Topic: Head Gasket


robmorais    -- 03-10-2023 @ 1:25 PM
  I am looking a purchasing a 41 Sedan that the current owner says has a head gasket exhaust leak. How difficult is it to replace the head gasket? I am pretty comfortable working on cars but never owned a flathead V8. Many thanks!


alanwoodieman    -- 03-10-2023 @ 3:48 PM
  is the engine overheating? take of radiator cap and fill to brim with water, see if bubbles come up, this usually indicates a bad head gasket if it is popping out of the exhaust then I doubt it is a headgasket, could be a burnt valve


robmorais    -- 03-11-2023 @ 4:49 AM
  The current owner said that it was low on compression and he thought that was because the head gasket was leaking exhaust. I am going to see the car Monday. What should i look for?


gwistrup    -- 03-11-2023 @ 5:47 AM
  I would agree with alanwoodieman that a head gasket probably won't give low compression without some sort of coolant loss and an exhaust valve may be the problem. If you have access to compressed air, you can prove exactly where the loss of compression is coming from. Your best bet would be to purchase a leak down tester and leak down the cylinder in question to determine how much leakage the cylinder has and where the leakage is coming from. A leak down tester works by putting compressed air into the cylinder and measuring how much leaks out. If there is excess leakage (more that 20% would be excessive for a cold engine), you can listen for the air coming out at the exhaust pipe if an exhaust valve is bad. Air will come out the carb if and intake valve is leaking. Air will come out the oil filler cap if the rings are excessively worn. Air bubbles will be visible in the radiator if the head gasket is leaking. You must put the cylinder on the compression stroke when both valves are closed before you hook up the tester. Good luck. Gil


TomO    -- 03-11-2023 @ 9:53 AM
  The above tests can give you an indication of where to look for the problem, but you won't know for sure until you disassemble the engine.

I would base my offer on the premise that the engine is going to need a complete rebuild. Then, if all it needs is a head gasket, you lucked out. If it needs a rebuild you are still on the right side of the deal and if it needs a block, you will still not have so much in the car that you can't fix it.

Tom


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