331 Marine Hemi

Discussion of the Marine / Industrial Hemis.

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S&S
Posts: 4
Joined: Thu Mar 10, 2011 2:39 pm

331 Marine Hemi

Postby S&S » Mon Mar 14, 2011 2:22 pm

Does anyone know what the compression pressure is for these engines?
Thanks!

mart
Posts: 536
Joined: Tue Mar 22, 2005 2:06 pm

Re: 331 Marine Hemi

Postby mart » Tue Mar 15, 2011 4:17 am

The factory specs show 8.2 to 1. That's nominal though and assuming the deck
height, gasket thickness and cylinder
head CC's are right on spec. With
normal production tolerances, the
actual compression ratio is likely
anywhere from a half to a full point
lower.

mart
=================================

S&S
Posts: 4
Joined: Thu Mar 10, 2011 2:39 pm

Re: 331 Marine Hemi

Postby S&S » Tue Mar 15, 2011 8:59 am

Thanks mart, but I'm looking for the test gauge pressure range (want to see if I need to do rings or not)

BlueDjinn
Posts: 44
Joined: Fri Aug 28, 2009 2:27 pm

Re: 331 Marine Hemi

Postby BlueDjinn » Wed Mar 16, 2011 12:07 pm

Compression pressure of 331 with 7.5:1 ratio is 135 psi minimum.
Compression pressure of 331 with 8.5:1 ratio is 140 psi minimum.

Whenever I do a cylinder pressure test on any engine I just check each cylinder while looking for a certain consistency
between readings. After I have my readings I look up the spec to see how they compare. A serious discrepancy denotes a problem and it isn't always just rings. I've had readings significantly higher than spec which turned out to be a valve problem; not opening.
I've also had pressure readings so low as to not support the combustion event. Once again a valve; not seating properly; bent or burnt.
Of course it could also be nothing at all to do with rings or valves.
Anyway, 135-140 psi as reference will expose the offending cylinder(s).

Beltran
Posts: 15
Joined: Thu Nov 11, 2010 5:45 pm
Location: Clarkston, MI USA

Re: 331 Marine Hemi

Postby Beltran » Thu Mar 17, 2011 6:01 pm

The copper gaskets they used to use are notorious for leaking coolant / water. I just tore apart two engines that were both leaking between the cylinder walls.

S&S
Posts: 4
Joined: Thu Mar 10, 2011 2:39 pm

Re: 331 Marine Hemi

Postby S&S » Mon Mar 21, 2011 2:42 pm

Thanks!


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