17th Dec 2015, 21:55

Both the Chevy 305 and Olds 307 were good, stout motors that can run forever. The reason why a lot of people say they're "bad" is because neither of them can make much power or have a lot of buildup potential.

18th Dec 2015, 16:23

If you are building an engine for power, a 350 is my best choice. I would also avoid the thin wall 400. Another nice choice is the 283 and 327. I do not especially like the 307 for any performance mods. A 427 is a great one, even over a 396 over cam concerns. 454 oil consumption. Go with a 350 crate.

24th Dec 2015, 03:15

Agreed. Another reason why a lot of guys see the Olds 307 and Chevy 305 as inferior motors is that they are basically the same engines as their larger respective 350 brothers, with the bore being making the difference in displacement. Because of this, swapping out one of these smaller engines with their bigger counterparts is easy and straightforward, with the mounts, exhaust, transmission, auxiliary components, etc. all being cross-compatible. Combine the fact that the Olds and Chevy 350 is more powerful and more buildable with the easiness of swapping, and there won't be much of a case for building up an Olds 307 or Chevy 305.

12th Jan 2016, 01:09

The 307 found in 1980-1984 GM models is a decent performer for its time. 1985 and newer GM redesigned the cylinder heads, instead of adding fuel injection to meet emission standards. Outside of a few Cadillacs and special editions like the Cutlass 442, the 307 was one of the only engines to actually lose power in the 1980s and become even more anemic. This while every other V8 in its class started to get a little power back (including the Chevy 305 and Ford 302).

Any true Olds enthusiast knows I am right... The 1985 and newer 307 V8 horsepower and torque figures are almost the same on paper, but the intake and exhaust ports are so tiny on the newer engine, that it simply cannot breathe above 3000 or so RPM. GM had the nerve to use this boat anchor in its full sized station wagons along with the Cadillac Brougham all the way to 1990, the largest passenger cars in the company. It was almost as bad as the Oldsmobile 350 diesel as far as acceleration.

13th Jan 2016, 01:03

The best remedy for a 307, even though it's a 300,000 mile motor when taken care of, is to swap it with an Olds 350 or 403 and delete all the emissions B.S. if you're in an area that doesn't require inspections.

This also goes for the Pontiac 301 used in the late '70s - early '80s. Another good motor, but a 350 or 400 Pontiac would be better in its place.

16th Jan 2016, 07:38

The issue is that the stock THM200-4R transmission in most of these early-1980s full-size Oldsmobiles can't handle the increased power, so it will need to be rebuilt and upgraded.

Removing the emissions stuff from the later Olds 350 and 403 engines doesn't necessarily yield a real power boost. It takes some upgrading on the engine to really get more power out of them, and even then, you'll be limited by the later engines' thin-wall casting blocks, as those can't handle too much power.

16th Jan 2016, 22:20

I wasn't saying to make a race car. If that's the case, a 455 will do. Any small block Olds such as a 350 or 403 will bolt right in place of a 307 and will supply the power that these cars need; backing the motor up with a 350 trans will also help.

If doing one of these swaps, removing the emissions components won't give you a gain of power, but will make the engine a lot less cluttered such as deleting the smog pump and all the hoses to the exhaust manifolds that cover the engine, and using a Qudrajet from the late '70s that wasn't computer controlled. Really the only emissions delete that will boost a little power would be removing the catalytic converter.