Compression

[bwestbrook]

Hey Rivets just wondering.....not questioning for sure. I want to know how a blown head gasket builds excess pressure. Just trying to learn from this but one would think that would cause less pressure. And since the mower won't run the leakdown test would be my only option right? Because normally I would spray carb cleaner around it while it is running.
Please don't take that has questioning you. I honestly don't know and want to.

 

[Rivets]

A blown head gasket will allow air to escape back into the through the valve cavity crankcase causing the buildup of crankcase pressure. You will also loose compression in the cylinder. The engine will still run but you will have some lose in power. I was a tech instructor for 34 years and understand that questions that seem obvious to me need to be explained. No offense taken.

 

[bwestbrook]

This engine does not run because there is so much compression it will not turn over fast enough to start.

 

[Rivets]

We understand that, but your original post talked about symptoms that would indicate a blown head gasket. You may be building pressure in the crankcase not allowing it to spin properly. If you look at a parts breakdown you will see that the head gasket seals between the cylinder and the push rod cavity.

 

[bwestbrook]

So is a leakdown test the only way to determine without the engine running? Or would I be able to tell by simply taking the head off?

 

[bwestbrook]

I put a head gasket on since no answer on the last post. It spun over a little better. But not enough to not hang up. So I guess it's time for a new cam.