late model 350 blocks 2 or 4 bolt mains?

[bradh]

Hi, new to the forum. I just bought a decent 72 C10 with 150k in unmolested condition. It runs and drives great but it leaks oil, leaks tranny fluid and burns oil so I was going to go ahead and build a 350/th350 to swap into it later. I also have a factory LT4 roller cam I took out of my car so I would probably be able to use that in the late model roller 350 as long as I use the correct timing chain (I think, I'll have to dig some more to find out). My question is do late model 350s all have 2 bolt mains or do some have 4 bolt and if so which ones? Thanks.

[67sss]

find a motor you want, then check the #'s on Mor Tec and it'll tell you whether it's a 2 0r 4 bolt.

[WIDESIDE72]

They came as 2 or 4 bolt. Mortec is a good source. IMO, 4 bolt mains not necessary under 500 hp. I have a 450 hp 383 w/ 2 bolt mains. i did install ARP main studs.

[bradh]

Thanks, I've checked Mortec before and it's a great resource. I found a couple out of mid 90s 2500s for 250 each. I'm guessing they are 4 bolt so I'll probably go that route. I agree 4 bolt mains are not needed but most of the time a rebuildable long block cost the same so I figure why not have them, besides I've got 2 other 4 bolt small blocks in my other toys so why change.

[Bpokey]

The 5.7 in the trucks came with dished pistons which would lower the compression, the ones in cars supposedly have flat top pistons. I think it was so trucks would not detonate as much under heavy load. If you planned on a rebuild with new pistons this won't matter.

[bradh]

Picked up a 98 L31 5.7 Vortec shortblock today at the salvage yard. It came out of a county truck that they put a new shortblock in with the heads off the old engine after a valve job. The casting # is 10243880. It has a one piece rear main seal, roller cam, hyperereutectic pistons, PM connecting rods, 4 bolt mains, windage tray and 3/4" oil pump pickup. After I got it home I pulled the pan and took off one main cap and one rod cap. Looks like I might get lucky if none of the journals are scored. Cylinder walls have no ridge and still show hone marks. I'll take it all down the the machine shop and have it all checked out but it looks like I might get lucky and get to reuse the stock pistons and not have to bore the engine. The pistons have a .075 dish with 4 valve reliefs and the engine has .045 deck clearance. The head gasket compressed thickness was .025. From what I can tell the factory compression ratio on the L31 was 9:1 or 9.4:1 with a 64cc head. That should be just about perfect and my measurments back up those numbers. The best part was they charged me 50 bucks for it and told me to bring it back if the block is cracked or the bottom end is no good. It came out of a running truck that was using oil so I'm guessing it should be fine (the salvage yard did the work on the truck for the county). Right now I'm kinda thinking these Vortec blocks are the way to go. I've got a 71 Z28 intake and a Performer RPM laying around so I'll probably just put regular heads on rather than spring for a vortec intake although the vortec heads are very attractive.