SBC Cylinder Head Decision

[75gmck25]

Also consider an option to get your compression up a little. The old 350 SBC only had about 8.2-8.5 compression ratio with 72 cc chambers, and I assume your new heads have 64cc chambers. You can use thinner head gaskets and it wil gets you a little more compression, but still run on regular gas. Gaskets run from .015 to .039 thickness so it can make a difference.

I used a 213/217 @ .050 Howard’s roller cam conversion with my aluminum heads and it has great low end torque. The relatively mild cam means my horsepower probably hits only about 300-325 with stock exhaust manifolds, and about 325-350 if I switched to headers. However, it has very “usable” low end torque for a heavy truck.

 

[rusted nuts]

307's were grocery getter engines. They also got a bad reputation with flat cam issues that didn't seem to effect other V8's at the time. There are better engines to start with that are cheap, 350. More CI is always better.

307 had more low end stuff than a 350 did though

 

[MikeB]

I never heard about the 307 cam problem, or why it would be unique to that engine. However, I think the little engine got a bad rap because there was only one version that I know of, and that was with 8.5:1 compression, small valve heads, and a 2-bbl carb. I'm not even sure dual exhaust was an option. Just read where GM made a marine version with a 4-bbl carb that made 20-40 more horsepower, depending on which article you read. It even used aluminum valve covers like a 302!

I want to add this: My 69 C10 came with a 307. The engine was totally stock when I bought the truck used. I ended up adding a Q-jet manifold from a 327 or 350, a 450 cfm Holley Economaster carb, and dual exhaust with "turbo" mufflers. Using the SWAG seat-of-the-pants method, I'd guess the engine made at least 20% more power than it did from the factory. And as a side benefit, the fuel mileage increased. Win-win!

A big part of that performance improvement was the dual exhaust, which I added a few months before the 4-bbl. The OE exhaust was very small -- 1-7/8 or 2" pipe with a highly restrictive muffler. It was only a step above having a potato in the tialpipe!

I actually gave that engine to a friend when I replaced it with a 350, but have always wished I would have kept it.

 

[Craig Nedrow]

I really like AFR, cause the parts they use are top of the line, Ferrea valves, Pac springs, often Titanium retainers. My K20 lives in the Cascades Wa ST, has had a circle track motor Crower cam on a 107 LSA, fair amt of overlap, knurly sounding, close to .500 lift, haul ass on the street. I also used it for towing a lot. Not optimum though, as the rpm moves up with a bigger cam. I build engines, to get one HP per cube is fairly easy now, but you will need better then regular gas, or it will detonate, unless you retard the timing until it is stupid, counter productive. Buy a used 454, thank me later.

 

[JKRamsey1991]

The motor is coming out of the truck in a couple weekends. Will tear it down and decide from there. Based on the feedback probably will go with the AFR's unless I run into unexpected internal issues.