rear main cap

[elba]

I am new to Model A engines. My friends A , sedan, needs the REAR main cap taken off. Does the engine have to come out or can it stay in the car ?

We are trying to find a noise that occurs at about 1800 rpm. The rods plasticgage by the book and the center main is ok also.

Thank YOU !!

[Purdy Swoft]

You can remove the rear main cap with the engine in the car if its a model A engine, probably not if its running a model B engine.

[elba]

I forgot to tell you, it is a "B" engine in an "A"

[Tom Wesenberg]

Using plastigauge on the mains can be tricky with the engine in the car. You have to push up on the crankshaft to make sure the weight of the crank and flywheel aren't flattening the plastigauge. I have put a jack under the crankshaft to push it up.

You might want to try the foil method, where you cut a piece of aluminum foil about 1 1/2" x 2" then fold it in half so it's 3/4" x 2", lay it lengthwise on the crankshaft and bolt the cap back in place. If the crankshaft can be turned, then remove one shim and try it again. Be sure to mic the foil so you know what thickness you are dealing with. You want to have about .0015" to .002" clearance when you are done.

[Purdy Swoft]

When the B engine is used with the model A flywheel housing, the larger model B main cap won't have enough clearance to be removed without removing the flywheel and flywheel housing. I suppose that if a larger opening was cut in the model A flywheel housing, the bearing could be removed in the car.

[Jim Brierley]

Sponsored Links (Register now to hide all advertisements)

Some A & B engines have vibration points, 1800 and 2300 are the most noticeable. Your noise could be this vibration and not a clearance problem??? If so, just avoid driving at this RPM. This noise is usually not noticeable with no load on the engine, just when driving.