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

I am trying to find a set of 030 crankshaft bearings for my 1940 216. Some suppliers in the US have them available, but I am trying to look at other options closer by (and prefebly a bit more suitable for my budget)

Can anyone confirm if the early 235 as used in the US G506 1,5ton trucks used the same bearings as the CMP 216?

Alex

According to TM 10-1475 Chevrolet master parts and price list 1941-1942 the engine bearing model symbol (ALL) indicates common usage in all engines produced during that time. 216 and 235, car and truck.
This TM applies to vehicles specifically built for the U.S. Army but I think it would be a safe bet that Canadian production was compatible.

David

To add to the fun
 

Hi Alex and Dave

Just to add to the fun of working with these engines both CMP and other Chevys of the time period. I have found the engines to be a mix of babbitted and shell bearings. I have even come across babbited bearing shells that when you knocked out the babbit material would accept a shell bearing with no other modifications.

Having had 216, 235, and 261 rebuilt the machine shops have had no problems finding the over sized shell bearings. Also replaced bearings on one 216 with stock size shells without having the crank ground.

Do know that you can take the early military 235 and put it on a CMP 216 but you have to change the pistons as the US 235 was a flattop piston engine and the CMP was domed and there is less than "0" clearance.

Keep us posted on your progress.

Cheers Phil

David,

Thanks for the feedbac! I read somewhere that the splash oiler 235 and 216 used the same main bearings and your responce seems to confirm this.

Can I ask you if there is any sign of partnumbers GM 609383 and 608421 in your master parts list? Both should be oversize main bearing sets (010 and 020).... I wonder if it lists the individual part numbers of each of the 4 bearings in a set and if the US manual also uses the terms "for line reaming", "hand scraping" and "precision" like the Canadian manual.

Alex

Alex , I might have some bearings in oversize , will have a look , I am looking for my block for standard size .

book
 

I have a little book published by GM , it describes how to install post war precision main shells in a early 1937 -47 Chev 216

The book consists of slide film pics ( eg from a lecture ) and a step by step procedure with the engine in situ in the car, a 1947 Chev sedan

I will scan the book and upload if anybody is interested

Hi Mike am very interested.

No Alex, I can find no mention of precision, line reaming or hand scraping in the TM.
Part number 608421 does appear and refers to bearing unit, crankshaft. The listing has a note that reads :- 608421 Consists of (1) 603943 Front Bearing Unit, (1) 603944 Front Inter.Bearing Unit, (1) 603946 Rear Inter. Bearing Unit, (1) 604359 Rear Bearing Unit, (2) 839125 Dowel Pin.
There is no mention of what the size is (I therefore assume standard) or for what application they are intended, ream, scrape or precision
The TM makes no mention of undersize main bearings that I can see though it does list undersize con rods and oversize pistons and rings?
I can find no mention of P/No 609383 in the TM

David

Hi Mike

Id be interested in a scanned copy as well.

Thanks.

scan
 

The first pages .

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.............................................

Thank you Mike much appreciated.

Thanks everyone for all the replies, info and suggestions.

David; thanks for checking the manual. Interesting to see that GM 608421 is advertised by a parts supplier as being 010 oversize; if it proves to be Standard in stead, than maybe this is the solution for Maurice!

Thanks Maurice; I am after a full set of (preferebly precision) main bearings size 030.

Mike; Thanks for uploading the booklet; very interesting!

Phil; I am a regular on your website; so much interesting info...and I still have a lot to learn when it comes to the mechanical side of our beloved CMP's!

Indeed, it's about time I update my resto-log. My focus is on the engine and rear axle for this winter, as I hope to have the truck running, nex year!

Alex

hmm....Even though the Canadian C8 parts list does not list the set "608421", it does list the individual bearings "603944, 603946 and 604359"....but all marked "for line reaming". The front crankshaft "for line reaming" bearing is listed as "604943"....a typo in the manual maybe?

Alex

Alex
I have checked the TM and can confirm that all part numbers I have transcribed are as they appear in the manual.
This may indicate that one or other of the manuals is incorrect, but which one?
Somewhere there must exist a compilation of all bearing part numbers and their applications. All we seem to have are fragments of information that do not neatly dovetail.

David

bearings
 

I have sets of precision main bearings NASCO brand . But not 100% sure if they fit the 216 .They appear to be the correct size for a 216 . both 20 and 30 under . I found them in Uptons shed at Corowa , must be 20 sets .

I posted a query on the GMH facebook page with pics of the bearings.

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.

babbit
 

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 .

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! :o. 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

measuring
 

I have measured these NASCO bearings and they do measure up as 216 main bearings . I've got a feeling these are rejects or 2nd grade , they are oval shaped , maybe this is normal. They squeeze down to a round shape when the caps are tightened down ? They might be useless :confused

Alex, I'd suggest locating some post war (commercial branded as opposed to NOS military) this should come up with steel backed precision bearings. (std from 48 on)
It is probably worth the extra money for a recently made set, from a reputable manufacturer.

Mike; do you mean the radius of the bearings is bigger than the radius of the caps? I guess that's a good thing....as it clamps itself inside the cap, rather than around the crank, right? (wishfull thinking maybe :D)

Did you use the NASCO bearings for your C8 at the time?

Lynn; thanks again for your ideas. Maybe, getting a proper newly made bearing kit is indeed the way to go, but I have some leads, one of them a very good offer from Mike, so I want to see if this could be the solution for my engine.
But I agree...with so many wrong descriptions of NOS bearings sets around, it could be wise to spend some extra cash on a set from one of the Chev parts dealers in the US instead.

Talking about oval shaped bearings......Do two bearings shells clamped together by the caps from a perfect circle?......or an oval, with shims needing to be added to get the result to be a perfect circle?

Alex

Alex, I am not 100 % sure about the shims, but logic says they are left out with the precision bearings.
These bearings are made to fit a given size bore (tunnel) a part result of the factory line boring of the block when machined.
The precision bearings when paired do not form a perfect circle in this situation as they are usually "sprung" to some degree.(Is this what you have Mike?) This helps them hold in place during assembly (before the caps go on) I think this is the "nip" part of the motor reconditioner's term "nip and crush"?

These bearings also have "crush" Basically when the cap is pulled (torqued) down, the ends of the bearings at the split line are crushed together, forcing the shells into a tight fit with the tunnel bore. This is important as it stops the bearing from rotating in the bore, and it achieves a metal to metal surface contact, essential for heat transfer.
To follow on, the block bores and the shell backs should be cleaned with a solvent and only fitted when perfectly clean and dry.
BTW. the locating tab would not stop the bearing spinning and in modern engines the manufacturers don't use them.

bearings
 

My C8 has the original babbit lined rod bearings, I removed a few shims from each cap and it's been fine. I polished the journals before re-assembly with a fine emery cloth .

A good engine machinist will fit the new bearings in the caps , then he bolts the bearing caps down and tightens to the torque specification ( no crankshaft in place ) , then he measures the bore of the bearing with a accurate gauge . The measurement tells him what size to grind the crank to , normally they allow about .001"per inch of diameter for clearance . eg for a 3"diameter journal, they aim for a .003"clearance

Measuring the bearing bores after the caps have been tightened down ( no crankshaft in ) is very important . I think a slight oval is acceptable.

I think Lynn explained the crush concept well. Anyway I hope the NASCO bearings fit .

Alex , I found several sets 0.30 , and 0.40 in my stock .