Bearing clearance

[Randy Lausch]

I asked if there is a mechanic within 50 miles of south bend in. I got no response, I’ve drove this modelA for the last several years this summer I noticed that when you first start it up I hear a small knocking noise & I’ve also noticed that it does leak more oil from the rear main. Being I can’t find anyone to check the clearance do you think it is something I should be concerned about. Like I said I only hear it when I first start it up.

[Marshall V. Daut]

Is it a low rumble knocking that you can almost feel or a higher pitch tap knocking? The former indicates main bearings, the latter rod bearings. The noise you hear is before oil reaches and lubricates the bearings and cushions the noise as the crankshaft turns. Because the mains receive oil from the top via holes and passageways through the block running from the valve galley, they are already primed. It is the rods that will usually make tapping noise upon start up (especially in cold weather) until the crankshaft rotates many times and scoops up oil into the rod cap dippers, thereby oiling the bearings. Then the engine becomes quieter, right? So, I'd still be inclined to believe it's the rods that need adjusting more than the mains. You should be able to do the job in less than two hours, even as a first-timer. Drop the pan, remove an equal amount of shims from each side of each rod (sometimes peeling through the layers is necessary to obtain the correct thickness), tighten the nuts until the crankshaft cannot be turned over by a hand crank or starter. If the engine locks up, replace one thin shim on each side of the rod (if possible) and try again. If the engine now turns over, you are good to go. Install cotter pins, new pan gaskets CAREFULLY installed, add NEW oil and start the engine. This is an abbreviated description of the procedure, but you get the idea. If you were able to remove several shims, that was the problem = loose rods.
The leaking rear main is a common Model A problem and can be caused by many things. The most likely cause, however, is loose center and rear bearing caps. It is far more difficult to adjust the main bearings than the rods because so much of the engine has to be disassembled before that can be done. Plus, the rear bearing nuts are a BEAR to loosen because of their location and tight quarters. For a first time procedure, it would be best to find someone who has done this before. Watch what he does so that you can do it yourself down the road. These engines are not a one-time adjustment and good to go for the rest of their lives. They need periodic maintenance, such as attention paid to bearing adjustment. The good news is that the rods are much easier to adjust than the mains and they will be the ones more likely needing to be adjusted. Piece of cake.
Marshall

[Bob Bidonde]

You should join the nearest Model "A" club, and ask for help. Check these sites: https://www.mafca.com/chapters_list.html

https://model-a-ford.org/top-page-1/regions/


If the engine was mine, I would drop the oil pan, measure & correct the main and connecting rod bearing clearances.

[1crosscut]

Randy if your not able to find someone nearby you will need to haul the car or have it hauled a farther distance to someone able to do the work. If that is not an option then it will be necessary to pull the engine out of the car and put it on a pallet and ship it to someone else.
Removing and installing an engine is much simpler than opening one up yourself and doing the work especially if your not familiar with the internals of an engine.
Myself I don't relish the thought of trying to adjust the bearing clearances with the engine in the car. I've always pulled the engine and done it on a stand. Once on the stand I disassemble the engine to the point that the crank shaft can be lifted out to assess the condition of the babbit in the block itself. Doesn't take a whole lot more work and then you will know the condition of the engine as a whole.

Another option is to try to ignore it and run it until...

[Randall]

Heres how I do it in car.https://youtu.be/8MH3HtTnshQ?si=YdLczUECjUbjgFYZ

[nkaminar]

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A quick search on Google Maps yielded several automotive machine shops in the South Bend area. One in La Porte was advertised as being "old school." Try calling around to see if any of them would be able to help or recommend someone. I searched for "automotive machine shop."

[8EL]

Knocking noise on start, goes away after journal receives oil, rear main leaking oil....

I would be concerned that clearances are excessive, or approaching this threshold. Check into this now before crank journals are damaged beyond being able to be reground.