Regulator placement for dual carb set-up...

[cjshaker]

Trying to figure out a good fuel delivery system for the new set-up. For a high horsepower deal, is it best to have a multi-port regulator that feeds each carb individually, or does a single port regulator that feeds a dual feed rail work fine? I'm leaning towards the dual feed regulator, but wanted some input from guys who race.

Along the same lines, is it best to mount the regulator separate from the engine, to avoid vibrations, or on the engine? I haven't looked into the NHRA rule book to see if there are requirements.

[BattlestarGalactic]

I've got a 1/2" line up to Mallory return regulator, split with two #6 lines to the carbs.   

At one time I had the regulator mounted to firewall, but got grief over fuel lines in line with clutch.  I then mounted it to a piece of square tubing on the frame rail(no inner fenders).

I would mount it to the inner fender and run two lines over.  Simple and effective.

[mike7570]

Ran mine from multi port regulator, never had any problems.
NHRA says you can't mount on firewall. No engine vibrations from solid front and mid mounts  (the whole car vibrated)

[cjshaker]

The engine shouldn't shake too much, being tied on one side. I do recall that firewall rule now that it was mentioned, and keeping it on the engine would help keep things tidy I guess....one less thing to work around when pulling valve covers. Down side being you'd have the return line running there also. Hmmm, maybe the fender panel would be best for me. Thanks for the thoughts, guys.

[Posi67]

I put mine outside the fender apron to help clean up under the hood. #8 line in and same out to a custom fuel log. I had tried a return line off the back end of the fuel log but it was too small and any fancy fittings with bends caused the pressure to spike. Ended up just using the return line off the fuel pump like tons of others do. Never caused any problems. 

[Falcon67]

I don't care for dead head regulators, so I just engineer the fuel delivery with the regulator on the back side of the carbs controlling returned fuel.  Echo, can't mount it on the firewall.  In the door car, the regulator is mounted on the back of a shock tower.  On the dragster, it's on the back end of the fuel log.

[cjshaker]

Dale, I like that idea. Simple and clean, and I like the idea of keeping the underhood area tidy. Less things in the road means easier to work on. I have this custom fuel log that I got when I bought the intake, so may just go ahead and use it.



I wasn't aware that some fuel pumps had a built in return. Some of this stuff is new to me. I have the Clay Smith mechanical pump, which doesn't have a return, but as always things are always subject to change.

I don't care for dead head regulators, so I just engineer the fuel delivery with the regulator on the back side of the carbs controlling returned fuel.  Echo, can't mount it on the firewall.  In the door car, the regulator is mounted on the back of a shock tower.  On the dragster, it's on the back end of the fuel log.

Chris, I've heard the issues with deadheads, so not going that route. Question though, if I get what you're saying, the regulator controls pressure on the pressure side also? I assume by regulating the return? I wasn't aware that's how they worked. I had it in my head that the inlet side of the regulator was whatever pressure the pump put out and that the regulator regulated the pressure on the exit side only, bypassing excess to the return. But you're saying the pressure side is controlled by bypassing excess to the return? It makes sense, just didn't realize that's how they worked. A big "DUH" moment for me..lol

[Heo]

This is what i used with Webers worked fine and Webers is kind of
sensitive to fuel pressure. And you got a fuelfilter in the same instalation
http://www.officinamalpassi.it/en/carburetter-fuel-pressure-regulators/converter-baypass.html

[BattlestarGalactic]

Pretty sure most aftermarket pumps have a relief built in(like an oil pump).  Some have a fitting that you can run back to the tank.  I've seen some of the big BG kind of pumps have bypasses built in.

My Mallory return keeps 6 psi to the carbs and lets the remainder go to the tank.  The pump inlet line is on the same side as the carb feeds.  It doesn't restrict the inlet side to the carbs.  Basically what Chris is describing.

[cjshaker]

My Mallory return keeps 6 psi to the carbs and lets the remainder go to the tank.  The pump inlet line is on the same side as the carb feeds.  It doesn't restrict the inlet side to the carbs.  Basically what Chris is describing.

Well that's handy info to have when coming up with a design for it..lol Thanks guys.

Heo, don't think those will work for me. I need something that will handle a #8 line minimum.

[Falcon67]

>But you're saying the pressure side is controlled by bypassing excess to the return?

That's it.  The theory is that the carb(s) can use the full volume of the pump if necessary and when using less, excess is returned to the tank.  Since pressure is a measure of resistance, if the reading starts to fall below - say - 6 PSI it means that the engine is really using up the supplied fuel, not that the pump is necessarily having an issue.  That would of course indicate the need for more volume in the fuel system to maintain the specified pressure at the carb(s).  Figuring .5 lb fuel/HP will usually over-engineer things enough that you should not see any fluctuation in pressure at the carbs because there will be plenty of volume to feed the engine.

Fuel feed in the front, pressure reading at the log, return out the back to the tank. 

[fekbmax]

I use a pump with pressure return directly off pump so on duel carb setups I like a regulator for each carb.

[Jim Comet]

Here is the setup I am going to run with my electric pump. 1/2 inch hard lines with 8an braided for both supply and return. Haven't run it yet but hopefully will know in a month or so. Jim