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Has anyone heard of 1954 235 Chevy blocks having Main Bearing dowels (or ma #1314539 Sun Jun 16 2019 08:04 PM
Joined: Mar 2013
Posts: 2
R
Ryleej3 Offline OP
Moderated
Has anyone heard of 1954 235 Chevy blocks having Main Bearing dowels (or mainline pins) and where do I find them?

Context:
My 235 Chevy straight Six in my 1954 Chevy Bel Air had a crack. Still usable but I need to replace it soon. I bought a new used numbers correct 235 (with hydraulic lifters). I pulled the new 235 block apart and sent to the machine shop. The machinist was about to order new main bearings but stopped short because the new used block I gave him didn't have main bearing dowels in it. He thinks the block had them at one time but they were removed when the engine was rebuilt prior to me owning it. I guess they are supposed to help keep the bearings from spinning. He says I need to find a set before we continue with the rebuild. Has anyone heard of 235 Chevy's having main bearing dowels? I'll pulled a few of these blocks apart and I haven't seen them before. If this sounds legit, do I really need them? Any idea where I can find a set? I've searched everywhere.

Re: Has anyone heard of 1954 235 Chevy blocks having Main Bearing dowels (or ma [Re: Ryleej3] #1314620 Mon Jun 17 2019 02:31 PM
Joined: Feb 2004
Posts: 18,691
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Hotrod Lincoln Offline
Boltergeist
No, they don't have dowels. The main bearings themselves have a raised nib on the back side of the bearing that fits into holes drilled into the main bearing saddles in the block. The later model engines, from 1956-62, use a different main bearing set than earlier models. Those bearings have anti-rotation tabs that engage the block and the main bearing cap at the parting line, with milled slots to accommodate them. Earlier bearings have the nibs in the center of the bore, top and bottom. Here's the two part numbers you'll need to look at:

1953-55: Federal-Mogul 853M These will also need a shim pack, F/M part number FSM-124S, to adjust the oil clearance if necessary.

1956-62: Federal-Mogul 960M These bearings do not need shims.

Be aware that there might be some overlap on the date of manufacture. The 261 we built for John's big pickup was supposedly an early model block, but the bottom end was machined for the later bearings with tabs instead of dowels. Since we already had the early style bearings on hand, I modified the block by drilling holes for the early-style bearings. Now either type can be used.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Has anyone heard of 1954 235 Chevy blocks having Main Bearing dowels (or ma [Re: Ryleej3] #1317832 Mon Jul 15 2019 09:16 PM
Joined: Jul 2014
Posts: 70
1
1Ton_tommy Offline
Wrench Fetcher
I have a second production '55 235 on which I changed main bearings in fall of '17. It has dowels pins in the block. Parts books don't list the proper bearings for early 55. I ordered mains for a 54 on the second go round and all was well or at least better. What a PITA! I had to drop the crank to change the bearings meaning I had to pull the transmission, radiator, timing cover, etc. I took the opportunity to renew the front and rear main seals and the clutch disc so it wasn't a total loss. Don't start this job in November outside.

Last edited by 1Ton_tommy; Mon Jul 15 2019 09:18 PM. Reason: change 1st production to 2nd production

51 3800 PU, 55 235 (w/cam, headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.
Re: Has anyone heard of 1954 235 Chevy blocks having Main Bearing dowels (or ma [Re: Ryleej3] #1317835 Mon Jul 15 2019 09:34 PM
Joined: Feb 2004
Posts: 18,691
H
Hotrod Lincoln Offline
Boltergeist
The change to tabs instead of dowels on the upper bearing shells was done mid-year 1955, according to the Federal-Mogul bearing specifications manual I use frequently. The early bearing set with the dowels top and bottom is F-M part number 853M. The later bearing set with tabs instead of dowels on the top side bearing shells is 960M.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

Moderated by  53moneypit, Woogeroo 

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