<VV> Fuel pump pressure

Mark Durham 62vair at gmail.com
Tue May 7 00:22:28 EDT 2013

Hi all, I've been tinkering with my fuel system as well due to a gas smell
in the garage the better half is complaining about. There have been some
great articles and comments here and elsewhere on corvair forums about the
dynamics of the function of the needle and seat, and the size of the hole
in them, to the size and function of the carb floats, the extra float
assist spring, fuel level in the bowl dynamics, and off course, fuel
pressure. I have found all of the dynamics to be true and must be

1. My car would not idle below 850 rpm. (due to low fuel level in the bowl
in trying to compensate for fuel smell, and a possible vacuum leak.
2. It would hesitate on acceleration and was a pain in the rear to drive.
(again, to low fuel level in the bowl (which affects how much fuel can be
sucked through the idle circiuts in that    transition period before the
accelerator pump kicks in.
3. It acted lean but could find no apparent air leaks.

I took apart my carbs, adjust the float levels several times, and added a
set of metal ball and seats (needle and seat) thinking the fuel pump was
overpowering the regular needle and seat. It seemed to help a bit,
but driveability was still poor. The fuel leak moved after adjusting the
carb floats down a bit, to a seep at the fuel pump outlet pipe fitting, it
was loose.

I finally attacked the air leak possibility by sealing off the only other
possibility, the PCV valve hose, and the engine was a different animal! So,
I replaced the valve and that helped with idle issues.

I bought a Spectre Performance fuel pressure regulator. It took several
runs and adjustments to the inner set screw with an allen wrench to get the
fuel pressure right for my engine, but it now purrs, has great
acceleration, and no longer smokes black smoke on startup. This also solved
the hot start issues I was having in the summer months. .

Some have said the Spectre fuel pressure regulator will not last. Well,
this has been on the car for over a year and I've had no leaks and perfect
operation. I took it apart last winter to check the diaphram. It showed no
degredation after a years driving. I did discover one thing, however, there
is an inner adjustment allen screw if the outside adjustment is not enough
to raise or lower the pressure for your engine. Simply insert a allen
wrench in through the center of the label in the adjustment knob, find the
set screw, and make needed adjustments to get what you need. This
information was not provided by Clarks several years ago, but I found it on
the Spectre web page. I sent it to clark's so they may be adding that to
their kits now.

Finally, my car is running (and smelling) like it should. It now idles
well.  And, I am getting 24 mpg. The engine is a 64-110 bored .030, with a
Isky 270 cam with mild porting on the heads completed. Also, the chambers
were previously welded up and machined, the spark plug moved closer to the
exhaust valve. I have added 140 exhaust logs and dual exhaust.

It runs great. There is a older Porsche 911, also red, around the lake I
want to chase and beat!

Mark Durham

On Mon, May 6, 2013 at 1:57 PM, <kenpepke at juno.com> wrote:

> Right you are, Clark … A spring is a spring.  Removing material increases
> the pounds / inch rate.  As long as the spring is captured in a manor such
> as the frame / moveable lower control arm or pump cap and moveable
> diaphragm … it will resist its compression by exerting force at its given
> rate on both ends.  If one cuts the fuel pressure spring short enough it
> will no longer be held in compression and the force exerted will be reduced
> to zero as will the fuel pressure.
> Ken P
> Wyandotte, MI
> 65 Monza 110hp 4 speed 2 door
> Worry looks around; Sorry looks back, Faith looks up.
> ************************
> On May 6, 2013, at 3:17 PM, "Clark Hartzel" <chartzel at comcast.net> wrote:
> > Someone suggested shortening the spring to lower the pressure.  Just like
> > the coil springs on your suspension when you cut a coil off you get
> stiffer
> > springs not weaker.  To lower fuel pressure you want a weaker spring.
> > The cam operated pushrod compresses the spring and when the cam drops the
> > pushrod the spring is what pressurizes the fuel.
> > Clark Hartzel
> >
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