Bearing clearance

Randy -
Unless you are physically unable to do this, adjusting rod bearings is not difficult and can be rewarding spiritually, as well as financially. The rods are the ones that usually need more frequent adjustment than the main bearings. They "sing" more often than the main bearings do. The main bearings are considerably more time-consuming and physically challenging than adjusting the rods. So, if you want all seven bearings in your Model A engine adjusted, perhaps it would be best to continue searching for a competent Model A mechanic in your area. But it wouldn't hurt for you to try your hand at adjusting the rod bearings. You might find afterwards there is no need to also do the mains, unless you have a pesky rear main bearing leak, which among other things can be caused by too loose clearances in the center and rear main bearings. The front main rarely needs attention or adjustment, unless the engine is very high mileage without periodic bearing adjustments.
Marshall
 
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A very big problem with doing the job yourself are those goofy sized nuts on the rods. I don't remember what size they are but finding a socket to fit is impossible here and I expect quite difficult even over there.
Never the less, I have done it several times and agree with those above who say you ca do it yourself.
 
Synchro909 said:
A very big problem with doing the job yourself are those goofy sized nuts on the rods. I don't remember what size they are but finding a socket to fit is impossible here and I expect quite difficult even over there.
Never the less, I have done it several times and agree with those above who say you ca do it yourself.
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21/32 inch sockets available on Amazon. Mine cost 5 bucks.
 
Yes, good point about the rod nuts, Synchro. They are "Weird Harolds", for sure. A metric size socket is perfect for those nuts. I don't recall which, but 17mm, 18mm or 19mm come to mind. ONE of those will work. :) If you have the standard size metric socket set like most of us do (and rarely use), you already have the right socket on hand. See? That's half the battle won already! The right tool for the right job. Why Ford put those odd-sized nuts on the rods is beyond me, unless the nuts we are obliged to deal with these days were added later by bearing pouring enterprises. And to what end? Perhaps the correct size castellated nuts were no longer available to the hobby 50+ years ago, so metric nuts were substituted? 'Dunno. I just know that I can count on needing a metric socket to adjust rod bearings this many years away from the factory.
The mains, on the other hand, are a piece of cake: 9/16" square socket for the bolt heads and 3/4" for the accompanying castellated nuts.
Marshall
 
Maybe mine were replacements, but they were a straight 5/8". Quite a disappointment after I ordered and received a 21/32" socket!
 
ursus said:
21/32 inch sockets available on Amazon. Mine cost 5 bucks.
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I have had too much trouble with Amazon to want to go anywhere near them again. I had a socket split on its first (attempted) use. Besides, what is the quality like and how much do they want to post it to me?
I think I'll keep on filing a little off each face so I can use a 5/8" socket. Even they are not carried by some outlets any more but 16 mm is very close.
Playing around with antiquated cars made with an antiquated measurement systems is getting harder and harder.
 
Synchro909 said:
A very big problem with doing the job yourself are those goofy sized nuts on the rods. I don't remember what size they are but finding a socket to fit is impossible here and I expect quite difficult even over there.
Click to expand...

I found a 17mm (0.669291) socket worked well on my rods. 21/32 = 0.65625
 
"Plastigauge" works. Mashes out to give you something you can measure to get a read on actual clearance. The box comes with "width markings" which correlate to a thickness, but the plastigauge itself can be carefully measured with a mic.


https://www.plastigaugeusa.com/how.html


If you're out of shims (i.e. metal to metal) you can "shave the caps" to remove possibly up to another 0.010. Problem with shaving the caps is once you get to a certain point, rebabbitting will not give you enough Babbitt thickness and makes for a weak Babbitt when the bearings are finally re-done.

I have used plastigauge and also found "feel" works just as well. Some of my acquaintances have used kesler radio-tv solder in the old lead-antimony formulation. Modern non-lead solder is "stiffer" somehow.

The usual problem found is the bearings wear "egg shaped" and while clearance can be found "generous" when the egg is "across" the opening, it will be "tight" and possibly bind when at 90 degrees. This is particularly notable on the rods. Engine bearings not so much. My hand-tightening is performed until the rod "just starts to bind."

And one wants to be sure the rod-nut is TIGHT. And use new cotter-pins. And be careful to bend the cotter pins so they can't "flop around."

I have told my story of losing a rod cap nut driving at 55 on Cape Cod's "Mid Cape Highway" during weekend traffic rush - and making my way back to my Cape house using the "service road" (which roughly parallels the Mid-Cape. With interruptions.) I didn't throw the rod but the engine complained mightily. 30mph or less keeps all the force on the bearing cap "one way" and allows forward motion. I found the lost nut in the bottom of the oil pan. This fail I put to egg shaped rod bearings, fatigue and break of the re-used cotter, vibration from the bind/loose cycling.

Anyway, my days of climbing under the car to tighten the main bearings are now pretty much behind me. I would pull the engine and put it on a stand to be flipped and worked on that way. It sounds like a lot of work but if you have the engine hoist, a frame spreader, and a system/organization, its not that bad.

Joe K
 
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Sorry that no one has responded that is close and is able to do this for you.
If you were in the Lincoln Nebraska area I could have helped you out.
Hope you find someone.
 
I'm in the same boat, trying to help a widow with getting her A going, got it started yesterday. It went to knocking immediately, engine not run in over 25 years. I cleaned the valve chamber, and pan before starting. No A clubs/shop close to me, ( Texas panhandle). I hate to tell her the bad news.
 
Randall, I just had to say that your videos have been an amazing help for my rebuild lately. Please keep them coming!
 
My experience with a severely worn but not yet stopped Model A engine is that they don't really make a "knocking" at speed but rather a "whuppa-whuppa" sound.

The 26K Model AA I once owned was just starting to get to the "whuppa-whuppa" point. You could hear it but obviously not killer. The seller opined that the engine had probably never been opened since new - but was now "due."

Well, the lost nut descriptive above DID knock above 30mph. But that was SEVERELY loose.

Joe K
 
People are different. Some cannot or don't want to do mechanical work for whatever reason. Randy is asking for assistance. Since no one responded with a local mechanic, there may not be one. My advice for Randy is to ask at the local club. Usually there is someone who is willing and able to do this work. Otherwise it may be necessary to take the engine, in or out of the car, hundreds of miles to get the work done.

In my opinion, the only way, and the best way, to adjust the clearance on the bearings, especially the mains, is to take the engine out of the car and put it up side down on an engine stand.
 
nkaminar said:
People are different. Some cannot or don't want to do mechanical work for whatever reason. Randy is asking for assistance. Since no one responded with a local mechanic, there may not be one. My advice for Randy is to ask at the local club. Usually there is someone who is willing and able to do this work. Otherwise it may be necessary to take the engine, in or out of the car, hundreds of miles to get the work done.

In my opinion, the only way, and the best way, to adjust the clearance on the bearings, especially the mains, is to take the engine out of the car and put it up side down on an engine stand.
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I agree with that. In the video, we were told about the heavy flywheel and how it bends the crankshaft down so we get a false reading with Plastigage on the rear bearing. Turning the motor upside down eliminates that but be careful not to bend a valve when you turn it over. An engine stand is easier here.
I am basically lazy so I thought about this and decided it was easier to drill and tap a hole in the flywheel housing near the drain hole so I could put a screw in there and hold the flywheel up. That worked well with Plasigage because we are not to turn the cranks while it is in there. Make sure to back off the screw before trying to turn the crank. If I have the engine out, I use a piece of aluminium foil folded to a triple layer (ours is 0.0005" thick). I place that under the cap and try turning the crank following the trial and error method outlined in that video.
 
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