Technical 302 GMC main bearing tech

OK I have searched everywhere to folind the main bearing bore sizes for the 302 GMC inline six.
I have a block that does not have the og main caps and I'm installing steel 4 bolt caps and need the factory main bearing bore specs.
Thanks in advance John Mullen

 

This is from my Federal Mogul book hope it helps

 

Do you have someone who will step bore the block? I have a 261 Chev block I'd like to save but have been unable to find someone to take it on.

 

I have a 270 block missing caps as well, so I'm watching with interest. I think the front cap will interchange with Chevy, make steel caps for 2 and 3. Did you know that GMCs manufactured for Staghound armoured cars had a Chevy style 4 bolt rear cap? These were made in a Chevrolet plant, not Pontiac. Here's a pic of one.

 

I just tore apart a GMC 270 if anyone needs parts, just pay shipping and they are yours.

 

@john mullen , what do we need?

Side cover?
Push rods?
Lifters?
Cam?
Distributor?
Oil Pan?

@Mainedrifter2 , does the crank have 4 or six bolts for the flywheel?

 

Yes, yes, yes, yes, I think so and yes. I’ll take some photos when I’m in the shop tomorrow and there are some photos in the classifieds. I’d love to see someone use them.

 

Gents - don't forget when align boring a gear driven cam engine, you risk losing the proper proper gear lash ...

 

Can that be compensated for? Bore it sideways a bit so the distance between centres remains the same?

 

Betcha you could buy a complete core (or 2) for what you'd spend align boring a 4 main GMC or Chev ...

 

I think you're right, but this was a fresh build that broke the center main bearing caps. Can't bring myself to scrap it.

 

If done correctly, you remove surface from the main caps. If the machinist knows his tooling he can take the minimum off the block and more from the cap to get the correct diameter.
The most difficult is adding steel main caps to a cast iron block.
Cloyes makes and stocks cam gears for Chevrolet/GMC that are made for engines that have been line bored.
The distance between centerline from 1937 to the last push rod inline is the same and so are the gears according to a Cloyes engineer I talked to 25 years ago when I wanted to buy offset keys and he said I didn’t need too. Just buy a set with 6 different keyways on the crank gear.