Electric fuel pump conversion

[richard guthart]

Could someone steer me toward info. on the optimal conversion to electric fuel
pump for a 455 retaining the stock carb?

My intent is to mount a pump down under close to the tanks, preceded by a large
filter (so it doesn't need changing every 12,000 miles). Then I was thinking
about running the fuel line as directly as possible to the carb, perhaps coming
up to the floorboard under the driver's seat then over to the carb fuel inlet
using a race- or aviation-type fuel line very well-insulated. Idea would be to
avoid that long run of steel line which goes all the way to the mechanical pump
at the front of the engine then back along the top to the carb. That has to add
a lot of heat to the fuel, and also lengthen start-up cranking time. I could
probably shorten the fuel's path by 6-8 feet this way.

I gather that many have added an electric pump and am wondering if this is the
way to do it. Also wondering which pump to use, and what sort of safety
switch(s) to incorporate?

Thanks for your help,

Richard

 

[bdub]

Check these sites:

http://www.gmcws.org/tech.htm Gas and fuel

http://www.california.com/~eagle/figs/pump.jpg

bdub

>Could someone steer me toward info. on the optimal conversion to electric fuel
>pump for a 455 retaining the stock carb?
>
>My intent is to mount a pump down under close to the tanks, preceded by a
large
>filter (so it doesn't need changing every 12,000 miles). Then I was thinking
>about running the fuel line as directly as possible to the carb, perhaps
coming
>up to the floorboard under the driver's seat then over to the carb fuel inlet
>using a race- or aviation-type fuel line very well-insulated. Idea would be to
>avoid that long run of steel line which goes all the way to the mechanical
pump
>at the front of the engine then back along the top to the carb. That has
to add
>a lot of heat to the fuel, and also lengthen start-up cranking time. I could
>probably shorten the fuel's path by 6-8 feet this way.
>
>I gather that many have added an electric pump and am wondering if this is the
>way to do it. Also wondering which pump to use, and what sort of safety
>switch(s) to incorporate?
>
>Thanks for your help,
>
>Richard
>
>

 

[richard guthart]

A couple of follow-ups to my recent question about converting to an electric
fuel pump :

I have learned that you do not want to put the filter upstream from the
pump, unless it is a simple screen-type filter.

I note that Holly makes a "street" pump that is set for a max of 7 psi. In
our appliation, would this require changing the idle mixture adjustment? The
pressure at the fuel inlet would be a little higher than that created by the
mechanical pump and I recall reading in Doug Roe's book that it can possibly
raise the level in the float bowl somewhat if you get the inlet pressure too
high.

Anyone know a source for the block-off plate to replace the mechanical fuel
pump?

Richard

> Could someone steer me toward info. on the optimal conversion to electric fuel
> pump for a 455 retaining the stock carb?
>
> My intent is to mount a pump down under close to the tanks, preceded by a
large
> filter (so it doesn't need changing every 12,000 miles). Then I was thinking
> about running the fuel line as directly as possible to the carb, perhaps
coming
> up to the floorboard under the driver's seat then over to the carb fuel inlet
> using a race- or aviation-type fuel line very well-insulated. Idea would be to
> avoid that long run of steel line which goes all the way to the mechanical
pump
> at the front of the engine then back along the top to the carb. That has to
add
> a lot of heat to the fuel, and also lengthen start-up cranking time. I could
> probably shorten the fuel's path by 6-8 feet this way.
>
> I gather that many have added an electric pump and am wondering if this is the
> way to do it. Also wondering which pump to use, and what sort of safety
> switch(s) to incorporate?
>
> Thanks for your help,
>
> Richard
>

 

[richard guthart]

Rick,

I had a feeling that you would contribute an informed response to my question.
I've come to rely upon your years of experience.........Thanks.

Now you've got me thinking that I should retain the stock steel line, insulate
it and use a short length of flexible aviation line in place of the mechanical
fuel pump.

BTW these 455's must not move much within the engine mounts. I was surprise to
note, when I traced the fuel line, that there is not a flexible section, but
only a loop in the steel line at the point it leaves the frame and heads toward
the engine-mounted fuel pump, to cope with any movement of the engine relative
to the frame.

P.S. -

What got me thinking about the conversion to electric pump was that I
experienced symptoms of mild fuel vaporization during a trip to the Black Hills
last weekend.
Made me wonder about travel plans later in the summer across Utah.

Richard

> If you must use an electric pump, down close to the tanks it should be.
> Routing the line is another story.... Once the fuel is under pressure from
> the pump, you ideally should use all-steel line from there on, as GMC did
> originally. Any leak in that line can spell disaster. Practically, you're
> going to need at least a short flexible section to connect the fixed fuel
> line on the frame, to the line on the engine, which of course rocks and
> bounces around. That flex section should be high-quality hose (If you want
> to use the braided stainless covered aircraft stuff, it's a nice touch.)
> Most importantly, that flex section should be well away from hot exhaust
> manifolds (both sides of the engine), and hot pipes and mufflers (rear of
> engine), both to protect it from deterioration by heat, and to minimize the
> chance of fire in case of a leak. This suggests running the fuel line up the
> front of the engine, like GM did it......
> As for selecting a pump, remember: the Quadrajet should never see over 6
> psi pressure, lest it flood over. According to Doug Roe (ROCHESTER
> CARBURETORS, HP Books, p. 116) the prefered pressure is 4 - 6 psi. Better to
> be a little below 4, than over 6.
> The subject of safety switches has been hashed over several times herein
> (it's one of my obsessions....), so you might check the archives. Basically
> you want the pump to run ONLY when the engine is running (oil pressure up,
> ignition sparking, alternator charging, are the usual ways of determining
> it's running) OR the engine is being cranked with the starter.
> Personally, I'm sticking with the stock mechanical pump for the
> foreseeable future, as it's simpler, safer, and more reliable. If vapor lock
> should become a problem (it hasn't yet) I'll experiment with insulating the
> fuel lines, possibly rigging a vapor return line, or something like that. To
> each his own.
> HTH.
>
> Rick Staples
> '75 Eleganza
> Louisville, CO
>