E85 fuel & carb dyno test

We explore just how much difference E85 can make with a blown 383ci Chev


We explore just how much difference E85 can make with a blown 383ci Chev

This article on E85 was originally published in the July 2014 issue of Street Machine

WHEN IT comes to pump fuel these days, E85 seems to be the drink of choice for those looking to maximise their bang-for-buck. But just how much difference does it really make?

As the name suggests, E85 is 85 per cent ethanol, with the rest being petrol, and United Petroleum says the stuff coming out of their pumps (which is what we’ve used here) is 105-octane RON. Which sounds great for performance use, but you have to also take into account that E85 contains 26 per cent less energy than petrol, so you need to burn more of it. Expect fuel consumption to increase by anywhere up to 30 per cent if you switch to E85.

It’s also not suitable for all cars. Being hygroscopic – meaning it draws in moisture – E85 can cause corrosion in the fuel systems of older vehicles, and as a solvent the ethanol can swell and deteriorate some rubber fuel lines and gaskets. While most EFI cars can handle a bit of E10 in the diet, very few can handle E85, so if you’re looking to make the switch then factor in a new stainless fuel tank or E85-compatible fuel cell, and ethanol-compatible lines, pumps, carbies or injectors. It can be an expensive exercise, but there are benefits too.

Obviously the octane rating is great for performance, and if you use race E85 from a supplier like Sucrogen the octane rating is even higher at 108. Many E85 fans tune their streeters on pump E85 for tooling around the streets and switch to a race E85 tune for the track. At the moment pump E85 is about $1.30/L, while the race stuff is around $2.50/L, which may sound pricey but it’s a hell of a lot cheaper than comparable race fuels.

But getting back to our main question, how much difference does it make to performance?

As it turns out, Powerhouse Engines in Warragul had just finished screwing together a tough yet streetable under-bonnet blown 383ci small-block combo that they wanted to test with both pump unleaded and E85, so Powerhouse’s Johnny Pilla invited us along to watch.

For the test Johnny had three carbies to try. The first was a basic HP Street Series 750 double-pumper Holley complete with manual choke and all the gear you’d expect on a street carb. This was supplied by the customer Neil Browne, but he was happy to see if Johnny would make more power with another carb. To find out, John had an HP Series 850 Holley to try with unleaded and an E85-capable Pro Systems 850 to use for the ethanol test.

The engine itself is pretty simple and relatively low-budget, which is exactly what Neil was after for his ’68 Camaro.

“Neil wanted a street engine, so we built something that would idle under 1000rpm and make maximum power under 6000rpm,” Johnny says. Neil supplied the Weiand 144 supercharger, Edelbrock E-Street heads, along with the Scat stroker crank and the 750cfm Holley. The rest he left up to Johnny, so to keep the budget down John used a new GM four-bolt block and filled it with 9:1 Mahle forged pistons, Callies H-beam rods and a Crane [email protected] hydraulic roller cam. Nothing too crazy, and naturally aspirated the set-up made 388.3hp on BP Ultimate fuel with Neil’s 750 Holley. So not only do we get to see what difference the little blower made, but also what difference E85 made over that. We won’t spoil the ending just yet; let’s just say the results were surprising.

But bear in mind that in the past we’ve seen almost no gain at all with E85 in some engines while others, especially boosted engines, have seen significant power increases. So remember that every combo is going to respond differently. But in this case, E85 was definitely worth using. Check it out.

1. To kick things off Johnny tested the engine in normally aspirated trim using the customer-supplied 750cfm HP Street Holley on top of a 4bbl adaptor bolted to the blower intake, and made 388.3hp. No doubt it would make even more power with a proper 4bbl intake.

2. Here’s the three carbies used in our test (l-r): the unleaded HP series 850cfm, the E85 Pro Systems 850cfm, and Neil’s 750 HP Street carb with manual choke.

3. With the Weiand 144 blower bolted under Neil’s 750 Holley, the stroker small-block came alive, making 512hp and 536lb-ft on premium unleaded. These little blowers work well in quick bursts but the high rotor speed means they heat up quickly, which hurts the horsepower in sustained performance applications like track work.

4. Johnny believes the Weiand 144 is probably a bit small for 383 cubes and recommends the larger 177 unit. With the smallest available pulley up top, the little blower only produced 6psi boost.

5. Bolting on the HP Series 850 gained another 16hp, and going up another two jet sizes gained an extra 6hp for a best of 534hp and 558lb-ft – a 22hp gain. Not bad for just a carby swap.

6. Now it was time to try the E85. With the Pro Systems E85-spec 850 bolted to the top, the power jumped another 20hp straight away, but there was still more to come. The blower was also cool to the touch immediately after the dyno run, which has got to be great for repeated or sustained use.

7. At this point the total timing was at 29.5 degrees, so Johnny added two degrees, which the engine seemed to like, then he dropped two jet sizes to reveal a best of 568hp and 590lb-ft.

8. And the proof: the low-blow 383 makes over 550lb-ft all the way past 5000rpm – that’s big-block grunt in a small-block package. Total gain for the E85 was 34hp and 32lb-ft over the best unleaded figures, and 56hp over Neil’s 750 Holley.

9. The best part is that all the E85 testing was done with basic pump fuel, not the race-spec stuff. We expect race-spec E85 would probably make even more power, but at almost double the cost per litre.


Terry Seng’s seven-second VC Commodore is a perfect example of what can be done with E85 on the street. “It’s pretty easy to get now,” Terry says. “We used to buy 600L at a time in drums, but now United guarantees it’ll be 85 per cent, and every time I’ve tested it, it’s come up at 85-87 per cent.

“If your tuning window is safe enough – as in you are fine with a couple degrees of timing either way – you’ll be fine with the pump stuff. But my advice is run a very, very fine filter. I’ve had a lot of trouble with injectors blocking up and I threw a lot in the bin. You need a 10-micron filter; 30 microns is not small enough.”