Fuel Blend for Hi Compression

[Garys1969RR]

I have a 440 six pack Roadrunner, supposedly ported 906 heads. Not sure what the C/Ratio is, but it is showing about 180 PSI on the compression gauge. It had some slight pinging once in awhile under hard acceleration. So I mixed 3 gallons of VP 100 with 2 gallons of E 85, drained out the old 91 and put 5 gallons of this mix in there. The pinging went away completely, and it ran alot better, even frying the tires in 2nd gear. I'm running almost 40 degrees total advance above 2500 RPM. So if anyone out there is having pinging problems, you may want to try this. I plan to pull the motor apart this winter and install some Ross 14cc dome pistons, Eddy Performer RPM heads, and a solid roller cam. My final C/Ratio will be right at 12.5 to 1. I like high C/Ratios along with good port flow. At 5200 feet, the higher C/Ratios really seem to help.

 

[super-bee_ski]

Sounds like a good combo
One question:
If you have a good set of heads why go with the Edelbrock?
A good ported set of 906s will outperform stock Edelbrocks....
Just saying...
Unless you are going with a different Combustion Chamber size (Combustion chamber volume: 75cc / 84cc / 88cc for Edelbrock Heads)
(It's your car, you do what you wish and none of my business)
With respect...
"super-bee_ski"

 

[Garys1969RR]

Well I was told the heads were ported, so I don't know whats been done, what pistons are in there, etc. I'm pulling the passenger side head next week to inspect it. #8 cyl is blackening the plug with carbon and oil. All the other plugs are showing a nice light tan color. So I will know more once that head is off, then I will go from there. By the way, Super Bee Ski, that six pack set up I got from you is performing flawlessly! Thanks! It picked up .4 sec and 5 MPH in the 1/4 mile, just by putting that on the motor! What a difference!

 

[Garys1969RR]

My Eddy heads are 84cc Perf RPMs. I'm not sure which ones have the better flow, but if the 906s still have stock valve size then I'm pretty sure the Eddy's will flow better. Just need to check it all out.

 

[HEMI-ITIS]

I didn't think one would mix gas with corn.If the E85 needed support,add Meth

 

[Garys1969RR]

Well it sure runs good on this gas and corn! Main reason for the E-85 is to reduce the cost. The 100 cost is $7.85/gallon, while the E 85 runs $1.70. Averages out to $5.39 a gallon, with a 60/40 mix. And I love to experiment. Have to be careful, as the E 85 has the effect of leaning out the mixture.......I was lucky enough to have recently moved to an area where both fuels are available within 2 miles of my house! Otherwise I probably wouldn't be trying this out.

 

[HEMI-ITIS]

You need to read plugs on a regular basis!

 

[lewtot184]

increasing the amount of alcohol in the fuel could have an adverse effect on air/fuel ratio for carbs jetted for gasoline. you may find that oil or other stuff is creating the detonation. 180psi is, in my opinion, with iron heads and no quench/ pump gas not a happy combo. contaminates in fuel, water/oil, are detonations best friends. i've played with cylinder pressures in the 180-190psi with a good quench/iron heads/pump gas and found it touchy. i've done 160psi with a good quench/iron heads/pump gas WITH contaminates and that didn't go very well either. i do have one engine that has alum heads, good quench, 9.75:1 comp with clean chambers and it's very happy with pump gas and performance timing.

 

[64 Post]

First, here's a link to Avgas supplies in our area and prices : https://www.airnav.com/fuel/local.html
Duggan's Petroleum on Sante Fe and Oxford-ish has a good supply of various octanes.

I ran similar cylinder pressure in my 383/450 stroker. 5 gal. of 91 and 2 gal of 100 gave me peace of mind.

The rule of thumb for building an engine in CO, is to add 25% more mechanical compression to try to regain some cylinder pressure and then fine tune with cam timing for a targeted cylinder pressure.

What works at sea level falls on its face at altitude. For example, an iron block aluminum head 440 with 10:1 pistons nets an actual compression ratio of 7.5:1 or less during hot summer days.

So if you want a decent running engine without leaving too much on the table 12.0:1 is really the starting point.

 

[Garys1969RR]

Oh I totally agree with you, 64 Post! None of my motors has ran really good at this elevation, until I got up into the 12 to 1 and up range. I live 20 miles north of Denver (Brighton) so I buy my race fuel there.