tshort

As per my engine builders advice, I'd like to install a fuel pressure regulator. I currently have a mechanical fuel pump and would like to stay with this setup. Few questions:
Do you have to run a return line to the tank to use a regulator?
Where does it mount?
What extra 'stuff' will I need to make it work?

PLEASE, if you are running a similar setup, PLEASE post some pics.

Muchas Gracias.

dath

Hey Travis,

I'm likely in the same boat. I'm thinking that I should probably have just skipped a mechanical fuel pump (which now seems to be lost in the mail) and went for an electric. My car has a return line right next to the feed line that normally hooks up to the stock mechanical pump. Since I don't have my new pump yet, I don't know if there is a provision for that.

There are two different kinds of pressure regulator. There is the bypassing kind, which would require a return line. There is also a "dead-heading" regulator which does not require a return line. I'm not sure if it would be wise to use a dead-heading regulator with a mechanical pump or not. Probably someone will chime in and say one way or the other. I'd like to know these sorts of things as well. In fact, fuel pressure is even more important to my application because I need a good constant pressure to my nitrous fuel enrichment jet.

Edit:
Hmm, just checked my "How to Install and Use Nitrous Oxide..." book and it says that for a low pressure fuel pump either type of regulator can be used. However, the book doesn't spend any time talking about mechanical pumps, so I wouldn't take that as gospel. Perhaps a quick call to Holley would clear things up...


[Modified by dath, 5:16 PM 7/29/2003]

tshort

Ummm, nobody running a fuel pressure regulator? :confused:

dually4wd

You could go with a Holley 803 (4 1/2 - 9psi) and dead head it with no problems. You can buy a carb heat shield with a regulator mount built in or make your own mount elsewhere between the pump and carburetor. Set up your pressure around 8psi at idle and it should be pretty close for wot.

dath

Just curious, doesn't the flow rate go down with increased pressure? I see on Holley's website they graph the flow rate "free flowing" and at 4.5 PSI. The 4.5 PSI rate is way lower than then free flowing number... As soon as Mark sends my pump, I'll be fighting the same battle. I just hope the pump he's sending is big enough to support 600+ HP (with nitrous) in my case...

442olds

Regulators will degrade your fuel flow, that is why alot of racers have started using a bypass regulator similar to a fuel injection setup. If you are running a holley street mechaical fuel pump it will put out about 7.5-8 psi all the time unregulated which is fine if you have a holley carb, but a q-jet won't survive. I have a C&S Specialties bypass regulator setup on my car with a 1/2" feed and 3/8" return line. follow this link to see how mine is setup http://www.geocities.com/etm_76_vett...stem/index.htm The bypass setup will allow full fuel flow to the carb and then the return will see the degraded fuel flow rate instead.

cicch95

Edelbrock sells a plate that mounts under your carb to hold a Holley type regulator. It is about 1/4" thick aluminum. I made my own which is 2" thick and made of phenolic, which is great for heat disbursement. It is an awesome place for your regulator. Keeps is nice and handy! Mount a small gauge right off the regulator and your lines to the carb from each side.

No, you do not "need" a return line.

-Rick

tshort

I will be replacing my current pump (which is leaking) with a B.G. street pump that has AN inlet and outlets. My carb is a Speed Demon 750. I don't have a return line so I don't know how a bypass regulator will work unless I am understanding it wrong. Mark, the engine builder, suggested running at 5 1/2 psi and all the pumps are higher than that. Is the regulator really necessary or should I forget about it?


[Modified by tshort, 4:24 PM 7/30/2003]

dath

I don't think strictly speaking that a regulator is really necessary, but it does depend somewhat on your carb setup and on the particular pump you choose. Some pumps claim to require the use of a regulator and some do not. I would probably not even bother myself if it weren't for running a nitrous setup which will flow differing amounts of fuel based on pressure...

dually4wd

Just curious, doesn't the flow rate go down with increased pressure?[/QUOTE]

Not if the head pressure is up where it needs to be. On the n2o side of our race motors, we run 22-25psi from the pump, which will dead head the regulator at about 10, but then when the n2o comes on, it will flow about 6.9psi. Holley type carburetors like 7psi at wot, so you need to be a slight bit higher at low demand to provide the right pressure under flow. Back to the nitrous side, if your pump doesn't put out enough pressure to flow your n2o regulator at 7psi, you're going to cook pistons if you start spraying much over 125hp.

tshort

So.....do you think Mark is feeding me some odd personal preferences or do you guys think I need a regulator for this setup? I still don't have my spec sheet (this was the second engine like this one built with these components and specific porting) but I think it's around 10 to 1 compression, I run 93 octane, about 38 to 40 degrees total timing, a 750 Speed Demon, no vacuum advance, around 440-470hp, a mechanical fuel pump, and no fuel return line. Of course, if I decide on one of the pumps that requires a regulator then I'll get one but what about some of the pumps that don't require one. I need to make a decision soon cause I want to use the Summit discount that expires in one week.
Thanks.


[Modified by tshort, 8:32 PM 7/30/2003]

dually4wd

If the mechanical pump puts out no more than 8-10psi at the most, no you don't need a regulator. But, if it puts out 10-15 or more, yes you should put a regulator on it. And if you'll be using nitrous, you will need a second regulator to control that fuel too.

AlwaysWave

tshort

Thanks for posting those pics, Biltogo. I still can't decide. :confused:

AlwaysWave

It's simple to hook in. The return line you see to the right of pic 1 goes to the stock return line on the frame rail. I have zero boiling gas problems, and it's been working perfectly for over 5 years. You set it to just below the needles pressure rating and you'd be all ready to drive troubles free.

tshort

I'm now thinking I'm just going to go with this pump:
http://store.summitracing.com/partde...1721&view=2047
and no pressure regulator. The pump puts out 110 gph at 6psi so I don't see why a pressure regulator would be needed and it puts me just about at what Mark said to run this thing at....5 1/2psi.

Crash Dummy

Travis,

For what it's worth... when I originally started giving Mark the information on the accessories(intake, carb, headers, fuel pump, etc) I put on their engine I had installed a high volume 110PSI Holley fuel pump. He told me the same thing.... if I was going to run that pump put a regulator in line. The concensous was that I did not need a high volume pump with the 355 and I just put on a new stock pump. Not cranked up yet, so I guess we will see.

AlwaysWave

That's the pump I have, regulated at 5 1/2 lbs. The pump puts out about 7 lbs. I used the bottom plate (extra piece and cost) on mine because the gas line routing was very, very tight on my 72 SB.

The pressure regulator does give you the opportunity to route excess fuel back and also avoid the vapor lock.

If the fuel pressure overcomes the carb needles, you'll be running rich all the time, no matter how you try to tune it.


[Modified by biltogo, 11:16 AM 7/31/2003]

tshort

Hmmm, good point. Back and forth, back and forth. I found a few BG pressure regulators on eBay for pretty cheap, maybe I should just try one of those out.

cardo0

Lots'a good ideas here Travis. :yesnod: Looks like the sky is the limit on fuel supply mods. For my two cents I'll say install as much you'll use/need. :auto:
Now for a high performance mechanical pump a regulator would help prevent forcing fuel past the carb bowls needle & seat. This ruins good MPG and causes rich mixure/flooding. So for a super duper pump a regulator would be a good idea.
The Demon I expect has same pressure requirements as Holley which I thought was about 5 PSI (6 PSI for Q-jet). But Holleys website says bigger motors need more. :rolleyes:
Been running the Holley 12-803 regulator (adjustable 4&1/2 to 9 PSI) on my Goodwrench crate motor (Q-jet) without problems. Also had one on my '70 GTO (400" ~350HP) and ran just fine. As for mounting I use a quality tube bender and make my own double flares so I get away with letting the regulator (and gauge) hang on the hard steel fuel line (3/8" brake line).
Now I like the recirc line idea as I do run out to the desert heat frequently. Have plans to run a line fed by small orifice near inlet (a controlled leak) and connect to my installed vapor return line back to tank. This should keep relatively cooler fuel in supply line and minimize chance to vapor lock pump.
Holley also markets an electric fuel pressure gauge for about $75 (Summit). I couldn't resist and it measures out to be a friction fit to replace my clock in the instrument console. :thumbs:
BTW last I read you were just looking to warm-up the stock 350? Now your Sig says you put in a woop-a.. 383. :cheers: