Farm Equipment - CA knocking but it can't come in

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CA knocking but it can't come in

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=37260
Printed Date: 08 Jun 2025 at 12:44pm
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Topic: CA knocking but it can't come in

Posted By: SteveC(NS)
Subject: CA knocking but it can't come in
Date Posted: 14 Sep 2011 at 1:15pm

I'm in the process of setting my CA up for front snowblower and rear blade for the coming winter.

I've had a come and go knock in the engine that worries me.

The last time I had a knock and didn't let it worry me I threw a Rod through the block.

This knock is coming from the engine I rebuilt (or reassembled) to replace the one with the hole in the side of the block, oh, about 8 years ago.

The CA hasn't seen much use but every time I have used it I get a knock that comes and goes. The knock will actually lessen as I put the tractor under load and almost disappear!

Anyway, I dropped the pan and looked for missing or loose rod nuts or anything else I could get some movement out of indicating excess clearance. I found nothing and remembered I had rebuilt this engine so there couldn't be anything wrong (cough, choke).

Just looking for any ideas and wondering if a governor weight or some thing else could be the cause.

Incidentally the only similarity between my CA and Mike Noonans is the extreme narrow track of the rear spin out wheels!

Replies:

Posted By: 427435
Date Posted: 14 Sep 2011 at 1:19pm

You might try using a mechanics stethoscope to try and pinpoint the location of the noise. I've also used a length of 1/4" ID hose, with one end in my ear, to isolate noise sources.

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Mark

B10 Allis, 917 Allis, 7116 Simplicity, 7790 Simplicity Diesel,
GTH-L Simplicity

Ignorance is curable-----stupidity is not.

Posted By: Dakota Dave
Date Posted: 14 Sep 2011 at 1:25pm

take it apart and look for a busted skirt up by the wristpin.

Posted By: SteveC(NS)
Date Posted: 14 Sep 2011 at 2:33pm

Dave, would such a crack be visible from below? I really don't want to tear this engine down, it looks gorgeous from underneath, doesn't lack power and starts like it's anxious to work.

I have a running replacement waiting in the wings if it does blow but I'd rather not be breaking any more cast iron.

Mark, when and if I put the pan back on I'll try the stethoscope.

Any opinions on the worth of looking under the valve cover, it could have been a half speed knock.

Posted By: Walker
Date Posted: 14 Sep 2011 at 2:46pm

Rod bearings will make the noise you describe. Under load they will quit knocking. I'd get in there with some Plasti Gage and check them very soon. Blocks ain't very pretty with rods sticking out the side of them.

Posted By: GregLawlerMinn
Date Posted: 14 Sep 2011 at 2:54pm

You should also check out the thrust bearing. The front main has a "lip" that prevents the crank from moving back and forth; if it does, you will hear "knock" as the engine loads and unloads. Sounds like a loose main bearing, but not as steady.

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What this country needs is more unemployed politicians-and lawyers.
Currently have: 1 D14 and a D15S2.
With new owners: 2Bs,9CAs,1WD,2 D12s,5D14s,3D15S2s, 2D17SIVs,D17D,1D19D;1 Unstyled WC

Posted By: SteveC(NS)
Date Posted: 14 Sep 2011 at 7:09pm

Well, I guess it's gotta come out. Since I gotta remove the sheet metal and valve cover to get me some lift points I'll take a peek at the valve train.

Walker, I don't wanna plastigage and de-shim etc. under the tractor (I'm too old) so , it'll be a bench rebuild. I have 2 reground cranks complete with inserts in "inventory" so I figure that's the way to go.

Greg, I'll sure take a look at the thrust play when it's on the bench/engine stand.

In the meantime, I'll stuff in the spare engine I have that seems pretty good and give it a test this winter.

Thanks guys, I'll be back to you with progress.

Steve

Posted By: Walker
Date Posted: 14 Sep 2011 at 7:17pm

I'm old also, but never turn your back on me. I'll grab one of your reground cranks and disappear in an instant.

Posted By: Leon B MO
Date Posted: 14 Sep 2011 at 7:42pm

Couple years back I had a "small knock" too, the last time it started, it was just sitting there idiling, warming up. The #2 rod broke in half and made lots of noise. You know it's time for some work it just depends on how far do you let it go. Good luck.

Leon B Mo

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Uncle always said "Fill the back of the shovel and the front will take care of itself".

Posted By: CTuckerNWIL
Date Posted: 14 Sep 2011 at 8:12pm

My CA started with an on again off again Knock. It took me a while to figure it out cause I couldn't get the location using a big screw driver for a stethoscope. Anyway, someone on here suggested checking the front crank pulley because if the setscrew gets loose it will cause a knocking similar to a bottom end knock. When I checked the pulley it mover for and aft about .090 of an inch but the crank went with it. She's setting waiting for a rebuild now cause I don't have a reground crank on the shelf. LOL It needs sleeves and pistons too so when I get my spare crank ground, I will tear into it.

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http://www.ae-ta.com" rel="nofollow - http://www.ae-ta.com
Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF

Posted By: SteveC(NS)
Date Posted: 15 Sep 2011 at 1:10pm

OK, I guess I better Fess up. I have two reground cranks & bearings because I'm dumb.

when I got the first crank ground I ordered the bearings from somebody else. The crank came back 30 thou under but the bearings I got were 20 thou. In the mean time I got the idea to get another crank i had stroked so I asked for 1/16 stroke at 20 thou under.

When I picked the stroker the guy said "all I had was std. bearings so seeing I had to build up the throws I bulit up the mains too, so there all std, no extra charge.

Now I've got 2 ground cranks and only the stroker has brgs. so I had another crank and decided to get it done 20 thou under and ordered 30 thou under inserts for it.

Well, obviously the stroker went into the then project and the other cranks went on the shelf.

Back to the stroker crank you ask?, it seems there was a bit of confusion as to 1/16 stroke. He understood 1/16 throw, so I ended up with a crank that gave me 1/8" stroke!

I had to machine my head to accomodate the rise of the piston beyond the gasket.

Starting seems hard, I don't know if it's all increased compression or poor amperage delivery. That project got stalled due to my move from Ont. to N.S. it's an IB conversion and I hope to get back to it soon.