I have a Door car I have been working on so my kids can start racing. I has a BBC 468 single alky 4150 900cfm pro systems carb with Magna 500 electric pump. Power glide trans.

This car is not very consistent currently and I believe its in the fuel system. It can move .03 from run to run. I have had the jetting all over and the pressure all over and it doesnt seem to make a difference in consistency.

The car will run faster with more pressure but blow past the seats at idle. I am not after et im just looking for consistency.

I would like to hear from people running electric pumps with alcohol.

I am wondering is the only way to get this to work is buy a new belt drive fuel system?

Bob
I don't run a electric pump on my junk but i do drive a dyno quite often. I have had a few customers who have used a vacuum reference fuel pressure regulator that worked pretty damn good.


Joe

edit assuming carb has .150 spring loaded needle and seats in it.

This message has been edited. Last edited by: sr4440,

This had a vacuum assisted regulator on it at first. I have sense plugged that and run the pressure at 7psi. Consistency was better with it plugged. The vacuum assisted regulator top end pressure would change all the time.

What size are the needle and seats? You should be able to run an electric pump with a normal dead head regulator with that combo!

If it goes faster with more pressure you draining the bowls. I know of larger more HP motors running just what I stated above so you definitely have a fuel delivery issue.

Just curious, is the carb sealed to the hood/scope? If not, try an air cleaner on one run.

This message has been edited. Last edited by: TOP38,

First thing I would always do is compare slips to try and ID where the change is if possible.

If its 1/4 mile racing you have a lot of incrementals to look at and compare.

I ran my dragster with a 509 and an APD 1050 supplied by an Aeromotive A-2000 and a dead headed Magnaflow regulator.

7.75 or 7.76 pretty much every track I was at in summer.

Once in a while it would toss out a fast run, 2-3 faster but was usually pretty good.

Engine temp to me is a real big factor when I ran alcohol....cold NG....warm...Good...

I'm betting it is lean, be it from a delivery issue or carb not set up to deliver enough.

On my relatively mild 468 with APD HP1000 carb, the fuel numbers get almost perfect on the dyno when the jets are completely out of it. I have 196 in it now just because it picks the fuel up a little better but I raced it for many years with no jets.

On the dyno I discovered that I could make the engine fatter/leaner with fuel pressure, even though there was plenty of supply with lower pressure. Since you go quicker with more pressure, it likes being fatter.

quote:

Originally posted by TOP38:
What size are the needle and seats? You should be able to run an electric pump with a normal dead head regulator with that combo!

If it goes faster with more pressure you draining the bowls. I know of larger more HP motors running just what I stated above so you definitely have a fuel delivery issue.

Just curious, is the carb sealed to the hood/scope? If not, try an air cleaner on one run.

Top I dont know the needle and seats. The carb is open with a cowl hood.

quote:

Originally posted by Bob Payton:
I have a Door car I have been working on so my kids can start racing. I has a BBC 468 single alky 4150 900cfm pro systems carb with Magna 500 electric pump. Power glide trans.

This car is not very consistent currently and I believe its in the fuel system. It can move .03 from run to run. I have had the jetting all over and the pressure all over and it doesnt seem to make a difference in consistency.

The car will run faster with more pressure but blow past the seats at idle. I am not after et im just looking for consistency.

I would like to hear from people running electric pumps with alcohol.

I am wondering is the only way to get this to work is buy a new belt drive fuel system?

Bob,
My car (1050 Dom on alky), has the same problem with fuel pressure, (faster at 7-8 PSI, but pushes past the needle/seats at idle), so I keep it at 6, and it is consistent. I gotta say, the Magnafuel 500 is a lot of pump. I am using a BG280, and it pumps way more fuel than I will ever need. Going to a bypass regulator helped a lot. And following Barry Grant's advice on the plumbing, which really makes sense if you think about it: (-10 cell to pump, -8 pump to log, and log to regulator, -10 on return line to cell). A lot of folks go -10 to carb, then -8 on return. You need to be able to return the full supply volume or regulating fuel pressure is nearly impossible. But I suspect you already know this.
3 things that helped steady the ET's on my son's Chevelle, were: 1. Cleaning up the mechanical advance- (Along with new bushings, and the lightest springs in the Moroso recurve kit); 2. Fabricating an air pan to bring in air from the cowl hood, and seal out hot/variable temp underhood air; and 3. New 180* thermostat, with 4 tiny holes drilled around the edge, to smooth out the variations in cylinder head coolant temps between open or closed stat.

This message has been edited. Last edited by: FootbrakeJim,

quote:

Originally posted by Bob Payton:

quote:

Originally posted by TOP38:
What size are the needle and seats? You should be able to run an electric pump with a normal dead head regulator with that combo!

If it goes faster with more pressure you draining the bowls. I know of larger more HP motors running just what I stated above so you definitely have a fuel delivery issue.

Just curious, is the carb sealed to the hood/scope? If not, try an air cleaner on one run.

Top I dont know the needle and seats. The carb is open with a cowl hood.

Bob

Unless there is an issue with the fuel system or a tank venting issue, the N&S are the restriction in the fuel system. Alky carbs normally have .150" N&S. Also with alky and the solid black floats, they can become alky soaked causing carb flooding issues so racers generally readjust the floats to correct this but when this occurs and they are readjusted to regain the correct float level, you loose float drop and this really restricts fuel flowing out of the N&S's which causes the bowls to drain too low during a run! If the floats haven't been changed in a while, I'd recommend changing them,, you can also take the bowls off and see where they are adjusted too,,, if they are alky soaked you will see how low they are in the bowl and how little float drop you can have.

Superb advice, TOP38! All of it true.

quote:

Originally posted by FootbrakeJim:
Superb advice, TOP38! All of it true.

When I decided to run an alky carb on my 565 BBC I already had a good electric fuel system so to be sure it would work I went to the dual needle and seat bowls (PCI). And once a year it needed 4 floats! LOL

What internal is it varying.

I don't mean to sound stupid,but I am assuming that you are a pretty experienced racer?

Some racers that are "beginners" could clearly lose .03 with inconsistent staging.

Just thought I would put this out there if you are new to the sport.

Answer the following please:

1. Front or rear cell?
2. What is the 60'?
3. What is the 1/8' et?
4. Your .03 et swing is in regards to what, 1/8', 1/4' ?

You need to mount the fuel cell in the front. A 16v Battery will make a heck of a difference in the pumps pph capability. Do not run a fuel filter, filter or strain it while going into the cell.

Sorry Guys was busy last night.

Cell is in the rear.
16v battery

All these runs listed below are at 7psi fuel pressure.
I recently installed an 02 which is reading 5.2. After the first two passes I started jetting this car down. My son lost 2nd round but we continued jetting and testing a couple more passes. I thought I was on the right track when the car et jumped again but the rest of the run looked better.


This is the from the second pass. I was not able to pull the data from the runs with 164 jets yet.

Just came upon this with my car after changing the transmission cooler believe it or not.

You are seeing the change from my quick math in the 60-330 interval on the last run. Your dropping back into your converter and seeing inconsistency related. To fix the problem you need to simply change your shift point up so your not dropping back into the converter stall.

I did this and it tightened up my interval and the problem went away.

For me the change that caused this believed it or not the trans cooler. I put a derale atomic cooler in my car that was much less restrictive - and I immediately saw a change in the cars low RPM behavior. My reaction times slowed and I later saw this interval change. Talked to Rossler and he said the cooler prior was restrictive and was making my converter appear tighter...when the pressure was reduced all the other items ensued.

Raise your shift point and I bet the problem goes away. The temp of your trans fluid is why sometimes its it showing and others times it is not. Easy fix.

After seeing your logbook,you don't have nearly the problem that I thought you were describing.

I think you will find your problem in short order.Trans fluid temperature is a very good place to start.

Maybe .164 ns if the .150’s are the restriction

Well, your reaction times are solid. So it doesn't seem to be anything to do with staging location. Your afr data to me doesn't look goofy trend wise. Not sure what 5.44 is on that scale, but lean comes to mind. But it is the same lean the entire run with little regard to rpm.
Does it always spin the tires? The initial leave seems clean. But there is spin well after the hit. The inconsistency kinda follows the 60' variance.
The spin just jumped out at me.