11:1 too high for pump gas?

[rumblefish360]

I feel the same way. As you have demonstrated, flow over squeeze.
While more compression helps, it’s not the end all.

 

[Jbarker]

Thanks for the advice everyone. Looks like 11 to 1 is totally doable, but you better have everything tuned in perfect. Since this is a streetcar, I like the idea of having a margin for safety before things start detonating. I think I will do as I did with the last build, leaving the compression at 9.8 to 1. That saves me a little cash too.

 

[mullinax95]

Went from 110 octane to E85. Dealing with the corrosion I experienced in my fuel system turned me off. Then I found out I could make more horsepower with 91 octane than most people could make with race fuel. I will never build another high compression engine. It's simply not worth it, to me.

I was talking to a fellow whose brother has a 900HP mustang running E85. I didn't get into detail about what compression he is running .. I wished I asked... but the car is EFI. I know it's doable but was interested in the pros and cons of E85.

I would like to hear the way you make more HP with low octane rather than race fuel... or is it top secret?

 

[rumblefish360]

Maximize everything but the compression ratio and make use of all the little tricks you can. Coatings, heat barriers, exhaust, cam timing, ignition, total seal gapless rings, intake porting, etc....
Everything is a plus one that adds up.

 

[IQ52]

I was talking to a fellow whose brother has a 900HP mustang running E85. I didn't get into detail about what compression he is running .. I wished I asked... but the car is EFI. I know it's doable but was interested in the pros and cons of E85.

I would like to hear the way you make more HP with low octane rather than race fuel... or is it top secret?

I didn't say I could make more horsepower with low octane than race fuel. I can make more power with race fuel (or E85). I said I could make more horsepower with 91 octane than most people could make with race fuel.

As to the E85. I didn't like having to run everything out of stainless steel or anodizing every aluminum piece that was coming in contact with the ethanol. I had carburetor internals that were getting a white powder all inside them and I had to flush the fuel system with gasoline after every use. I also had to make my own E85, as none is available in this mountain valley.

 

[Hot Metal]

As an example, back in late 1989 we put together a bone stock '68 440-6pk motor for the '69 Cuda with a view of upping the CR to 12.5:1 later which never happened cos I retired from racing in 1991...Stock bottom end, 906 heads template ported 2.14/1.81, .039 fel-pro blues so scr was approx 9.8? we ran the CC .650/650 [email protected] SFT cam, working it out without any concrete actual numbers back then we had>
Static compression ratio of 9.8:1.
Effective stroke is 2.80 inches.
Your dynamic compression ratio is 7.57:1 .
Your dynamic cranking pressure is 148.77 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 7.57 :1.
V/P (Volume to Pressure Index) is 150
I do not have the exact Int valve closing point ABDC of that cam but inputted 68deg.

The motor made an on track 490 fly hp with a crappy Team G int, 4781 850DP and 2" hdrs and ran 10.7@125mph in a 3000lb car, idled at 900rpm and ran sweet, far from the best set up, but it worked and I would've gone 10.5's as I was killing the tyre and the 60 on the hit. CR is not everything, but it would've helped, shame we never got to try to see the difference.

 

[440 Mike]

I think we calculated in about 11.3 to 1? I've been running a 100LL since the beginning and mostly just drag racing in the car or cruising around town. This year I plan to put it on the street more and would like to start running some pump gas through it. I know my cranking compression is down around 190 195. But my cam should have enough bleed off I think to get away with high octane pump gas. We'll see...

Most important concept in this thread, IMHO.

 

[famous bob]

Went from 110 octane to E85. Dealing with the corrosion I experienced in my fuel system turned me off. Then I found out I could make more horsepower with 91 octane than most people could make with race fuel. I will never build another high compression engine. It's simply not worth it, to me.

10.3 c.r. here , alum. heads, .037 quench. 91 dog piss is all we can get at the pump here. no pinging.