Hi Folks,

Been having these bizarre fuel pressure problems, can't think I am the only one to ever experience this. Trying to keep this short of a novel but here goes;

496BB.
Edelbrock performance 130GPH mechanical pump.
1/2" fuel lines.
Matching edelbrock regulator set to 6lbs.
New Holley HP series 950.
Piece of garbage Holley mech pressure guage between regulator and Holley.
Good hi volume large cannister filter before pump.

So it goes like this, fuel would stream out of the vents on the carb when I would reach 3500RPM under load. As I could never see it I thought the problem was a vibrating centerforce, it wasn't. Turning the regulator all the way down to 3lbs problem decreased but still significant. Hooked up return line which helped a lot but would still happen but only on sudden deceleration with the pressure cranked down as far as possible. Regulator diaphragm finally ruptured. Disgusted with this I did some research to find the mallory regulator was designed for an electric pump, also the pump for whatever reason according to Edelbrock was not designed to run with a return line? Why it would matter I can't imagine, however, for me this is a good thing as the return leaked by the tank anyways. So, replaced the mallory with the matching (expensive) regulator for the pump, Improved again but would still intermittently flood even at idle. Very dangerous condition indeed given the volume of fuel that would stream from the vents. Car ran great for a couple days then suddenly started barfing fuel everywhere again, stranded on the side of the road with nothing helping, no stuck floats, pressure cranked down etc It just would not stop overflowing. Took it to the local performance carb shop who tell me the regulator is bad although they haven't taken it apart yet but observed pressure readings in the TEENS (randomly).

So..... How the heck is this possible? I have not yet replaced the pump but it is just a diaphragm? Could it vary like that and create these problems. I would understand low pressure problems but high? I am also disgusted with myself that I had to resign myself to just taking the car someplace. Just concerened that I am replacing yet another regulator that is the symptom and not the cause.

Any thoughts or similar experiences greatly appreciated!

Thanks
-Andre

 

You could solve all your problems by reverting to the stock pump and ditching this aftermarket crap. The story you are relating is quite common.

 

Have you tried a pressure gauge between the pump and regulator? Have you tried a different float in the carburetor? It may be partially sunk.

Also, why do you need so much fuel flow?

BigBlockk

Later.....

 

Have you removed the floats and taken a good look at them?? They could be faulty. I had this problem and upon inspecting the floats they were defective and I got new ones on warranty.
It could also be dirt in the fuel line causing the needle not to close fully. Needles and seats are easy to remove and blow out.
I don't believe in the cheap regulators but alot of people have had no problems with them.

 

Check for dirt lodged in the needle and seat also. 6 lbs pressure is fine for a carb.

 

Thats a BIG carb for the street...have you checked your float level??
...redvetracr

PS: I run 7 1/2 psi

 

Thanks for the replies.

I replaced both floats as one looked bent to me but it made no difference. Set the float levels even trying them very low with no avail. Cleaned out the float needles and tried a different one to see if it would help. Nothing does. As I mentioned before the only thing I haven't replaced is the pump but it just makes no sense to me that a deffective pump would create pressures so high that two what should have been quality regulators could not control it.

It is a big carb but it is a thirsty beast. 496 BB with roller cam, Brodex RR heads with 500HP at the rear wheels. Irony is that when it is behaving which it often does it is actually a little lean at WOT. I'm concerened that with a stock pump I just won't provide enough fuel volume. Perhaps I'm just going to have to go electric.

Thanks
-A

 

Go back to "L88" stuff with the engine and keep the fuel system all stock. A 130 GPH pump and 1/2 " fuel lines and regulators are not necessary unless it`s a all out racer and supercharged.

 

Thanks IronCross. No question this could all be a lot simpler;-) Perhaps I can get away without the regulator and instead use stock pump. I'm simply concerned about potentially starving the engine. I have more cubes than the original 427, way more cam and heads that flow a lot more. I am paranoid about ruining my engine at WOT given a higher possibility of lean condition. Seems safer to have more fuel available than you need but of course I have been way overboard dumping raw fuel down my new engine probably doing horrible things to the rings.

Engine builder just put together an engine very similar in configuration to mine which It ran 585HP on the engine Dyno. Can anyone tell me what fuel volume is needed for this amount of HP? In other words could a stock mechanical pump keep pace with it's needs? I really don't race the car but do occasionally attend track events and hope to do more in the future.

Thanks
-A

 

Why don't you get a stock pump from NAPA and see if it solves the problem? Go ahead they're cheap. You can't even drive it down the road right now, what could it hurt to try? After you find that it runs great with the stock stuff you can always go back to your current setup.

The BSFC (break specific fuel consumption) for performance engines of our vintage is about .5lbs of gasoline per HP per hour. Now let's see... gasoline weights about 6 pounds per gallon and we got a fuel flow of 130gph. So each gallon will..... I always hated math. So each gallon will produce about 12 HP per hour. Does that sound right? Now we multiply that by 130gph and get......SHAZAM, 1560 rompin' stopin' horsey powers. JUST DAMN DUDE!!!

Wate a minute! I'm a little disapointed in you young man. You're only pumping a little over 2 1/2 times the fuel the engine actually needs. You go to bed without supper!

BigBlockk

Later.....

 

This probably one of the times bigger or more is not better. Inches help and are important, but maybe not in this particular situation. I can think of another situation where a bigger "tool" brings more satisfaction though. Just think of what a 427 L88 or a 454 LS7 is comprised of. 12.5-1 and 12.25-1 in the latter because of a copper head gasket as opposed to a composition used in the LS7. Wild camshafts in both and properly tuned are good for nearly 600HP in box stock configuration with the addition of a good set of headers. My point here is that they use a stock mechanical pump at around 6-7 psi with 3/8 lines and never lean out. Take a look at the fuel line inlet nuts on your carb. The actual hole in them is only about a 1/4 " feeding the carburator. I would say without knowing much more about your set up is that your trying to push too much fuel and blowing the needle and seats. Fuel in the oil is often a result and much worse than a lean condition. See what the plugs tell you. You can get a lot of information by reading the plugs to tell you whats happening in the cylinders. You have obviously gone to considerable expense with this engine and want it right so you can go out and have fun with it. Get an opinion from a local racer similarly situated {same engine} in your area and tell him what you have, most of them would be glad to help with a hands on fix.
PS good luck

 

Good advice from all thank you. I even have an extra stock fuel pump lying around but of course in my never ending misguided quest to do what I thought was the right thing I went ape crazy and did all my lines with steel braided hose an A&N (sp?) fittings rendering it impossible to hook up a stock pump again without hacking into my pretty hoses. LOL Someday I may actually learn but I doubt it.

Thanks again for the advice.

Cheers
-A

 

It has 10AN inlet and 8AN outlet to Carb. I had a new POS Edelbrock pump and the pressure ranged from 4psi to 9psi. Looked trick but did not perform worth a grap. The Carter is a high volume race pump with 6-7 PSI. Does not require a regulator.

SolidLT1 recommended it to me and he has been running it for awhile now.

 

I am sure there is an equivalent pump for the BB. Carter is a far better product.

 

here is the description from Jeg's:
Big-time fuel flow for big-time performance. Carter Competition Series Race Super mechanical fuel pumps deliver big-time fuel flow. Their free-flow output is 172 gph. Despite this high capacity, their compact size means that they often fit where other high-performance pumps won't. In addition, they're ''clockable,'' which allows rotation of the inlet and outlet. They have heat-treated, high-speed levers, plus -10 AN inlets and -8 AN outlets, with fittings included. With 7 to 8.5 psi operating pressure, no regulator is required.

Mine runs a steady 7PSI.

 

Thank you very much for the part #. I will order it right now!

Cheers
-Andre

 

on the receiving end of help like when SolidLt1 recommended this pump to me, so it's nice to share.

Not sure where you got your pump/regulator from but if from Jeg's or Summitt they are pretty good about refunds within the first year. Fortunatley I decided to keep all my parts boxes so I was able to return mine in the box. But if yours is defective they should refund or perhaps provide credit towards a replacement.

Have fun !

 

Usually run the cheapie 6lb Carter street pumps, keep up just fine, never once had a failure.