Chevrolet 216 235 (early) main bearings? The same?

[Lynn Eades]

Hi Alex.
I cannot confirm they are the same engine, or if they use the same bearings.
However, I can confirm that that the main bearing journals for the Chevy Cargo G 506, are he same diameters as Chev. cars from 1939 to 1951.

A "Motors Auto Repair Manual" describes The main bearings as "35 to 47 engines are Babbitt lined steel half shells. For replacement however, precision type bearings are furnished. These precision brgs. are of the same design as are used as standard for 1948 and later engines."

Your Question about "hand reaming" and "precision" bearings may be clarified a little by this: (my words)
The G506 book (TM 10-1557) explains a procedure where bearings are fitted and reamed to a finished size with a hand operated boring bar (which is first centered in the bell housing (clutch housing) gearbox pilot hole + front jig)
This operation could I guess, be carried out in the field.

I have heard of bearings being called "pre finished" (where they are made to first fit and then the Motor machinist line bores them to size)
What they mean by "precision" bearings, is a bearing shell that you just install because it is already finished to fit.

TM 10-1557 describes the main bearings : "Chevrolet main bearings are steel back babbitt- lined. The Babbitt is centrifugally cast or "spun in" into the steel lining. This method assures a positive bond" It continues.

Essentially the difference is Babbitt is very soft, will tolerate larger clearances and is somewhat forgiving. They can be adjusted (shims removed) The Babbitt is thick and by comparison The thin bearing material of a precision bearing (shell) when damaged, becomes junk.
The difference between the G506 motor (July 42) and the 50-51 car engine seems to be a very minimal difference in compression ratio. This may not sound much, but the crankshaft might be quite different. (counter weights?)
As Phil said, there is the pistons to consider, and there might be valve timing?
I don't know much about Chevs and the TMs don't give history or model comparisons.
I hope that's some help.

[Mike K]

Relining steel bearing shells with new babbit, it is possible to achieve good results with basic equipment . Some of the vintage car people with rare cars ( replacement parts not available ) have successfully relined steel bearing shells with new babbit in a home workshop . You need to find the correct flux and some new babbit . I'm not saying its a quick and easy job but the other option is to pay somebody 300-400 bucks per shell.

With babbit rods, if you have a lathe with decent throw, after the babbit reline you can bore the rods to size. Make a mistake, no problem , go back to the beginning and melt out the babbit . Try again .

Years ago at the Melbourne Showgrounds swap, they had a line boring demo setup, an old chap had the block set up and the cutters slowly went through each bearing .

[Alex van de Wetering]

Thanks guys; your reactions are very much appreciated!

David; I agree....there must be a typo in one of the manuals, as the other 3 bearing numbers do match. They were thorough though as the index shows the same number.

Lynn; thanks for the explanation on the different bearings. At first I thought the quality of the wartime blocks was rather poor which meant line-boring or hand scraping was always necessary....which is why I couldn't figure out why "precision" bearings would also work. Silly me! . That was before I noticed the line-boring type bearings only come in one size....and "hand sraping" and "precision" bearings in several oversizes.

I now understand the benefit of the line-boring type bearings (at the time)....from what I have heard there is a lot of "meat" on these bearings, which means the supply line would only have to provide one set of bearings which could than be line-bored to the neccessary oversize.....in stead of supplying several bearings sets in several oversizes. But, of course the downside is extra labour and equipment to do the line-boring.

The problem I have found so far in finding bearings for my Chev is that a lot of the Ebay adds have incomplete or incorrect decriptions....often it's not clear what type of bearings is being offered (line boring, precision etc.) or sets are mismatched or incomplete. One set currently being offered as STD bearings display the same numbers that David posted earlier...which according to the Canadian manual would make them the lineboring type!
Same with a dealer in France.....a set marked "010" again uses the same numbers, which would again make them the "lineboring" type.....which nowadays seems to be a rather expensive procedure at the engine rebuilders.


Mike; Yes, I did read about some tractor restorers here in Holland that do re-babbiting themselves...however I wonder how these bearings would hold up? Maybe for a tractor it would be good enough....but for a fire-breathing CMP?

Alex