Bad Oil Leak

[james1savage]

I just got my '29 roadster fired up for the first time. The previous owner who never got to the point of starting the car said the engine was apparently rebuilt some 30-40 years ago and never fired.

Now the issue is I have a rather large oil leak coming out of what looks to be the Center Main Bearing Nut on the left side of the engine, between 2 and 3 cylinders. Why would this be and any thoughts on how to stop the flow?

Your thoughts and advice is appreciated.

[old31]

Remove the oil pan and see what is going on underneath.

Make sure it has a dipper tray, clean the oil pump, check the torque on the nuts.

Main 80, rods 35

[nkaminar]

On the Burtz engine, the instructions say to add a small O ring on the nuts or use some quality sealant. I think you are going to have to do what Old31 said and drop the pan to check things out. This is a prudent thing to do on any engine where the history is hearsay. Even more prudent is to remove the engine from the car and do a thorough inspection. But drop the pan first as this may not be necessary in your case.

[Marshall V. Daut]

Take a 3/4" open end wrench and place it on the nut in question. Try to turn it, even though there should be a cotter pin through the castle nut. If you can turn the nut and bolt easily, the nut is too loose, which is allowing the oil to leak past the bolt's shank. I should think that if this were the case, the oil leak would be more of a dribble than the gusher you describe. Model A oil pressure is only about 3 psi, which is not enough that high up in the block to cause such an oil hemorrhage. I wonder if the engine has been converted to a pressurized oiling system, which has a much higher pump pressure. The higher pump output could force oil past any place that is marginally sealed, usually past the rear main bearing or rear pan seal. But if that center main bolt nut beneath the water inlet neck is loose, the oil could also escape from there.
Marshall

[old ugly]

maybe the center main has been shimmed with an open or horseshoe style shim. the shim for those main bearing bolts should encircle the bolt.
you will not know unless you take the pan off.
OU

[james1savage]

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Well I appreciate everyone's responses. I'm going to pull the pan and see what I can see, and go from there. I'd rather put some more time into it rather than half ass it and end up way farther behind the ball.

[Cape Codder]

Originally Posted by nkaminar

On the Burtz engine, the instructions say to add a small O ring on the nuts or use some quality sealant. I think you are going to have to do what Old31 said and drop the pan to check things out. This is a prudent thing to do on any engine where the history is hearsay. Even more prudent is to remove the engine from the car and do a thorough inspection. But drop the pan first as this may not be necessary in your case.

I have a question on the above statement. I don't understand the instructions of adding a small "O" ring on the nuts in a newly made engine! Why would you have to do that AND what does that do to the torque value on the nut?

[Kurt in NJ]

if lock washers were used that will leave a leak path
if it was converted to pressurize the center main that would help make a leak path leak more,

[Bob C]

[QUOTE=Cape Codder;2254974]I have a question on the above statement. I don't understand the instructions of adding a small "O" ring on the nuts in a newly made engine! Why would you have to do that AND what does that do to the torque value on the nut?[/QUOTE


The following is from the builders Guide


The 3 main bearing studs that have nuts on the exterior (2 at main #1 and 1 at
main #3) that need to be sealed to prevent oil leakage at the tall exterior castle nut.
Methods of sealing can be:
1) Epoxy (Loctite 1360700)
2) A flexible sealant (Permatex “Black Gasket Maker” 27037) or (Permatex “The
Right Stuff” 29208).
3) A 10 mm ID x 1.5 mm width O-ring that fits into a 0.079-inch-wide x 0.031
inch deep groove in the 0.500 inch diameter of the stud shank can be machined
into the stud. The groove should be located at 2.17 inches below the 1/2-20
UNF threaded end. The McMaster Carr part number for the O-ring is
1295N162. This was suggested by Brian Weber. If you choose to use this
method of sealing, push the stud up and install the O-Ring where the castle nut
is and then pull the stud down. This method lessens the possibility of damaging
the O-Ring on assembly. John Lampl at www.burtzblock.com has the studs
with the O-Ring groove in stock and available for a small cost.

4) A packing (cotton string and Permatex #2, 80011). If the decision to use a
packing is made, then the Permatex impregnated string must be wound around the
7/16-inch shank and firmly packed with a curved tool that is .030 inch thick.
5) An O-ring between the 7/16-inch diameter stud and the 1/2-inch bore in the
cylinder block. Lawrie in Australia reported that a 1.5 mm cross-section x 10 mm
ID (0.059 x 0.393 inch) Viton O-ring worked for him (McMaster Carr 1295N162).
A 1 mm cross-section x 10.5 mm ID (0.039 x 0.413 inch) Viton O-ring (McMaster
Carr 1295N129) should also work and be a little easier to install. If the choice is
made to use an O-ring, the O-ring and mating parts need to be lubricated with motor
oil to prevent installation damage.
A tool made from a piece of tubing that is 0.500-inch OD and 0.444-inch ID
(McMaster Carr 89955K471) can be used to help with packings or O-ring
installation.