Small block 350 2-bolt build up.

[ladybird]

I am helping a friend build up the engine in his 1985 firebird. It was a 305 but he bought with a junk yard 350 2-bolt transplanted into it. I am trying to figure out what the block came out of. If I pull all the numbers off the block, is there a website that can tell me what the block came from? I want to know the exact car for part ordering purposes. Also is it possible to drill a 2-bolt block for 4-bolt main caps. He said he is looking to make about 400hp. Is it possible with a 2-bolt block? He really wants to use the engine I am just trying to get some info for him because im on the forums all the time anyways. Thanks for any info.

[five7kid]

You don't really need to know exactly what it came out of. The casting numbers from the block and heads is all you really need to know.

The block casting number is behind the driver's side row of cylinders, on top of the bellhousing casting. The head casting numbers are under the valve covers between valves/rocker studs. Get the casting number for each head, they might be different.

Go to www.mortec.com, you'll get the information about what those castings are. Come back with that info, and we'll talk about what you can expect. Most likely, the heads will not be able to support 400 HP.

A 2-bolt can easily handle 400 HP. You can drill the block for 4-bolt mains, but if you do, it's best to get aftermarket caps with the outer bolts "splayed" out, that pick up more meat and don't weaken the block. Believe it or not, factory 4-bolt main blocks are weaker than factory 2-bolt main blocks. The reason they went with 4-bolt mains had nothing to do with being able to withstand more power. For 400 HP, I wouldn't bother with 4-bolt main conversion.

[Chris 96 WS6]

Agreed. I'd just put a good set of ARP main studs in it and be done with it. It can get expensive converting to 4 bolt mains.

[five7kid]

I'd go farther and say that rod bolts are much more important than main bolts, including both the type and number of main bolts.

[Chris 96 WS6]

Agreed x2. I've frankly never heard of the mains failing on a SBC, 2 bolt or 4 bolt.

[ladybird]

The engine is a 69-80 350 2-bolt casting# 3970010
The heads are 80-86 305 heads casting# 14014416 1.84/1.5 58cc

[five7kid]

That's a pretty good combo. The heads would do a lot better with some 1.94" intake valves installed by a machine shop. A little basic port and valve bowl cleanup also does wonders for them. With those things done, they'll outrun most any head that was put on that block from 1969 through 1980.

If it is being rebuilt, you'll need to use pistons with a little bit of dish to them. The valve reliefs themselves usually add up to about 5cc, you'll need 15-20cc or so total of dish to keep compression in the pump-gas friendly range.

But, you can make a really nice running engine with that combination.