Help rear main leak

[bigdaddyslotrat]

Hi guys i have a question !! THIS IS A NEWLY BUILT MOTOR my oil leaks out the back of the motor is as follows, running at idle steady stream out the hole in the bell housing slightly higher rpms the leak seems to stop until you turn of the motor then a stream starts up again for about 4 table spoons of oil. ok this motor has about 1 hours running time and i did not build it! but was told by the builder himself that he changed the gears in the oil pump and it should make around 100 psi ?? will that much pressure make the oil leak out the back?? thank you all very much

[30 Closed Cab PU]

Stock oil pump is very low pressure around 2-3 PSI max, high volume.


The usual reason for an A to have a pressurized oil system is if you are running an oil filter kit system. Even then 100/lbs. seems high to me, am uneducated what an A pressurized system normally runs. Seems you may be running a modified Motor?


If no one here knows, then perhaps ask on the HAMB forum, or perhaps ask on the Barn Hot Rods and Custom forum.

[midgetracer]

The stock oil pump will put out at least 40 psi. The reason you only see 2-3 psi is because there is no back pressure. The pump pumps oil to the valve chamber and it drains back to the dipper pan or runs down to the main bearings and the timing components.

[30 Closed Cab PU]

Originally Posted by midgetracer

The stock oil pump will put out at least 40 psi. The reason you only see 2-3 psi is because there is no back pressure. The pump pumps oil to the valve chamber and it drains back to the dipper pan or runs down to the main bearings and the timing components.

Thanks for correcting me, learned something new.

[bigdaddyslotrat]

please forgive i forgot to say the motor is a 1932,33,34 "B" diamond block.


has high comp. head and pistons with a isky cam. and an oil leak out the back.
my next question is will an oil filter system lower the pressure in the motor and relieve the pressure after turning off the motor???

[Ernie Vitucci]

Sponsored Links (Register now to hide all advertisements)

Good afternoon...I would contact the engine builder and let them know what is happening. If you can drive the car over to them, do so and let them see what is happening. If you can't drive to them, can they come to you? A fresh engine should not be opened except by the folks who built it, or they might well claim that the problem is not theirs. Ernie in Arizona

[PC/SR]

Do you have babbitt or inserts, and pressure oil system? The oil pump will not cause a rear main leak no matter what the pressure unless some modification has been made.

[Dave in MN]

IMO: A couple things could be causing your leak:
1) The rear main clearances are excessive
2) The rear main seal may not be installed with the proper sealant
3) The cap may not be set or machined correctly
a) The cap or mating surface my not be flat
b) The oil passage in the rear main cap may be restricted
c) If the engine has inserts, the thrust washers may have excessive gap between
them
The clue to your problem is the leak after shut down. The oil from the valve chamber is running down to and through the rear main faster than the drain system can remove it. This typically indicates a component in the rear main that has excessive clearance.
Good Day!

[johnneilson]

Had a customer with a new motor and the rear leak problem.
It turned out to be the flywheel housing was not flat over the cam opening.
Yes, this was a pressurized motor so it is exaggerated but none the less a new housing corrected the issue.
J

[figment]

Make sure the gasket between the flywheel housing and the engine block is installed correctly . If it is installed backwards it will leak oil out the camshaft and it will run down the rear main area . I'm not sure if the Model B engines are the same .

[bigdaddyslotrat]

Pc/sr
what do you mean by modification ??
This pump has been modified and all i know is he put different gears and told me it should have 100 lbs.




Well now it looks like i will have some more work ahead of me now.


Thanks for all the information guy
i'll keep you posted

[PC/SR]

What I meant by modification was inserts, pressure oil, modern rear seal, that sort of thing. A stock rear main properly installed will not leak more than a few drops. Other posts point out what defects to look for.

I cannot imagine an A oil pump, even modified, being able to pump 100 psi, and if it did you do not want it to. Would be curious teo know what gears were installed.

[James Rogers]

Originally Posted by bigdaddyslotrat

please forgive i forgot to say the motor is a 1932,33,34 "B" diamond block.


has high comp. head and pistons with a isky cam. and an oil leak out the back.
my next question is will an oil filter system lower the pressure in the motor and relieve the pressure after turning off the motor???

Sounds like the builder didn't know how to rebuild the B engine. The pump in an A or B has the capability of as much as 100 PSI but without any restriction in the system, it won't push but about 2/3 # in an A and 5/7# in a B with the stock system. There is a marked difference in the A bearing design and the B bearing and one won't work in the other application without leaking. I can be available for consult if you want to know more. Just go to my website for the phone #.

[bigdaddyslotrat]

well sorry i haven't been on for a while but guess what?????

i went ahead and made a new valve cover for the motor and in it i drilled and tapped 3 holes 3/8 national pipe threads.


then i routed the oil from the tapped hole and back to the oil pan through the fuel pump block off plate.


today ran the motor for about 1 hour and not one drip out of the rear main.
so i ordered an remote oil filter adapter kit and will install it Wednesday.
so my conclusion is that the pump just put out to much pressure . i hope this won't make the pressure rise to muck after.
i want to thanks everybody with all the ideas to help and they were good ones too !!!

[Railcarmover]

That makes no sense but if it fixed it woohoo

[alexiskai]

Looks like this issue has been resolved, but for anyone coming here in the future I just wanted to post this link I came across recently to a web page that has troubleshooting tips for rear main leaks on Model A and B engines.

https://www.antiqueenginerebuilding....RMAINLEAK.html

[johnneilson]

So to be clear, you put a bypass line from the oil galley to the pan with no restrictor?

Are you making any oil pressure to feed the bearings?

Typically the oil is picked up from the block pump retention hole, passed thru a filter and then back into the oil galley thru side cover.

Better make sure you have pressure to bearings, better sooner than too late.

John

[Terry Burtz, Calif]

I had a pilot friend that owned a Funk airplane.

The Funk used a Model B engine that was dry sump and inverted (cylinders down).

He changed the valve chamber gasket and went for a test flight.

Upon take-off, the oil pressure gauge was pegged (lots of pressure).

Just as he cleared the end of the runway, the engine started to clatter.

Luckily, he throttled back, circled and landed without incident.

Turns out that he forgot to poke a hole in the valve cover gasket that would feed oil into the galley that provides oil to the mains and camshaft.

[Conaway2]

If the flywheel housing gasket between the housing and block is installed backwards, oil will leak badly from the end of the camshaft exactly as you describe. You can easily check this by looking at the starter side of the engine where the housing meets the block and see of you see a round portion of gasket sticking out....it you do see it, the gasket is in backwards.

[Dave in MN]

I am not sure tapping three holes directly into the oil galley and externally drawing off oil flow will leave enough flow to the bearings, cam and timing gear area. I guess time will tell. Hope it works.

The attached photo shows an alternate way to decrease the oil pressure to the rear main bearing. The installed pop off valve will keep some flow to the bearings and the modification is hidden from sight. If the small size of the pop off will not handle the flow of the pump, an additional one can be installed on the other side of the oil galley. If you are wondering about the carb jet you see: I have restricted the oil flow to the cam bearings in the photo by installing a carburetor jet. The opening over the cam gear is also restricted. When this photo was taken, I was developing about 45# of operating oil pressure in the system.


Good Day!

[Benson]

Dave,

That must be a drilled crank to feed rods?

What is the ID diameter of the popoff valve?

Originally Posted by Dave in MN

The attached photo shows an alternate way to decrease the oil pressure to the rear main bearing. The installed pop off valve will keep some flow to the bearings and the modification is hidden from sight. If you are wondering about the carb jet you see: I have restricted the oil flow to the cam bearings in the photo by installing a carburetor jet... I am developing about 45# of operating oil pressure in the system.

I am not sure tapping three holes directly into the oil galley and drawing off oil flow will provide enough flow without being detrimental to your engine's bearings. Time will tell. Hope it works.
Good Day!

[Dave in MN]

Originally Posted by Benson

Dave,

That must be a drilled crank to feed rods?

What is the ID diameter of the popoff valve?

Yes, I use this system for drilled cranks that provide oil to the rods. When first assembled, I started out at 45 psi and then backed down when I added the second pop off.

I will need to measure the ID to answer your question.

Is it enough oil relief? Not enough to provide full relief of the high volume pump installed. I have another pop-off installed at the pump (see below) as the one included with the pump seems to open at about 60 psi and that is too much pressure IMO and for my purposes.
The small one I show in the earlier comment is set to open at 35. The one I have at the pump is set for about 37#. I found at higher rpm, the flow was greater than the single pop-off at the pump would flow. With the higher flow pump, I am able to maintain about 15 - 18 psi at normal warm idle and about 35# warm at about 2500 rpm.
When cold at start, the pressure is 38# and both pop offs are working to relieve pressure. With the single one on the pump, the pressure was spiking above 60 psi when cold. With the second smaller one added, it will not exceed 40 psi when cold unless you really rev the engine.
Through all this adjustment, there were no leaks at the rear main seal but likely because I have a SBC rear seal adaptation installed. The SBC seal holder is manufactured by Dan McEachern who resides in California.
The dippers you see on the rods are plugged with a set screw. I left the dippers on the rods as this engine is still in the testing phase and doing so allows me to re-use the rods for a dipper build by removing the plugs should I abandon the project.
Good Day!

[Benson]

Dave,

Looks like Stipe oil pump and Stipe oil filter?

Have you ever installed the Stipe filter on a stock B with stock oil pump?

I suspect that the 3/16ths hole in front of oil galley which normally keeps dipper tray full with splash rods will have to be reduced some.

Rods should be OK as long as oil filter returns the oil to the front of the dipper tray?

Your setup looks like the B block build that we did in 1976.

We followed Dan Iandola's 1970 article in Hot Rod magazine.

Drilled crank and all standard sized crank was already cross drilled.

We increased the size of main and camshaft oil feed holes and replaced the "rolled steel oil feed pipes" to the main bearing saddles with larger push rod tubes.

Oil pump was stock A which we modified with the two "Half moon" pieces of brass brazed to top of pump to force all of the oil downward. Then drilled a hole in block so oil could be piped out of block and back into galley. Normal oil input hole in galley was plugged and of course the extra hole in the gasket!

3/16ths hole in front of galley was plugged and 0.060. Hole drilled.

Oil pressure was around 100 with cold engine and the valve chamber cover, the cast iron one was lifted and oil flooded chamber. Drilled and tapped extra 10 32 screws to hold down chamber cover

Partial solution was to drill hole in oil pump and weld on a V8 oil pump relief cut from V8 pump.

Still too much oil pressure when hot.

Then things went down hill from there!!

Oil leaks out rear main etc etc etc

Then water in the oil pan ... Cracks in roof of valve chamber, cracks from bore to valve seats. Etc etc. Stitched cracks.

Engine guy swore on a stack of Bibles that he magnefuxed the block like Ipaid $ 125 For.

In 1976 a stock B engine rebuild was about $600. When this mess got to $1800 and still no light the end of tunnel ...

The only light in the tunnel was on the front of the freight train coming from the other direction.

Finally I pulled the plug and built another totally stock B block which was standard everything. Came out 0.010, 0.010 and 0.040.

It has 40,000 and still no problems.

[johnneilson]

Benson,


Welcome to Old Motors, and yes we still smile when we get one to stay together.
Jim Brierley has a pretty good book or two out on "A" and "B" motors complete with instructions on how to set up the oiling systems.


My block prep is a little bit different, I do drill the main feed holes from the galley to the tubes, but I restrict the cam feeds and 3/8" hole to the drive to 0.025.
I block the front galley hole over the timing gear and use no gasket on cover, but my cover is 3/4" thick, no additional holes drilled and tapped into block. I do add a 1/8" drain hole to the back of the rear side of the rear cam bearing to relieve the oil buildup. I typically run external oil pump, have run as much as 95 psi by accident and not had the rear main leak.


Glad to hear you are having success, and remember this. There are a lot of blocks that get magnafluxed, the key is to find one that passes the test........
I suspect yours did pass but was prone to cracking due to core shift and/or corrosion.


Best of luck, J

[Benson]

J,

Thanks I checked my notes from 1976.

rear main and front main were drilled 1/4 inch in galley.

Did enlarge tubes to bearing saddles. Local idea was that split tubes might leak.

Center main since feeding 2 rods 5/16ths

cam bearings plugged and number #60 drill bit.

Front galley plugged and #60 drill bit.

I suppose that I could have eventually gotten pressure under control and rear main sealed up but the expense of the cracks was the killer.

Originally Posted by johnneilson

Benson,


Welcome to Old Motors, and yes we still smile when we get one to stay together.
Jim Brierley has a pretty good book or two out on "A" and "B" motors complete with instructions on how to set up the oiling systems.


My block prep is a little bit different, I do drill the main feed holes from the galley to the tubes, but I restrict the cam feeds and 3/8" hole to the drive to 0.025.
I block the front galley hole over the timing gear and use no gasket on cover, but my cover is 3/4" thick, no additional holes drilled and tapped into block. I do add a 1/8" drain hole to the back of the rear side of the rear cam bearing to relieve the oil buildup. I typically run external oil pump, have run as much as 95 psi by accident and not had the rear main leak.


Glad to hear you are having success, and remember this. There are a lot of blocks that get magnafluxed, the key is to find one that passes the test........
I suspect yours did pass but was prone to cracking due to core shift and/or corrosion.


Best of luck, J

[40 Deluxe]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by bigdaddyslotrat

Hi guys i have a question !! THIS IS A NEWLY BUILT MOTOR my oil leaks out the back of the motor is as follows, running at idle steady stream out the hole in the bell housing slightly higher rpms the leak seems to stop until you turn of the motor then a stream starts up again for about 4 table spoons of oil. ok this motor has about 1 hours running time and i did not build it! but was told by the builder himself that he changed the gears in the oil pump and it should make around 100 psi ?? will that much pressure make the oil leak out the back?? thank you all very much

Did your builder explain why he thought 100 lbs. oil pressure was a good thing?? And explain how changing pump gears would do it? What type of rear main seal did he use?
Did he come up with any other "tricks" that may cause problems later on?

[Dave in MN]

[QUOTE=Benson;1771373]Dave,

Looks like Stipe oil pump and Stipe oil filter?

Have you ever installed the Stipe filter on a stock B with stock oil pump?

I suspect that the 3/16ths hole in front of oil galley which normally keeps dipper tray full with splash rods will have to be reduced some.

Rods should be OK as long as oil filter returns the oil to the front of the dipper tray?

We are getting a bit off the subject of the original poster's questions but it appears he may feel comfortable with his modifications and reduced oil flow to the main bearings so a reply to your questions:

The oil pump and oil filter/valve chamber cover were supplied by Stipe Machine.
I have not used a standard B oil pump yet. I used the high volume pump to increase the pressure at lower rpms. I did install a drilled plug in the front of the oil galley that has a directional hole in it that sprays oil at the top of the cam gear rather than at its side.

The rods are supplied oil through the crankshaft so they do not need dipper oil.

So far, the following issues have surfaced:
Excessive oil mist from the crank vent/oil filler tube. Replaced it with a B breather made by Stipe. Problem solved.
The overhead valve head chews up the push rods at the push rod guides. I am sourcing (harder) hardened pushrods. The tips are hardened but not the sides where the guide contacts.
The block is being replaced as two of the three head studs that required Helicoils on the left side of the engine adjoining the exhaust headers developed a crack that travels to the closest water passage and out to the manifold/header mounting surface. I am building up a full pressure A block that has a B crank installed. (Mains ground just under 1.78") Hopefully, the A block will provide better service.

When I get the modified A block ready for assembly, I will start a thread with photos to share the project

In the meantime, I am building a somewhat stock B engine to use in the car while I finish the modifications on the overhead build.
Good Day!