Blown Hi-Torque E85 Chevy Small Block
By guest contributor: Mike Petralia
Lately, everyone thinks that E85 gasoline is all the rage when it comes to cheap horsepower. While we're not denying that, E85 certainly has its drawbacks. Mainly that you must burn almost twice as much of it to make power. So it's low cost at the pump doesn't really have an effect on your wallet, since you're filling up twice as often.
We view E85 from a different angle. We build a lot of blown street engines that naturally burn up lots of fuel to make power. And since E85 has a much higher octane equivalent than unleaded pump gas, and blown engines need higher octane, we thought it might be the perfect fuel to get over 625hp out of a mild little blown street engine.
SUPERCHARGED E85 POWER
The key to power for this particular 383ci engine was the 177-cid Roots-style Weiand supercharger, (a.k.a: the blower). It's compact dimensions are designed to fit under many stock hoods. And it produces lightning-quick throttle response and instant boost as soon as you mash the pedal. But, it's small size also means that it can't make as much boost as its larger 71-series cousins. That doesn't matter here, because all we wanted was about 7.5-psi boost for this build. Combine that with our static 8.7:1 compression ratio and we get a corrected 13.2:1 Final Compression Ratio, which we feel is alright to run on E85.
Plus, we run a pretty large camshaft in these engines to give them a nasty idle sound, and bleed off some of that compression for engine safety. We won't share all the cam specs, but it's a custom-ground hydraulic flat-tappet to keep the cost low, and the valve lift is right around .510" intake/.530" exhaust.
"We have our E85 carbs custom-built for us with supercharger calibration to run boosted on the street."GM reconditioned 4-bolt truck blocks from the late 1990's are good up to 625hp+ and feature 1-pc rear main seals for less leaks.
The rest of the engine is standard 383-stroker stuff for us. Besides running a wider ring gap, there's not too much else we do differently from our N/A 383 builds. The rotating assembly is from Scat and Wiseco with file-fit AP steel rings from Total Seal. Since the crank is nodular iron, we use King Racing's special "SI" bearing that works very well with it. Ignition duties are handled by an MSD billet distributor with the vacuum advance left disconnected and Autolite plugs fire the mix. Engine sealing is courtesy of Fel-Pro with MLS head gaskets to handle the boost pressure.
|Since the cam is a flat-tappet hydraulic, we run the break-in sequence with the inner valve springs removed. Then we re-install the springs and change the oil and filter for tuning and power pulls on the dyno.|
As an added bonus, we dressed the engine to the hilt with a Billet Specialties front accessories system featuring A/C, 105A 1-wire alternator, GM Type II power steering pump, and a cast aluminum water pump. But this kit was not designed to run with a blower, and likewise, the Weiand mini-blower was not designed to run with this kit, so we had to get creative and swapped the blower's drive snout with a different length unit that we had to buy direct from Weiand and we had to machine up a crank pulley spacer so the blower belt would clear the Billet Specialties pulley. After we had the whole front dress system installed, we dyno tested it once again to make sure nothing would fly apart at 6,200 rpm. The system worked flawlessly, but it bled off about 5% horsepower to run it.
|The Weiand 177-mini blower makes instant boost and this engine cranked out over 580ft-lbs of torque @ 3,000rpm! Plus it still pulled hard to 6,200rpm where it peaked with 628hp on just 7.6-psi boost.|
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