When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Rebuilding the car and trying to work out what mods to do on the engine (355 or 383). I want to confirm my understanding of what is there. I have the 3970010 block with 2 bolt mains (visually confirmed) but i understand it could be machined for 4 bolt. I understand it is a cast steel crank and cast Al pistons. Once I determine the plan I will certainly post and ask for feedback. Plenty of posts out there. Might as well ask about the value of machining for 4 bolt mains while here. Planning ~400HP. Is there value in doing that extra machining at that level of power?
TIA
john s
From: At my Bar drinking and wrenching in Lafayette Colorado
4-bolt mains are grossly over-rated. I run 2-bolt mains on a 500-hp 407 small block, and I shift it at 6800 rpm. A 400-horse engine will last forever with 2-bolts. Save your money - don't **** it away on needless, non-value-added operations.
From: At my Bar drinking and wrenching in Lafayette Colorado
4-bolt mains are grossly over-rated. I run 2-bolt mains on a 500-hp 407 small block, and I shift it at 6800 rpm. A 400-horse engine will last forever with 2-bolts. Save your money - don't **** it away on needless, non-value-added operations.
Rebuilding the car and trying to work out what mods to do on the engine (355 or 383). I want to confirm my understanding of what is there. I have the 3970010 block with 2 bolt mains (visually confirmed) but i understand it could be machined for 4 bolt. I understand it is a cast steel crank and cast Al pistons. Once I determine the plan I will certainly post and ask for feedback. Plenty of posts out there. Might as well ask about the value of machining for 4 bolt mains while here. Planning ~400HP. Is there value in doing that extra machining at that level of power?
TIA
john s
1972 base 350" likely has Cast Alum pistons as well as Cast Iron crank; not cast steel, not forged steel. Cast Iron crank is fine for 400hp sbc.
4-bolt main conversion on a 400hp 010 block sbc is waste of time & resources.
You can make that kind of power with a 350". Majority of significant gains are in the heads and cam. Choose piston in concert w/ cylinder head.
All Modern motors use thin metric ringpak: For many good reasons; but with no significant drawback I'm aware of.
Having a good ignition timing curve in a good quality distributor a requirement; perhaps have a pro with a distributor machine service yours.
There is power to be found in thin rings w/ less friction And in good oil control via pan w/ good windage tray & scrapers.
Perhaps consider acquiring a core L31 350" sbc Vortec OE roller cam truck motor, and build upon that base.
Might be helpful to acquire a more recent edition of a "How To Build Performance SBC" assembly manual.
Good advice above.
But there is really no replacement for displacement.
A 383 will run much stronger than the 33 cu in difference.
In the lower rpms, where you daily drive it, there could easily be 50+ lb Torque increases vs a 350.
They feel extremely strong on the street.
These days they may only cost a few hundred $ more.
'72 base 350 engine
