383 Street Fighter
I'm almost ashamed to admit this, but truth be told, I've never purchased a dual-plane manifold before. Sounds a bit odd, right? If you've followed any of the engine builds I've been involved with over the years, you'll find that I've always been into peak power figures and have had little concern for idle vacuum whatsoever. As for drivability, I've generally held a steadfast opinion that anything is drivable. Then again, my background has been more heavily influenced by dragstrip antics than street light blasts.
This time around, things are a little different. Recently I had the opportunity of cruising the streets of SoCal in two sexy hot rods: a '66 Chevelle and a '71 Camaro, both powered by mid-400hp 383s. And considering I rolled around in them for nearly a week straight, it hit me like a runaway train that I thoroughly enjoyed their mild yet potent street demeanor, and as a result, pushed me into the build you see here.
The angle of attack for this mule was to build something that could propel a 3,400-pound street machine out of its own way, but again, in a manner that wouldn't compromise streetability. This had to be something you could drive on a daily basis with little concern for anything but enjoying the road. It also had to have gobs of torque and only crave pump gas swill, which is the No. 1 reason I opted for the added cubic inches of a 383 with a moderate 9.4:1 compression. Handling the bottom end was Coast High Performance out of Torrance, California, while up top an Edelbrock RPM Air Gap manifold was mated to a killer set of AFR 195cc Eliminator cylinder heads. For the choice of cam, with the help of Tony Mamo from AFR, we felt Comp Cams' hydraulic roller with 224/236 degrees of duration at 0.050 and 0.502/0.520-inch lift on the intake/exhaust was the way to go. Let me tell you, the mild cam didn't hurt us one bit and this combination flat-out works.
It's hard to beat Coast High Performance's $2,800 short-block that comes with a 4340 crankshaft and rods, including the company's line of SRS pistons. If you're looking to shave a few bucks, Coast also offers a cast crank with 5140 forged rods and FPS pistons that are 75 percent stronger than their cast and hypereutectic counterparts for just $2,400.
On the dyno, curiosity got the best of us and we wanted to check out the differences between the Holley 650- and 750-cfm Street HPs. We figured the big numbers would come from the larger 750 while the smaller 650 would produce better street manners. We'll have to test the latter part of the theory once we drop it in the mule, but given the cubic inches, I'm fairly certain that the 750 will be just fine. The results: The 750 HP produced 491 hp at 6,000 rpm and 489 lb-ft at 4,600 rpm, which is 11 more horsepower over the smaller 650 HP with 480 hp at 6,100 rpm and 8 lb-ft over at 4,500 rpm. This baby even pulls well over 14 inches of vacuum at 850 rpms!
Admittedly, we searched for that last bit of power in hopes of cracking the 500 hp mark, but it just wasn't meant to be. We ended up testing a 1-inch open spacer followed by a 1-inch tapered spacer, only it didn't make a bit of difference on this combination. For what it's worth, we originally planned on using a set of 1.6 ratio rockers; unfortunately, we had the wrong rocker studs and had to instead go with a set of 1.52 rockers. It's hard to say whether or not that would have gotten us over the hump; that'll be a test for another day. Until then, read up and check out this bad boy. -HD