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Old 05-01-2007, 06:35 AM
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Fuel pressure setting question for bypass regulator system

Guys,

I installed a new 4309 Mallory bypass style regulator on the camaro last night to go with the Comp 140 pump (I previously had a dead-head style regulator and I was wanting to let the pump run cooler etc). I was planning on using my old 3/8" steel lines for the return (bypass) lines. Upon opening up the regulator and reading the instructions, I see that it calls for 1/2" return (or larger) like I had suspected it might. I was not expecting the extra expense of running big lines back to the tank again.

I decided to try the 3/8" anyway to see if it would work okay or what. Got everything set up and turned the pump on. I cannot set the fuel pressure any lower than about 6 psi- just won't go any lower. Is this due to the backpressure for pushing the fuel back to the tank in the 3/8" line?

Thought about running -8An back to the tank using Summit push to seal hose and fittings. Also, I know the 8AN is only 7/16" ID. Is that 3/8" steel line actually 3/8" OD?? So, that would make the ID like only 5/16 or something? I am not sure how much different 7/16" would be from 3/8" as far as flow would go. Maybe I need -10AN??


I have 1/2" ID aluminum line from tank to pump to the reg. all the way already.

I haven't tried running the car yet to see what would happen with it. Do you guys think I need to replumb the return to make it "right?"

Any thoughts? Thanks for any help!

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Old 05-01-2007, 02:39 PM
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I have a bypass in the 59

I actually mounted the regulator in the rear close to the tank
with the 454 and edelbrock 1411 (?) I seem to recall setting it at 6.
I really do not know if it will go lower----I think the spring was for 3-15 and the other spring was for 16-60.

But I am using a stock Ford pump in the tank----(Big Bronco 25gal)

Bryan
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Old 05-01-2007, 02:44 PM
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Quote:
Originally Posted by Bryan59EC
I have a bypass in the 59

I actually mounted the regulator in the rear close to the tank
with the 454 and edelbrock 1411 (?) I seem to recall setting it at 6.
I really do not know if it will go lower----I think the spring was for 3-15 and the other spring was for 16-60.

But I am using a stock Ford pump in the tank----(Big Bronco 25gal)

Bryan
wait a minute. You mounted it near the TANK? How does that work out for ya? Never heard of that style of install before.

I guess I would still have the same pressure restriction, though. I've always heard it's best to keep the regulator as close to the carb as possible to minimize the reaction time of the system.
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Old 05-01-2007, 02:58 PM
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The fuel line runs from the tank to the carb and excess is going all the way back to the regulator in the rear and then returns to the tank.
It is regulated way downstream----cause I did not want to find a spot for it in the engine compartment.

Has not caused any issues---pretty much gauranteed cooler fuel (so. Tex resident), but is a ROYAL PITA to crawl under the car to check or adjust pressure.

Seems to work okay for me-----but, I'm not drag racing-----just playing

Bryan
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Old 05-01-2007, 03:06 PM
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Oh, forgot to mention.
Only using an electric pump and bypass for a couple of reasons

Fuel shut-off--------Anti Theft
Possible Fuel Injection in the future
Cooler fuel.

Bryan
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Old 05-02-2007, 06:47 AM
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That reminds me that I've got a little "extra" wiring to do before I take the car on the power tour. Would suck to come out and not find it in the parking spot.

Update: Tried running the car last night to see what it would do. It ran great. Fuel pressure didnt drop after a long WOT period, so I know that this bypass style system is working better than the other deadhead regulator. Fuel pressure only dropped about .6 psi on the datalogger, so I think I'm good.

Still don't know if it would make sense to plumb a larger return line or not. It seems what I have right now will work, so I guess why bother? I dunno.

I did measure a chunk of 3/8" steel line, and it is measured OD like tubing normally is. So that means that the ID is only 5/16. -8AN is 7/16" ID, which IS in fact a big difference.
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Old 05-02-2007, 07:10 AM
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Glad to hear you got it fixed I know in other posts folks have gotten all bent out of shape when people (like me!) trash talk deadhead regulators. They say that they have used them in drag race engines for years and they worked fine, but IMHO bypass regulators are much better at keeping a steady pressure under varying flow, period!
283s with hogged out power pack heads used to be the hot ticket for drag racing too, but we've moved on!


"Still don't know if it would make sense to plumb a larger return line or not. It seems what I have right now will work, so I guess why bother? I dunno."

I it's working I'd leave it alone. IF you start having trouble with fuel pressure spikes when you come OUT of heavy throttle or pressure creep at idle that you can't adjust down consider a bigger return.

Did you keep the same fuel filter? I think you were looking at replacing that in a previous post...

Last edited by SlowGTA; 05-02-2007 at 07:18 AM.
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Old 05-02-2007, 11:04 AM
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Oh

3/8 feed and a 5/16 return
dammit was that not one of your first questions?????

Bryan
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Old 05-07-2007, 10:26 AM
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Quote:
Originally Posted by SlowGTA
Glad to hear you got it fixed I know in other posts folks have gotten all bent out of shape when people (like me!) trash talk deadhead regulators. They say that they have used them in drag race engines for years and they worked fine, but IMHO bypass regulators are much better at keeping a steady pressure under varying flow, period!
283s with hogged out power pack heads used to be the hot ticket for drag racing too, but we've moved on!


"Still don't know if it would make sense to plumb a larger return line or not. It seems what I have right now will work, so I guess why bother? I dunno."

I it's working I'd leave it alone. IF you start having trouble with fuel pressure spikes when you come OUT of heavy throttle or pressure creep at idle that you can't adjust down consider a bigger return.

Did you keep the same fuel filter? I think you were looking at replacing that in a previous post...
Still have the same filter. Haven't done the gallon flow test yet to see how the system performs.

Summit has this line and fittings selection (called Twist Tite) and they look like they would work great for the return line. So the question is: will I get in trouble at tech inspec. at the strip if I have a 20 ft. "rubber" return line. It's definetely better stuff than regular fuel line, I just don't know what they would say, and I dont' have a rule book to look at either.

A link to the aforementioned product:
http://store.summitracing.com/partde...5&autoview=sku

Anyone know the ruling on that?
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