Danger Mouse Part 10

By now, you're probably used to seeing us test the next bolt-on on or swapping in a new cam or changing rocker arms to see what kind of power Danger Mouse could make. Well, this month is no different, except our new cam and bolt-ons gave us over 600 hp on pump gas! And although the parts we tested this month were truly just bolt-ons, the power they gave makes their added cost a more than fair trade. Besides, when you've got an otherwise mild small-block under your hood that can kick out 600+ ponies at a moment's notice, who's going to fault you for spending a little more bucks to get it?

SUPERCHARGED POWER
While the key to power this month was the addition of a Roots-style Weiand supercharger, (a.k.a: a blower), we first had to install a couple of complementary components to make sure that the blower wouldn't blow the engine. The first big change for DM this month was the installation of a pair of Trick Flow Specialties (TFS) aluminum cylinder heads that we got from Summit Racing. The TFS heads did several things for DM. First, they lowered the compression from 9.25:1, which is what the iron Vortec heads gave it, to a more blower-friendly 8.5:1. The reason low compression is better for blowers is simple. By effectively forcing more air into the cylinders than the engine could normally breathe, the blower increases the volume of air that is subject to the compression ratio. And that extra volume of air creates much higher combustion chamber pressures, because any time you squeeze more air into the same size space, the pressure will go up. Increased cylinder pressure can quickly lead to detonation on pump gas. So, if we'd kept the original 9.25:1, the engine probably would have pinged and we'd have holes in our pistons. Besides, with a blower it's easier to make power by adding boost, so we choose to lower the compression ratio with larger combustion chambers in the TFS heads. Also, since they're made from aluminum, which tends to transfer combustion heat into the engine's cooling system better than cast iron does, the TFS heads helped further delay detonation.

The other change we made to prep DM for the blower was the installation of a Comp Cams Nitrous HP camshaft. While the name of this cam would lend one to believe it's strictly for nitrous engines, the truth is that both blowers and nitrous supercharge an engine in a very similar way. They both get more air into the cylinder then the engine could on its own, so a nitrous cam can substitute for a blower cam. And this cam is still mild enough for the street, but it did add some lift and duration over the last XE268H camshaft we ran (see: Parts 7 & 8). But, the supercharger also calms down a wild camshaft and you can easily get away with a lot more duration on the street once you install a blower. And the Nitrous HP camshaft is ground with a wider lobe separation angle, which blower motors typically like.

PUMP GAS POWER
At most Southern California gas pumps we can only buy 87, 89, or 91 octane fuel. Some other states have unleaded gas going up to around 94 octane and, while that's certainly better than 91, it's still not enough to keep 10-plus-psi boost from rattling your engine. Luckily for all of us, the chemists at 76 Racing have been inhaling fumes for way too long and they've cooked up a 50-state legal, 100-octane unleaded pump gas that's available at many 76 gas stations nation wide. If you can't find this pump gas in your town you can email for locations at: race76@pacbell.net.

The whole reason we bring this up is because as boost increased, we added the 100-octane gas to keep DM from detonating. During all tests, we monitored detonation using a knock sensor screwed into the block and some special electronic equipment to keep track of how much DM was pinging until we added the extra juice. Without the 100-octane gas, the detonation was slight, hardly enough to hear over the noise in the dyno cell, but it was clear as day on our monitor. And to get the most power possible on the very last two pulls, we increased ignition timing by four degrees and just to keep the knocking beast at bay, we topped off the 100-octane gas in the dyno's tank with a can of NOS Racing Formula octane booster just to be safe. The extra timing and high octane worked magic on our motor and DM is now officially a 600hp Street Mouse.

The 64cc iron Vortec heads...        read full caption The 64cc iron Vortec heads we'd tested in the past gave DM too much compression, so we swapped on a pair of larger 72cc TFS aluminum (PN TFS-30400013-CNC) heads using Fel-Pro PN 1003 gaskets.

To see how much power the...        read full caption To see how much power the blower added by itself, we first tested DM with a carburetor and Edelbrock intake manifold (see: Test 19).

The TFS heads require a longer...        read full caption The TFS heads require a longer pushrod, which Summit Racing offers under PN TFS-21407850. This photo shows the too-short stock pushrod under a Lunati Pushrod Length Checker (Summit PN LUN-80120).

In preparation for the blower,...        read full caption In preparation for the blower, we installed a Comp Cams Nitrous HP camshaft (NX274H). Contrary to its name, the cam worked equally well as a blower cam.

On top of the blower we installed...        read full caption On top of the blower we installed a new Holley 950HP blower carb (PN 0-80577) It had a very good fuel curve right out of the box, but after the first couple pulls, we increased jetting by four numbers to give DM a little safer BSFC figure.

Testing a blower like this...        read full caption Testing a blower like this involves lots of pulley swaps. We used this trick new Chicago Pneumatic (www.chicagopneumatic.com) 14.4v cordless electric impact wrench to speed swaps up. The tool is offered in both 3/8- inch (PN CP8730) and 1/2-inch (PN CP8740) drives.

Autolite plugs were used in...        read full caption Autolite plugs were used in all tests. The plug on the left is the cold blower plug (PN 3932) and the one on the right is the motor-only plug (PN 3923) after a few pulls on the dyno.

Pulleys are the key to making...        read full caption Pulleys are the key to making more power with a blower. The Weiand line of small superchargers has many different pulley sizes to choose from. We tested five different drive ratio pulley combinations.

Proper timing is critical...        read full caption Proper timing is critical with any blown engine and the more boost you run, the less timing you need. Adding race gas or octane booster can help make power by allowing you to run more ignition advance. We checked DM's advance using a dial-back timing light from Matco Tools.

Baseline Power
To find out just how much power the blower added, without any help from the cam or heads, we first tested DM wearing it's favorite Edelbrock Performer RPM Air Gap manifold and the same Demon 750 carb we've used in every test session except No. 8 (April '03).

Surprisingly, even with 3/4 of a point less compression and a lot more duration on the cam, the TFS heads cranked out 17 more peak horsepower and lost only 5 lb-ft of peak torque compared to the smaller-cam tests and the iron Vortec heads. However, average torque fell off as much as peak horsepower gained, which is the same result we've come to expect from bigger cams, less power down low traded for more power upstairs. In fact, the nitrous cam extended DM's top-end by more than 600 rpm, but it traded a lot of low-end power to get there. The lack of low-end can also be partially attributed to the lower compression ratio. If we had not been planning to add a blower, we'd never have gone with so much cam and so low compression. The loss of low-end would make the car drive like a pig. But the end result was still quite impressive on the dyno and if we'd had the time to test it normally aspirated on 87-octane fuel, we might have seen just a bit more power, which is something to think about.

7TH SERIES OF DYNO TESTS
Even tough we've skipped a few months while DM was being prepped for this undertaking, we'll still continue to number the series of tests consecutively. However, the last tests you saw in the April issue were done on a different dyno and involved only carburetors, so we've left those out of the numbering sequence. We begin this month with Test 18, which was the last test we ran at Westech, prior to building the engine for the blower. Test 19 is the normally aspirated test to see how much power the engine made in its blower-prepped configuration. And test 20 shows the power we made at maximum boost with the Weiand 177-cid blower installed. Although there isn't room to print all the blower pulley/boost combinations we ran, you can see more test results online at www.superchevy-web.com. Unless listed, no other changes were made for any test.

Test 18:
Scoggin-Dickey Vortec iron heads (PN SD8060A, 64cc chambers, 170cc runners, 1.94/1.50 valves), Edelbrock RPM Air-Gap Vortec manifold, Speed Demon 750 carb, Wilson 1 1/4-inch open carb spacer, Comp Cams XE268H camshaft (268/280 adv dur, 224/230 dur @ .050, .477/.480 lift, 110 LS) straight up. Comp Cams 1.6:1 Magnum roller tip rockers.

Test 19:
TFS aluminum heads (Summit Racing PN TFS-30400013-CNC, 72cc chambers, 195cc runners, 2.02/1.60 valves), TFS pushrods (Summit PN TFS-21407850), Edelbrock RPM Air-Gap Vortec manifold, Comp Cams NX274H camshaft (274/292 adv dur, 230/244 dur @ .050, .487/.501 lift, 113 LS) straight up. Comp Cams 1.6:1 Pro Magnum roller rockers.

Test 20:
Weiand blower running a 3.07-inch diameter top pulley and 7-inch diameter bottom pulley (228% overdrive, i.e. at 5,000 engine rpm the blower is spinning 11,400 rpm). Peak 10.3-psi boost at 6,500 rpm, 36 degrees total timing, Holley 950HP supercharger carb, 100-octane unleaded pump gas from 76 Racing Fuels & Lubricants and NOS octane booster.

Send your test suggestions to:

SUPER CHEVY MAGAZINE
Attn: DANGER MOUSE
774 Placentia Ave.
Placentia, CA 92870
Or Email: mike.petralia@primedia.com

When testing any blower on the dyno, it makes sense flog a bunch of different pulleys since that's how you make more boost and boost=power in the blower game. For this test, we ran DM in the most common drive ratios that would be used with this size blower on a 355cid small-block. Remember, as engine displacement goes up, blower displacement must also be increased. That means that a small 177cid blower like the one we tested would not really be the best choice for a big 400+cid engine. For that, you'd want a larger blower, like Weiand's 250cid unit. All of the small cid superchargers sold by Weiand operate in a constant overdrive condition, which means that they're spinning faster than the crankshaft at all times. While all the big 6- and 8-71 blowers we're used to poking through hoods usually operate under driven.

Test W1:
3.25-inch top pulley
6-inch bottom pulley
Drive ratio: 184% overdrive
Ex: at 5,000-rpm engine speed the blower is spinning 9,250 rpm
36 degrees ignition timing
92-octane unleaded pump gas from 76 Racing Fuels & Lubricants
5.0-psi peak boost at 6,600 rpm

Test W2:
3.07-inch top pulley
6-inch bottom pulley
Drive ratio: 195% overdrive
Ex: at 5,000-rpm engine speed the blower is spinning 9,750 rpm
32 degrees ignition timing
92-octane unleaded pump gas from 76 Racing Fuels & Lubricants
6.7-psi peak boost at 6,200 rpm

Test W3:
2.85-inch top pulley
6-inch bottom pulley
Drive ratio: 210% overdrive
Ex: at 5,000-rpm engine speed the blower is spinning 10,500 rpm
36 degrees ignition timing
100-octane unleaded pump gas from 76 Racing Fuels & Lubricants
8.0-psi peak boost at 6,500 rpm

Test W4:
2.85-inch top pulley
7-inch bottom pulley
Drive ratio: 244% overdrive
Ex: at 5,000-rpm engine speed the blower is spinning 12,200 rpm
32 degrees ignition timing
100-octane unleaded pump gas from 76 Racing Fuels & Lubricants
10.7-psi peak boost at 6,100 rpm