does it matter?
chevcamaro_86
02-04-2007, 02:43 PM
i am currently trying to find a 350 small block to swap for my stock engine in my camaro and my grandpa told me to make sure that the engine that i find is a four bolt main and not a two now i know that four bolts were built for higher performance but does it matter that much, can a two bolt be built up as much as a four?:uhoh:
MagicRat
02-04-2007, 10:14 PM
4 bolt mains do not give you any better performance, but simply have the capacity to hold up better under high revs and power output of a high performance engine.
Most 4 bolt main blocks, that are available used, were originally placed in trucks (all 3/4 and 1 ton 350 cid trucks were supposed to get 4 bolt blocks) and marine engines, which were expected to occasionally function at or near full throttle for extended periods of time.
Performance cars (Corvette, some Camaros, etc) often, but not always got them, too.
If you really want one, start with a light truck block, they are cheaper than the performance car blocks.
IMO a 2 bolt main block will do just fine, especially if you are not going to rev the heck out of it (5000 + rpm) for extended periods of time.
You can improve a 2 bolt block by using NEW high quality cap bolts (try ARP) specifically designed for the application. Also try using cap girdles as well, to support the caps.
Most 4 bolt main blocks, that are available used, were originally placed in trucks (all 3/4 and 1 ton 350 cid trucks were supposed to get 4 bolt blocks) and marine engines, which were expected to occasionally function at or near full throttle for extended periods of time.
Performance cars (Corvette, some Camaros, etc) often, but not always got them, too.
If you really want one, start with a light truck block, they are cheaper than the performance car blocks.
IMO a 2 bolt main block will do just fine, especially if you are not going to rev the heck out of it (5000 + rpm) for extended periods of time.
You can improve a 2 bolt block by using NEW high quality cap bolts (try ARP) specifically designed for the application. Also try using cap girdles as well, to support the caps.
chevcamaro_86
02-04-2007, 11:02 PM
performance is my goal is a two bolt main capable to handle the amount of power a four bolt can?
MagicRat
02-04-2007, 11:44 PM
performance is my goal is a two bolt main capable to handle the amount of power a four bolt can?
No , it cannot.
However, you would need to make some serious power AND drive the engine really hard to break a 2 bolt block. IMO its probably better to ask yourself if you really NEED a 4 bolt block.
As I wrote earlier, it is not just the amount of power the engine has, but its also the revs you will expect the engine to make. . IMO most streetable engines with reasonable camshafts that are not driven at the track will work just fine with a 2 bolt block.
If in doubt, start with a 4 bolt block. However, they are much more scarce and more expensive than a 2 bolt block. Be prepared to spend many hundreds of $$$ for just a rebuildable core.
No , it cannot.
However, you would need to make some serious power AND drive the engine really hard to break a 2 bolt block. IMO its probably better to ask yourself if you really NEED a 4 bolt block.
As I wrote earlier, it is not just the amount of power the engine has, but its also the revs you will expect the engine to make. . IMO most streetable engines with reasonable camshafts that are not driven at the track will work just fine with a 2 bolt block.
If in doubt, start with a 4 bolt block. However, they are much more scarce and more expensive than a 2 bolt block. Be prepared to spend many hundreds of $$$ for just a rebuildable core.
curtis73
02-05-2007, 02:05 AM
I agree. 4-bolts are stronger, but its not a big deal until you get to 450 or so hp. I've seen 600 hp on 2-bolts but I don't recommend it.
Don't fret over it. Unless you're going nuts with revs and hp, a 2-bolt is great. If you find a deal on a 4-bolt, get it. If not, get a 2-bolt and run it as-is. The 2-bolt blocks have a little bit more metal around the mains than the 4 bolts, so what you can do is have a machine shop drill and tap a 2-bolt block for 4 bolts and be a bit stronger for not much money.
In order of strength, it goes 2-bolt, 4-bolt factory, and a very slight edge goes to a 2-bolt modified for 4 bolts. Call a machine shop and ask how much that service is so you can factor it into your research. Keep an eye on Craigslist and the local paper. I have three 4-bolt engines right now. One I found in the paper for $250, another I got free when I picked up a free wasted boat (and sold the boat and trailer for $400 :)) and another I got free from a friend who is going through a divorce :(
Anyway, they're around. 2-bolts are fine for 95% of performance street engines. If you're going nuts and building a really hot 500-hp engine I'd go 4-bolt, but 350hp won't know the difference.
Don't fret over it. Unless you're going nuts with revs and hp, a 2-bolt is great. If you find a deal on a 4-bolt, get it. If not, get a 2-bolt and run it as-is. The 2-bolt blocks have a little bit more metal around the mains than the 4 bolts, so what you can do is have a machine shop drill and tap a 2-bolt block for 4 bolts and be a bit stronger for not much money.
In order of strength, it goes 2-bolt, 4-bolt factory, and a very slight edge goes to a 2-bolt modified for 4 bolts. Call a machine shop and ask how much that service is so you can factor it into your research. Keep an eye on Craigslist and the local paper. I have three 4-bolt engines right now. One I found in the paper for $250, another I got free when I picked up a free wasted boat (and sold the boat and trailer for $400 :)) and another I got free from a friend who is going through a divorce :(
Anyway, they're around. 2-bolts are fine for 95% of performance street engines. If you're going nuts and building a really hot 500-hp engine I'd go 4-bolt, but 350hp won't know the difference.
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