Anyone running an SBC with H618P/H618CP pistons? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 06-30-2008, 05:50 PM
v8hed's Avatar
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Anyone running an SBC with H618P/H618CP pistons?

This is what I have... H618P pistons 0.025" down the hole. I'm looking for feedback from folks with this same set-up and aftermarket heads. What heads are you running and did you have any problems with dome clearance?

Thanks,
Ian.

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Old 06-30-2008, 06:55 PM
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Ian, you seem extremely reluctant to do this checking yourself for some reason. Go ahead and get the 20 degree heads and check them yourself. At the worst, you may have to use an Isky tool to re-cut the valve reliefs a little in the pistons. No big deal.

No matter what answers you get from others, if you don't check YOUR stuff YOURSELF, you won't have a definitive answer. There are simply too many variables between motors to say whether one guy or another had or didn't have clearance problems. Possible differences are as follows...
Block deck height difference
Rod center to center difference
Piston compression height difference
Block deck to valve seat dimension difference
Rocker arm ratio difference
Camshaft timing events difference

Here's a tutorial from Isky to help you check the clearance properly. Hope this helps.
http://www.iskycams.com/camshaft.php

You can rent the piston notching tool for US$40.
http://www.iskycams.com/onlinecatalog.html
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Old 07-01-2008, 05:03 AM
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Quote:
Originally Posted by techinspector1
Ian, you seem extremely reluctant to do this checking yourself for some reason. Go ahead and get the 20 degree heads and check them yourself. At the worst, you may have to use an Isky tool to re-cut the valve reliefs a little in the pistons. No big deal.

No matter what answers you get from others, if you don't check YOUR stuff YOURSELF, you won't have a definitive answer. There are simply too many variables between motors to say whether one guy or another had or didn't have clearance problems. Possible differences are as follows...
Block deck height difference
Rod center to center difference
Piston compression height difference
Block deck to valve seat dimension difference
Rocker arm ratio difference
Camshaft timing events difference

Here's a tutorial from Isky to help you check the clearance properly. Hope this helps.
http://www.iskycams.com/camshaft.php

You can rent the piston notching tool for US$40.
http://www.iskycams.com/onlinecatalog.html

Yea, I was just trying to avoid the possibility of purchasing heads that I can't use. But, you're right, there are probably too many variables. I'm getting the heads for a good price (used), so I could probably flip them for what I paid if I can't use them.

I'll clay-up a piston and see what's what when I've got the heads.
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Old 07-01-2008, 10:29 AM
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The issue is not going to be piston to valve clearance (with any type of a street cam and conventional 23deg heads). Its going to be the edge of the piston dome hitting the edge of the combustion chamber.
The piston domes were made to fit the old GM stock heads.
Any of the modern heart shaped heads may touch the piston dome at TDC.
Minor clearance grinding on the combustion chamber edge may be required. Its up to you to check.
Any clearance grinding required won't be a big deal.
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