It had to be done. In one corner of the shop was our fresh 4.3L Chevy V-6 (see "The 3/4 350," Aug. '02), and at the other end was Vortech's new centrifugal supercharger system for carbs ("Vortech Blower for Carbs" in the same issue). Bringing the scenario to its logical conclusion, one would have to meet the other. The Vortech system was designed for the small-block V-8, but in our sick dreams, there was no reason it wouldn't bolt right up to the sawed-off six. We couldn't stand it until we proved ourselves right--so we did, and ended up with 501 hp and 437 lb-ft in the process. We also got greedy and managed to puke a head gasket at 12 pounds of boost.

 

Let's review. The 90-degree, even-fire V-6 in question shares much of its design with the small-block V-8, which is why the blower bracket bolts to the head and why the pulley setup works. Our lil' puppy is 0.060-over for 270ci with Speed Pro LW2256 forged pistons for 9.1:1 compression, and for beef it's got Milodon rod bolts, main studs, and a windage tray. The ported stock heads use Milodon 2.02/1.60 valves bumped by Comp Cams' biggest V-6 hydraulic roller, a 280HR with 224/224 duration at 0.050, plus Comp Pro Magnum 1.6:1 roller rockers for 0.560 lift. The manifold is an Edelbrock Performer, and in naturally aspirated trim we made 301 hp at 5,500 rpm and 316 lb-ft at 4,400 with a 650-cfm Mighty Demon carb. That's through dinky, 15/8-inch-tube Hooker S-10 headers.

 

Bench racing ensues. When we tested the Vortech S-Trim setup on our HT383 crate engine, power jumped from 476 naturally aspirated to 675 on 8 pounds of boost and 91-octane 76 Performance Products pump gas. Applying the same math--a 42 percent increase, or 1.76 hp per cubic inch--it looked like the 270ci wee 6 would make something like 425-475 hp. But it seemed like 500 hp was the magic number, and we were willing to see what it would take to get there.

We bolted the Vortech blower to our Vortec engine and added Electomotive's HPX direct ignition system because a distributor would not clear the carb enclosure. Everything else was exactly as it had been on the 383 V-8, including the 6-inch crank pulley and 2.95-inch blower pulley; this combo made a bit over 8 psi at 6,000 rpm on the V-8, so we anticipated much more on the V-6 with 112 fewer cubes. We even used the 383's 750-cfm Mighty Demon carb with 88/97 jetting and the secondary high-speed air bleeds cut down from 0.040-inch to 0.028. Remember that the pressurized carb box requires a boost-referenced fuel system so that fuel pressure increases in direct proportion to boost. We fooled with the V-6 timing and discovered that it liked 32 degrees total under boost on 76 Performance Products 100-octane pump gas. Then we whacked it good, and much to our delight, the little sucker made 475 hp at 5,800 rpm with a peak boost pressure of 9 psi.

As we noted with the Vortech on the HT383 engine, the rpm at peak horsepower and torque increased with the blower's ability to continue to deliver airflow as rpm climbed. In fact, the V-6 kept making more power the higher we revved it. It was a rare circumstance where the hydraulic lifters didn't float around 6,200 rpm, and the blower kept making boost until, on one glorious pull, the V-6 made 501 hp at 6,200 rpm and 439 lb-ft at 4,800. Then we tried another at 6,400 rpm and gacked the head gasket. You can't really blame it: We were cramming 12 psi into the poor engine and asking it to deliver a power increase of 70 percent over the baseline. That's about when stuff breaks.

 

02. There was no way this setup was going to work with a conventional distributor because the carb enclosure is almost as long as the V-6 valve covers, making it too long for a distributor to fit. We went with Electromotive HPX direct ignition, and this plug is needed for the distributor hole to prevent an internal oil leak at the lifter gallery.

We'd never had firsthand experience with the Electromotive HPX direct ignition, but we found it almost easier to use than a distributor. Shown here from left to right are the Crank Trigger Simulator, to mimic a signal and allow you check the spark or adjust timing without the engine running; a Remote Timing Control for on-dash adjustment of plus or minus 7 degrees of timing; the multiple coil pack, this one with three coils for a six-cylinder; the trigger wheel; the crank trigger sensor and two optional mounting brackets for small Chevys; the distributor plug; and finally, a MAP sensor that can be used to retard timing as the blower comes into boost for perfect streetability and mileage

 

04. Setting up the HPX is as simple as this: Just align the crank sensor with the trailing edge of the 11th tooth after the gap in the trigger wheel. That will provide 0 degrees of timing under 400 rpm (during cranking), or you can move to the 13th tooth for as much as 12 degrees of timing during cranking. We had to do that to avoid some backfiring through the exhaust because the coil packs fire companion cylinders simultaneously (power stroke on one cylinder, exhaust stroke on the other).

Here are the adjustment dials on the HPX. Once the crank trigger is set and the engine runs, you set the Initial knob to 0 and check the timing. Ours was 12 degrees--therefore, all the remaining timing numbers on the dials must be considered cumulative. For example, the Initial knob was set to 3 degrees to achieve 15 degrees initial timing (12 plus 3), and the Total knob was set to 20 degrees for 32 degrees of total timing (12 plus 20). It's all very easy once you mess with it. The HPX also has a built-in rev limiter and a timing retard that can be triggered by rpm or with an external switch (for nitrous or boost, for example). We used Performance Distributors Live Wires plug wires.

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One solution would be to add copper head gaskets and O-ring wire (SCE Gaskets makes 'em for 4.3Ls) and keep throttling, but it would be more prudent to fling a bigger blower pulley on there to calm down the boost, then be happy making a stone-reliable 450-475 hp all day long on 91 octane. Put that in your S-10 and smoke it.

 

The Shriek of Power
RPM	HP	TORQUE
3,500	245.2	367.9
3,600	253.7	370.1
3,700	264.2	375.0
3,800	275.0	380.0
3,900	287.4	387.1
4,000	299.3	393.0
4,100	311.2	398.6
4,200	321.8	402.5
4,300	331.4	404.8
4,400	340.7	406.7
4,500	349.5	407.9
4,600	362.1	413.4
4,700	371.4	415.1
4,800	380.8	416.7
4,900	391.5	419.6
5,000	401.6	421.9
5,100	414.9	427.3
5,200	424.3	428.5
5,300	434.8	430.9
5,400	445.4	433.2
5,500	454.8	434.3
5,600	461.5	432.9
5,700	467.4	430.7
5,800	475.1	430.2
5,900	480.6	427.8
6,000	488.2	427.4
6,100	495.9	426.9
6,200	501.4	427.4

 

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We really wanted to step on the V-6, so we worked with the Comp Cams team at 800/CAM-HELP to design a custom solid-roller cam based on the flow numbers for the cylinder heads and the knowledge that we wanted serious rpm and big boost. We installed the cam and got the engine running only to discover a huge loss of oil pressure. It turns out that the lifter gallery on theV-6 block is drilled much lower than on a V-8, and when the solid roller lifters were installed, they allowed oil to escape when each lifter was pushed all the way up at max lift. The hydraulic rollers have a deeper skirt and do not pose this problem. So we were unable to use our trick custom cam. We later found that the GM Performance Products race blocks have priority-main, V-8-style oiling that's totally different than the production V-6 blocks, and only those race blocks can accommodate solid roller cams. Dang.