How do I check for a Blown head gasket

[Navigator]

I have an old '79 Johnson 6hp with low compression. 83 in one cylinder, 60 in the second.(but it always fires and runs for hours on the first pull) I was chatting with me dealer the other day and they mentioned it may be a blown head gasket. I haven't had time to take the heads off yet so I cant tell what the "internal" condition is or even if the cylinders are scored.<br /><br />Is there a quick way to check to see if it is a head gasket?<br /><br />Thanks,<br />Nav

 

[Walker]

Re: How do I check for a Blown head gasket

The only way I know of is to take the head off and visually inspect the head gasket. We're talking about lost compression here so there should be a spot wher the gasket is burned through at the edge of the cylinder. A gasket for that motor should be very expensive, so go ahead and replace it. I doubt that is your problem though. Most likely just age and wear is causing your compression. You mechanic should have a scope that he can see inside your cylinder through the sparkplug hole. He should be able to tell if there is any cylinder of piston damage.

 

[dmessy]

Re: How do I check for a Blown head gasket

Run the piston up past the ports then pump up the cylinder with pressure and a gauge. Note the time it takes to do a "leakdown". A blown head gasket goes down rather quickly.