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1984 Bertram FBC; 350's. Due to operator error, starboard engine was intermittently overheating. Eventually full overheat with radiator cap release. Determined apparent cause to be mis-plumbed expansion tank. Corrected, replaced coolant, engine ran OK at dock. Subsequent sea trial showed white exhaust, coolant loss, and overheating. Preliminary Diagnosis: blown head due to over-heating.

To confirm, ran compression test. Cylinders 1 & 2 showed 130 PSI, #4 showed 110, all others at 120. 18 months ago ( and very few running hours ago) all cylinders were 130-140 PSI. injected 3-4 cc oil into cylinders 3 & 5, compression went to 135 & 142.

We know there is a leak, due to white exhaust and coolant loss. Low compression makes me wonder if overheating could have damaged cylinder walls and/or rings, resulting in low compression readings. Is this engine is worth saving, or should I buy new short block? If so, any recommended sources?

Thanks,

Steve

My shadetree/hot cockpit approach would be to double check everything, and then pull the heads off. SBCs are pretty indestructible. Could be a headgasket, or a cracked head, and your cylinders/pistons are OK. Take the heads to a machine shop and have them checked, although you'll see a bad head gasket and sometimes can see a cracked head-maybe all the time if you know what you're looking for. I've missed cracked heads until someone pointed the crack out.

If you decide on the replacement route, given that you think you have a problem with the heads, I'd go the long-block route rather than short-block.

My 2 cents from a non-mechanic.

Check the swap and sell page today…..

The other thing with a blown gasket, is that you may get water in the oil. Do you have any oil foaming?

I second John's thoughts, pull the head, check the gasket and then take it to a machine shop for a check. You will also be able to see if the cylander walls got scored. If you had bad rings, you would blow blue smoke due to oil burn not white smoke due to water.

Thank you for your thoughts - very helpful. Engine is stripped; heads come off today. For a 72 year old who has never been past an oil filter, this is exciting stuff.

Just wait till it is time to put it all back together! That should bring even more excitement. Hope it goes smoothly for you.

Pulling heads and putting it back together is the easy part. Get a good tourque wrench. You need it for the heads. Also make sure you have the specs for putting the heads back on. It is not just a turn a bolt in order. Their is a pattern to it.

You should be able to get the specifications either from the engine manual or online I am sure.