The Manifold
474 hp at 6,200
440 lb-ft at 5,100
The tunnel-ram is the ultimate head-turner for the street-machine guy. In terms of average torque, horsepower, and screaming power at the top, there is no beating it. We scoured the Internet for an Edelbrock AMC UR-18 tunnel-ram and found that they have become vintage collector's items and therefore crazy expensive. For you Chevy, Ford, and Mopar guys, there are a million tunnel-rams in catalogs, at swap meets, and on the Internet ripe for the choosin'. We had the ram made at Hogan's Racing Manifolds for the purposes of this test. The upside to a custom manifold is that it can be made specifically to suit your particular engine needs.
To build torque on a small engine with a big cam, the intake runners on this manifold were 4.850 inches, about 0.500 inch shorter than the ideal length that Hogan calculated from our bore, stroke, and rpm information. The runners are also tapered 22 percent from top to bottom. This is another trick used to increase the speed of the air at low rpm. | 
The manifold also has provisions for an oil fill and a PCV valve. Since our original valve covers from Indy Cylinder Head have no provisions for either, this was handy. |
The carburetor bases are twisted to line up with each runner. Check out the straight shot each venturi has to the intake port. | |
The idea behind the ram is simple: Increase torque by increasing the length of the intake runner and therefore the virtual length of the intake port on the cylinder head, creating a column of air that fills the cylinder when the intake valve is popped open. In theory, this should shove more air into the cylinder.
After the ram was installed, we tinkered with the carbs at Westech. The Race Demon 650TRs worked out of the box, plus a bit of jet on the secondary side. | 
We haven't fully mathed out the street linkage yet, but on the dyno we used a kit from Weiand designed for side-mounted tunnel-ram carbs. |
Since we didn't order the manifold with bungs installed, we went to Fast Eddie's in Orange, California, for the how-to on the welding 'cause he is a better welder than we are. This is worth the $150 he charges. Here, he marked the location of the holes about 1 inch from the base of the intake and centered them. | |
On the engine dyno, all of our pulls were from 4,000 rpm to redline, because that's where tunnel-ram power lives. The ram beat the single-plane Torker manifold and 750 carb by about 10 hp at the top, boosting the torque peak from 431 to 440 lb-ft and adding an average of 9 lb-ft of torque and 8 hp average from 4,000 to the power peak. Plugging that info into the Comp Cams DeskTop Dyno just sneaks the Rambler into the high 11s. The program has been within 0.10 or so against actual track times, so we tend to believe it.