Electric Fuel Pump Choice

[magwakeenercew2jh]

I'm running my stock tank in the cab and an electric fuel pump set up along the frame rail, into a filter,
then into an adjustable fuel pressure regulator... and then into the carb.

Seems I made a quick choice on the fuel pump. The one I initially installed works....
But it only pumps 4.5 or 5.5 psi....

Yeah, it works. But I'd like to crank it up a bit.

I'm looking for one that pumps about 12 or 15 psi (or so) so I can throttle it back with the regulator
when I find the "sweet spot".

Any options? Or, "stay away froms"?

[Katrina/10]

I think carbs only need 2-4 psi, adding more pressure won't make it run any better as long as the float bowl stays full.

[Fitz]

Originally Posted by magwakeenercew2jh

I'm running my stock tank in the cab and an electric fuel pump set up along the frame rail, into a filter,
then into an adjustable fuel pressure regulator... and then into the carb.

Seems I made a quick choice on the fuel pump. The one I initially installed works....
But it only pumps 4.5 or 5.5 psi....

Yeah, it works. But I'd like to crank it up a bit.

I'm looking for one that pumps about 12 or 15 psi (or so) so I can throttle it back with the regulator
when I find the "sweet spot".

Any options? Or, "stay away froms"?

If your engine has a Holley carb, it wants to see between 5.5 and 6.5 PSI...not more. A quadrajet can run on pressures a bit lower, but not below 4 PSI. On any of them pressures above 6.5 psi causes flooding and it is unlikely your engine will run at all. Most in-line pumps use an internal regulator. My Holley black pump is internally regulated to exactly 6 PSI and flows a maximum of 150 gallons per hour. With a flow volume that high, that pump never starves the carb on my motor and there is no fluctuation in pressure when going from idle to full throttle. You can get the same results with an external regulator if the flow volume of the pump is high but that just adds two more connectors that can leak. Why bother?

[Matt Cramer]

Originally Posted by Katrina/10

I think carbs only need 2-4 psi, adding more pressure won't make it run any better as long as the float bowl stays full.

This. The whole point of the fuel pressure is to get the fuel through the needle and seat area, unless you're doing a blow through supercharger or turbo install.

[magwakeenercew2jh]

Originally Posted by Matt Cramer

This. The whole point of the fuel pressure is to get the fuel through the needle and seat area, unless you're doing a blow through supercharger or turbo install.

Okay.

Street DeMon 625 stats call for between 5 and 6 PSI. I just wanted to get a piump that allows me to "throttle back" the fuel pressure
using the fuel pressure regulator so I can fine tune the flow.

I seem to getting lean "pops" after being into the secondaries for a few seconds (). Of course, there are a ton of reasons for
that symptom. Most of which, I've checked out.

Just wanted to make sure the bowl wasn't empty. And, since I get some readings in the four psi range (with a clear shot...new fuel
filter, blown out carb filters, timing adjustments, air leak checks, etc.), I'm just interested in eliminating this factor.

It's no big deal. The old 350 runs strong....with a little pop once in a while...like I said...But I don't like to leave "almost well
enough" alone.

[Fitz]

Originally Posted by magwakeenercew2jh

Okay.

Street DeMon 625 stats call for between 5 and 6 PSI. I just wanted to get a piump that allows me to "throttle back" the fuel pressure
using the fuel pressure regulator so I can fine tune the flow.

I seem to getting lean "pops" after being into the secondaries for a few seconds (). Of course, there are a ton of reasons for
that symptom. Most of which, I've checked out.


It's no big deal. The old 350 runs strong....with a little pop once in a while...like I said...But I don't like to leave "almost well
enough" alone.

Your street Demon is similar to the Holley 850 CFM 4150 on my big block. It will "pop" when coming off the secondaries if the rear float is not set right in the middle of it's range. A little time spent tweaking it and mine is just fine. Here in Arizona density altitude fluctuates almost 5000 feet between winter and summer. That's like setting your truck up to run in Kansas then driving to Denver. It won't be happy and when the seasons change and the engine leans out I have to change jets to get rid of that 'pop". Changing fuel pressure doesn't get it done on my Holley!

[geezer#99]

[QUOTE

It's no big deal. The old 350 runs strong....with a little pop once in a while...like I said...But I don't like to leave "almost well
enough" alone.

[/QUOTE]

If you're getting little 'pops' what's your timing curve like?

[magwakeenercew2jh]

Originally Posted by Fitz

Your street Demon is similar to the Holley 850 CFM 4150 on my big block. It will "pop" when coming off the secondaries if the rear float is not set right in the middle of it's range.

Originally Posted by geezer#99

If you're getting little 'pops' what's your timing curve like?

Thanks, Guys.

The popping...and very slight at that, was when coming *on* to the secondaries, mostly when the trans kicked down and a
couple of seconds after the higher RPM had been achieved.

Because of not having a proper calibration on the timing mark, and TDC being elusive because I don't feel really EXACT about
TDC, even usinbg all the methods, I have adjusted the timing for optimum performance...meaning no advance symptoms, and
no lean symptoms...rather than call it from certain degrees BDC. When the heads come off, I'll mark it properly.

Also, as far as the curve goes, I just installed a new module in the HEI dizzy and didn't play with springs.

I've got some playing around there...And with the idle mixtures on the DeMon. Plus, I need to get in there and look pretty
diligently for some air leaks...just in case there are some. I suspect not. But who really knows.

Also, it seems that popping now...since I've been driving some more...may have been symptomatic of a cold motor. Jumping
on it before it's fully up to operating temp.

Side note: Vintage Air. Just got off the phone with Mark at CVintage Air. I was having strange (to me) problems with the readings
on high and low side being okay...yet, when the RPM were over about 1,000, the temp in the cab started north...With ambient in the
cab temps at 88-100, all the way up to 77 degrees if I let it get that far. Back on idle, the temp would start to drop and settle at about
44 degrees until I was driving again at road-ride RPMs.

Mark asked for the readings at the a/c gauges. Then, when I got back to him, suggested taking the heater core out of the equation,
as there is a possibility that if even slight amounts of hot water got into the cooling side of the evaporator, the system would get mad
....and not cool down.

I messed with the VA hot water "gate" on the heater hose. It moved. I have the GenII system that has cables. It moved. Seems I had
the cable fubared to the point that just a very small amount of hot water was getting through to the heater core.

With Mark's sourcing of the problem, I'm now down to a system output of a consistent 38 degrees.

Vintage air service after the sale. I'm a fan.