Modified Banger Questions

[petew]

I have a 1929 A motor in my 27 T hot rod. The motor has been modified as follows...
Counterweights on the crank, insert bearings, full pressure oiling system , aluminum head and a 40lb flywheel.
The car is a blast to drive but the rear main leaks like mad . I took the car for a 10 mile ride tonight and when I shut it off oil flowed from the hole at the bottom of the flywheel housing as if a faucet had been turned on.
Now I just resealed this motor and it probably has a grand total of 15 miles on it. The seal didn't leak a drop at first but it sure does now.
The crank was modified (slinger removed) and the rear seal is one of those rubber o ring style jobs.
My question is where do I go from here ? I have heard more bad than good about that o ring style seal and would like to know what my options might be.
Has anyone ever used a rope seal on one of these engines ?
I bought the car with the engine in it and it came to me with the modifications I described . There was excessive end play in the crank so I took it apart to get the thrust surfaces straightened out. The end play is within spec now and I put a new rear main seal in before buttoning it up.
So what seal should I use to plug this leak ?

[James Rogers]

Use the cork seal available from Brattons. I also sell these and use them when the slinger is removed. I will never use another rubber seal called the Burtz seal.

[old1928fordguy]

Be sure the oil is actually from the rear main seal,There is a paper gasket between the flywheel housing and the back of the block.This seal plugs the rear bore for the cam.If this is not installed corectly/with much silicone or the like, it will leak out the hole in the in the bottom of the flywheel housing just like a bad rear main,Leaves pizza sized puddles !of oil.Also check to be sure the rear main return oil tube did not fall off ,or is not plugged.Same oil leaks results as above.Believe it or not it may not be the seal.Been there /done that.Hope this gives you some other constructive ideas. Phil Turner,Berts Model A Center,Denver

[Benson]

Pete,

This info may help locate the source of the leak ... although this procedure is for a stock engine the ideas may apply.

http://www.antiqueenginerebuilding.c...RMAINLEAK.html

[petew]

Thank you all for the very helpful information. I have already had the inspection plate off and found the back of the flywheel loaded with oil so I am pretty confident that the rear main seal is the issue.
I will of course double check everything mentioned just to be sure.

Pete

[1931 flamingo]

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Oil tube "loose" on the rear main?? You would have to drop the pan to ck.
Paul in CT

[amodel25]

Is the oil tube too tight in the rear main cap? In my early days with Model A's I heard about someone losing the return tube so I made sure that mine was in tight, so tight that it completely closed off the return path for the oil. It all went past the slinger and out the flywheel housing. Light tightening and a tack weld solved the problem.

[petew]

*Update* The pan and rear main cap are off . The rubber rear main seal appears very loose and at the advise of Jim Rogers (Dreamwerks) I am going to replace it with a two piece cork seal.
The drain pipe was clear and before I removed it I checked to be sure that air would pass through it. Again thanks for all of the help.

[Cajun]

Long shot-be sure you are not overfilling the oil. The Model A only takes 5 quarts if the engine and dip pan is empty.

If you are not sure where the oil is coming from, Autozone sells a dye that can be put in the oil. They will lend you a black light to help look for the leak.

[petew]

Jim Rogers, I have another question regarding my rear main. The motor no longer uses the original aluminum "rear seal" in the block but instead uses a brass insert (Snyders part # A-6334 ) that acts as a thrust surface and a holder for an aftermarket seal. The groove that accepts the seal has a different shape than the original which has a bevel in it. The brass insert is a "U" shape. Will the cork seal work with that ?

Pete

[James Rogers]

Originally Posted by petew

Jim Rogers, I have another question regarding my rear main. The motor no longer uses the original aluminum "rear seal" in the block but instead uses a brass insert (Snyders part # A-6334 ) that acts as a thrust surface and a holder for an aftermarket seal. The groove that accepts the seal has a different shape than the original which has a bevel in it. The brass insert is a "U" shape. Will the cork seal work with that ?

Pete

should work but, I have never had any experience with that part. Without looking I wouldn't even make a guess. You may have more problems than I can suggest fixes for here. This brass insert may be the whole problem anyway.

[Benson]

Pete,

If you posted some detailed pictures of the oil system plumbing maybe it would help since this is a pressure oiling system. There are several different ways to pressurize the A crank.

[petew]

Ah, yes pictures. One shot is of the brass insert in the block with the offending seal. The insert is identical to the factory aluminum except for the thrust surface and the slightly different shape of the groove that receives the seal , the depth of the groove is the same.
The other shot shows the block w/o the crank or bearings in it. If you look closely or zoom in the picture you will see the tubes that are entering the tops of the main bearing bores and the coresponding holes that feed the oil to the bearings. These were taken when the motor was out during the winter

[Tom Wesenberg]

Originally Posted by petew

Ah, yes pictures. One shot is of the brass insert in the block with the offending seal. The insert is identical to the factory aluminum except for the thrust surface and the slightly different shape of the groove that receives the seal , the depth of the groove is the same.
The other shot shows the block w/o the crank or bearings in it. If you look closely or zoom in the picture you will see the tubes that are entering the tops of the main bearing bores and the coresponding holes that feed the oil to the bearings. These were taken when the motor was out during the winter

Pete,
There's a lot of empty space on the rods, where there should be a bearing. I think they now make a full width bearing for the rods with inserts. What controls your rod side play?

[petew]

The rods are aftermarket and those are the bearings that they came with. I didn't build this engine but rather bought it in the car along with all of it's issues. There does not seem to be excessive side movement in the rods. They are pretty nice rods and I'm sure they would hold together long after the crank split in half.

A couple of pictures of the aluminum insert with the brass insert to show the difference in the groove

[James Rogers]

Originally Posted by petew

The rods are aftermarket and those are the bearings that they came with. I didn't build this engine but rather bought it in the car along with all of it's issues. There does not seem to be excessive side movement in the rods. They are pretty nice rods and I'm sure they would hold together long after the crank split in half.

A couple of pictures of the aluminum insert with the brass insert to show the difference in the groove

You may have to modify the half of the seal that goes into the bronze part and I would use a thin skim of RTV on that part to make sure it seals. I think it will work. Now for the bad part. I don't see a bronze thrust in the bottom or cap part of the rear setup. I believe if the rear is built with only a half thrust in the top it is doomed to failure and, constant leaks.

[James Rogers]

Originally Posted by Tom Wesenberg

Pete,
There's a lot of empty space on the rods, where there should be a bearing. I think they now make a full width bearing for the rods with inserts. What controls your rod side play?

This engine is built using MG midget rod bearings and there is lots of jury rigging involved. I did 2 using this method when I first inserted motors and was not too successful. I lost 1 and the other is still going. I guess that's batting 500. I have done 8 or 10n using the bearings from Antique Engines and have never had a failure. That's batting 1000 and I like it. I do use a full rear thrust and a half thrust on the front of the cap.

[petew]

Jim,
The motor has 360 degree thrust at the rear , half in the cap and half in the block. It only has 180 degrees at the front. That bronze insert is part of the thrust control. Again, this is the Hand I was dealt . When I originally disassembled the motor over the winter it had .035 of crank end play and only That bronze insert to control the cranks desire to move forward when you stepped on the clutch. I had the rear cap machined to accept a brass insert by Rich at Antique Engine. The end play is now within spec. It will have to do for now. As I told you I will be moving near your shop later next year and will most likely be bringing the motor to you to get straightened out.
For now I just want to get it sealed up and drive it . I don't plan on driving it hard .

[petew]

I think we are now leak free.
I used the 2 piece cork seal as Jim Rogers suggested and reshaped the back side of the upper half of the seal to fit the brass insert . I used some 80 grit sand paper to match the seal contour to that of the brass insert. The cork was quite easy to shape with the sand paper. Then I broke the seal in a per the instruction sheet before giving it some revs and the result was no oil leak.
The rubber o ring seal that I replaced had an obvious pucker in it that was visible when I removed it.

Pete

[MN Stumpjumper]

Good job!!