Actually, I did a compression test a few months ago - this is what I recorded:



Logically, A+B must equal C, but how could I get those kind of readings if the cylinders or rings were bad - wouldn't that show up as low compression? But yet, the results of the leakdown test were not good.

I tell ya, this is driving me batty!

 

I think "good" compression is better than 135-140 psi.

 

Nothing to do with the road draft tube that was being discussed?

I will let that statement speak for itself.

Norm

 

Classic definition of worn oil rings.

An engine rebuild, by a competent machine shop, might be a good choice.

Norm

 

While it's still on the choke?

Idle mixture/speed adjustments and/or vacuum leak.

Norm

 

How is it accomplished?

No. As I said, it's function relies, solely, on the placement of the tube.

No different than they used in the '30s, and earlier.

Norm

 

I have not seen anything to indicate a problem with the heads.

Norm

 

Yes.

Referred to, in post number3, for anyone who might have missed it.

Was the battery fully charged? Engine at normal operating temp? All plugs removed? And the throttle valves (plates) fully open?

103 is more than 80% of 115, and 103 is above the 100 PSI minimums, as shown in the '54 Service Manual.

If all of the above conditions were not met, these numbers would have been higher.

It does, if the right values are used. In this case, the needed values are in the basics.

They show the total pressure that is built up, during that compression stroke, in that cylinder, at that time. Leaking valves, rings, gaskets, etc, can contribute to a "less than ideal" combustion environment. Unless one can identify, and evaluate. each of the variables, the test can only show the "relative" condition of the entire cylinder.

One thing to think about, is the difference in maximum pressures, during compression vs power strokes. Most blowby occurs during the power stroke. Very little during compression.

Leakdown and compression tests are the same, only different.

They both show cylinder leakage, but the leakdown can tell the source.

Happens when one doesn't stay focused on the basics.

Norm

 

For a "high compression" '54 Olds, as it left the factory, that would be a good guess.

Norm

 

Battery was fully charged and I let the engine run until it was nice and warmed up. The throttle plate was all the way open - the only thing I did not do is take all the spark plugs out before I did the test. Would that have made much of a difference in the readings?

 

I'm leaning towards rings as well. Does the motor have to be taken out for a ring job?

 

No.

Back in the day, it was common to "recondition" an engine, without removing it.

Whether it would be practical, in your case, would depend on its condition and your budget.

Norm

 

I plan on finishing my leakdown tests and do another compression check this weekend - I'll let you know if I find anything new then.

 

If you are able to plug the two holes in the crankcase:

Apply air pressure to each cylinder, while listening at the carb inlet and the exhaust outlet, for the sound of escaping air.

Norm

 

Found this post, while looking for, the above, vacuum hose information.

It's identical to the one on my '63 Plymouth and the one on my Dads '66 Dodge.

Yes, and they looked nothing like the one pictured.

Norm

 

Your engine may or may not need a rebuild, but definitely get the stock crankcase breather vent operating normally before you proceed. My '54 Olds started burning oil prematurely, and it turned out to be simply a clogged breather filter. Don't rely on someone's attempted retrofit of a PCV valve to operate correctly, and mislead you. Also be aware that , if your engine has a fuel pump with a booster vacuum pump on top , a broken diaphram in the vacuum pump section can result in crankcase oil getting into the intake manifold, and in some designs even into the gasoline, giving the appearance of your engine burning oil for other reasons. Check out any lines into or out of the vacuum pump for evidence of oil.