Model B Rear main oil leak: What to do next?

[Doctor's Ford]

Now on my 4th attempt to fix large oil leak on the rear main. This is where I stand currently with the engine apart

1) Cut grooves in Babbitt in main cap replicating the original pattern (shown in prior post)
2) Today I measured crankshaft clearance. I could not locate plastigauge around here so used aluminum foil to estimate clearance and this is what I found:

It took 7 layers of aluminum until the crankshaft would not rotate easily. With 6 layers it felt correct. I used my micrometer and measure the stack of aluminum foil thickness several times and got between 0.0027 and 0.0039. There was a small play on the crank that could be felt by hand when trying to move it upwards.

Questions:

1) If this measurement is accurate, is this clearance large enough that can explain massive oil leak on the rear main? I understand 0.0015 is the ideal.

2) I have NO ACCESS TO PROS WHO CAN POUR NEW BABBITT, so I would like to fix using less conventional methods. For instance, can this be fixed by removing a couple of thousands inches from the main cap so the crank will fit correctly? I read many strongly oppose to this. Can you educate me why that is a problem?

Appreciate your input, thank you. Manuel

[Mike B]

The problem with filing the cap(s), is you no longer have a round hole, and can only get proper clearance in a small area, well maybe 1/2 the crank shaft anyways?

As to excessive clearance causing the leak, I can't answer that, as I know nothing about those engines.

[flatheadmurre]

Ok theres a right way and theres a way to get it done....
That said if youre gonna solve it by grinding of the caps.
If you have .003-.004 you can take .002-.003 of the cap DONT touch the babbit of the cap.
Bolt it back forcing the babbit on the side to expand.
Depending on how brave you feel a copper sledge might be involved.
Then its old school fitting of the babbit...dye and take it away one chip at the time until youre good to go.

[Terry,OH]

You may be able to find a NOS rear main cap. Comes with the oil return tube and the bearing.

[flatheadmurre]

Doing it the backward way...how worn is the crank ?

[OHV DeLuxe]

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This might have been addressed in earlier threads but both piston blow by and too much oil pressure may cause rear main leakage, especially on engines like these with only slinger for the oil. WW2 Jeeps after mid 1943 I think have a progressive valve between the valve gallery and the intake manifold, making a slight vacuum on idle and pulls a bit more at high speed. I put one of these on my jeep and no more crankcase pressure and no more of the milkshake looking stuff from condensation in open breathers. It worked absolutely wonderful.

[jimTN]

I suggested a check to see if there was a hole in the bottom of the slinger grove and have not heard if there was. Answer may have been posted and I missed it. There should be a drain hole there and if it is not oil will leak.

[Doctor's Ford]

Originally Posted by flatheadmurre

Doing it the backward way...how worn is the crank ?

Thanks for your input. Crank and new babbitt were machined several months ago but the machine shop did not follow recommended specifications (and I did not know them until recently so could not check what they did). So the crank is ground down. I will measure the crank journal diameter and add to my post.

Originally Posted by jimTN

I suggested a check to see if there was a hole in the bottom of the slinger grove and have not heard if there was. Answer may have been posted and I missed it. There should be a drain hole there and if it is not oil will leak.

Sorry, I am the one who missed your suggestion. There is a good hole in the bottom of the slinger groove. The main cap tube is wide open. I cleaned up and tested the drain tube and seems perfect. This seems to be ruled out as a cause of an oil leak for now.

[Walt Dupont--Me.]

Well lets see, you said you had a new babbitt job a few month ago, there should be a shim pack on both sides of the cap, you can peel those shims, there about .002 thick to take up clearance, you ask about filing cap, it sounds like the Babbitt man didn't install shims before line boring the block, I take out that plug on the front of the cap that goes into the drain back and see if the pipe isn't screwed in so it plugs half the hole, I take a rat tail file and file out the extra thread that is up in that drain back passage. You can bye those dish block plugs at Napa ect. You should shoot for .001 --.0015 clearance. Walt

[Doctor's Ford]

Walt. The shop that did the babbitts about a year ago did not put any shims at all so can't do any adjustment there.
Regarding the plug on the main cap, he welded the drain pipe to the cap so the plug is gone. The inside of the tube is clean but can not see how deep the pipe is screwed in. Is it safe to remove the welding and try to do new thread? I will have a machinist do that unless there is a strong risk of further damaging the cap. What do you think?

[Kurt in NJ]

The plug is the is the round disc that is on the side below the pipe that is welded---it covers the hole that goes back to where the slinger drains

[Doctor's Ford]

No plug left. The guy welded everything as shown in photo. This is why I asked if it is safe to try to remove the tube, make new thread to screw it and open a "window" for the plug. I can have it done by a machine shop, I have no tools to mess around with welding. That is the only way to be certain if the tube is inserted at the correct height which every one tells me is critical to prevent oil leaks.

[1931 flamingo]

BE CAREFUL..................Too much heat there is going to mess up your Babbitt. JMO

Paul in CT

[Kurt in NJ]

I would drill where the plug was---this way you can clear the hole all the way to the end,no need to disturb the welded in pipe, and trim any excess pipe sticking up into the passage, then tap it for a pipe plug---trim the pipe plug so it only uses a few threads so it won't block the drain pipe passage, then once tight (not very tight so as to not risk splitting the thin possible brittle weld) trim the outside of the plug so it won't interfere with the crankshaft movement

[jimTN]

Kurt has it right. The way that works is oil goes by the main and out the rear of it where it hits the slinger(disc) which is on your crankshaft. As the crank turns that disc slings the oil outward and it should collect in the bottom of the grove where the slinger turns. There the oil should run back down that tube to the inside of the pan. If the tube sticks up in the grove or is plugged up in any way, oil has to gon on out past the slinger and to the outside of the pan.

[Doctor's Ford]

Today got help from a machine shop owner who spent time with me taking precise measurements. He also proposed to drill where the oil pipe plug was and not to touch the welding just as Kurt in NJ suggests. Will do it during the coming week.

Clearence measurements done by him at his shop show a large gap:

Crank journal 1.947"
All three main caps mounted have an ID 1.958"
Clearance is the difference: 0.011"

Front-end clearance: 0.010"

I think this is the reason for the oil leak, too much clearance everywhere.

[flatheadmurre]

Ouch...10 times the desired clearance.
How about just stopping and going back to the machineshop and getting your money back before messing with it more ?

[flatheadmurre]

Next step is to find out where the machine shop failed.
Wrong babbit...to soft.
Crank incorrect ground and polished...wears the babbit out fast.'
Or just machined to the wrong specs.
If the babbit is done correct and the bore is still round have a crank ground to fit the bore.

[Doctor's Ford]

Originally Posted by flatheadmurre

Next step is to find out where the machine shop failed.
Wrong babbit...to soft.
Crank incorrect ground and polished...wears the babbit out fast.'
Or just machined to the wrong specs.
If the babbit is done correct and the bore is still round have a crank ground to fit the bore.

Money back? Not in these latitudes. This engine has essentially zero miles, just ran for testing when it leaked all over. It was machined to the wrong specifications to begin with, it is not worn out. The machinist I just met has been in business for over 40 years and he says has done many babbitts before but not in the last few years. He offered to pour new babbitts and bore to the exact clearence I asked for. I may give a try since my main problem was unavailability of guys who can do babbitts and now I found somebody willing to do it. With the huge clearance I have my engine will require machine work and precision tools, beyond what I can do at home.
Plan B is to ship caps to be poured by Bill Barlow in Bend, Oregon. Thanks tbirdtbird (Dave) for providing advice and Bill phone number.

[flatheadmurre]

Have the machinist check the crank first so its polished correct then pour and bore it to fit the crank.
Hope it works out for you...you had some real bad luck this far.

[Mike B]

Wouldn't the whole block have to be shipped (to Oregon)? You can't just babbit the caps can you?

I'd also look at the rod clearance as well, if the mains were done wrong, then I'd suspect the rods were as well.

[jimTN]

Redo the mains both in block and caps. Make sure there is very little end play, there should be a thrust side to mains. Make sure there are shims galore for each main.

[Doctor's Ford]

Originally Posted by jimTN

Redo the mains both in block and caps. Make sure there is very little end play, there should be a thrust side to mains. Make sure there are shims galore for each main.

That is the plan. Who sells shims of the correct thickness? I have a set of main bearing shims from Snyder part # B-6340 for 4 cylinder 32-34 but the thickness is a big 0.016". I read in the Fordgarage.com (Vince Falter's page) that the original ones where much thinner, about 0.002". Without the thin ones, the purpose of shims is forfeited.

[flatheadmurre]

You can always exchange the shim to a thinner one lets say .014 when that time come.
As long as you got something to start with.
And its better with one thick shim then a stack of thin ones when it comes to strenght.

[Chuck Kuntz]

Unless that shim pack is different from the one I bought from Snyder's, it is composed of layers of shims that are .003 as I recall. You just need a razor blade to delaminate the shim pack to the thickness you want.

[Kurt in NJ]

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Since the crankshaft has been cut so much---.050 undersized you need to check the centerling, it should be set up on V blocks and the runout of the timing gear surface and the flywheel flange ---the Ford spec is --less than .001"

If you could find another crankshaft that is .030 or less you could add shims and bore the existing babbitt to the size

[Doctor's Ford]

Originally Posted by flatheadmurre

Have the machinist check the crank first so its polished correct then pour and bore it to fit the crank.
Hope it works out for you...you had some real bad luck this far.

OK Guys. May be my bad luck will now finish.

I am back to report to you what is going on with my 33 model B engine. For several weeks I worked together with an enthusiastic machine shop owner who accepted the challenge and took the job very seriously. He worked with much care to pour new babbitt and then bore everything to the correct specifications. I spent many evenings with him at the shop after hours to watch his work and provide the necessary technical information I gathered here at the Barn and from several other sources. Yep, we worked late evenings odd hours. The record was one Friday until 3 in the morning when I gave up but he continued till dawn.

The following is a summary of the process with photos that show what was done. Please keep in mind the logistic limitations so you don't make harsh judgements if something is out of the ordinary.





Babbits look good, certainly better than what it was before. To pour the babbits he melted a tin-based chunk of metal. It is avaiable here only from one supplier. They called it "white metal" and is mostly tin but don't know the exact components. You see that we added shims this time.







He is creating oil wells. They were essentially non existing in my prior babbitt job so this will help oiling



He placed marks before cutting oil grooves. The design of the grooves for model B is different than model A. I used photos from a sample provided by James Rogers, a barner who is a fantastic model A/B rebuilder in North Carolina and whom I had the plesure to visit at his shop last Summer to learn about these motors.




The grooves go all the way to the front edge and from there down to the oil pan. My previous job did not carry the grooves forward and that was a factor that favor flowing oil to the rear.



Likewise, the front and middle cap were poured, machined and then the oil grooves were cut.




The oil tube that was welded before was removed, new metal added, new thread to place not only the oil tube but he also created a thread for the plug. Excess metal was cut to keep clear from the crankshaft. The plug is very thin and made of bronze but has enough thread to keep the plug tight. There was rust and debris inside the oil channel of the main cap which surely contributed to poor oil flow and the rear leak. It was thoroughy cleaned.




The babbitts were cut/bored/machined to specification. I insisted 0.0015 inches clearance between the bearings and the crankshaft. He said it was too tight but agreed to do it if that is what this motor requires.



To double check the clearance I sourced Plastigage from O'Reiley in the US




Put a 2 inches strip of Plastigage on the crank journal and torqued to 100 lbs




Well, not bad at all! 0.002 seems very close to ideal. The crank rotates by hand and gives the feeling that is fitted. I don't have photos to show the front-end clearance but it was 0.004 inches which I believe is within the correct range



The crankshaft was checked for any distortion, I believe that is referred as "being true or not". He found 0.002, a slight deformity and was able to apply some heat on certain spots that corrected it. It took him literally one minute to know where to apply heat to accomplish this.




Shims added to all bearings



The caps were replaced, bolted, sealer added sparingly to edges, bolts.



After the crankshaft was fitted and the sealer cured (next day) we added oil through the oil tube and used 10 lbs compression and showed no leaks. He decided to test with up to 30 lbs and still there was no leak. So the engine was picked up and brought home to complete the job. Few days later it was finished, painted and dropped into the car to formally test. Sorry, we have no engine stand to run it so decided to drop in the car and see what happens. Click on these 2 photos to open a video link.






So far very good! I see not even one drop of oil. But it only ran about 25 minutes. I could not test further because a different problem presented that required to shut off the engine. I will relate it in a different post.

Thanks to all who have given advice and provided information and in particular to James Rogers from Leicester, NC (Dreamwerks, model A & B Ford engines) for his invaluable insight and generous advice.

[bigdaddyslotrat]

Hi guys i have a question !! 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

[Bob C]

Do you have stock gravity fed oil system or modified with pressure to the mains.
Probably would have been better to start a new thread.


Bob

[JSeery]

I agree, think your post would get more attention as a new thread.

[bigdaddyslotrat]

thanks guy i'll do just that