350 2bbl vs 350 4bbl

[NavyCPO]

Another Question.......  So my car is a 350 2bbl, and I'm wondering what is the difference between the 350 2bbl and 350 4bbl motors?  Other than 50HP!  Is it just the Intake and carb?  Did they use different heads?  Different pistons?  Do they still have the 10.25/1 compression ratio?  Any of you Engine Guru's out there I'd like to know the REAL differences between the 2bbl and 4bbl 1970 350's.  Thanks in advance!

[Scott S.]

I'm thinking the biggest difference will be that a 4bbl block is more likely to have 4 bolt main caps, as the 2bbl wasn't intended for the stresses a 4bbl would. (the 0010 block)

The cam, pistons, heads and intake will all also vary as well, seeing as the 2bbl was aimed at economy over power. I don't believe the 2bbl came with 10.25/1 compression from the factory.... But that ratio has a lot to do with the heads chamber size. (cc's)

[MC1of80]

Camshaft, dual exhaust. 

[stangeba]

My 71 350 4BBL came with single exhaust.

There are 2 bolts, not 4 bolts on the main bearing caps on my engine.

If I remember, I will ask my brother in-law who worked at Chevrolet at the GM tech center in Warren Michigan in the engine dept back then.

In 71 they lowered the compression ratio for the unleaded gas that was in the future.

[NavyCPO]

5 hours ago, stangeba said:

My 71 350 4BBL came with single exhaust.

There are 2 bolts, not 4 bolts on the main bearing caps on my engine.

If I remember, I will ask my brother in-law who worked at Chevrolet at the GM tech center in Warren Michigan in the engine dept back then.

In 71 they lowered the compression ratio for the unleaded gas that was in the future.

This sounds more like facts here.  I've also seen several 4bbl 350's with 2 bolt mains.  And my 1970 300HP 350 4bbl I used to have also came with single exhaust, so I know that some of the 4bbl 350's had 2 bolt M's and s. exhaust.  Would appreciate it if you could ask your brother, we could all benefit from this info!  Thanks!