I have my 527 C.I. SR headed stroker motor apart due to a pushrod breaking in the middle and hurting a roller lifter and one lobe on the cam. I don't have the good Indy valley cover that has the removable center so I pulled the head off of the side that broke the pushrod. The #1 piston is .007 above the deck and I used a Fel Pro 8519PT head gasket thinking they where the same thickness as trhe Fel Pro 1009 head gasket, WRONG The 8519 PT is .035 thick after being compressed, the used Fel Pro 1009 I have from another tear down is .042 thick compressed. I will post two pictures, all four pistons on this one and the two rear pistons on the next post. Sorry for the poor quality on the pictures but you should get the point on the head to piston contact or almost conatact, no room for carbon
"EDIT" I remove the right head today after church, the pistons on that side of the motor are all at least .002 down in the hole at the wrist pins rocking them front to rear, none are above the deck No sign of piston to head contact, #2 piston has a spot that looks like it was not allowing carbon to stick in the upper right front corner of the cylinder, similar to piston #1 That will teach me to not check the deck height on every piston at least once after having the machine work done I ended up using the 8519 PT head gasket on that side to try and make the compression ratio some what close, left side is .007 above with a .042 thick head gasket and the right side is .002 down with a .035 thick head gasket I have a chance to put this motor back on the same dyno soon so I will, hopefully, dyno test it again and try the tunnel ram after retesting the motor with 440-2 with the adapter and the 9375-2 Domintor to see if it makes the same power or close to what it did on the first test before the pushrod broke I will probally take this motor apart this winter and have the decks cut so both sides of the motor have the same deck hieghts and use a SCE Titan head gasket on it to get the quench I want, probally right at .035 Ain't engine building great

The two rear pistons actually look like they are polished on the upper right part of the piston that has no carbon, the head is clean also, no carbon in the quench area. Obviuosly .025 piston to head clearances isn't enough on a iron block with steel rods, I hope .035 is I'll pull the right head off tomorrow and inspect it, the #2 piston sticks up .002 above the deck according to my blueprint sheet, I'll know soon

Good Info... Looks like the PT8519 is gonna be perfect for me... My pistons are .005 in the hole...

I think mine is around 0.037, 0.025 is cutting it fine.
Mick

A lot of guys will tell you that it's just fine, provided you're not caving a ring land. But that's just too close for comfort, IMO. I know a guy that builds dirt motors and runs them real tight, but they are using super light stuff, which will be a bit more forgiving.

I would get custom a thickness Cometic and be done.

MB

Bad news.

I run .100" quench in the 605" , but this is a nitrous built motor , some of the guys on the bullet have them around .025" (on motor) , just crazy , is it worth running this tight for maybe a bit more power? i don't think so , if anything i would think it would heed performance with a VERY tight tuning window. , detonation won't be so forgiving with a tight quench built motor.

could the piston rocking on the pin give closer quench than you think.i think it can be .010 more out with the rocking.

The piston to wall clearances is .0048 on the # 1 piston, I usually rock the piston both ways and meaure the high and low on the cam side and divede that for the average deck hieght I have seen .003 on the high and .010 on the low on the looser clearance piston materials, this motor has the tigher alloy pisons in it

On my 3.58 stroke small blocks we found with tight clearance kb hyper pistons we started kissing the heads @ 7500 rpm with .030 quench but with no damage, similar carbon pattern on quench pad

If it's workiong right, there shouldn't be much for carbon there... All the burnable mix gets moved to the chamber... I dont think .025 is fatal. I know of bigger bores that run less with steel rods and rpms under 6K. I don't like to run more than .035, but I've never run less than .030. The rpms depend, but abotu 6500 is max for what I do.

Update under the EDIT on my first post