bbc question
 

what is minimum piston to head clearance on steel rod bbc?

I typically run "zero" deck clearance and a Felpro #1027 head gasket which has a compressed thickness of .039. So my piston to head clearance is .039. Hope this helps. I'm sure others do it differently.

TS1955

Watch your piston rock depending on how "big" your BBC is. RPM will also play into it some. Just some things to think about in the equation.

Curtis

We recommend a min of .040 between the piston and the head.

my motor builder said once upon a time they set up thier pistons .005 thousandths in the hole

russ,
That doesn't tell you what the p to h clearance is. You could still have .060".

Curtis

Plus the gasket....

I think russ67 meant .005" = a "std" style gasket say 0.039" compressed & you'll generally be ok. X2 As doorracer says depending how "big" & rpm. I don't understand the last post.

I dont see what would be hard to understand. .005 in the hole plus the gasket .039 would give you .044 clearance, between the flat part of the piston and the head. Which is where most pistons hit. Especially if because of the piston rocking in the cylinder.

Mine hit on the dome right by the intake valve...Motor was already together so I had to grind on a brand new set of heads. :(

I bought a set of Sonny Leonards BBC heads with the heart shaped chamber. When I put them on my motor, the pistons were hitting the heads where the chamber rolls in between the valves. Sonny told me to relieve the piston and not to touch the head.

TS1955

Your absolutely right TS1955, its usually better to relieve the piston. But on Todd's post he said he already had his engine toghether. Under those circumstances I would have relieved the head also. No rebalancing or metal in the engine.

I see, you were answering russ not doorracer,not as appears,in order. Just looking @ my typo = should read +, sorry.

I ran a drag motor all last year,4.155 bore,.007 cyl.clearance .005 out of the hole and .041 gasket .036 piston to head,shift at 76-7800.When I took it apart 4 pistons had been hitting the head,all on the right bank,the deck clearance on all cylinders were set the same when it was first built.The top ring grouve was still good so i took .003 off the pistons and now have .039.I won't have it apart till next winner to see if they still hit,unless there's a problem.Just saying .036 might be to close in my combo.Bill.

i like to run zero deck with .041" gasket. I ran a 598 on the dyno once that was down to .035" total turning to 7500 and when we pulled it apart the piston part number was stamped onto the head. (it was a test engine and the pistons had a part number eched on the top) That was a 630ish gm piston on a scat H beam rod with .007-.008" clearance.

Just another vote for .040"+

Steve

SORRY FOR CONFUSIONS...I MEANT .005 TOP OF PISTON BELOW THE DECK.THATS JUST A LITTLE SAFETY NET....I DONT KNOW MORE ON THIS SUBJECT

IM ALWAYS INTERESTED IN WHAT MY MOTOR GUYS HAVE TO SAY.THEY BUILT BRIAN METZENHEIMS 540 ENGINE LIKE 7 OR 8 YEARS AGO AND ITS STILL IN HIS CAR, I THINK....WHICH RUNS CONSISTANT MID 7'S!!!

BRIAN METZENHEIM(http://www.metzperformance.com/about.html) WORKED WITH THE JEGS PRO STOCK TEAM AND IS WELL RESPECTED AT THE GREAT LAKES DRAGAWAY UNION GROVE WISCONSIN