[540z]

Hey Guys,

I have been having a problem with my 327 running overly rich for quite sometime. I have been thru 3 different carbs, adjustments and various tuning tricks all to no avail. I have even gone as far as changing to a milder cam and adding a CDI box to my ignition setup.

Today, just for laughs, I installed a fuel pressure gauge. I was watching the gauge while the engine was running at idle and the needle on the gauge jumped back and forth rapidly, then settled back down to about 7 psi, waited about a second and jumped back and forth again. This was accompanied by a slight shudder in the engine and kept happening over and over again. This engine has always run rough and pig rich for no good reason.

I have a Carter Street and Strip electric fuel pump with an internal regulator and no return line. I was told at the time of purchase of the pump that it did not need a return line or an external fuel pressure regulator due to it's having internal pressure regulation.

I guess my questions are:
1. Is the needle jumping around normal when the regulator 'pops' and releases pressure?
2. Is it possible the gauge needle jumping is just caused by fuel inlet needle valve in the float bowl?
3. Could this be the cause of the pig rich condition?

I have had this pig rich problem with this engine for since I installed it 6 years ago and the only thing left to suspect is the fuel pump.

The engine details:
327 SBC, .030 over
10:1 Pistons
.202 Chevy Heads
Comp Cams "RV" flat tappet camshaft w/ hydraulic lifters
Mallory 6A Ignition box w/ Unilite distributor
Weiand Action Plus dual plane intake
Summit 600 CFM Carb

Thanks for your help,
TR

 

[SNTGreg]

First I have a question.

What the heck is "pig rich"?

Ok now for your question. I believe what you may be seeing is the needle actually being pushed off its seat by the pressure. I would doubt that the regulator in the pump would be doing this but I would think the pressure should be closer to 5 pounds.

 

[SSedan64]

Can't hurt to try a regulator.
Pump #'s from Fbird88
Carter P4594 7 to 8 psi 72GPH free flow.
Carter P4070 6 psi 72 GPH free flow.

 

[Tech @ BG]

It sounds like you could be seeing the bypass opening and closing in the pump based on your description. Does the fuel pressure ever go over 7ps1? WHat kind of gauge are you using? How much timing does the motor have at idle and is the rich condition just at idle or all the time?

 

[Jake_Dragon]

Sounds like my car, I had a dead head regulator and after changing over to a Holley bypass regulator it will hold 5.5 psi rock solid no mater what the RPM. The dead head would bounce between 4 and 7 psi and caused my needle valves to leak and the engine would stutter just like your experiencing.

 

[540z]

"Pig Rich" is a local term for when a car is running so rich that you can smell it coming before you can see it. Eye-burning rich.
The gauge I put in the fuel line is a non-liquid filled pressure gauge from Spectre. Not a great brand name, but it has given me an indication that something is happening in the fuel system that deserves investigation. The base timing is at about 12 BTDC.
I have a regulator on hand and I'm going to install it tonight, dial the fuel pressure down a bit and I'll let you know what happens.
Thanks,
TR

 

[Tech @ BG]

"Pig Rich" is a local term for when a car is running so rich that you can smell it coming before you can see it. Eye-burning rich.
The gauge I put in the fuel line is a non-liquid filled pressure gauge from Spectre. Not a great brand name, but it has given me an indication that something is happening in the fuel system that deserves investigation. The base timing is at about 12 BTDC.
I have a regulator on hand and I'm going to install it tonight, dial the fuel pressure down a bit and I'll let you know what happens.
Thanks,
TR

Depending on the duration @ .050 of the cam you may need more base timing in the engine as well but definitely try the fuel regulator and see if it helps. I am guessing but your base timing prob need to be 2-4 degrees high then it is right now and then readjust the mixture screws if the regulator does not correct it.

 

[BogiesAnnex1]

"Pig Rich" is a local term for when a car is running so rich that you can smell it coming before you can see it. Eye-burning rich.
The gauge I put in the fuel line is a non-liquid filled pressure gauge from Spectre. Not a great brand name, but it has given me an indication that something is happening in the fuel system that deserves investigation. The base timing is at about 12 BTDC.
I have a regulator on hand and I'm going to install it tonight, dial the fuel pressure down a bit and I'll let you know what happens.
Thanks,
TR

I suppose "pig rich" is opposite to lean being described as "dryer than a pop corn fart"

I wouldn't be pleased with the pressure surges. To define them a little do they go from 7 psi to less pressure and back or do they exceed 7 psi and drop back?

I have to second the motion on a bypass regulator. These keep the fuel moving without pressure spikes.

Bogie

 

[540z]

Well, I installed an inexpensive "dead head" style pressure regulator in the fuel line and dialed the pressure down to 5 psi as suggested. It worked! For the first time in about six years, I can actually adjust my idle mixture. The timing I set up to about 14 BTDC and the engine calmed right down.

Then the lovely China made regulator died! Fuel pressure dropped to zero. So, just for grins, I replaced the regulator with a piece of fuel line and the over-rich condition came right back. So, I guess the problem is in the fuel pump's internal bypass regulator. I have one more day with the car before it goes into off-site winter storage, so I 'll replace the pump and regulator with Auto Zombie crap to get it there and install a good pump and regulator in the spring.

Any Suggestions as to good, reasonable Pump/ Regulator combinations? It seems that I need about 5 psi.

Thanx,
TR

 

[techinspector1]

Get this return style regulator.
http://www.summitracing.com/parts/MAA-4309/

Mount a fuel filter close to the tank where the supply line comes out of the tank. Immediately after the filter, mount the electric fuel pump. Immediately after the pump, mount the regulator. Run the supply line out of the pump and into one side of the regulator and out the other side of the regulator, then to another fuel filter in the engine bay and then on to the carburetor. Tee off at the carb inlet and install a fuel pressure gauge. Run a line out the bottom of the regulator as a fuel return line to the tank. With the regulator mounted at the back of the car with the pump, it will only take a short piece of line to make the return line from regulator to tank. Scroll down to Figure 3B here to see the schematic....
http://go.mrgasket.com/pdf/4309.pdf
Adjust the regulator to 5 psi with motor running and pump running and you're done.

This will be easy on the pump because it will not have to push fuel "deadhead" against a restriction. It will like you for it. :thumbup:
By the way, I always use the rubber off muffler hangers to mount the pump and use a short piece of quality fuel line hose just before the pump inlet and just after the pump outlet. This will isolate the pump and lines from vibrating against the pump mounts and transmitting a "droning" sound inside the car. The black rubber muffler hangers I'm talking about look like they were cut from a tire, you can still see the white fabric cord in them, about 3/4 inch wide x 1 inch wide. Bolt or weld the hangers to the car, then bolt the pump to the hangers.

 

[airboat]

I agree! The Mallory techinspector1 posted is the only regulator I would use. I have herd a lot of people complain about overpressure with the Carter pumps and mine was putting out so much pressure the first regulator I bought (holley dead head) couldn't stop it.

The Carter is a great pump but you need the Mallory regulator to make it reliable! why would someone use a deadhead type regulator in a performance application? it's just a big restriction in the fuel line.