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#1
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340 head gasket thickness
Anyone know what the standard head gasket thickness was on a early 68 340stock engine with X-heads? I think I might have screwed up by using thicker head gaskets after a valve job. I had some gaskets that were in a rebuild package and I believe they were steel fel-pro but I'm not sure. They seemed rather thick to me when I put them on but I didn't even consider compression when I used them.
Anyway I may be taking it apart again this winter. A compression test showed about only 125 to 130 lb in each cylinder. I would think it should be more than that. Im using a racer brown flat tappet cam with I believe 470 lift and 230 duration at .050. Also the heads were surfaced as well as the block to clean everything up. The old Motors Manual says compression should be 180lb for the stock 68 340. The pistons could also be the problem for lower compression as they were replaced with what was supposed to be stock flat top pistons with a bore of .040. The engine runs strong but seems slower since the rebuild. I have been wondering about those head gaskets. |
#2
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Never seen one stock that would pump that kind of pressure.
OEM on that car would have been the steel shim gasket. No longer available for several years. If you can find them use the P4120094 Mopar Pwerformance gasket that is .024-.028 compressed thickness. I don't feel that you are too far out of line withthe gaskets that you are using if you had the heads trued some will take up some of the thickness and are you sure that the engien has never been apart and updated pistons installed in it. IMO be a pretty rare bird to be a virgin. |
#3
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The difference in compression between the steel shim gasket and the typical 0.040" thick composite gasket is about 0.3:1. Definately not the difference between 130 psi and 180 psi cranking pressure.
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