Running Too Rich?

[jaudette3]

My '67 SWB is running great, except for one little thing - when I back off from high revs in 5th gear, say from 6,000 to 5,000, there's a little roughness for a short time. The feel is that things are loaded up a bit. I'm wondering if it's running a little rich. Here's the setup:

o original 2.0 built to 2.7 specs
o 901 "Solex" cams
o 40mm PMO's
o open venturis with tea balls
o jetted for the 4,000' elevation that I live at

I don't get any stumble when I'm shifting up through the gears, just when backing off from high revs in the same gear. It works through it in a couple of minutes. A little rich or something else?

Thanks,
John Audette

[MarkS]

When mine did that it was a fuel pressure issue. I had to run dead on 3.5 PSI or would stumble/hesitate a bit when backed out then back in as you describe, very crisp and clean going up. IDA 40's on 2.5 SS same altitude.

[Steve@Rennsport]

John,

Mark is right on,.....

JMHO, but Webers MUST,.................MUST get 3.5 psi of fuel pressure to work properly.

There is a whole myriad of ills from incorrect fuel pressure and float levels so close attention to details is needed for these to run well.

Hope this helps,

[jaudette3]

Thanks guys. I haven't dealt with fuel pressure issues before. I'm running a Facet fuel pump rated at 2.75-4.00 PSI. Can I install something to regulate the flow at the pump or is it handled by installing some type of in-line regulator? Any recommendations?

- JohnA

[Steve@Rennsport]

Thanks guys. I haven't dealt with fuel pressure issues before. I'm running a Facet fuel pump rated at 2.75-4.00 PSI. Can I install something to regulate the flow at the pump or is it handled by installing some type of in-line regulator? Any recommendations?

- JohnA

Are you using the little solid-state Facet (square) or the electric (cylindrical) one?

You need a low-pressure Holley regulator (0-5 psi).

[jaudette3]

Are you using the little solid-state Facet (square) or the electric (cylindrical) one?You need a low-pressure Holley regulator (0-5 psi).

Steve...

It's the cylinder shaped one with a Bendix sticker on it - looks just like an original. Since I enter this car in shows from time to time I try to keep it looking as period original as possible. I'm wondering if there is a "stealth" way to mount the regulator. Right now the only thing between the fuel pump and the hard fuel line is a fuel filter. Perhaps I could replace it with the regulator and tuck it in the back and place the fuel filter in front of the fuel pump?



Or maybe early competition cars did have regulators and pressure guages mounted at times? I do like the look of the pressure guage mounted in the center.

Thanks,
John

[304065]

Those are modern Facet pumps all right, you can tell by the wire. Looks like you have the ones with the 1/4" NPT fittings, and someone has cleverly adapted the M12x1.5 banjo fittings. Unfortunately, the most common one of those puts out 6.7 psi. . .I have a special one I ordered from a yacht supply place that puts out 4.0.

Anyway, get yourself a "malpassi filter king" which is a combination of a filter and a pressure regulator, and you can even put a gauge on it. Get the one with the STEEL bowl. That can hide back on the firewall and nobody will see it.

What coils are those, Summit? Accel? Those are cool.

[jaudette3]

Anyway, get yourself a "malpassi filter king" which is a combination of a filter and a pressure regulator, and you can even put a gauge on it. Get the one with the STEEL bowl. That can hide back on the firewall and nobody will see it.

Thanks John - ordered the Malpassi filter/regulator combo. What a great solution.

And thanks also to Steve and Mark. What a great forum - problem and solution identified in one day.

Regards,
John Audette

[jaudette3]

Here's the filter/pressure regulator combo that I installed. I'm posting a link and a picture mainly for Tom Ching who asked about it in Palos Verdes - I can't find his email address.



Cheers,
JohnA

[Bruce M]

A nicely made part that does the job well and reliably.

If you have large needle valves fitted (the valve that the float shuts) then you may need to keep it below 3psi but normally 3.5 is ideal.