Hi everyone I bought a 307 block(unintentionally). I've been looking into ways to get more power out of it and one thing I'm considering doing is boring it out to 4 inches and putting in 350 rods and pistons. I've already looked into te block its a 68 2bolt main block so the cylinder walls are thicker than the 70's 307. Anyone else tried doing this?

 

There isn't that much extra meat in the cylinder walls to bore them out anywhere near that. I used to have a 307 in a previous 69, and all I can suggest is to use that block as a boat anchor and put your money into building up a 350 block. A stock rebuild between the two will cost you the same, so it's not worth putting money into a 307 unless it was a numbers matching situation.

 

I've seen it done by a lot of people tho. N that's partially the reason why I wanna use this 307 with the 350 parts. So that I can have something better than my dieing v6. And the bottom ends fine all it needs is rods an pistons then it'll be good to go

 

While I build a 350 on the side*

 

A rare number of 283 block castings had extra thick piston wall thicknesses that could be bored out to 4", but no 307's that I ever heard of. If this has been done to a 307, I'm sure there's an article about it somewhere in internet land. Get your block sonic checked to find out. You'd definitely want to get that done before having any bore work done anyway.

 

There was a thread on here a while back regarding this...or a 302 to 350 build. Without knowing 100% for sure what material is in your block I would say going to 4" seems like a difficult task. Even if you can pull that much material away without going into the jackets you'd be mighty thin and would most likely have some issues. I know its apples to oranges, but I use have a ford industrial motor at work that has very very thin cylinder walls. It overheats in the cylinder, not the water which leads to horrific after running and just a very inconsistent fuel burn. Not saying it can't be done, but seems a bit unpractical.

 

Then what pistons would you guys recommend? Cause I can't find aftermarket 307 pistons anywhere and I want something a little bigger.im trying to get as much displacement as safely possible since its going to be a low revving na motor

 

Not anywhere? http://www.summitracing.com/search/p...size/5-0l-307/

 

Yea just found those yesterday. Weren't comin up when I originally searched. N I can't see why it would but does it matter if it says there for Oldsmobile?

 

Hmmmm..... never mind that link then, that's not right. The Chevy 307 has a 3.875" bore, the (Olds) ones shown are 3.80" based. No idea why Summit is referencing the Chevy 307 to those, it's a totally different engine.