whats the biggest down fall of the little 305. I have a 85 motor that Im going to rebuild for another project.(I know get a 350.) Why is the 305 such a looked over motor.The 85 factory cam seems one of the better ones offered in the 305. But to me the heads are suspect. Whats the best combo for this little motor.I guess I should also include that its being changed from MAS to speed density.Dont know if this would factor into the combo.Thanks Tim

 

Fro a smaller displacement V-8, the 305 is no slouch. It got GM through almost ten years as the primary engine in larger cars, and most light/medium trucks. Many lines had no 350 available during those years.

The fact that the architecture is common to many other Chevy V-8s doesn't hurt it from a parts availability and price perspective. It shares the same basic parts with the 302, 327, and 350s, and a lot of parts with the 400-based SBCs. The most significant differences are the piston diameter and crankshaft balancing. Nearly everything else is 100% compatible. The only differences with the 400 are the bore, crankshaft stroke and journal sizes, and the rod lengths.

The 305 has a very good bore/stroke ratio for producing significant torque while maintaining good control over combustion efficiency (emissions and mileage factors). The smaller bores actually help the durability of the engine overall, since the extra iron that could be cast around the cylinders (could be, but wasn't always) strengthens the block even further. It's a very stable casting either way. That same factor can also hamper cooling slightly, making heat transfer to the coolant a little less efficient. Still, a properly maintaind 305 can expect to outlive many other engines due to its inegrity.

The biggest negative is the smaller bore, and the necessarily smaller head/chambers. While this is great for low-end torque, cleaner burning, and mileage, it limits the valve size and possible arrangement, and squeezes the spark plug to what may be a less than optimal position for high RPM ignition efficiency.

If you're going to stay below 5,500 RPM most of the time, and can use more torque low than higher in the RPM ranges, and want an engine that you can count on for 200,000 miles, the 305 is a good basis.

That said, the 350 can be built to the same specification, with similar resutls. There is absolutely nothing wrong with the 305. For a few reasons, it is even more durable than a 350. In reality, you'll probably never reach those limits with either engine, so it comes down to a coin toss. Can you sacrifice a little daily driving mileage, or a little peak HP/torque?

As for the "best combo", that depends on what you intend to do with the engine. What works well in a 2,400 pound sprint/roadster may not be ideal in a half-ton truck that may do some moderate towing and hauling.

 

Wow, Vader,Thanks for the reply.The 305 is going into a 62 impala an low end will help move the car it weights 3450 compared to the car it was removed from 3273. Ive read that the 305 in stock form runs out of gas at around 4200 rpm. this car will be a cruise for the most part but would like handle more like a sports car. So Im looking for a combo to meet me needs.Im not knocking the 305 at all.Thats the motor I have and thats what going in the car.I was wondering why a 69 302 was a ruler of its time and the 305 was not. I just want the car to hold its own. but still be reliable. This goning to be a pro touring car.

 

- The 302 is a large bore/short stroke. 302's had the same bore as the 350's, but a 3.250 stroke crank instead of the 3.480. - They were good motors in their time, because they didn't have near as good of heads as we have today, and the smaller stroke(thus smaller ci) would rev higher on the same heads.
- As Vader said, the 305 is a great motor. Nothing wrong with it. - For all out hp, larger bore makes better use of better heads, thus is more desireable. So, many people dislike a 305.
- That being said, there are several people on this board making great power with 305's. For what you're saying you want out of the car, freshen the 305, put a mild cam in and enjoy.

 

I happen to have an old set of 283 heads, (13/16" plug), and was wondering if anyone had an opinion about putting them on the 305 in my '85 Trans Am, code "F". Someday it will need an overhaul, and I may as well have fun doing it! From what I've read, the TPI shouldn't have a problem with it. I'd appreciate any info, or enlightenment.