VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc 216 Main bearings, what is the difference

I have weird question, I had to get a different block for my 41 Master Deluxe and I picked up a 1948 216 motor to use as a doner. So I am trying get bearings.010 over and they seem to be hard to get for a 1948-53, but 1941-47 are readily available.

Does anyone know the difference between these 216 blocks that makes the mains different. The rod bearings are the same for both date ranges so I was just curious. I have a good 41 crank that I can use If needed.

I have access to a machine shop and can do modifications if necessary

The 1948 (first year) has the newer and better precison type main bearings. They do not require line boring as the pre 1948 style did. Also they have thinner babbitt for lnger life betweem adjustments. Aso that allows for replacement f just one insert if necessary....
The rods are not as wide (bearing surface) due to the longer life thinner babbitt. Many went 100000 miles with out a rod adjustment.

Thank you for that information, I know the service manual shows that you are supposed to line bore the engine when installing main bearings. I kinda thought with fact that you can buy the early ones in all the same increment's as the later ones it wouldn't need to be line bored.

Also the replacement block GM sold later in 1950 fit 1941-1953 and I guess that would really cause a problem when rebuilding.

In addition to what Gene says,

I believe the main bearings in 1948 and later 216's were narrower.
So main bearings from the 2 engines will not interchange.

Especially the thrust bearing (#3 or rear intermediate bearing).

It has been about 48 years ago since I rebuilt the engine in my 37 but i am pretty sure that I bought precision main bearings for my 37 and it is still running. I did not have to line bore it and it is the original engine. I think they offered them for that engine at the time. I don't think they were for a later model but it has been too long ago for me to be sure. The rods were converted to insert bearings so I don't know about whether there was a difference in the rods.

Yes

I believe that after 1948, precision bearings were sold to fit the earlier 216's that formerly had to have their bearings line bored.
But the bearings for engines made 1948 and later still would not fit engines made 1947 or earlier.

The above is correct. After the year of 1948 Chevrolet main bearings for all 6 cylinder engnes were changed to the precision type for replacement.....you had to replave all three or 4 when used.

Thanks again for the info everyone, I guess I am just gonna just keep looking or waiting until they become available, especially for a better price..

I did find one person who has 1 set left but I am not paying $400 for just the main set, I am not that desperate for them.

Has the crank been turned or verified that it will turn .010??

A local supplier I use can get .020 fairly quickly but would have to search for the.010 however whether std or not they are all about $330.00. Ebay list a Sealed power set # 648M10 for $240.99 . Best I can tell it is for a 216 but do your checking as they do not specify 216 rather 3.5 Base engine.

The 1941-1947 216 and 235 engines used thesame main bearings...........the 1948-1953 216 and 235 engines used the same main bearings,

That is good to know Gene as there are others listed on Ebay but only show as for a 235 so I did not list them.

sorry to get back late, So here is the deal,

I took the 1948 block and the crankshaft to my friends machine shop to have everything cleaned up tanked and gone over.

We ended up boring the block to .020 over and the crankshaft cut to .010 under. If I knew it would be so tough to get .010 under I would have gotten .030 over because I can find the anywhere and for $125

The other reason is that I have a good crankshaft from the original motor with a cracked block the was completely rebuilt and never run.

I never looked under eBay for 235 bearings, but I'll look into that.

Yet again thank you all for the help.

Just a note;
Cylinders are bored over sized so require over sized pistons.
Rod and mains are turned under size so require UNDER sized bearings

.010" is desireale because larger udersizes may just have thicker babbitt to get to the smaller size.
Thicker babbitt cmpresses more and requires adjusting the bearing more often.

Did you try NAPA?

YES !! 👍

I was going to point that out too.
An over sized bearing would knock pretty bad! 🙂

In all fairness, I have seen this misstated far more times than I can remember.

The point on babbit thickness is an excellent one too.
Manufacturers may have thickened the steel backing, but we just don't know that.
So Gene's recommendation is a good one.

Sorry about the grammar mistake, don't know what I was thinking, probably had bearings on the mind.

So after trying different places (including the local napa and carquest) I ended up chasing eBay as Chev Nut and m006840 suggested.

I put in chevy 235 instead of chevy 216 and I ended up finding a set of Clevite MS163P10 main bearing under antiques for $60 shipped.

I went on google and looked into the Clevite vintage parts catalogue and these are the right bearings for the block I have.

I just received them today and they look perfect, I will be checking fitment this weekend, Thanks for all the information and help.