Before: 355 hp and 429 lb-ft
In the Aug. '09 issue, Ted Toki and the guys at Westside Performance stuffed a 4.00-inch crank into a 350 block as an alternative to the same old 383 build. While the primary point of the exercise was to see if the short-block could be built inexpensively and easily, we couldn't resist scrounging up some long-block parts for a test. Using a set of 882 iron heads that had been modified with a set of 2.02 intake valves, the engine made a respectable 355hp peak at about 5,000 rpm and a big, fat table of torque right off idle to about 4,500 rpm, with a peak of 429 lb-ft at 3,700. We could have been satisfied with the iron combo, but we wanted to test Edelbrock's newest low-cost aluminum head called the E-Street. For $949.95 per pair, the E heads fit right into the budget of this street stroker. While we were at it, we spiced up the whole deal with a dual-carb intake so we can sit and stare at it when we're not out burning rubber.
Edelbrock Dual-Quad Air-Gap Manifold
381 hp at 5,100
442 lb-ft at 3,800
After: 431 hp and 479 lb-ft
The glory hounds wanted to go directly to a single-plane and a 750 carb, but we decided to give up a little top end power for the fairground appeal of the RPM Dual-Quad Air-Gap. The primary differences between the Air-Gap and the standard Edelbrock C-26 manifold are the 1 5/8 inches of additional height and the space between the runners and the valley pan. That height could cause hood clearance issues, but this engine is destined for a straight-axle Gasser '55 Chevy, so it isn't going to be a problem. Edelbrock also warns that your stock HEI won't work on the taller manifold. The reality is that it does; we just had to get the timing perfect when we stabbed the distributor because there is little room for adjustment. Another option is to face the vacuum advance away from the carbs. This works on the dyno, but we can't guarantee it won't hit the firewall in the car. Another distinction between the two is the lack of an oil-fill tube boss, so if you want the 283/327 look, use the C-26. And neither the Air-Gap nor the C-26 has a provision for the stock alternator bracket, so you'll have to use an aftermarket setup. Edelbrock sells the intake alone or as a kit that includes two 500-cfm Thunder Series AVS carburetors, carb linkage, a manifold gasket, and a fuel line.
We ran the carburetors out of the box with the recommended linkage arrangement that opens the primaries on the front and rear carb simultaneously then opens both sets of secondaries when you hit WOT. We were pleasantly surprised with the fuel curve even though we were running 1,000 cfm worth of carbs. At full-throttle, the air/fuel ratio was around 11.5:1 below 3,400 rpm then cleaned up to 12.5 at horsepower peak. We decided to leave the carbs alone on the dyno even though leaning them out in the midrange would likely score us some torque. Instead, we were curious to see how they would run in the car in out-of-the-box condition, so we'll save that tuning for another story. The duals come with an electric choke on the primary (rear) carb and a manual choke on the front, even though a nice full-throttle pump shot in the morning usually does the trick without using the chokes at all. With 37 degrees of total timing in the MSD Street Fire, the manifold and carb swap picked up 26 hp and 13 lb-ft for a peak of the 381 hp and 442 lb-ft. The peak rpm remained the same; the engine just picked up a lot more power through the entire curve.
The Air-Gap is named for its design that separates the runners from the hot engine oil in
The bracket holes for the alternator go away when you replace the stock manifold with the
The RPM Air-Gap comes in a kit with two 500-cfm AVS carburetors, a linkage kit, a fuel lin
The AVS carbs can be set to open progressively (rear primary first) or at the same time (f
The first run at Westech was a straight comparison of the iron factory intake and the Air-