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Author Topic: Dead head vs return line, car runs rich  (Read 2342 times)
66 galaxie
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« on: May 16, 2015, 11:03:14 AM »

A big subject to be sure.
I'm just looking to get some insight and learn what I can.

I switched my car from mechanical to electric fuel pump a few years back. Its a 393 stroker, mild build. It was suggested by a cam guy to make the switch.
I got a Holley blue pump,filter and ran -8 line to the carb. It is a dead head style with the pressure set at just over 6 lbs. Carb is a pro systems 750.
The car runs really rich, like wet plugs rich, with the rear cylinders being the worst.

I understand this is kind of a hard diagnosis over the internet. I'm wondering if a return line would be a better way to go.

Anybody want to wiegh in on the subject? Any info is appreciated :)
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66 Galaxie 500, 393 Windsor, 9.7 to 1,  Victor jr, Pro Systems 780 carb, Lentech AOD, 4.11 gears, stock suspension
DragBoss
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« Reply #1 on: May 24, 2015, 08:55:19 PM »

I ran a dead head system for years and fuel pressure would be about 7.5 lbs. I never had any wet plugs from that. You got something else going on. Ck all the basics, fuel level, power valves , jets, or  I have had it happen where needle and seat o rings leak and eventually crack and flood you over.
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408 Cleveland, 9.69 at 136mph with a 1.27 60 ft. Just starting to fine tune.
66 galaxie
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« Reply #2 on: May 25, 2015, 10:32:11 AM »

Thanks for the advice DragBoss.
I'll check that stuff out and report back.

I was wondering if the dead head system could force too much too much fuel to the carb. Trying to figure out what happens with all the fuel that is being pumped all the time...  I guess only so much can go through the regulator...
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66 Galaxie 500, 393 Windsor, 9.7 to 1,  Victor jr, Pro Systems 780 carb, Lentech AOD, 4.11 gears, stock suspension
DragBoss
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« Reply #3 on: May 25, 2015, 08:13:50 PM »

66 Galaxie, the Dead head system is limited by the regulator, you are right. You can over power it, or if it is faulty, it will not do its job. All the fuel that it pushes, majority gets burned, the rest can cause heat in system, and not good to let car sit with fuel pump on and not running. I ran the same Barry Grant 280 for 15 years, and just rebuilt it, but went with a BG 400 with return.

I ran the Holley blue before the BG280, with Holley regulator, 1203 I think it was, and fram Chrome filter. I ran 3/8 to regulator and 5/16 to carb if I remember.

For your car, -10 from pump to regulator and -6 to carb are fine. Bigger is better. so to speak.
What size line from pump to to regulator?
 How are you measuring the fuel pressure?

Do you need a return, not necessarily, are they better, I would say yes, does keep fuel cool and pump cool.
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408 Cleveland, 9.69 at 136mph with a 1.27 60 ft. Just starting to fine tune.
66 galaxie
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« Reply #4 on: May 26, 2015, 06:05:19 AM »

Thanks again DragBoss.
I ran -8 from pump to regulator. I think I have my fuel pressure gauge after the carb. I'll have to go look to be sure.
I checked float levels and they are ok. I have to go through my parts and see if I have a power valve in there. Like you said, coud blow one of those easy enough.

My car is street/strip and its mostly street.
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66 Galaxie 500, 393 Windsor, 9.7 to 1,  Victor jr, Pro Systems 780 carb, Lentech AOD, 4.11 gears, stock suspension
DragBoss
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« Reply #5 on: May 26, 2015, 11:30:31 AM »

I would want fuel pressure before the carb, at regulator, JMO,,,Not sure how you measure after Carb...
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408 Cleveland, 9.69 at 136mph with a 1.27 60 ft. Just starting to fine tune.
66 galaxie
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« Reply #6 on: May 26, 2015, 02:40:51 PM »

Yep, I had it after the carb  :death:
Your right, it doesn't make any sense to have it after the carb. I'll have to get some different fittings and take care of that.
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66 Galaxie 500, 393 Windsor, 9.7 to 1,  Victor jr, Pro Systems 780 carb, Lentech AOD, 4.11 gears, stock suspension
DragBoss
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« Reply #7 on: May 26, 2015, 07:44:44 PM »

You interested in my BG280 Fuel system? It includes the pump with matching regulator, all of the steel braided lines, and AN fittings?

How could you measure it after carb?
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408 Cleveland, 9.69 at 136mph with a 1.27 60 ft. Just starting to fine tune.
66 galaxie
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« Reply #8 on: May 27, 2015, 10:05:57 AM »

Well, like you said, it cant be an accurate measurement after carb.
I'll see if I can post a couple pics of what I have going on...







The line after the carb feeds goes to my fuel pressure gauge.
« Last Edit: May 27, 2015, 10:10:58 AM by 66 galaxie » Logged
66 Galaxie 500, 393 Windsor, 9.7 to 1,  Victor jr, Pro Systems 780 carb, Lentech AOD, 4.11 gears, stock suspension
DragBoss
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« Reply #9 on: May 27, 2015, 06:06:22 PM »

That should work, as you can compress a liquid. I just rather have 2 separate lines going to the carb, and like a -6 adapter for a gauge. You still should not soak plugs with gas, if fuel press is 6 lbs. like you say.
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408 Cleveland, 9.69 at 136mph with a 1.27 60 ft. Just starting to fine tune.
66 galaxie
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« Reply #10 on: May 27, 2015, 08:51:28 PM »

Thanks, I'm going to try and order some power valves this week. I'll take it apart and see whats up.
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66 Galaxie 500, 393 Windsor, 9.7 to 1,  Victor jr, Pro Systems 780 carb, Lentech AOD, 4.11 gears, stock suspension
DragBoss
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« Reply #11 on: May 28, 2015, 07:33:32 AM »

I would ck the needle and seat and make sure the o rings are good, Measure the vacuum at idle, power valve should be below that number. I have a bunch of power valves, some new some old, labeled.  new 6.5, 4.5, 2.5, used 5.5, 6.5, I don't use them with my pro system carb, if you want them pay me shipping, which is like 5.95 for small box from post office and I will send them to you....
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408 Cleveland, 9.69 at 136mph with a 1.27 60 ft. Just starting to fine tune.
66 galaxie
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« Reply #12 on: May 28, 2015, 11:43:24 AM »

Oh nice. Thats cool.
PM sent
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66 Galaxie 500, 393 Windsor, 9.7 to 1,  Victor jr, Pro Systems 780 carb, Lentech AOD, 4.11 gears, stock suspension
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