Malcolm Jeffcock wrote:
>This spring I replaced my head and head gasket. The head was cracked and the
>gasket was blown between 1&2 (about an inch and a half gap) and also from #4
>cylinder to one of the oil pathways. Anyway I had a head rebuilt and planed
>and also checked the block top with a steel carpenter's sure it was true.
>Anyway I think I have blown the gasket again. Odd sounds, hard to start and
>when I checked compression bad news. Now when I got the engine I had been told
>that it had a "hot" cam and that it was high compression. When I put in the
>gasket I didn't check compression but today the readings are 1-4: 40 psi; 30
>psi; 190psi ; 50 psi.
>
>Now here's my question: when I look in my Bentley manual the Engine Data part
>says for compression: H.C:160psi and L.C. 130 psi
>In the "Competition Equipment" listings it lists competition type cylinder
>head gasket, part #C-AEH 768.
>
>So my question is since I used a "standard" head gasket could I have too much
>compression for a standard gasket and that is leading to the apparent failure
>of the gasket? I'll take off the head either Friday night or Saturday and see
>if it has failed (as suspected) in the same places as the last one.
>
>Before the failure the car went like stink and pulled hard.
>
> Malcolm
>
>
>
>
13:1 compression in #3. I assume the other 3 were similar in the past.
Where did you get fuel for such a beast? Bentley defines high
compression as around 11:1. Do you know how much they took off when
they decked the head? I'd put 2 head gaskets at a minimum if I owned
this engine.
And before you all go off- if you take the pressure indicated on the
compression tester and divide it by 14.7 which is atmospheric pressure
you have actual compression ratio. If you take volume at bdc and divide
it by volume at tdc you get a theoretical compression ratio which
doesn't take into account leakage around rings and valves (or through a
blown head gasket). I'd expect the theoretical compression ration would
be higher than 13:1. It all goes back to PV=nRT.
Bill
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