307 Chevy Engine Build - Danger Mouse - And Now for Something Completely Different

Taking a mundane 307 and turing it into a respectable performer

Rob Fortier Feb 12, 2007 0 Comment(s)
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As you've undoubtedly noticed, our Danger Mouse series has morphed from the constant reworking of the same basic engine to a series of performance-based builds on a variety of different engines. Many of these we're happy to say have or will soon find homes in a myriad of project cars, allowing them to enjoy the open road rather than just a thrashing on the dyno. So, in the name of diversity, this month's subject will be-believe it or not-Chevy's much maligned 307.

Chevrolet hit a home run when they designed the then revolutionary OHV small-block over half a century ago. But, were all the variations admirable pieces of mechanical art? No, not exactly. While all different configurations of the V-8 basically share the same concept, there were a few black sheep among the flock throughout the years-enter the "economical" engines.

Horsepower may have been the name of the game in the early- to mid-'60s, but by the end of the Flower Power era, economy started to enter the picture. Paling in comparison to the weak 262ci (110hp) engine that was introduced later in 1975, the 307, as well as the subsequent 305, was developed in response to increasing federal regulations and a continual consumer demand for better fuel economy. This resulted in a small-journal small-block with a 3.875-inch bore (same as the 283) and 3.250-inch stroke (same as the 327) compared to the 350's bore of 4.000 and 3.480 stroke. The cylinder heads were primarily the same small-valve type, only with a smaller quench area, which was again done for emission's sake.

While it may be a machismo thing for rodders to avoid the "three-oh's," many smaller trucks and hot rods would actually benefit from the non-350s. Sure, there is a definite loss of performance experienced from these engines, but not everyone needs 400-plus horsepower. In response to the extremely high price of gasoline these days, we wanted to come up with an engine that offered good all-around performance yet didn't empty the wallet every other day at the pumps. Knowing all of the above, as well as the fact that most non-350s are almost as plentiful as V-6s, we decided to see what we could do with a stock 307 and a tight budget.

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Running and nearly complete, we picked up this '68 307 for next to nothing.

As it turned out, another magazine project vehicle had just surrendered its old '68 307, which still had the Tonawanda stickers on the valve covers. It didn't smoke, used very little oil, had served its previous vehicles well, and only set us back $250-just what we were looking for! From there, we sat down and mapped out what we thought would be the most logical game plan for the future of the engine without having to touch anything in the short-block (unless we absolutely had to). Edelbrock E-Tec 170 cylinder heads, a Performer intake manifold with a Performer 600 carb, MSD Pro Billet HEI, and a complete COMP Cams kit that included a CS X4 262H-11 hydraulic cam and Magnum roller-tip rockers seemed to fill the bill perfectly-and didn't drain our entire account.

To perform our test, we hit up John Beck at Pro Machine and Eric Weinrich at Dyno-Motive, both in Anaheim, California. Beck would do the wrenching, while Weinrich would verify the results. With everything in our possession-including pulleys, a water pump, a fuel pump, a flexplate, etc. on the engine-we scheduled a day with Beck and Weinrich to see if we could turn the "red-headed stepchild" into an A+ student.

The 307 was placed on Weinrich's dyno with a stock QuadraJet, the vintage Edelbrock intake it came with, and points ignition-internally, it was anyone's guess on the contents, let alone the condition of them. As you could imagine, there was some slight cringing going on during those first pulls. But, lo and behold, the little guy put out some very impressive numbers on the baselines, which got us to wondering more about the internals. For a 37-year-old engine, a peak of 230hp at 5,000 rpm and 278 lb-ft torque at 4,000 rpm are quite impressive. What made those numbers even more impressive was the fact that after we had removed the stock cylinder heads, we finally learned the truth about the 307's internal components-stock bore with the same pistons GM installed in 1968! Somewhere along the line, a bit hotter cam had been installed, but other than that, it was as stock as you're going to find for an engine of this vintage. Now we wanted to see how strong the 307 would be with a few new goodies.

A couple hours were spent installing the COMP cam and lifters; bolting on the new Vortec-style Edelbrock heads; dropping in new stock-length COMP pushrods capped with Magnum rockers; installing the Performer Vortec-style intake and electric-choke carb; and finally dropping the MSD ready-to-run Pro Billet distributor in the hole. A new Edelbrock fuel pump was also used, but since it was still in good condition, we reused the older Edelbrock aluminum short water pump. A set of Champion plugs were gapped (0.045) and screwed in the new heads, the MSD wires run, timing set at 39 degrees, and the miscellaneous parts put on before Weinrich and Beck reconnected the 307 to the dyno. If there were cringing expressions before, the looks on our faces were now of eager anticipation.

The anticipation would have to wait 20 minutes or so, as Weinrich idled the engine at or above 3,000 rpm to properly break in the new cam. When the time came and the throttle was finally hammered, the little engine that could, did! For our collaborative efforts-not to mention the efforts of the new parts-the 307 put out a very respectable 315hp at 5,200 rpm and 330 lb-ft torque at 3,800 rpm. Our hopes of a 100hp gain fell short, but then that was a guess based on the lower baseline we had originally anticipated. For a stock-bore 307 with a mild 262/270 cam, aluminum 170cc heads, electronic ignition, and a strong 600-cfm carburetor, that's nothing to be ashamed of.

For a lighter vehicle, this is a perfect engine to stick under the hood. You're going to get plenty of power, have more than enough torque to move the weight, and just as importantly, you're not going to spend a fortune at the pump. If you're in the market for an engine for a new project (or an existing one) and want to keep things relatively simple, flip open the classifieds and start calling on some of those 307s (or 305s) you always see listed for almost nothing. Do what we did and you'll be thanking yourself for years to come.

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