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MG MGB GT V8 Factory Originals Technical - Mallory fuel pump redux ... got a new one, but ...

A while ago I posted about a Mallory Series 70 fuel pump (model #4070) going kaput. At considerable expense, I purchased a new one ... my question is: the manual says that this pump is pre-set for 6psi. My fuel pressure gauge (which I believe to be accurate ... it always showed 6psi with the old one when the car was on) tells me this one's putting out 16psi!!! (I checked, and no, I didn't accidentally buy one for fuel injected cars.) The car does seem to run fine, though ... it's not as though extra gas is drooling out the top of the carb or anything. (It has your basic Weber/Edelbrock/Carter 4-barrel carb.) Should I just leave well enough alone, or need I rectify it, e.g., with a pressure regulator?

-- sorry, scratch that. The motor can't _stand_ running w/this much fuel pressure ... the pump must be jamming gas in there beyond what the needles/seats can hold back, because boy oh boy is it running rich and indeed it smells like gas. The car won't even idle; it just floods and you have to wait 15 min, then it will restart with a huge choking puff of smoke!

Gotta get a fuel pressure regulator!

Why not send it back if it the wrong one? You can buy stronger springs and valves for float to handle uprated pressure, but is hard on the seats. Get a good regulator if that's the route you'll take. I've had bad experiences with those common $30-40 regulators with a 0-6 psi dial that you adjust by pushing down and turning. Depending on what engine you have, those cheap regulators might not flow enough at high speed.

Get a regulator and bring the pressure down. The DP holleys like 5-7, 9psi max, I think the Edelbrock carbs like the 5psi rang also..

higher pressure will push fuel past the floats a bit which raises fuel level in the bowls and will make an annoying rich condition...

16psi would not be high enough for EFI, most EFI's will want 30+

The Mallory should last a long time.
Larry Embrey

You guys are so right. I got one of those cheapo chrome disc-type regulators just to try it out, hooked it up before the pressure gauge, set it to 5psi and all is well. At some point I'll get a nicer regulator so I don't run into Joaquin's problem, but certainly this is the answer!

Yeah get the Holley unit. Uses a alen wrentch to set pressure then has a nut over that to lock it down. You chould even mount the guage on the side of it so only have to look in one place depending on where you put things.. I have one for my Carb and it is great.

Larry Embrey

I don't wanna hog this space or anything, but this fuel pressure gauge is what I should have put on the car long ago! A couple of you may remember that I have always had a problem with the car shuddering when you come off the gas ... it kind of burped and then continued on its merry way. Also, I had the problem that a lot of Carter-carb owners have, which is that when you corner really hard the engine can die. Both of these problems, I'm happy to report, went away completely with the pressure gauge installed. As noted, one of these days I'll spring for a higher-quality one -- sounds like this Mr. Gasket disc thing is pretty low quality -- but even with this one, the car acts like a totally normal car again!

I had that same stalling issue on corners last year. of all things it was TOO MUCH fuel pressure.. I dropped back to like 6psi and she ran great..

Glad she is running good for you!!
Larry Embrey

I wouldn't waste money on a "better" regulator ... an amateur just-for-fun dirt-track racer friend of mine, in desperation, blew out his Holley regulator and had to put on one of those dial-type chrome things and finds the car runs equally well. I believe he's running a mildly built sbc. Most of us don't keep the V8 motor at 5K rpms for long anyhow! I mean if you were running a Winston Cup car, sure, get a serious unit that entails a return line and all that yadda yadda. If it works, don't "fix" it ... that's half the reason we get into all these precidaments, right? ;-)
Bill Withum

The Holley unit I am talking about is not the fancy one, is the "cheap one" I think about $25-30, no return line. But yeah if the one you got works, then no reason to change it.
Larry Embrey

This thread was discussed between 29/05/2003 and 02/06/2003

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