[adam83]

I want to know, when picking the right race fuel (which I've never bought before), is this one of those times I should be following the labels exactly for my particular engine, or do I just buy the highest octane one they have for maximum performance?

Now, I have a fresh 440 +30 in a 73 Duster, somewhere between 9:1 and 9.5:1 comp, ported 902 heads, very nice flowing custom hooker exhaust, torker 2 intake, weiand 1" spacer, holley 850 double pumper, turbo action 3500 stall, 30in tall street slicks, 3.93 diff. It's making around 460hp in the higher rpm range, I dont know exactly where I've never dyno'd it, the power is just a guess but I know Im close...

I run pump gas. I want to see what happens with some leaded racing fuel, and sunoco is the brand I looked up and they sell it in Auburn supposedly so Im gonna go get some. According to their chart, their basic PURPLE 110 octane standard fuel would be what I should get, but I want to know, would it be a bad idea to try out the 116 octane RED maximal??

Im not totally clueless, I did read that the Maximal's description, it's for engines up to 17:1 compression and 10,000 rpm, but from lack of experience, I dont know the answer here, IS THIS ONE OF THOSE "BIGGER IS BETTER" SITUATIONS? Should I stick with the recommended fuel, or get the top level fuel?

[poncho62]

From what I have read about fuels, there comes a point where more octane makes no difference or can actually harm performance.....I am not expert either

[cool rockin daddy]

Does your car run fine on the pump gas? Have you had to take timing out of the engine to prevent it from pinging on the pump gas? If so, race gas may help you, but you will not benefit or notice a difference from running high octane racing gas UNLESS you are going to add more timing to your engine when running it. Octane is not a hp adder by itself.

[MouseFink]

If you have no detonation problem with 93 octane pump gas with the initial timing advanced as far as possible and will still allow the engine to start, there is only one reason to use high octane leaded racing fuel. That is if you have over 125 lb. valve spring seat pressure. Leaded racing fuel will prevent the exhaust valve spring seats from premature erosion. IMO, using leaded racing fuel is an expensive way to keep the seats from being pounded out when it could be avoided just by using valve springs with no more than 110 - 115 lb. seat pressure.

High compression ratio and high valve spring seat pressure pressure is for race cars that do not see any street use. When 104 octane leaded gasoline was available at the pump, it was common to see cars with 125-150 lb. seat pressure and 11:1 compression ratio from the factory.

[adam83]

Sorry for the late reply, I've been busy. I ended up trying both the Leaded Trick Racing Fuel (blue) and the Leaded Sunoco standard (purple). They sell them both at the pump in Auburn, WA. It could have been a placebo effect, but it really did feel like the car ran better, on both. it didnt gain much power, if any, but it seemed to run better. I know the lead lubricates so it's better anyways, but if I could afford it I'd run this stuff all the time. I didnt notic much of a difference between the 2 race fuels, but the guy told me something about end point temperature differences between the 2, which I still dont really understand, but the Trick Fuel had a lower end point temp so he recommended that one. He said the sunoco would run better with bigger jets in the carb, but I didnt notice much difference. Plus, my Holley has jumped up several jets sizes already

[S10xGN]

Originally Posted by adam83

Sorry for the late reply, I've been busy. I ended up trying both the Leaded Trick Racing Fuel (blue) and the Leaded Sunoco standard (purple). They sell them both at the pump in Auburn, WA. It could have been a placebo effect, but it really did feel like the car ran better, on both. it didnt gain much power, if any, but it seemed to run better. I know the lead lubricates so it's better anyways, but if I could afford it I'd run this stuff all the time. I didnt notic much of a difference between the 2 race fuels, but the guy told me something about end point temperature differences between the 2, which I still dont really understand, but the Trick Fuel had a lower end point temp so he recommended that one. He said the sunoco would run better with bigger jets in the carb, but I didnt notice much difference. Plus, my Holley has jumped up several jets sizes already

Lower end-point components boil off quicker, making for easier starts. That's the primary difference in summer and winter fuels...

Russ

[adam83]

I see. My engine had absolutely no problems running on sunoco, I wonder if that will change in winter?

[cool rockin daddy]

Strictly a placebo effect. If you didn't put more timing into it and assuming this is not a computer controlled engine that would put it in for you, there would be absolutely NO performance difference from higher octane gasoline.

[cobalt327]

Originally Posted by adam83

I want to know, when picking the right race fuel (which I've never bought before), is this one of those times I should be following the labels exactly for my particular engine, or do I just buy the highest octane one they have for maximum performance?

Now, I have a fresh 440 +30 in a 73 Duster, somewhere between 9:1 and 9.5:1 comp, ported 902 heads, very nice flowing custom hooker exhaust, torker 2 intake, weiand 1" spacer, holley 850 double pumper, turbo action 3500 stall, 30in tall street slicks, 3.93 diff. It's making around 460hp in the higher rpm range, I dont know exactly where I've never dyno'd it, the power is just a guess but I know Im close...

I run pump gas. I want to see what happens with some leaded racing fuel, and sunoco is the brand I looked up and they sell it in Auburn supposedly so Im gonna go get some. According to their chart, their basic PURPLE 110 octane standard fuel would be what I should get, but I want to know, would it be a bad idea to try out the 116 octane RED maximal??

Im not totally clueless, I did read that the Maximal's description, it's for engines up to 17:1 compression and 10,000 rpm, but from lack of experience, I dont know the answer here, IS THIS ONE OF THOSE "BIGGER IS BETTER" SITUATIONS? Should I stick with the recommended fuel, or get the top level fuel?

100 octane gas would be all that's needed w/the CR you're running, provided that estimate is correct or not much higher. 93 may even be all you need.

To find out you need to run at the track using both fuels under the same ambient conditions. Baseline it on the 93 pump gas (this assumes you've optimized the tune for 93 octane), then use the high octane gas and vary the total timing and possibly jetting to see if it picks up ET. Seat of the pants dyno estimations are basically useless when you're talking about 0.10 second changes in ET.