Big-Block Chevy High-Compression Fuel Test Reveals Surprising Trade-Offs | Engine Masters

Added: 2026-05-06

[00:00:00]This is Engine Masters presented by Amsoil and finally we're doing the test that you've asked for. It's going to be gasoline versus E85. And I admit I resisted doing this for a long time. And here's the reason. If you're going to go to the pump, which is what an average guy is going to do, and buy gasoline or buy E85, you don't really know what you're getting. There are so many different blends of fuels depending on location, emissions, time of year, and an E85, theoretically that's 85% ethanol and 15% gasoline, but legally it can be as low as 70% ethanol, and it can be more than E85. And so, doing a comparison of stuff that you pull out of the pump is not going to be representative of what might happen in your neighborhood. And so, it's kind of a worthless test. But here's how I solved that. We're going to use Rocket Brand products. This is Rocket Brand 114 octane racing fuel.

[00:00:57]It's consistent. You know exactly what you're going to get when you buy this thing anywhere and any time of the year.

[00:01:03]And the same is true for the Rocket brand E85 racing fuel that we're going to use. So now we have a level playing field. In the gearhead world, there's really three markets for E85. There's guys with boost who want to be able to run higher octane on the street. Then there's guys who just have a regular hot rod that would run on pump gas and they just want to know what E85 would do for them. But what we're going to address is the third category, which is like this engine right here. It's a big block Chevy. It's going to make 750 or 60 horsepower. It's 489 cubic in. And the main thing you need to know about it is that it has 13 and a half to one compression. So it will not run on pump gas. Therefore, you're stuck with race gas with an engine like this. And what we're going to show you now is what your option might be to run E85 instead and find out what the differences are and also does it make more power. And at the end, we're going to wrap up this whole show with a bunch of considerations about how you might run E85 or not. So, we're going to go ahead and test it first with the Rocket Brand 114 racing fuel before we hit it with some of the E85. We're going to head into the dyno and do that right now. AMS oil time. So, this engine is sort of a freak because on one hand, it's a street motor with a hydraulic roller cam and regular bearing clearances. And on the other hand, it has 13 and 12 to1 compression and makes a whole bunch of power. So, this time I'm going to choose the Dominator racing oil because we're not really worried about like, you know, drain intervals and things like that on it. Has a high film strength. It's going to protect the bearings with that high compression. And man, I got to tell you, the audience has just disappointed me with their demands for an actual funnel.

[00:02:49]>> Okay, so we have this thing on the dyno already to run Rocket Brand 114 through it, right?

[00:02:55]>> Yeah, it's a 13 to1 compression motor.

[00:02:56]It' get away with 112, but I just feel comfortable with 114.

[00:03:00]>> So Steve's already got this thing tuned up. Um, this thing likes 35 degrees of total ignition advance.

[00:03:07]>> Well, let's show them the baseline. So, where do we go from there? I mean, I feel like basically we tuned it up on gas and it was perfect. We took this carburetor out of the box. It was perfect.

[00:03:17]>> I know. It feels like we should be doing something to it, huh? But >> we did and it didn't change any >> I know. Salad bowl.

[00:03:28]>> That's all.

[00:03:30]>> Yeah.

[00:03:30]>> Power-wise, there's no downside.

[00:03:33]>> No. Right.

[00:03:33]>> None whatsoever. What we're looking at here is the black line being E85, red line is gasoline, and our peak numbers are not very much different. So, what you really have to pay attention to is the difference in area under that curve all the way from 3500 up to 6,000.

[00:03:51]>> There's 13 pound feet of difference.

[00:03:53]>> Yeah, the 85 >> significant >> is better and cheaper and stinks.

[00:03:58]>> Race gas smells good. This smells well, not so good. Let's have a look at the difference in intake manifold temperature. Ambient versus manifold temperature up. Okay, so all the way up at 6,800 RPM. On the E85, we had 87° in the room and 47 in the intake manifold.

[00:04:16]So, a 40° drop. On gasoline, it was 90 in the room and 51. It makes me want to get educated on it more and come back and do it on boost because I think that is more what the average guy is looking to do with it. You just made me actually realize another benefit of what we just did with E85. It means you can have a 13 and a half to1 engine and drive it on the street.

[00:04:37]>> Exactly.

[00:04:37]>> Ding.

[00:04:39]>> I thought that was the whole point all this time.

[00:04:42]>> That's why we picked this motor because we didn't think it was much of an advantage with 10 to one.

[00:04:46]>> Well, I was thinking it was more like, oh, save money on race gas and find out, you know, what the difference is in power. But yeah, if you can pull pour the 8085 out of a pump into your 13 and 12 to1 motor.

[00:04:56]>> Yeah.

[00:04:57]>> Yeah. That's the big deal for any sense to live in the Midwest >> and you wake up the, you know, like boosted stuff. Yeah.

[00:05:03]>> Run the boost way way up that you can't do on 91 octane and you can on this.

[00:05:06]>> Yeah. For some reason, I got that, but the compression didn't >> cylinder pressure.

[00:05:11]>> Yeah, my cylinder pressure is leaking out my ear. It It tells me it's worth learning more about.

[00:05:17]>> I think octane per dollar, the ratio, it makes it a great value.

[00:05:21]>> I didn't even think of octane per dollar, but you're right. That's the perfect way to state that. So you can get basically high octane race gas on the street. So that's pretty good. It can be cheaper to buy than gasoline, too. People think that adds up to being cheaper, but it gets worse miles per gallon. So I think it just adds out.

[00:05:38]>> Did you know that the pump version is actually 105 octane?

[00:05:42]>> Yeah. I mean, you don't know what you're getting though. Depending on the alcohol content, it maybe higher, maybe lower.

[00:05:48]Maybe they just picked the random number and said, "We'll call it 105." Here's the other thing about it is even though it's rated at 112 octane, its numbers for the research and motor method for the octane rating are offset from gasoline in a way that means it's actually susceptible to pre-ignition.

[00:06:05]>> I'll just take your word for it on that.

[00:06:07]>> No, it's I mean this is research that I did. I I read last night some Marlon Davis stories and some SAPE papers and stuff. You need to run a couple ranges cooler on your spark plugs if you're going to run E85 and make sure you don't have any like carbon or hot spots in your chamber. I didn't know this one at all until I read it last night. You can't run paper fuel filter with the 85.

[00:06:25]>> Oh, it'll eat it up.

[00:06:26]>> It'll disintegrate. You got to have a stainless steel fuel filter. So, there's even more expenses stacked up. And here's the last one that's sort of on that same note. If you have an electric fuel pump, whether it's submerged or whether it's a horizontal kind, the fuel flows around the pump and the motor mechanism >> and lubricates it. Well, the 85 doesn't have the lubricity of gasoline. And so you can foo bar your electric fuel pump even sooner than you normally would.

[00:06:52]Aside from the fact that you're already working it harder because it's delivering more fuel.

[00:06:55]>> So what's the fix? Do you have some additive or something like that you can put in your E85?

[00:06:59]>> Don't use the E85.

[00:07:01]>> I kind of like the E85.

[00:07:03]>> What? I didn't expect that outcome. I have to admit I think it's really cool that you can buy high octane gasoline at the pump for cheap. I think it's really cool that it makes power. But all of those downsides for me personally add up to no. I like the fact that it's better than ad gas at a lower price as far as octane. So >> So you would use it in your car?

[00:07:24]>> Yeah, that's a win.

[00:07:25]>> You would use it in your car?

[00:07:26]>> Oh, yeah.

[00:07:27]>> No, come on.

[00:07:28]>> You may not know this, but in science lab in high school, my project was converting an engine to run on denatured alcohol, which is ethanol.

[00:07:36]>> Steve Doulich invented E85.

[00:07:39]>> Pioneer. There'll be that and other fun facts to know and tell on future episodes of Engine Masters presented by Amsoil.

[00:07:47]>> I even got an A on that project.

[00:07:50]>> You failed this one.