Recommend How Much To Mill Heads
Recommend How Much To Mill Heads I picked up an SRD cam ground by Cam Motion, 228/232, .587/.570/ 112+2, has 6 degrees overlap. Mocked up with GM MLS gasket .051 thick, 853 heads (no notch), solid lifters and clay, I am getting PTV clearance of .110 to .120 intake, .150 exhaust and .055 piston to head clearance.
The piston to head is throwing me off. The pistons are out of the hole .010. I don't think this modeling clay is moving after it is compressed but I was expecting around .040 clearance.
I was thinking of going to a .040 thick head gasket and taking .010 to .020 off the head. What do the experts say....?
The piston to head is throwing me off. The pistons are out of the hole .010. I don't think this modeling clay is moving after it is compressed but I was expecting around .040 clearance.
I was thinking of going to a .040 thick head gasket and taking .010 to .020 off the head. What do the experts say....?
Last edited by ironmanLS1; Dec 9, 2017 at 11:20 AM.
Something is not right. Your piston must be square while measuring out of the hole dimensions. You need a deck bridge to do this correctly. Basically the piston will rock, 12 ocklock to 6 ocklock, in the bore at TDC, even with hyperuetectics. Forged pistons will rock much more due to PTW clearances. This rocking will give you a false number. You must make sure the piston is out of the hole equally at 12 and 6, to get an accurate number to determine quinch.
You also MUST ensure that you at top dead center to find this number. This is why a deck bridge is so important here.
Measure each cylinder to find your out of the hole numbers. If your block isn’t square decked, it will show up in your numbers. This will greatly affect your gasket thickness.
You also MUST ensure that you at top dead center to find this number. This is why a deck bridge is so important here.
Measure each cylinder to find your out of the hole numbers. If your block isn’t square decked, it will show up in your numbers. This will greatly affect your gasket thickness.
Found a set of depth mics I forgot I had. For piston height drivers side, I get .011-.012 front to back, passenger side, I get .009 to .013 front to back. I know it isn't using a bridge but I am confident in these measurements.
The gasket is a constant. It’s .051” compressed. You have to use your GREATEST out of the hole number, which is .013” subtract the two and you get .038” clearance. .035” is pretty much it for safe quinch, and .038” sounds better. Your good. Milling the heads won’t affect the quinch numbers, only the chamber size, which affects compression. What are you shouting for with compression?
Your PTV numbers are good as well.
Your PTV numbers are good as well.
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Looking over some of these numbers a little more, I think I am pretty much stuck with the GM MLS head gasket at .051" thick. If I mill .020" off the heads it should put my compression roughly at 10.87:1 which still gives me a little wiggle room on the PTV.
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