Just replaced the head gasket in an 1982 D150 slant. Stock Felpro replacement from NAPA. I noticed a slight decrease in compression by 2 to 5 psi after the replacement...I assume this would be due to a slight increase in thickness in the new Felpro gasket as compared to the stock factory one.

Am I correct?

The head gasket swap was done to fix the leak from the sixth cylinder into the cooling system. Much nice to drive something that doesn't pump its cooling medium out on the side of the road.

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Slanted D150

yes that the reason for pressure drop....last I knew charlie s had stock steel shim head gaskets....maybe if you get on knees and beg pretty ,he might let you have one LOL

Probly not. It's more likely just the result of most compression gauges not being high-precision instruments, the battery having been drawn down a little from the previous compression test, and the oil having run down off the cylinders while you were busy swapping the head.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I figured it was on the edge of instrument accuracy but I recalled some discussion on head gasket thickness some time ago here.

I can only imagine how much easier life would be when removing the head with an aluminum head and intake manifold! That is one heavy chunk of iron...and I used a hoist...

Thanks for the reply's...

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Slanted D150

Stock head gasket for hydraulic-lifter engines is thick composite, not thin shim steel IIRC.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.