1939 Desoto using lots of oil after rebuild

[desoto1939]

My friend that has a 39 Deoto found out that over this last winter he had two piston inwhich the upper two rings were broken.  He had the standad size pistons still inthe car.  Hed eventually got some from Haggie along wit the new piston rings to fit the pistons.

 

He told me they just honed the 6 cylinders and replaced the 6 piston with rings. He drove his car to the National desoto convention this past june and was pushing blue smoke out the tail pipe upon acceleration and deceleration. On his way home he told me that he used 3 qts of oil on the return trip.

 

This past weekend he did a compression test and basically here are the restults 80-90 on cylinders 1-5 and then on number 6 a reading of around 30.  Sounds as if either rings broke again or never seated correctly.

 

I do know that he was running 20-50 weight oil inthe car on the trip, also not sure if he had used any breake-in oil during the initialy running of car after the new rings and pistons.

 

He is going to pull the engine over the winter and take it down to a bare block. Sounds as if they did not measure the size of each cylinder but just did a hone on each one. He did say that there was no taper in each cylinder but to determine if there was any taper you would still have to micrometer each cylinder prior to ordering new pistons.

 

Rich Hartung

Desoto1939@aol.com

 

[greg g]

Seems to me he needs to have a long conversation with the shop that did his work.  Didn't they do a compression check before they took his money?  Did he do a break in procedure?  Sounds like they might have not staggard the rings during reassembly.

[desoto1939]

He told me that the rings were all staggered. He did do a breakin and drove the car on back roads before taking it home and then when he got home he noticed the blue smoke after shutting down the engine on the initial run home from the shop.  Not sure if he used any breakin oil during the initial startup of the engine. i am hoping that he did or should have used.

 

During our trip to Altoona we met up to travel in a caravan and he told me he was traveling at 60mph for the trip. I asked him why since you just had the lowere end rebuilt and you are getting blue smoke.  He still wanted to go at 60mph. He got on the road and drove at 60 while I drove my 39 desoto around 50 and at the next gas sop he arrive around 5-10 minutes before me.  When these cars were originally built the average road speed was psoted around 50 so Itold him we have plenty of time to get to our destintation so why push the engine and car?

 

So he might have done more damage to the engine than he thinks.

 

Rich Hartung 

[Sniper]

Break in oil isn't going to affect ring seating, synthetic oil may very well affect ring seating.

Edited September 5, 2022 by Sniper
typos

[kencombs]

Rings installed upside down can cause oil burning and low compression.  60mph shouldn't hurt it and may even help seat them.  Lots of acceleration/decel exercise will help too.  Breakin oil is not a big issue IMO.  It only serves as a reminder to do an early change.   I think an oil change, 30w dino and some more driving before giving up. 

 

Another thought, often engines with a broken top ring will develop a wear ridge at the second ring.  If not removed, that will cause havoc on the new ones.

[desoto1939]

he put on over 500 mile after the 6 pistons and all rings were installed. The 500 mile trip was back in June and he is still getting the oil issue. I also asked if they installed the correct rings in the correct order and he said yes.  I am still thinking that a ring might have broken in the 6th piston.

 

Also could the smoking because by the tighter pistons and then the oil is being drawn up to the value and the guides might be worn and allowing the oil to be consumed and then burned via the manifold.  They did adjust the valves and also lapped a couple of valves.

 

 

Not being a mechanic and have not worked on internals on an engine this is my time to learn more.

 

Rich Hartung

[Sniper]

Here's a generic list of what usually causes blue smoke out the tailpipe.

 

Piston wear (possible, but doubtful, unless the piston to bore clearance is too large)
Worn piston rings (possible, but doubtful, unless there is an installation issue or the bore issue mentioned above).
Worn valve seals (seals are not applicable, but this also could be a guide issue)
A malfunctioning PCV valve (unless he doesn't have one)
Worn engine oil seals (I guess this means a leak on the exhaust pipe)

Intake or exhaust manifold gasket leaks (not applicable for the flathead)
Head gasket failure (not applicable to the flathead)

 

How do the plugs look?  A shiny black deposit means oil burning.  That could help narrow which cylinder is the issue.  A black sooty looking deposit means it's running rich.

[DJ194950]

Maybe a compression leak down test would be the quick check for some issues and the tools are not way expensive to buy (borrow?).

 

DJ