It's been a long time since Danger Mouse (DM) has seen gains this big with only one bolt-on, well, ok maybe three bolt-ons if you count both carbs and the intake. Some of the coolest things about this month's power gains were that the engine didn't have to be revved any higher to get there-in fact, peak power came in at a lower rpm-and, along with the torque gains, there was a tremendous increase in mid-upper rpm range horsepower as well. DM did lose 5 hp at 6,800 rpm, but we'd gladly accept 25 more hp at 5,400 and 32 extra ft-lb of torque at 4,000 rpm any day!
So what made this month's extra power? A part that's not typically attributed to torque gains, due to its faulty, ancient reputation. The Weiand Hi Ram, (a.k.a. Tunnel Ram in some circles) has been around since the days of the Flat head and it's the sole reason we made so much more torque this month. In fact, this month's test revealed the most naturally aspirated torque DM has ever seen! And any 355-cid small-block that can make over 480 ft-lb of torque on pump gas, without a power-adder, is a serious force to be reckoned with.
Hi Ramming TechnologyIt used to be that Hi Rams were considered a high-rpm-only piece. But, what a Hi Ram actually does is simply "ram" the air and fuel into the cylinders, packing in more mixture than a low-rise manifold could. In days of old, the Hi Ram had a pretty nasty reputation as a temperamental part that could not be tamed for the street. But that's more likely to do with the fact that the Hi Ram was developed long before really good cylinder heads were available to average user. And without good breathing heads, the Hi Rams kind of lost their effect.
Also, carburetors have never been better than they are today and Holley's twin HP650s we ran worked perfect right out of the box, which couldn't be said the same decades ago. The fuel curve was dynamite and we didn't need to touch the carbs all day! Setting up the side-mounted, dual-carb linkage was a bit of a challenge, but after just a few checkout pulls on the dyno, we got it completely dialed in. None of this is to say that our day did not have its share of problems, one of which really ticked us off, until we found and corrected it. We've told Weiand about the problem and are sure that it'll be fixed by the time you read this story, so it's not something you'll have to worry about.
There's Probably More Power In ThereTwo things occurred to us while this month's test was going down. One was that we had the wrong cam needed to increase top-end power. The other was that we should've port-matched the Hi Ram for maximum effect. Our first problem is easily cured with another cam that we plan to test soon. It might lose a little torque, but should give us more top-end, and since we've already found lots of torque why not try to find some extra horsepower?
However, port matching would take us away from DM's "always off-the-shelf" parts rule we've employed from the beginning. So, even though there was obviously a mismatch between the cylinder heads and the intake manifold, as well as a mismatch within the two manifold halves themselves, we won't take the grinder to them just yet. Besides, the torque gains we got were so impressive that this is an awesome bolt-on in anyone's book!
Dyno Testing Part 25Instead of comparing this month's test, T42, to the last test from last month as we usually do, we're comparing it to a different test from last month, T40. That's because in that test we were running locked-out ignition at 38 degrees and 91-octane gas, which is closest to how we ran things this month.
Note that the power for T42 does not begin until 3,600 rpm. That's due to the fact that dynos load engines differently than cars do. Instead of accelerating up through the rpm band from right off idle like a car would, a dyno must first let the engine accelerate past the point of its lowest test rpm, which we've always set at 2,500 rpm for DM. Once past the starting point, the dyno actually loads its water brake harder in order to pull the engine rpm back down below its starting point an then the dyno releases the engine to accelerate up through the rpm band after the operator gives the command.
It's like trying to climb a hill at WOT, but that hill keeps getting steeper and steeper, so much so that your engine won't move the car anymore and the engine just gets bogged down! It's hard to explain, but keep in mind that with 1,300 cfm of carburetor sitting on top of the manifold, the engine does not meter fuel that well when loaded so heavily like this either. So sometimes the dyno does not act like a car. But, if this engine were in a car, we're sure that it would be able to accelerate strongly from well below 2,500 rpm.
Danger Mouse specs for Part 24 - Test 40:*Previous test from last month 355 cid, 12.5:1 cr, 4.030-bore 4-bolt Motown block, 3.48-stroke Lunati crank, 5.7-inch Lunati rods, Lunati domed forged pistons, Total Seal ductile iron Gapless top rings, Edelbrock Victor Jr. heads (64cc chambers, 215cc runners, 2.08" intake valves, 1.60" exhaust valves), Edelbrock Super Victor intake manifold, COMP Cams XR286R solid roller camshaft installed @ 105 intake CL (248/254 @ .050, 286/292 adv, .606/.612 lift w/ COMP 1.6:1 rockers, 110 LS), Carb Shop modified Holley HP950, 35 degrees ignition advance starting at 2,400 rpm, ramping up to 38 total at 5,500 rpm, 91-octane
Danger Mouse specs for Part 25 - Test 42:Same as above but with Weiand PN 1984 Hi Ram and twin Holley HP650 carbs, 91-octane
We're always looking for new ideas. Do you have a better one for Danger Mouse? Send your test suggestions to:
Super Chevy MagazineAttn: Danger Mouse720 Hundley WayPlacentia, CA 92870Or e-mail: firstname.lastname@example.org