Pilot bearing recess in flywheel

JohninKuranda

JohninKuranda

Senior Member
As part of trying to solve my transmission noise issue, I am thoroughly checking everthing possible that I can think of to check.

The original flywheel was replaced with a lightened one machined to take a V8 clutch - replacing the previous multi-disk setup. The recess for the pilot bearing machined into the flywheel is 9mm. Not all the way through giving a definite seat in the flywheel for the pilot bearing. I note that the thickness of the A7600 pilot bearing is 12mm. After searching this forum I see numerous posts stating that the pilot bearing should be flush with the flywheel. There are a few others saying it does not matter.

Question - as the transmission is off anyway, should I get the recess in the flywheel machined out those 3 pesky miliimetres? Or does not it matter if the pilot bearing extends by those 3mm?

As always, any advice appreciated!

John
 
I've told about bushing the pilot shaft, and placing the bearing on the stub as a "force fit." In that case the bearing was lined up with the flywheel hole to receive it and the assembly made by putting the bell housing up to the flywheel housing and bolting them together.

If you can assemble it like this it's probably good to go. If the recess is not deep enough to allow assembly then you'll need to deepen it.

I can't say I've ever seen a Model A flywheel without the hole "bored through."

Joe K
 
If nothing is interfering with the bearing as-is, (witness marks on the input shaft "nose" will show where it's been running) you won't gain anything by boring through. Having that seat is actually beneficial as long as clearance exists.
 
JohninKuranda said:
As part of trying to solve my transmission noise issue, I am thoroughly checking everthing possible that I can think of to check.

The original flywheel was replaced with a lightened one machined to take a V8 clutch - replacing the previous multi-disk setup. The recess for the pilot bearing machined into the flywheel is 9mm. Not all the way through giving a definite seat in the flywheel for the pilot bearing. I note that the thickness of the A7600 pilot bearing is 12mm. After searching this forum I see numerous posts stating that the pilot bearing should be flush with the flywheel. There are a few others saying it does not matter.

Question - as the transmission is off anyway, should I get the recess in the flywheel machined out those 3 pesky miliimetres? Or does not it matter if the pilot bearing extends by those 3mm?

As always, any advice appreciated!

John
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Good question, John. If the pilot bearing is pushing against the input shaft all the time, I could see that being an issue. However, likely not the root cause of the noise you describe. If the input shaft was being pushed back forcefully by the pilot bearing all the time, the pilot bearing would get destroyed long before the shaft bearings.

Like JoeK said, I have never seen a Model A flywheel without the hole bored all the way through either.
 
I’m not clear on this but is there a difference in either the flywheel housing or bell housing for the multi disc clutch?
If so were those switched out?
 
John - It is critical that the flywheel fit flush against the crankshaft, thus there should be zero protrusion of the throw out bearing on the front. My experience is that when the bearing is installed properly in the flywheel there is usually a very slight protrusion in the aft (transmission) side but nowhere near the 3mm you suggest. I don’t know how much leeway there is on the front but 3mm sounds like way more than there should be. I’m with Richard Knight, remove that lip from being a potential problem. (I also cannot recall seeing a flywheel with that retention lip you describe.) Depending on the thickness of this lip you might get away with doing it by hand with a die grinder, but of course the best way would be to chuck it up in either a mill or lathe and use a more precision cutter.
 
Install the pilot bearing & the clutch housing. Then test fit the transmission & check the fit of the transmission's input shaft. If there is some clearance between the shoulder on the input shaft & the bearing, it is good to go.
 
I wonder if this problem may have occurred from machining the flywheel housing. That would put the transmission closer to the flywheel.
 
Measure from the face of the bell housing to the rear face of the pilot bearing. Then measure from the face of the transmission case to the face of the shoulder on the input shaft.
 
Any American I have spoken to about imperial vs metric, say that you tried metric years ago and it didn't work. Reading this thread reminds me that Henry used metric bearings throughout the transmission, including the pilot bearing. Years ago, I dismantled a gearbox that had (I'm sure) never been taken apart since new. ALL of the bearings were made in Italy! Did Henry import Italian bearings for his cars in the Model A years?
A little research confirmed to me that the bearing numbers quoted for Model A gearboxes were indeed, metric. Seems metric worked in the US in the 1920s/30s.
I would love to have been a fly on the wall in Henry's office in the day but first, I would make sure his fly swat was somewhere else!!
 
Synchro909 said:
Any American I have spoken to about imperial vs metric, say that you tried metric years ago and it didn't work. Reading this thread reminds me that Henry used metric bearings throughout the transmission, including the pilot bearing. Years ago, I dismantled a gearbox that had (I'm sure) never been taken apart since new. ALL of the bearings were made in Italy! Did Henry import Italian bearings for his cars in the Model A years?
A little research confirmed to me that the bearing numbers quoted for Model A gearboxes were indeed, metric. Seems metric worked in the US in the 1920s/30s.
I would love to have been a fly on the wall in Henry's office in the day but first, I would make sure his fly swat was somewhere else!!
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My recollection is that the most recent "metrication" push in the US was when Jimmy Carter was president in the late 1970's. However, it was made as a "transition" with no deadline, which meant that both systems were in use simultaneously, rather than a drop dead "by this date, we will be metric". Naturally, inertia prevailed, and we still purchase our gasoline in gallons, still buy our potatoes by the pound, and still measure our speed in miles per hour. I do not sense any movement to change at this point.

I attended two university systems during my engineering education - one was completely metric (undergrad), and one was imperial (graduate). Same textbooks! Having been brought up using imperial units I at first found the metric units less intuitive, but eventually adapted. I think that if the United States had simply had the political will to mandate a switch to metric fifty years ago rather than dance around it, by now we would have educated two generations in metric and this would be a non-issue. As an interesting note, it appears that England may be gradually switching back to imperial units as part of Brexit.
 
JayJay, I haven't heard anything about England going back to imperial and I don't think they will. What you heard is probably gossip started by one of those Americans who found the conversion too difficult.
It sounds as though you (like myself) are of an age where we are quite comfortable with either even though the imperial system we used was different from yours. We converted in the late 60s/early 70s and I have adapted so well that I work in metric most of the time now except for some of the old, imperial measuring equipment my father used when he was working. In my work as a Land Surveyor, I started working with links and chains, then feet and decimals of a foot. I can convert from one to another in my head easily and from decimals of a foot to feet and inches. Then came metric. That only added another layer to things but didn't make it more difficult. Links to metres, feet to whatever - not a problem.
My children were born during the conversion and look puzzled when anything is expressed in imperial measure. Our grand kids laugh at it!!
 
Synchro909 said:
JayJay, I haven't heard anything about England going back to imperial and I don't think they will. What you heard is probably gossip started by one of those Americans who found the conversion too difficult.
It sounds as though you (like myself) are of an age where we are quite comfortable with either even though the imperial system we used was different from yours. We converted in the late 60s/early 70s and I have adapted so well that I work in metric most of the time now except for some of the old, imperial measuring equipment my father used when he was working. In my work as a Land Surveyor, I started working with links and chains, then feet and decimals of a foot. I can convert from one to another in my head easily and from decimals of a foot to feet and inches. Then came metric. That only added another layer to things but didn't make it more difficult. Links to metres, feet to whatever - not a problem.
My children were born during the conversion and look puzzled when anything is expressed in imperial measure. Our grand kids laugh at it!!
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One place where metric has largely taken hold in the US is in automotive design. Today almost everything automotive (except for Harley Davidson motorcycles) is metric, even "American" manufacturers such as Ford, Chevrolet and Chrysler (yeah, I know it's "Stellantis" since that merger with Fiat, but it will always be Chrysler to me). I ended my first run with Model As in the mid-70s and worked on metric motors for 45+ years - MBZ, Honda motorcycles, BMW motorcycles, and the like. I've had seven Toyota trucks over the years. Come early 2020s when I got back into Model As and I had to resurrect my imperial tools. Amazing how many I had stashed away.

My daughter and son went to school in the 1990s (both engineers - go figure) and were taught in metric. When they entered the real world they had to quickly switch back to imperial - we don't use 15 cm pipe for water lines here, we use 6".

And metal machining - we use decimal portions of inches (e.g., 1-5/8" is 1.625"), not fractions. But not in woodworking or sheetmetal fab. Talk about confusing!
 
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Getting back to the O.P.s problem. Clearly his protruding bearing is wrong. Is it THE problem. Probably. 3mm is a "small" sounding number to those unfamiliar with metric. As a machinist .120 is a huge amount. The normal stick out might be less than .060.i have seen hundreds of flywheels, and never one with a lip or shoulder. Something very wrong there. Either a misinterpretation of the problem or it is afu. A technical term I know. You have symptoms of a problem and you clearly have a bearing sticking out that is wrong. It is the solution to your problem, I don't know. But at least deal with the obvious and then see what else you might find. Model A issues are often composed of many layers, not just the obvious.
 
Hmm, not necessarily wrong

The flywheel at least unmodified does not have a step in the pilot bore

The crank sometimes has a recess step to allow the pilot bearing to seat deeper in the flywheel

J
 
JayJay said:
. As an interesting note, it appears that England may be gradually switching back to imperial units as part of Brexit.
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. Nope ! I don't know where that rumour came from, but although Brexit ( a self inflicted economic wound) has been responsible for a lot of stupid things, the United Kingdom certainly ain't switching back to imperial. Thank goodness.
 
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johnbuckley said:
. Nope ! I don't know where that rumour came from, but although Brexit ( a self inflicted encomic wound) has been responsible for a lot of stupid things, the United Kingdom certainly ain't switching back to imperial. Thank goodness.
Click to expand...

There is no future in going backwards!
 
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