compression results and spark plugs

[tcslr]

With some overheating issues, I performed a compression test to determine IF I had head gasket issues.  The engine is a 249ci Chrysler flat head.  The compression results 1 to 6 are: 55,60,50,60,60,60.  I repeated three and got the confirmed the results.

The plugs look such: (1 to 6 again) little darker than 'normal', little darker than 'normal', wettish foul, wettish foul, little darker than normal, normal.

 

Other facts to consider: recently rebuilt carburetor - seems to operate fine. ( Updraft carburetor and engine starts fine and quickly). rebuilt water pump. flushed and checked radiator ( at shop that understands 'old' style systems).  Checked intake gasket ( with propane) and no leakage.

 

Would folks give me your interpretations of this info? should I consider head gasket replacement?  What about chemical clean of engine ( I am frankly wondering if that is a 'reasonable' and 'easy' fix - and lazy vs complete engine rebuild). If so, thoughts?

[Larry Schramm]

I had the same thing on my truck.  I drained out all of the water, put in 4 gallons of regular household bleach and drove it about 6 hot/cold cycles on a hot Saturday.  Drained all of the remaining bleach out of the engine and flushed real well with water for at least a 1/2 hour and filled it back up.  Never had an overheating problem since.

[hchris]

You don't say what year your engine is, post 1935/6 most of the Mopar engines introduced a distribution cooling tube behind the water pump which were designed to enhance coolant flow around the valve seats, they are notorious for corroding out with resultant lack of cooling in this area of the block

 

Compressions look reasonable (I`m assuming this is an older engine), if you had a leak between cylinders I would expect a larger variation in compression figures.

 

At what stage are you assessing the plugs - idling in the driveway ? after a lengthy run ?

 

Describe "wettish / foul" - are you talking oily wet or coolant wet ? 

 

Can you determine the flow volume with the radiator cap off ?

 

Is the ignition timing correct ?

[Spinneyhill]

What was done to clean out the radiator?

 

Based on OP's signature, it is a 1929 Chrysler 75.

Edited August 17, 2017 by Spinneyhill (see edit history)

[Rusty_OToole]

29 Chry 75 comp ratio 5.2:1 which suggests compression pressure should be about 75 psi. So compression is not great but not bad and it is reasonably even. Spark timing too far advanced could cause overheating. Another thing, low compression engines run best on low octane fuel. Some owners of similar cars have reported more power, smoother and cooler running by adding up to 25% kerosene to the fuel.

 

Depending how bad the problem is, I think I would try some engine flush or CLR cleaner,  10% kerosene and a long drive of at least 50 miles then drain flush and refill the cooling system.