im looking for a chevy 4 bolt main 350 block... i was wondering what year 4 bolt main blocks are a direct replacement for a l98 block... i know all gen 1 sbc are the same but i think some have little diffrences... im building an engine from scratch and a wanna use my aftermarket tpi system on it... i just dont know which block is physically externally identical to the l98 engine thats in my 88 gta.....

 

'87-up, as long as it's Gen I (including Vortec) and not Gen II or III.

 

thank you very much....

 

by the way, '87-up block or pre-87 block has nothing to do with your TPI system. That's about the heads.

 

Hey man, I also have the same prob. Well I have L98 in 87 Iroc with 173,thensome. But I have a built 355 with dometop pistons that I would rather have in thirdgen than the (S10 Roller I was going to put it in). I as well would rather use TPI then holley 750 but, I dont know either, if it will work. I do know that Mortec.com, or NastyZ-28.com will give engine, or head info. related to the numbers, on your block or heads. ( even Trannys). If you happen to find out anything to help us, hit me back. I will let you know as well when I find out. . . I do know as well, the L98 corvette heads started Aluminum in 87, but wont work with ours, without some troublesome mods(well emissions wise). . . And to think the vettes were better, LOL.

 

Don't forget about Chevy trucks and vans. Some had 4-bolt mains in them.

 

The 4 bolt main isn't significantly stronger than the 2 bolt for street use, don't worry too much about trying to find one.

 

Stock 4-bolts tend to crack where the extra bolts go into the main..... the weakest and thinnest part. A 2-bolt has held for me a number of times all the way to almost 600 hp, but it isn't to safe past 450 or so. If you got more then that, then just get splayed caps and get the block line honed.

 

not on a 350. on a 400, yes.

 

The 400 4-bolts are more susceptible because their larger main journals reduces the material even more, but it is the weak point in 350 4-bolt blocks as well.

 

A 2 bolt block with main studs is just as strong as a 4 bolt block. Probably stronger because of how the studs distribute the load. There's a different clamping force with studs.

 

well i have a 93 4 bolt main block that came out a of heavy duty truck.... its been bored and lined honed with new milodon 4 bolt main forged steel cap bolts.... is this a strong 4 bolt main....

 

A factory 4-bolt setup isn't significantly stronger than a factory 2-bolt setup. If you need more strength, buy a 2-bolt block, and have a set of splayed 4-bolt caps installed. Splayed caps have the outter two bolts going into the block at an angle, which is a much stronger setup.

 

This isnt a common issue though. By common I mean something that happens frequently. That is a weak point in almost any block configuration, but not necessarily a problem, like GM intake gaskets are. It seems all of the cracked 350 blocks I have seen have been through a cylinder wall(overbore) or across the deck surface. 400s, thats a whole nother critter.

 

Yep. Just depends how deep you want to get into the subject.

88fastgta, don't worry about 2- or 4-bolt main. Just get a good one-piece RMS roller lifter block and go for it.

 

oh i already have that 4 bolt main block.... im putting in my forged rotating assembly in it next week.... should be a very strong bottom end block... thanks for all your help..