OIL control ring issue here (218 P23)

[choppa]

Hi all.. new to the forum.

 

I got a problem.... hoping for some insight as where to look as a rebuilder in my area looking at 3K plus to rebuild top to bottom!

 

OK...I bought used,(so I was told)  running P23 engine that had been in storage, outside, under a caprport and canvas tarp...for about 3 years total.

 

Its a Plymouth flathead P23 engine (218 ci) of about 52 vintage (I believe)

I bought this for my project, but now looking at some readings, I think this is a little worn. You guys with much more experience can tell me your thoughts please.

 

HISTORY:
when I got it, I cleaned it up, installed a new oil pan gasket, pick up screen and general "de-gunking of the motor.

Inspection of the cylinder walls from the underside looking upward revealed good clean cylinders walls with no scoring.. cam lobs lokked good, crank seemd fine, tight and no blueing of the caps indicating high temps...all seemed tight, so the decision to forge ahead and installing it in truck went on.
 

FIRST START: Once started, I found it smoked, white smoke, so we did a compression check (DRY) and found these numbers, indicating a head gasket failure between #3 and #4. and a bad valve in #1

I didnt get to run it long.. no radiator hooked up at the time and didnt really get up to operating temperature either as the WHITE smoke was so bad so we shut it down.

 

I got compressions readings (dry):

 

#1 75+/- lbs
#2 90+/- lbs
#3 35+/- lbs
#4 38+/- lbs
#5 90+/- lbs
#6 90+/- lbs

 

took off the head, and found the #1 exhaust valve pitted (probably why the 75 lb reading) and a head gasket failure between #3 and #4 as expected

Did a complete in frame valve job using new stainless steel valves and NOS valve springs. DID NOT replace the guides..
we cut the seats and lapped the valves in their seats

buttoned it up and started up. oil pressure (cold) was in the same area, like 35lbs or so.

 

Once warm, still about 12-15 lbs

compression reading NOW 90+ across the board. valve job helped.

 

BUT, now that I could run it longer, and installed the radiator, I seen the oil pressure hover at or about 10-12 LBS at a very slow idle once completely warmed up..

getting blue smoke, only intermitently.. white smoke gone.

 

however, the more it ran, the better it was sounding...in fact the oil "puffs' were getting less and less as it ran, so am thinking that this engine sitting 3 years, perhaps some of the oil control rings or even the compression rings were stuck, and still are, to a degree.

 

After a few oil changes, a few cans of marvel mystery oil, etc, I got a cold start the next day compression reading as follows:

 

#1 100+/- lbs
#2 105+/- lbs
#3 110+/- lbs
#4 105+/- lbs
#5 100+/- lbs
#6 110+/- lbs

 

Now that its been running more, its sounding better and better.. I replaced the plugs to remove any oil fouled units to get a uniform firing on all cylinders.

the motor runs great. NO smoke during normal idle.. no smoke during acceleration,

BUT as soon as I let off the gas, I get blue smoke.

 

what would that indicate? worn oil control rings? Valve guides? I was under the impression that flat heads, having guides in the block, and under the combustion port made little difference in oil control.

 

Maybe I am wrong.. maybe this is part of the problem? I didnt address the guides when I did the valve replacement last week.. dont have those tools. besides, I think they get pressed in from the underside?

 

anyway, I am getting better than 100+ lbs across the cylinders on compression now that its been running awhile... engine sounds good and smooth actually.. its just that blue smoke when letting off the gas.

 

I really dont think its getting better now, either...its a pretty good plume when I let of the gas...ugh

So, where to look next?

the valve guides?  or the pistons/rings?  its getting great compression numbers now, so I am leaning toward the oil control rings being the culprit.

 

What do you all think the area of concern is?

guides? oil control rings causing oil smoke at deceleration?  or other?

[Don Coatney]

When you decelerate intake manifold vacuum increases and it sounds like it may be sucking oil past the valve guides. Were it me (with the good oil pressure and good compression) I would drive it a few thousand miles and see if the problem continues. If and when the problem becomes unbearable then spend the money on a rebuild.

[Young Ed]

When you decelerate intake manifold vacuum increases and it sounds like it may be sucking oil past the valve guides. Were it me (with the good oil pressure and good compression) I would drive it a few thousand miles and see if the problem continues. If and when the problem becomes unbearable then spend the money on a rebuild.

 

I'd drive it some and see if it improved and then do the guides. Unless you really want it 100% fresh-otherwise you should be able to get a lot of miles out  of it with those #s. And yes a p23 is a 51-52 plymouth 218.

[Sharps40]

Agreed.  With the compression readings, its going to run well for lots of miles.  Might dirty the plugs once in a while but who cares, plugs can be cleaned and burning a bit of oil is no real worry.....its 70 odd years old. 

 

Go ride!