88CamaroZZ4

Has anyone used an external regulator on a 4bbl Holley TB? I have a Turbo City pump and everytime I turn the presure down the car runs faster. Now I can't turn the regulator down anymore. Would it be possible to open the regulator in the TB all the way up, plug the return and use a Mallory external regulator that has a return and has a 3-50psi adjustment?

89RS355

Sounds like it should work. What pressure(s) are you running right now? I can't think of why you can't et the correct setting with the one on the unit.
Also, can the injectors work if they are "dead headed" so to speak? So the fuel would come from the tank, and the regulator has two outs, one regulated out and one flow through. Hook the regulated out to the TBI inlet, and plug the flow through on the regulator. Then just leave the return from the tbi on where it is at. Easier to try that first, if it does not work properly, try capping the return off the tbi and use the unregulated output of the regulator. It would work, I don't know about how ideal it would be, but it would work, and if you really need the range adjustment that the Holley one can't do (low), open it all the way and reglulate the input. Makes sense, am I missing something?

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Jerry

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89 RS Lt Blue T-Tops T5
355 Crate, Compucam 2040
Pst Front Hotchkis Rear
Edle. TES 3" Flowmaster
Harwood hood, bla, bla, bla...
94 Z28, LT1 6M, Black
Most of the bolt-ons
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steve8586iroc

88,I think the way you have it is the best wy to do it. Plug the return line at the tb and run the return line from your external reg back to the return line going to you tank. Should work great.

88CamaroZZ4

I guess I'll give it a try when I get the car out of storage. Right now the lowest I can get the fuel presure is 16psi. I know it would run better with it a little lower.

FastBroker

Somethings is not right 88C. You must have a restricted return line or something. Or it (return line) is less than 5/16" somewhere along the line and/or it is kinked OR it is blocked by something in the line which is hard to find/fix.

OR you have a BIGGER pump than you need, but probably not.

EDIT: My reasoning is you should be able to get the FP don to 10 psi with the Holley reg... The directions/manual for the unit should state the operating range of the reg. Check that first. If it says it can get lower than your 16psi, you got probs...

[This message has been edited by FastBroker (edited March 02, 2001).]

88CamaroZZ4

I'll e-mail Holley to see how low the presure should be able to be turned down, with the internal regulator. I ordered the TB as a service part to use with GM wiring/computer, so no manual. I must have to much of a pump. Its an Airtex from Turbo City and is a high volume pump rated at 25-30psi. I know for a fact that the return line is not restriced. I followed it from the TB to the frame, back to the tank, all the way to the sending unit/ hanger when I did the pump. The presure could be reduced more with the stock pump.

FastBroker

Be careful. Pumps don't "make" pressure, restriction does.

Just because your fuel line is ok-looking doesn't mean it doesn't have an internal blockage, like a piece of rock or gasket or something. Sharp bends cause LOTS more restriction than you think, to, so if you have LOTS of bends, that is bad with a high-flow pump.

Also, the internals of the fuel tank could be messed up and/or less than 5/16", but again, probably not.

You'd be surprised at how many return lines have a built-in orifice somewhere along the line to restrict flow, too. Do a flow test on only the return line to check its flow/pressure characteristics to ELIMINATE it from the equation. Don;t cost nothin' to test it.

89RS355

Hey fast, you'll get a kick out of this:

Today we finished with my friend's 94 mustang. 331 stroker, 14psi Vortech unit. Should be good for 450+ horse as soon as we can get it dynoed. So we start it up today, and the damn fuel pressure is at 90psi. Tried to adjust it down and it wouldn't budge. As we reached boost, the fuel managment unit (really just a back pressure regulator) would lower the pressure, not increase it as it should. Like the darn fuel lines were backwords. I found the problem after way too long: IT WAS A RESTRICTION IN THE RETURN LINE!!!!! On a whim, I took it off and tried to blow through it, and I couldn't. Blew it out with the compressor, worked just fine. Loosing traction at 98mph takes some getting used too. Learned alot on that project.

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Jerry

-------------------------
89 RS Lt Blue T-Tops T5
355 Crate, Compucam 2040
Pst Front Hotchkis Rear
Edle. TES 3" Flowmaster
Harwood hood, bla, bla, bla...
94 Z28, LT1 6M, Black
Most of the bolt-ons
-------------------------