Chrysler M45S Hemi

[Shady Lady]

I have a 1955 CC Continental with the Chrysler M45S hemi engine. I have suffered a recurring problem of oil running out the breather vent. I have been told that the cause is overfilling and that I should just run it a little low on the dipstick. I have done additoinal research and found that water in the oil can also cause frothing and possilbe overflow from the breather. The engine runs cool. Yesterday, while adjusting the valves I noticed a good deal of condensatoin under the valve covers. I am wondering if a faulty thermostat could casue the engine to run too cool resulting in water in the oil, frothing and overflow. If not, does anyone have any other ideas what may be causing my problem. This has been very frustrating. Any input would be appreciated.

[57 Sport]

This is from having to much air in the crankcase. This could be coming from the motor not being sealed up and having excessive blow by the rings or a leaking headgasket. It could also be simply not having enough crankcase ventilation where an extra breather or PVC valve is needed. Excessive oil level can also cause this if the crank is splashing the oil around to much.

I would confirm its not the rings or headgasket first. If you have it apart to run the valves and have access to a leakdown gauge I would do a cylinder leakdown test. If you dont have a leakdown gauge I would at the very least do a compression test and find out what the health of the motor is first. Also look at the spark plugs.

[Peter M Jardine]

Agree with Sport. You have an issue that is indicative of more than a minor problem

[Paul P]

I am not familiar with your particular motor but many have an exhaust crossover passage. If that casting gets a pinhole in it, it can pressurize your sump and give the impression of blowby even if the rings are in perfect shape.

The crossover is left over from automotive design from which the marine motors originated, and the evolution of the GM based Q series of small block marine motors eliminated this crossover. Virtually all of the Edelbrock aluminum intakes made for the Ford FE series, for example, have the crossover eliminated, and many have blocked it off with a piece of stainless steel shim stock because it really does not do much if anything for a marine motor. Yes it does allow for motors to warm up faster, but it also cooks the carb and adds a lot of unnecessary heat in the motor box. If you have the crossover I would certainly check it, and also if you don't then check the intake (and head) gaskets because they can potentially leak the same pressure into the sump, depending on the style of intake used.

Good luck,

Paul

[Shady Lady]

Thanks to you all. I will perform the leak down test and see what happens.

[Oberon01]

Hi Tim - I hope it doesn't turn out to be as major an issue as blow-by usually portends, but you'll figure it out soon enough. If it is blow by, at least you can keep using your boat through the season and repair it over the winter.

Hope to see you again this summer!


Paul