Racingjunk Forums

Racingjunk Forums (
-   Carburetion, Induction, Nitrous (
-   -   Fuel System - gas and alcohol (

rooniew 08-22-2007 06:33 PM

Fuel System - gas and alcohol
I have a question regarding fuel systems.
I currently run a gas system with a rear mounted fuel cell with an electronic Product Engineering pump and regulator. Can you run alcohol with this set up to a alcohol carb? The pump is rated for both. I have been doing some reading on the subject and it seems that most recommended system for alcohol is a front mounted tank with a belt driven pump.
Any thought or duggestions would be greatly appreciated.

gdmii 08-22-2007 08:30 PM

I'm hesitant sometimes in answering this question because invariably someone will chime in and say I'm full of crap and that this won't work. So what I will say is that it works for me. Your mileage may vary!!

A couple things first. A belt driven pump with a front tank is a simpler system IF you have room on the front of your motor for the pump and room up front for a tank AND you don't mind taking the hood or in some cases the whole front off the car between rounds to refuel.


...if you already have an electric rear mounted fuel system with adequate sized fuel lines and a sufficient pump, then yes it will work. Keep in mind that you will need to deliver almost twice the amount of alky to the motor than gas.

Here's my setup:

A 4 gallon rear mounted fuel cell
BG400 electric fuel pump
Holley 12-704 regulator
Rupert modified 1150 Dominator with PCI fuel bowls
-12 line from tank to pump
-10 line from pump to regulator
-8 line from regulator to carb

I have also run this same setup with dual Holley (Rupert) 750s with standard fuel bowls. I have the PCI bowls on the 1150 because they have 2 .150 needle/seat valves in each bowl plus the bowls are a little larger. Again, we're dealing with twice the amount of fuel and that's the key with alky. You've got to get enough of the stuff to the motor. I have got mine to work with 8 psi fuel pressure but you really need about 9.5-10 psi of fuel pressure to the carb at WOT. You won't be able to do that with a carb as you will blow the needles off the seats and flood the motor unless you do a little mod to the regulator. I have only done this to a Holley 704 regulator but it will work with others. You need to take the diaphram cover off the regulator and drill a 11/64 hole in the side and then tap the hole with a 1/8" NPT tap. Put a AN4 to 1/8 NPT elbow fitting in that hole and then drill and tap your intake or carb spacer and put another elbow there. Connect the 2 fittings together with a AN4 line or you can use rubber line and hose barb ends of the elbows if you don't want to use the AN4 line. When you crank the motor up, disconnect the line from the intake and plug the intake or have a helper hold their finger on it and then set your fuel pressure to 9.5-10 psi at the regulator. Then connect the line back to the intake. You will find that for every inch of manifold vacuum you have at idle you will have a 1 psi DECREASE in fuel pressure. This will get your fuel pressure down where you don't blow the needles off the seats at idle. When you open the throttle, intake vacuum drops and you will see your fuel pressure rise. At WOT where you have very little to no intake vacuum, your fuel pressure will be where you set the regulator, i.e., 9.5-10 psi. At this point you don't really care if the needles are getting blown away as you will be using all the fuel you can pump in there.

As I said above, you can get by with 8 psi and not have to do the regulator mod if your carb has 1:1 linkage where the secondaries open with the primaries. Otherwise, what I have found is that doing the burnout with a carb that has the old style progressive linkage, you are really using only the primary bowls as the motor doesn't have enough load on it to have the secondaries open and you run out of fuel in the primary bowl. If you have the 1:1 linkage then both font and rear throttle blades are open the same amount burning fuel equally out of both bowls and that will work fine with 8 psi.

Does it work? I run a 496 in a 2546 lbs. Camaro to a best of 5.46 @ 125.77 in the 1/8th with a 1.18 60'. It works for me and as Forrest Gump would say, "That's all I gotta say about that."


cepx111 08-23-2007 10:59 AM

That was awesome dude, very well written and very informative. I really liked the regulator trick too, thats a very good idea. I hope to convert my 496 to alky next year and I wasnt to thrilled about possibly having to relocate the fuel cell and everything else. I'll definetly dig this post up and refer back to it when I do.
Thx, Charles

gdmii 08-23-2007 09:05 PM

Thanks Charles. Glad it helped.


rooniew 08-25-2007 03:50 PM

George - Thanks for the information
Sounds as if it would simplify things to get a 1:1 carb.

novawagon 08-28-2007 09:58 PM

What Jets to use in a 1050 alcohol Dominator on a 489 BBC???
This has been very informative and I thank all who have written.

My question is about tuning...
I just bought a Rupert Alcohol 1050 Dominator and enderle belt driven pump which I will mount under the hood of my malibu. The carb came off a 540 but I am running a 489 BBC. Does anyone have any idea what I should be running for jets front and rear?? I dont want to flood the engine.

I have run enderle injection standard and blown alcohol but this is my first attempt at an alcohol carburetor.

Any help would be greatly appreciated!


gdmii 08-28-2007 10:18 PM

I don't think you have to worry about flooding the motor. I had a float stick once and had raw alky pouring out the collectors with the motor running. :D :D

On the tune it depends on how Rupert set them up but it all boils down to how much air you are able to pull through the motor. The last carb he did for me was the 1150 I run now and I have 184 jets front and rear. I had a 1050 he did and I think I had 180s in that. I have a friend running a small block that has 209s in it. That will get you started. You want it jetted to pick up somewhere around 5-10 degrees water temp on a pass. More than 10 and you're too lean. Less than 5 and you're a little on the fat side. If you're looking at EGTs, ideal for mine is between 1050-1100 on an eighth mile pass. It's not unusual to see upwards of 1300 in the 1/4. Rupert will be the first one to tell you to throw the EGT away and jet the thing for max MPH. BUT, for consistancy, alky likes to be on the fat side. You won't run as fast but you'll be more consistant.


davis419b 08-29-2007 07:37 PM

JP, I think that is too fat, 154,s would be my chioce with a 496. I ran a 1050,1150 and 1250 on my 565 with never bigger than 165,s. Call Rupert and ask him whatever he tells you will be a little fat!

topsportsman1 08-29-2007 07:49 PM

I'd listen to George

George Knows :P

Guys please fill out your profiles,atleast tell us your location,State would be fine Thanks


gdmii 08-29-2007 08:09 PM

Originally Posted by davis419b
JP, I think that is too fat, 154,s would be my chioce with a 496. I ran a 1050,1150 and 1250 on my 565 with never bigger than 165,s. Call Rupert and ask him whatever he tells you will be a little fat!

The reason you can use a smaller jet is because you have a larger motor that is pulling more air through the carb at a faster rate and this rate (velocity) will determine what jet you can use. I think you will find that, in general, the smaller the motor the larger the jet has to be with a similar sized carb. But that's just my experience. In the end, it doesn't matter what I, Rupert, or anyone else says. The motor will tell you what it wants. All you have to do is listen to it.


All times are GMT -8. The time now is 09:30 AM.