Hey guys. I built my cousin a 355 sbc derby engine. Typical simple build. Dart heads,flat tops,flat tappet cam. Have ran 4 derbys so far done really good only died 1 time. This was using a gas rochester carb with a cheap mechanical pump. So last week I put a holley 4412 alcohol 2 barrel on it with a holley blue electric pump and a return style regulator set at 6lbs. Engine runs great and will idle all day long. So he started running the derby and after about 5 minutes it would die every time he lifted off the throttle. He would have 2 hold the throttle open and refire. It would idle fine but after a full throttle blast when he lifts it will flood out. Something I noticed after reviewing his go pro video I noticed his voltage gauge is showing like 17.8 volts when the rpm is. This is only a 12 volt setup with a small 12 volt alternator. Next derby is Saturday and I would like 2 resolve this b4 he gives up and goes back 2 gas. Am I on the right track of believing that going from 12 volts to 18 volts could be causing the flooding condition?

float setting or needle and seat issue

It's a new needle and seat. I have float set where when running i have 2 shake the car 2 get fuel 2 come out of the sight hole. Could the extra voltage cause pressure 2 go high causing the flooding?

some thoughts,

*check the voltmeter against a known good meter

*maximum alternator output should be around 14.80. The 18-volt reading points to either alternator problem or wiring problem.

*carefully check all grounds, junctions, terminal connections.

*I do think the 18-volt reading is a problem and could be the root of the trouble.

*I think the high voltage has the potential to spike fuel pressure too high.

[this is all assuming the voltmeter is in fact correct]

Larry is right. The high voltage is causing the pump speed to spike - causing psi to blow fuel past the reg and n/s. Get the voltage under control and you should be good to go.

also, if in fact, the alternator has been outputting 18 volts to the battery it is likely the battery has been damaged.

Thanks guys... Checked it earlier with my fluke multimeter. Showed 18.1 volts. So pump pressure before the regulator will cause pressure change at the carb correct?

You didn't mention how much pressure you have at the carb. If you are over 9 lbs or so you could blow the needle off the seat. Even if you are overspeeding the pump, thats what the regulator is for, to keep the pressure steady. Make sure you have the correct pressure at the carb.

quote:

Originally posted by eigthmile:
Thanks guys... Checked it earlier with my fluke multimeter. Showed 18.1 volts. So pump pressure before the regulator will cause pressure change at the carb correct?

If your voltage was lower when you set fuel pressure, then your voltage goes up, it can be the source of your problems. If for example, you had 20 psi line pressure, and set the regulator for 6, and pump voltage was at 12, a change of 6 volts will substantially change pump output....change flow, restriction that creates the pressure needs to change as well......You need to do what Mike said, find out why the voltage is going so high and fix that....

You need a fuel regulator between the pump and carb. This would help. Just a heads up,....the larger the needle and seat the easier it is to leverage it with pressure. So alcohol needle and seats which are usually larger can be sensitive to pressure.

quote:

Originally posted by Ron C.:
You need a fuel regulator between the pump and carb. This would help. Just a heads up,....the larger the needle and seat the easier it is to leverage it with pressure. So alcohol needle and seats which are usually larger can be sensitive to pressure.

He said it has a return style regulator.

I do not think the voltage is the problem. As others have said check float level and fuel pressure settings. Generally flooding is too high float level or fuel pressure or bad needle and seat. I would also add you may need to check you vent tubes and put a vent tube from front to back.

quote:

Originally posted by Curly1:
I do not think the voltage is the problem. As others have said check float level and fuel pressure settings. Generally flooding is too high float level or fuel pressure or bad needle and seat. I would also add you may need to check you vent tubes and put a vent tube from front to back.

On a 2 barrel?? LOL

Be interesting to see if the pressure does rise at the carb when alt output is at 18V+.
Even though it is a 2-barrel carb, I think Curly might be on the right track. I would imagine there is a whole lot of fuel slosh going on in a derby type event. I would try adding an extension tube to the bowl vent.

Lol, I guess I missed the 2 barrel part. Ooops. Still it comes down to too high fuel pressure or float level or possibly slosh.

Bad float is another, weigh the float.

Float weights in grams
Plastic 10.7
Nitrophyl front 13.0
Nitrophyl double angle cut 9.5
Nitrophyl notched 10.8
Brass 15.0