I have recently torn down the engine in my 73 vette for a complete rebuild. This is not the stock 350 I am sure. I discovered that it is a 2 bolt main. This would not cause me undue concern but I am thinking of putting Nitrous on the rebuilt engine. My question is, should I search around for a 4 bolt main? Or would the 2 bolt be strong enough? Any suggestions would be appreciated.

Thanks
:cheers:

 

Lots of stock 350's for Corvettes were 2-bolt mains. If it were me, and I was building for competition, using nitrous, then I would want everything as strong and tight as possible. If it's just an once-in-a-while shot of nitrous for street fun, then if you build it right you can use a 2-bolt without much concern.

 

Yep. :yesnod:

 

I don't know how Chevy can get away with putting 2 bolt blocks in Corvette. GM is a bunch of cheap bastards. When you buy a Corvette you expect racing components and even the base engine should be a 4 bolt main like you find in most pick up trucks. On another note I don't think that 4 bolt mains are really needed. My engine is a 2 bolt main and I have been pushing around 400 hp for 15 years. I have spoken with many engine builders and they say that the 2 bolt is still not the weakest link in the engine.

 

I wouldn't rule out that your engine is not the origiginal, based on 2 bolt mains alone. As mentioned, many Vette's came with them, and starting in '73 when power and compression started taking a nose dive, GM started cutting costs and weight wherever possible.

If you are going to really hammer it with NO2 (150hp shot or more), you should either find yourself a 4 bolt-main, or even better, convert your block over to a splayed cap 4 bolt main. In the end, it will probably cost about the same. Most good 4-bolt main blocks, that haven't already been overbored, decked, align-honed, etc, are approaching $350-$400, about the same as buying a set of splayed steel caps and having your machine shop drill and align-hone your block to fit them.

It's not that level of NO2 would break the mains or crank, but the sudden increase in cylinder pressure can cause the mains to move around slightly. This is indicated by shiney areas between the caps and main webs upon dissassembly. The problem is that it causes significantly increased bearing and journal wear, as well as possible slight amounts of crank binding. At a minimum, it's not a bad idea to stud the 2-bolt with ARP hardware. For the extra $50-60 or so, it's cheap insurance.