Verified Low Compression Problem

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MitchB

Post subject: Verified Low Compression Problem

PostPosted: Sat Oct 26, 2002 10:16 pm

A while ago, I posted that #5 had low compression and the lash on the #5 exhaust had tightened up by 0.006. I pulled the head and removed the #5 Exh valve. The entire valve and seat was pitted. In one spot, combustion was leaking past the seat as evidenced by a small white plume or jet visible on the seat and into the pocket. The same was visible on the back side of the valve. I am going to have the head rebuilt with exhaust seat inserts. I was surprised to find a steel head gasket installed OEM. Has anyone else seen this? So if the engine was built with an 0.020 steel gasket and the compression is supposed to be 8.4:1, what is my chamber volume? Can't be 54cc. I was also surprised to see the hone marks still visible on the cylinder walls with close to 120K on this engine. Oh yeah, does anyone know if replacement valves are available?

Thanks

Mitch

m5black@aol.com

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Dart270

Post subject: Re: Verified Low Compression Problem

PostPosted: Mon Oct 28, 2002 10:10 am

Quote:

: A while ago, I posted that #5 had low
: compression and the lash on the #5 exhaust
: had tightened up by 0.006. I pulled the head
: and removed the #5 Exh valve. The entire
: valve and seat was pitted. In one spot,
: combustion was leaking past the seat as
: evidenced by a small white plume or jet
: visible on the seat and into the pocket. The
: same was visible on the back side of the
: valve. I am going to have the head rebuilt
: with exhaust seat inserts. I was surprised
: to find a steel head gasket installed OEM.
: Has anyone else seen this? So if the engine
: was built with an 0.020 steel gasket and the
: compression is supposed to be 8.4:1, what is
: my chamber volume? Can't be 54cc. I was also
: surprised to see the hone marks still
: visible on the cylinder walls with close to
: 120K on this engine. Oh yeah, does anyone
: know if replacement valves are available?
:
: Thanks
:
: Mitch

Glad you found your problem, although it's a little spendy...

As far as I know, all factory Slants had steel head gaskets. All I've seen apart anyway (which are all pre-80). You can get new valves, just ask at your machine shop, or parts store. Your chamber volume should be around 54 cc, but could be +/- 5 cc or so factory, or less if it's been milled.

Cheers,

Lou