Thread: Getting more power out of a 307

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From 1968 Chevrolet literature:

"200-HP TURBO-FIRE 307 V8. This standard V8 engine is all new. Two-barrel carburetor and automatic choke. Replaceable element oil filter. Uses regular grade fuel. 9.00:1 compression ratio."

Bear in mind, this was the stock configuration. As mentioned by Tech, this thing is 40 years old and may not be so stock any more..

Thanks Guys. I guess Ill find out how stock it is once we pull it apart.

Beautiful Nova, John. If the block has not been decked and it has flat top pistons, your compression ratio is somewhere between 9 and 10:1 with 305 heads. You can use a compression ratio calculator on one of several websites to determine the static compression as well as dynamic compression. Try the Keith Black website if you don't have one bookmarked.

I'd take a 307 over a 305. I had a mild one in a 66 pickup that ran pretty strong. Super Chevy built one a few years back called "Danger Mouse." Here's a link to the article.
http://www.superchevy.com/technical/...nce/index.html

Wished I'd read this earlier. Nova, in your very first paragraph, you stated "it's leaking from everywhere".

Don't want to stir you up, but an old mechanic like me would be wary-- an engine that leaks from everywhere can easily do so because of positive crankcase pressure- pushing oil out anywhere it can. And that pressure is produced by poor ring sealing.

Hope you've already ruled this possibility out.

Good luck!

I am also building on a 307, what aluminum head would work best??

Originally Posted by gte436e

I am also building on a 307, what aluminum head would work best??

Depends on what duty you have planned for the motor. A rule of thumb for a street/strip motor is to use heads with intake runner size at 1/2 cubic inches. 307 cubic inches X 1/2 equals choosing a runner size of 153.5 cc's. Moving up to the first commercially available aluminum cylinder head, if I were tasked with choosing heads for you, I'd choose the Edelbrock #60879 fully assembled units. These heads have the early manifold bolt pattern so you can use any of the standard early Gen I manifolds, although you'll have to use centerbolt valve covers. The small 165cc intake runners and 60cc chambers will be an excellent match for a "stroked 283" motor such as the 307. Springs are rated for max valve lift of 0.575", so you can run just about any cam you want to with them, within reason.

Cutting the block decks for 9.000" block deck height, using an Edelbrock #7310 head gasket and flat top pistons with a 1.675" compression height will put the static compression ratio at 9.74:1 and the squish at 0.038". I'd choose a cam with duration around 225-230 degrees at 0.050" tappet lift and use a 2800-3000 stall converter.

If you want, I'll put all the info into my DynoSim and choose a cam that will be tailored to your application. You may have to change the rear gear though, you can't run this compression ratio and a bigger cam using a stock 2.73 rear gear (for instance).

If I were not going to go to the trouble of building the motor and just wanted some aluminum heads on it, I might choose an Edelbrock with a larger chamber (64cc's), even though the runners would be larger and port velocity would be down some over the 60879 heads.

hey 63BoxNova, did you guys ever complete this project? if so how did she run? I have a stock (all original) 307, I found a set of 601 53cc heads 1.84/1.5 valves and I'm doing about the same thing on a budget. already mic'd the cylinders and crank, all is still within stock specs, planning on using stock pistons, crank & rods. bought new Clevite bearings, and a new set of stock rings. If you have video I'd love to see it. If anybody else would like to add their input, I'd appreciate all the help I can get.