A tiny blower, off-the-shelf aluminum heads, and a small green carburetor running E85 fuel
Two of our most successful dyno tests last year involved the Magnuson-supercharged, Vortec-headed, 350ci small-block Chevy that appeared in the Sept. '06 issue ("Big Power From a Little Blower") and the Nov. '06 issue ("The E85 Solution," the story on dyno testing a 12.5:1 compression small-block Chevy on E85 ethanol-gasoline blended fuel). Like some of the best duos in history-Batman and Robin, Abbott and Costello, Rogers and Hammerstein-we decided that partnering that 105-octane ethanol fuel with a blower would be a very successful merger.
Here's why this works. As you may remember from our first E85 story, ethanol offers up roughly 30 percent less Btu heat-output per pound of fuel compared with gasoline. That means to make the same power, we have to use 30 percent more fuel. This requires basically a methanol-style carburetor (or 30 percent larger fuel injectors with EFI) to make up the difference in fuel flow. While this may not sound good on the surface, keep in mind we're talking about a 105-octane fuel (R+M/2). Plus, E85 sells around the country at roughly $2.80-$3.00 a gallon, which is far cheaper than race gasoline at the same octane rating. True, E85 is not available everywhere, so the difficulty will be for those of us in states where E85 is not yet available, which includes California. For you Midwest horsepower junkies, E85 should not be hard to find. For the rest of the nation, be patient. E85 is coming to a gas pump near you soon. If you can't wait on this idea, a good substitution that would not require a custom carburetor would be 100-octane (or higher) race gasoline.
Our plan was to upgrade our little cast-piston small-block Chevy to forged pistons and retain the same Crane cam, Vortec heads, and Magnuson blower from the last test. This time, the higher-octane fuel would allow us to add more ignition timing that we couldn't run last time for fear of falling victim to the destructive forces of the evil Dr. Detonation (who lives in a jar in the kids' room and escapes on a regular basis). But, just like any good performance test, we discovered a hidden limitation: Vortec-head rocker studs. That turned out to be a blessing, since it gave us the excuse to flog a set of TFS 215cc aluminum heads to make even more power-to the tune of 601 hp and 631 lb-ft of torque. This baby rocks.
Crane Powermax 288 Cam Specs
|DESCRIPTION ||DURATION ||DURATION ||LIFT ||LOBE SEPARATION |
| ||(Adv.) ||(0.050) ||(inches) |
|Intake ||288 ||226 ||0.488* ||114 |
|Exhaust ||296 ||234 ||0.504* |
*Stock lift at 1.5:1 rocker ratio is 0.458/0.473 inch. The above lift numbers are the result of using Crane's Gold Race 1.6:1 roller rockers on the aluminum heads.
Iron Heads,Blowers, and E85
If you remember our story on the Magnuson 122ci High Helix blower, then you also know we made an astonishing 504 hp and 512 lb-ft of torque with nothing more than cast, flat-top pistons, a mild hydraulic flat-tappet cam, unported iron GM Vortec heads from Scoggin-Dickey, a set of headers, and a simple 750-cfm Holley carburetor.
By substituting E85, we wanted to see the difference in power we could generate with a much higher-octane fuel and also see the benefits from the fuel's greater inlet-air-charge cooling ability. We planned to push this little small-block to the limit on cylinder pressure, so the idea of cast pistons pushing well past 500 hp didn't inspire confidence. We decided to increase the durability factor by adding a set of forged flat-top pistons. We found a Speed-Pro forged flat-top, 0.030-over piston kit with 11/416-inch rings from Summit Racing for less than $350, which fit into our budget perfectly. Combined with the 64cc iron Vortec heads, this pushed the compression ratio up from the cast-piston ratio of 8.6:1 to a far more aggressive 10.2:1. We obviously had to bore and torque-plate-hone the block, and the entire rotating assembly had to be rebalanced, which was ably handled by Jim Grubbs Motorsports.
This is not a normal compression ratio for a supercharged engine, but the idea here was to push the cylinder-pressure envelope. This also meant our spark timing would have to be very carefully curved to prevent over-advancing the timing and causing detonation, even with E85's 105-octane rating. We also stepped up to a stronger spark with a Mallory electronic distributor and HyFire VI spark box.
We retained the Crane PowerMax 288 flat-tappet hydraulic blower cam that we used in the first test. The iron Vortec heads along with the higher compression didn't cause any detonation problems, and we quickly achieved 555 lb-ft of torque, a gain of more than 40 lb-ft of torque over pump gas, and 519 for horsepower, a jump of exactly 15. As we expected, torque improved with the combination of the additional compression and the ethanol fuel. The horsepower gain we saw with this blower test is attributable to the roughly one-point-higher compression ratio, which is worth about 3 percent, equal to roughly 15 hp.
We were on our way to an even more aggressive boost curve when the two pressed-in studs for cylinder No. 4 pulled out of the head and shut down that cylinder. We decided to swap on a better set of heads rather than to try to fix these production castings.
Big Heads Equals Big Power
Superchargers employ a very simple power plan. Use lots of pressure to stuff the air and fuel into the cylinders. The little Vortec heads are great for mild power, but realistically, their tiny intake ports created a restriction in our path for more power. What we really needed was a pair of heads that could flow some big-time air. We decided to go with a pair of TFS 215cc intake-port heads that would offer some serious airflow capability. The only serious change this demanded was a swap to a different Magnuson supercharger intake-manifold base, since the TFS heads use the standard small-block Chevy intake bolt pattern, not the Vortec pattern.
We began testing the TFS heads with the same tune-up as the prior Vortec heads, and the power jumped slightly. As we began to tune the combination, add more timing, and bump up the boost by running a smaller blower pulley, the power numbers really jumped. This put us well past the 600 lb-ft of torque range and boosted the horsepower right past the 575hp mark. Up to this point, most of our tuning efforts had been very successful. With between 8 and 9 psi of boost pressure and with timing set at 35 degrees total, we now had the power at 616 lb-ft of torque and 584 hp.
The final tweak was going with slightly richer high-speed air bleeds. Tuning with the Innovate Motorsports air/fuel ratio meter, it appeared that a Lambda reading of 0.75 (roughly equivalent to an E85 air/fuel ratio of 7.25:1) was where the engine made best power. This change, along with a smaller blower pulley and exchanging the high-ZDDP-level diesel 15W-40 oil for some Quaker State High RPM synthetic 5W-30 kicked us over the top of 600 hp, at which point heavenly angels began to sing and there was rejoicing in Car Craft land. When our little 355ci small-block pushed past 600 hp, we were thrilled.
What's impressive is this is a tiny little 122ci supercharger sitting on a mundane 355ci small-block Chevy with medium-size ports and a very mild hydraulic flat-tappet camshaft running on E85 fuel. Another amazing result of this test was the blower discharge temperatures. At 8 psi at 5,700 rpm, the air temperature exiting the blower and entering the intake ports was a mere 91 degrees F. Granted, our carburetor inlet air temperature was a conservative 70 degrees, but mixed with the E85, the alcohol (along with a very efficient Magnuson supercharger) kept the discharge temperature very low. That's the big reason, along with E85's 105-octane rating, this engine never rattled.
Green Carb Power
If you read the previous E85 story, you know that from a fuel-delivery standpoint, ethanol carburetors must be capable of supplying a much larger volume of fuel to make up for the fuel's lack of heat output. In our first story, Quick Fuel Technology supplied us with a pair of metering blocks hoping they alone would make a regular gasoline carburetor work with E85. While we got by with this, the whole gasoline carburetor was right on the edge of what it was capable of flowing. This is why we had to go so big with the jetting.
The owners of Quick Fuel, Marv Benoit and Marty Brown, agreed this next step would require a specific carburetor, since we would be using this carb on a blower making even more power. What they sent us was a 750-cfm carb with more traditional drop-leg boosters whereas the original E85 carb used on the normally aspirated engine was of annular-discharge design. And to call attention to this custom E85 setup, they colored the throttle plate and metering blocks green and attached an E85 decal to the float bowl just in case the bright-green color wasn't enough of a clue. Both the idle and main metering circuits were enlarged to compensate for the additional E85 fuel demand.
Out of the box, Quick Fuel spec'd this carburetor with 80-primary and 90-secondary jetting with a power valve only on the primary side. We added five jet sizes to both ends and a rear power valve to bring up the fuel curve. We also experimented with high-speed air bleeds in an attempt to tailor the fuel curve to what the engine wanted. From our previous experience with E85, we knew the max power air/fuel ratio window can be slightly rich and still make max power, so to be safe, we stayed with the 7.25:1 air/fuel ratio throughout most of the testing.
E85's Special Spark-Plug Demands
One of the things we learned the hard way while testing our first E85-fed small-block was that cold spark plugs are absolute necessities. In our normally aspirated tests, we melted a plug. Later, Bosch Product and Technical Support Manager, Matthew Hallis, told us ethanol is particularly sensitive to pre-ignition. In other words, it doesn't take much of a heat source to initiate combustion. Pre-ignition is caused by a heat source in the combustion space that begins the combustion process before the spark plug fires. Any kind of hot spot, like a glowing spark-plug ground strap for example, can light off the intake charge during the compression cycle long before the spark plug is supposed to fire. This creates dangerous cylinder-pressure spikes and can cause massive engine damage in the form of melted pistons. In our first test, we were lucky the only damage was a bunch of nuked spark plugs and two warped intake valves.
The solution to this E85 pre-ignition problem is to run a minimum of three heat ranges colder than the heat-range that spark plugs would normally survive on gasoline. Cold plugs are designed to transfer as much heat as possible away from the spark plugs so they won't melt. Supercharged, turbo, or nitrous'd engines demand a nonprojected-nose spark plug, which minimizes the length of the spark-plug ground strap. While platinum and iridium plugs are very popular for mild street cruising, they should be avoided when pushing an E85 engine hard, such as on the dyno, since these materials tend to retain heat and could cause pre-ignition problems.
Also, because the supercharger boosts cylinder pressures, we knew a smaller plug gap of 0.030 inch would help to get the fire lit. Very cold plugs tend to not want to start as well as hotter plugs on a cold engine, so if you decide to build a similar package, you will need to experiment with heat ranges by starting out cold and going warmer until you see excessive heat evidence in the plug.
Test 1 shows the best power numbers from our first dyno test of the Magnuson 122 blower from the Sept. '06 issue. Static compression was 8.6:1 and max boost was 7 psi at 6,000 rpm. This test was performed on 91-octane pump gas.
Test 2 used forged Speed-Pro pistons, which bumped the compression to 10.2:1, a Quick Fuel 750 annular-discharge carburetor, and E85 fuel. Max boost was 7 psi but at a low 3,300 rpm. At peak power, the boost was only 6 psi.
Test 3 replaced the stock iron Vortec heads with a pair of aluminum 215cc TFS heads and a set of Crane Gold Race 1.6:1 roller rockers. Compression was slightly lower, but we added a smaller 2.70-inch-diameter blower pulley to generate 10 psi at peak torque and 12 psi at peak horsepower.
|RPM ||TEST 1 ||TEST 2 ||TEST 3 |
|HP ||TQ ||HP ||TQ ||HP |
|2,000 ||412 ||162 ||--- ||--- ||550 ||209 |
|2,200 ||426 ||178 ||--- ||--- ||563 ||237 |
|2,400 ||449 ||205 ||--- ||--- ||575 ||263 |
|2,600 ||462 ||229 ||--- ||--- ||587 ||290 |
|2,800 ||476 ||254 ||--- ||--- ||599 ||319 |
|3,000 ||470 ||268 ||537 ||308 ||611 ||349 |
|3,200 ||480 ||292 ||535 ||325 ||620 ||378 |
|3,400 ||495 ||320 ||545 ||354 ||626 ||406 |
|3,600 ||500 ||343 ||551 ||379 ||630 ||432 |
|3,800 ||511 ||370 ||554 ||400 ||631 ||456 |
|4,000 ||512 ||390 ||555 ||422 ||630 ||480 |
|4,200 ||512 ||410 ||555 ||444 ||628 ||502 |
|4,400 ||510 ||427 ||551 ||462 ||624 ||523 |
|4,600 ||509 ||445 ||540 ||474 ||618 ||542 |
|4,800 ||500 ||457 ||523 ||478 ||610 ||558 |
|5,000 ||499 ||475 ||506 ||481 ||599 ||570 |
|5,200 ||490 ||485 ||494 ||489 ||587 ||581 |
|5,400 ||472 ||485 ||491 ||505 ||575 ||591 |
|5,600 ||461 ||491 ||485 ||519 ||564 ||601 |
|5,800 ||449 ||496 ||459 ||507 ||541 ||598 |
|6,000 ||441 ||504 ||386 ||441 ||484 ||552 |
|6,200 ||420 ||496 ||283 ||335 ||--- ||--- |
|DESCRIPTION ||PN ||SOURCE ||PRICE |
|MagnaCharger ||122 ||Magnuson ||$2,395.00 |
|Speed-Pro piston kit ||8KL2491F30 ||Summit Racing ||349.95 |
|*Vortec heads, mod ||SD8060A ||Scoggin-Dickey ||679.90 |
|Crane PowerMax 288 ||113821 ||Summit Racing ||109.88 |
|Crane lifters, hyd. ||99277-16 ||Summit Racing || 89.99 |
|Crane 1.6:1 rockers ||86757-16 ||Summit Racing ||319.88 |
|TFS 215cc heads ||32400006 ||Summit Racing ||1,461.95 |
|Hedman headers ||68190 ||Summit Racing ||135.88 |
|Bosch cold plugs, 8 ||7566 ||Rock Auto ||12.96 |
|Bosch race plugs ||F07DC ||Bosch ||N/A |
|Fel-Pro head gasket ||1094 ||Summit Racing ||18.95 |
|Intake gasket ||12529094 ||Scoggin-Dickey ||21.95 |
|Fel-Pro oil-pan gasket ||1802 ||Summit Racing ||9.88 |
|Mallory distributor ||5048201 ||Summit Racing ||225.89 |
|Mallory wires, universal ||937 ||Summit Racing ||63.39 |
|Mallory HyFire VI ||685 ||Summit Racing ||239.88 |
|**Proform valve covers ||141-800 ||Summit Racing ||259.95 |
|Quick Fuel E85 carb ||Q750-E85 ||Quick Fuel ||625.00 |
|Total: ||$6,340.38 |
*not included in final price**$259.95 valve covers are optional
Quick Fuel Technology
530 Fentress Blvd.
5 Jenner, Ste. 100
Scoggin-Dickey Parts Center
Jim Grubbs Motorsports
28130 Crocker Ave.
Trick Flow Specialties
1248 Southeast Ave.
26555 Northwestern Hwy.