Thread: 4-bolt main or not

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i just bought an 82 chevy truck. it has a 350 and i need to know if it is a 4 bolt main. the dude told me that it might be a 4 bolt because it has a bigger then norman harmanic balancer and he said something about the location of the oil plug or filter. i dont know if that is enuff info. if anyone can help that would be cool

jerry

There is no way to tell from the outside.

82 was a big gas crunch year like now, they strayed from bigger is better. is it a 1/4, 1/2, 3/4 ton truck? it is pretty hard to truly tell without dropping the pan. unless you are going to throw alot of horses through it, it will be fine.

Look for the casting numbers on the block. They are located behind the left head on the flange where the bellhousing bolts up. If it is a 3970014 casting, it is a regular 2-bolt main. This is the most common of the 350 castings. If it is 3970010, there is a 50% chance that it is a 4-bolt. If it is a 3970010, look for a small oil plug on the front of the block, near the top center between the base of the intake manifold and the top of the water pump. If that little plug is there, it's a 75% chance it's a 4-bolt. As Mooneye said, though, you can't be 100% sure until you pull the pan off. There are other casting numbers that have 4-bolt mains also. If the casting numbers begin with 14 and end with 776, 777, 778, or if it says 5.0L next to the casting number, it's a 305...

A 2-bolt block is good for occasional forays into the 6,000 rpm range and are plenty good enough for the street. Most of the time we are loafing around at 3500 or less. If you are going to thrash it frequently at the drag strip and consistently twist it up above 6500, then you need a 4-bolt.

If you have access to a borescope, run it up through the drain plug hole.If not, I'd drop the pan.

I thought it would be nice to have a borescope, so I began pricing them the other day. YIKES!!!!!

Hey Rich, just keep telling yourself " it's only money ". Hmmm, maybe that's why I'm always broke?

if your going to twist above 6500 you need a what?????????????????? i just had to say something

Maybe you could borrow George W's borescope he's done with it now.

Originally Posted by JeffB2

Maybe you could borrow George W's borescope he's done with it now.

How many horses is it generally safe to put to a two bolt?

If your going to spend enough so that it matters, buy the right block also.

I think I read in another forum that the machine shop doing the build could machine your 2 bolt block to 4 bolts?

According to my machine shop.... In the realm of street engines, 4 bolt vs 2 bolt is the most overated SBC issue.

In my opinion, the 2 or 4 bolt controversy hinges on several things. The weight of parts in the reciprocating assembly, the rpm's and the power being made. You might be able to spin a 283 to 7,500 or even higher with no problem on 2-bolt mains, but trying the same thing with a 383 might end in disaster if using off the shelf parts. With super light parts, you could probably do it time and again. You might bolt a 4-71 onto a 283 and blow it up at 5,500 because power exceeded the design of the webbing in the block. I'm talking in a relative manner here, so take it with a grain of salt.