To20 bad rear main

[Fergster]

I rebuilt the engine on this thing around 15 years ago and it made noise since basically first started. The noise stopped when I pushed the clutch in so I finally split the tractor and started looking for the problem. Nothing wrong with the clutch so I started it while split and started the diagnosis.

I ended up disassembling the engine to find the #3 bearing burnt up.everything else looked good. The engine had 25lbs of oil pressure which is right in the middle of the factory spec. Plus the pressure port is at the end of the main oil galley where the cross drilling for the rear main is. Not only that but the #4 rod bearing looked good.

The block had been furnace braized to repair cracks and align honed. One thing I did notice is the #3 main bore was .0008 to lose and the bearing clearance was .003 on the rear main.

The pump was rebuilt and checked out good. This time I machined the pump housing to get the end clearance down to .002 and I checked the discharge pressure and bypass valve. These things have that stupid oil pressure system that partially filters oil after going through the #2 main so they basically have an oil leak in the system.

I'm putting the thing back together now. I tightened up the rear main clearance. Did what I could to increase the pump volume by getting the internal clearances tightened up. I made a mandrel and spun the pump on the engine to check for internal oil leaks. Everything checked good. I never did find a smoking gun. Best I can figure is the pressure was to low at #3 due to too much clearance and the pressure drop from the leak in the center main. Any udeas?

 

[Ericp351]

You should have plenty of oil with factory by-pass sys./filter. The spring loaded ball should maintain your pressure, volume designed ample with
bypass. A loose brg., however , can and will rob your flow- with or without proper press. The fact that you had good press speaks well of your pump,
ever before you stoned it. Work on that loose brg.

 

[Fergster]

(quoted from post at 13:29:01 12/26/23) You should have plenty of oil with factory by-pass sys./filter. The spring loaded ball should maintain your pressure, volume designed ample with
bypass. A loose brg., however , can and will rob your flow- with or without proper press. The fact that you had good press speaks well of your pump,
ever before you stoned it. Work on that loose brg.

I agree but
003 shouldn't have been enough to cause problems. Another thing I was a bit worried about is that I wasn't getting any oil out of the oil galley to the deck for the rockers. The cam has an offset drilled hole that has to he lined up with the oil galleys to supply oil or timed I should say. Turning the pump with a drill I just started seeing oil come from the rear cam journal after about 15 seconds. It probably just needs to be running but I'm going to start it with the vc off to check for top end oiling.

 

[John Deere D]

Good day..Are you familiar with the terminology Bearing Crush? I have never worked on a T0 20..however,if the bearing shell was not tight in the block bore,then you have no Bearing Crush,and this can and will cause a lot of problems on the Journal as well as bearing bore.
Bob..

 

[Fergster]

yes im very familiar. The #3 main bore was 8 tenths larger than the max spec so the bearing crush wasn't enough. I don't remember what the bearing clearances were on the first go round but with the crank journal on the high side it still had right at .003 this time. I polished the main cap on a granite block surface plate to tighten it up some. It's less than .003 now

 

[Steve@Advance]

I'm sure you checked this, but the knocking associated with pushing or
releasing the clutch is often associated with the crank thrust bearings.

Never actually dealt with one, but they had some strange ideas that gave
problems. There were some aftermarket fixes, I think. Something to look
at...

 

[Fergster]

(quoted from post at 17:20:20 12/27/23) I'm sure you checked this, but the knocking associated with pushing or
releasing the clutch is often associated with the crank thrust bearings.

Never actually dealt with one, but they had some strange ideas that gave
problems. There were some aftermarket fixes, I think. Something to look
at...

first off appreciate all the responses. The thrust bearings which are bronze thrust washers in this case were in perfect shape. The reason it stopped knocking was that pushing the clutch in pushed the crank off the worn area of the rear bearing. After it ran a bit it still made noise. Thrust end play was a bit more than spec but was still only .010

 

[Ericp351]

.8 or 8 thou??? sounds like you were lucky your brg did not spin!---- or did it??? Over 1/16 shift can reek havoc on non chamfered oil holes!
Seams like you think you got her nailed down. If so-good. Anyway- full discloser from (another ??) old guy: Officially file-fitting caps when out of
style about when VJ Day Celebrations died down. That said- we all do what we do, right? I trust you remembered to punch-mark. Surfacing on a Granite
slab interesting. At work I had a True Plate for the Lap Compound. Go Clover!, Anyway , I now use a heave piece of Borcilicate Boiler Gauge glass at
home. Just trivia- but an old Model A guy used to swear by well worn-shiny rail track, Between Trains, of course. Sadly, I doubt he is still with us.
Good luck, rock on.

 

[Fergster]

First thats .0008 or 8 ten thousandths. The block was line bored and the bore is to tight on the front and the rear main bore was to lose. Not by alot .it will work. This is a 2000 rpm max old tractor engine if it was an 8000rpm supercomp 632 I wouldn't accept it. Taking a half thou off the rear main cap tightened the bore up a bit to get the bearing clearance better. I did it by lapping the cap with 320 on a surface plate. Having the block line bored again would cause other problems. Can you still get undersize cam and crank gears?. It's still over 2and a half thou. 2 would be where I would want it. Appreciate the response. I didn't find anything I can say definitely caused the problem

 

[Fergster]

I just started it and let it run about 10 minutes. It had 32 lbs of pressure at idle 34 full throttle

 

[Duner Wi]

You have good numbers IMO.

 

[pomester]

Can you still get undersize cam and crank gears?

They are not available. Depending on how bad you need one, I have a source which will custom manufacture over/undersized gears. I spent a few months overhauling a Z134, basically the same engine, and the block was stamped for .002 oversized. I searched and found no old stock gears anywhere. I got ahold of the original microfiche engineering drawings for the gears and found a firm in northern Indiana which will make gears to order. In the end, after boring the block and installing cam bushings, tolerances were close enough with standard gears that I didn't spend the money on a custom machined unit.

You will want to be careful with your line bored block, there are stories here and in the Ferguson Furrows magazine of tight gears and broken camshafts.

 

[Bruce(OR)]

Well, your gonna love this one.
Once you get that shiny new engine all put back together, Hee-Hee. . .
And the noise is still there~~ WHA?!!
Pull it back apart and replace the transmission input shaft main bearing.
Foot on clutch makes that input bearing stop rotating. Hence, NO NOISE.
Foot on clutch makes noise is usually the clutch release bearing.
Your shiny new engine thanks you.
That bearing you missed is still there.
Told'ja you would love it.

 

[Fergster]

The rear main was bad. Also I ran the engine on a test stand before I pulled it apart to verify it wasn't in the transmission