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Aftermarket Parts - Are Premium Parts Worth The Price?

We Test A Pile Of Speed Parts To Discover

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Parts List
DESCRIPTION PN SOURCE PRICE
Edelbrock Performer RPM Air Gap 7501 Summit Racing $209.88
Edelbrock EPS 800-cfm carb 1412 Summit Racing 304.95
Edelbrock C-26 dual-quad intake 5425 Summit Racing 259.95
Edelbrock Air Gap dual-plane kit 2025 Summit Racing 999.95
Edelbrock finned valve covers 4145 Summit Racing 155.95
Edelbrock dual-quad air cleaner 4235 Summit Racing 119.95

Dual-Plane Vs. Single-Plane Vs. Tunnel-Ram
Much of the action that happens on the street is influenced by dragstrip chic-of-the-week. That includes such audacious displays of horsepower as 8-71 blowers and tunnel-ram intake manifolds protruding through the hood like a real-world version of a Rat Fink cartoon. Much of this is done strictly in the name of fashion, but there are those hard-core car crafters who believe in tall-runner manifolds. We wanted to see for ourselves, so we fashioned a quick comparison test for our Dart-headed Lunati 383. Configured with the Dart Pro 1 Platinum 215 heads and 280 Comp roller cam, this engine was ripe for an intake manifold face-off. Summit has long advertised a budget-based Weiand tunnel-ram intake configured with a pair of 600-cfm Holley carbs at an affordable price, so we tagged that as our eight-barrel heavy-hitter. For comparison purposes, we decided on a good single-plane intake and came up with one of Holley's Keith Dorton-designed single-planes. Then just to make it even more interesting, we decided to throw down one of Weiand's new Stealth Air Strike dual-plane intakes as the baseline. This way we would test the entire range of intakes from dual-plane to single-plane to tunnel-ram.

Dual-plane manifolds are known to enhance torque based on a longer intake-runner path compared to the shorter intake length of a single-plane manifold. The tunnel-ram offers the best of both worlds with longer intake runners like a dual-plane combined with a straight shot between the carburetors and the intake ports. The main reason tunnel-rams aren't more popular for the street is the simple issue of hood clearance. Not everybody wants to carve holes in their hood.

As for our test, theory dictates that the dual-plane should make the most torque, given the smaller plenum and stronger signal to the carburetor. The single-plane should make more peak horsepower than the dual-plane but at the sacrifice of midrange torque. The tunnel-ram should best the single-plane in peak power and in theory generate a solid torque curve as well. The only hiccup in this concept is the size of the tunnel-ram's pair of carburetors and dialing in a decent fuel curve.

After we were done making all kinds of noise, we immediately noticed that even with a strong 480hp small-block, the dual-plane intake still made the most overall power of all three manifolds. Weiand's Stealth Air Strike dual-plane beat both the single-plane and the tunnel-ram in torque, and the only place the single-plane intake combo made more power was at the top of the rpm curve. Given that scenario, our money is on the dual-plane every time with a combination like this.

After bolting on the tunnel-ram with a pair of 0-1850 Holley carbs right out of the box, we discovered that perhaps the twin 600-cfm carbs were a bit too much for this engine combination. It became impossible to load the dyno below 3,500 rpm at wide-open throttle, necessitating testing the tunnel-ram system from 3,700 rpm and above. Plus it appeared from the testing that the engine really wasn't happy until at least 4,500 rpm, where the induction system seemed a bit more stable. But only around peak horsepower did this system show any kind of advantage over the dual-plane, and then only by a couple of horsepower. Part of this disadvantage came from the fact that the 4160-style Holley carbs use metering plates in the secondaries rather than metering blocks. Without additional metering plates, we couldn't adjust the secondary metering. This is something you should put on your shopping list should you decide to add one of these tunnel-ram kits to your small-block. We couldn't convert to metering blocks since the fore-aft carbs would then be too long to fit on the tunnel-ram. It would have required placing them sideways, but we didn't have the proper linkage to accomplish that.

Based on input from guys like Pontiac expert Ken Crocie, a choice of the smaller 450-cfm Holley carburetors would have resulted in a much cleaner-running engine and more powerful dyno curve that would have allowed us to start the test at a lower rpm and generate stronger torque numbers as well. It's possible that fuel metering was not quite as good as it should be because the flow velocity through the larger 600 carbs was just too slow to accurately meter the fuel. Another advantage of the 450 carbs is that they are slightly less expensive. Since this test was in the midst of our mad dyno thrash, we didn't have the luxury of time to dial in the carburetors, but with a little tuning time we could have made this combination work much better, especially in the midrange and lower-rpm levels.

Parts List
DESCRIPTION PN SOURCE PRICE
Summit tunnel-ram kit, 600 cfm CWND403S Summit Racing $749.95
Summit tunnel-ram kit, 450 cfm CWND303 Summit Racing 709.95
Weiand tunnel-ram manifold 1984 Summit Racing 279.95
Holley Keith Dorton manifold 300-110 Summit Racing 239.95
Weiand Stealth Air Strike manifold 8501 Summit Racing 209.95
Holley 750-cfm mech. sec. Street HP 0-82751 Summit Racing 509.95
Holley 450-cfm mech. sec. carb 0-9776 Summit Racing 29.95
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