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Workshop => Engine and Bottom End => Topic started by: atvmxr on June 11, 2020, 10:52:15 AM

Title: compression for stock motor, jug, head, etc + CR head gasket?
Post by: atvmxr on June 11, 2020, 10:52:15 AM

Just rebuild a motor, .060 over, cr head gasket.  gauge is only showing 155 psi.  It should be more like 190, right? full throttle, about 10-15 kicks.

Pretty sure the gauge is bad. another R motor only had 120 psi.  My sons 70 had 0psi, which started this whole train of me testing motors.  I guess either way that 70 needs a topend!


Maybe its because all the motors were cold, warmed up adds 20-30 psi?

Title: Re: compression for stock motor, jug, head, etc + CR head gasket?
Post by: broken1 on June 11, 2020, 11:41:48 AM

I got 2 86's, one with a long rod crank & virgin 88 cylinder at 66.75 & the other with a short rod crank & 86 cylinder also at 66.75 with clean up porting. Both have ATC head gaskets & they both have just over 200psi. Sounds like it could be your gauge. With that CR shim gasket it should be up around 220psi & you will have to run race gas.

Title: Re: compression for stock motor, jug, head, etc + CR head gasket?
Post by: 2ndmoto on June 12, 2020, 12:10:00 AM

You seat the rings by doing a few heat cycles?