I ran the numbers on what i was told was a rebuilt 350 turns out it is a 307?? My Bad--My 67 is not numbers matching --came origionally with a 6--origional sag 4 speed trans and 308 rear (10 bolt)--runs good near as i can tell rebuilt but now i don't know--Has aluminum intake and new edelbrock carb and rams horn exhaust--I was planning on putting aluminum heads but now don't know?? I'm not racing it so the 308's are fine--What would you do it it was yours and YES i am keeping it a long time --waited 45 years to get it?? Thanks in advance

 

GM's 307 did not last long, maybe until 1969-1972.
A PO of an '88 MCSS I owned had installed a '71 307-Eddy 600cfm/THM400 with OE 3.73 gears and it got 7 mpg. But, it did chirp second gear upshift.

Only problem with a 307 is the bore is too small, 3.875" diameter, for large valve heads. 2.02/1.6's do fit, but the cylinder wall shrouds the valve making filling the cylinder difficult.

I would look for another 350CID, '86 and later to get roller lifters and '88 and later to get at least, GM's TBI. for drivability. Of course, this means getting the ECM & harness from the donor vehicle and dist.

 

You could take the large journal crank from the 307 and stick it in a late model roller 350 block and balance it and you would have a high winding 327. Nice set of vortec heads and your set. Very nice late model 327 roller motor for not a lot of money.

 

I've had a 307 in a previous 69. Compared to a 350 of the same era, the 307 makes for a wonderful boat anchor.

 

It all depends on what you want to do with it. A daily driver, good street performance, mileage etc.. There's not a substitute for cubic inches, but if your looking for decent mileage and performance it all depends on how much $ you want to spend. If the 307 is running good enough for what you want, run it until it won't. The 327 is a great set up and I've had a very fast one that also got decent mileage. I've also had 350's that would out run it and a 383 that was smokin fast but both liked the gas stations to much.

As usual, decide what your wanting out of your car first and go from there. If you just want to pep up the 307 a bit, stick a set of Vortec heads and exhaust manifolds on it. The Vortec heads flow better than any cast iron head made and the manifolds will flow better than the ram horns. It's cheap mods for good gains of performance and not difficult to do. Why replace an engine that doesn't have problems?

 

Thanks guys--the 307 runs fine as is just not as peppy as i would like --I was looking at the patroit 85cc aluminum heads-with the P/S headers would be a tight fit--the engine i was looking at was Jegs 355 reman engine with aluminum heads 375 hp i think it was rated at for 3k$$ any thoughts on that engine--??