loaded spring anywhere from .010 to .070,always use the biggest diameter pushrod that will fit,always check ptvc with gasket,lash and full load springs,also check net lift at valve compared to cam card.Bill C.

[Skip Fix]

Something also to consider is how your lash changes change the V-P. If you are planning on trying tighter lash you need to check it also.

Example my 409/470 project on the intake with the 1.7 rockers lashed at 0.026 per card 0.875, 0.020 lash 0.815, 0.030 lash 0.091. The 1.8s I was hoping to try 0.026 lash 0.075, 0.020 0.645 V-P. So much for JE getting the notches deep enough! And it's only a 251@ 0.050 solid roller. All these were with light checking springs and 10 ATDC where it was closest.

Closest exhaust was 0.224 with no notch, but the block needs notching for lifts over .570.

[cfmcnc]

Skip,try checking with real valve springs and see the difference! Bill C.

[mgarblik]

I Agree with most who posted here. With BME rods I run .045-.050" on the intake. The exhaust is not a factor with our cam profile and the late cam timing. We are over .150" on the exhaust. We do run a quality triple spring with 360-375 lbs. on the seat.
Darrin Morgan in a conversation last year said he likes his best pro-stock engines to "just kiss" the pistons at max RPM and load. How you get it there without damage is beyond my personal abilities. Pro-stock engines are as cool as it gets in NA drag racing. IMO

[Skip Fix]

There was a missing zero in a couple of those numbers 0.0875, 0.0815.

Might have to give that a try Bill since the heads are on and they are all lashed.

[goquick]

When we built Pro Stock Truck engines,the perfect clearance was the valve just slightly smear the carbon on top the piston at max rpm and as stated earlier under load. There is a formula to figure that out that also takes in heat of the engine,rods (to figure the stretch) etc.

[WDCreech]

Originally Posted by John Langer

I have ran .050 on the intake but you better bet your a$$ that you have a very good valve spring in there. When you have less then .045 with an aluminum rod, the valve will kiss the piston.

This is my dads computer so im probably already in trouble. I've run .050 on the exhaust , the pistons and everything on a big block chevy and it all kissed ecsept the intake. I've never run less than .050 on the intakeke s o ivenever seen it touch with good valve springs except wear the the valve notches were f t up.

Marty Creech