Just bought this block from a guy at a swap meet for $200. Want to build a 383. The block casting number says 14093638.....roller block, 350, 2.45" mains 1 pc rear main seal. I checked the cylinder walls...its already bored to 4.030" ready to go. Went ahead and bought it. Better than paying $700 for a brand new one from GM. So I get it home....measure the main journals...they are at 2.65".....400 block size. Is this something that should concern me? The guy said he only bored the cylinders...nothing else. It seems Scat Cranks (who I was going to get a crank from anyways) would beable to get me a 3.75" stroke 1pc seal crank with the 400 main journal size....I need to call them on Monday and make sure and see what the price is.......should I just roll with it and build using the block...or should I call the guy up and complain? Is this something that was straight from GM or did someone modify the main journals?

 

You can buy bearing spacers for the mains. They've been around for a long time for people who wanted to put a 350 crank into a 400 block.

 

any drawbacks to using bearing spacers? I have heard of these. But shouldnt scat beable to make me a crank to fit everything?

 

I would assume if you ask Scat they will probaly make you anything...for a price...
The only problem you would have buying a special crank is just that its special...
It may be tough finding another block like yours if you have problems with the one you have...
I would find out about the bearing spacers first.....
You could probaly ask Scat thier opinion...

 

you might want to make sure you are measuring the mains correctly. I think the 2.45" is measured at the crank diameter, not the block journal size, due to bearing thickness. I can see the bearing thickness confusing the issue. I don't think a production block was ever made with 400 mains and a 350 bore, only the bowtie blocks had that configuration, and I think only 2 pc rear seal. You should double check before you have a custom crank made. Hope that helps.

 

Yeah I think thats what the problem is....I am measuring without the bearings in there. I talked to an engine builder today...and he said that if he remembers correctly...the 2.6x Im reading without bearings is correct for a 350 block. So when I get bearings...I get the standard bore one right? The non standard ones are only for cranks that have been ground down or something right?

 

the bearing size totally depends on the crankshaft. if you have a crank cut .010" on the mains, then you need bearings made for the additional .010" material. If you want to measure the stock journal diameter, you would need standard bearings. The journal diameter should never change, like even with a line bore, they correct by either milling the caps a small amount or using new caps, then boring the holes to the stock dimensions. In otherwords, the outer diameter of bearings never changes, just the internal diameter. HTH