New Carburetor Woes

[antnip]

I recently installed a rebuilt carb on my 455 GMC. The old set up was the
original carb however the fuel pump had been altered. There is no mechanical
pump on the vehicle, with fuel being delivered via a Carter electric pump. I
know, from reading other posts that many feel this is a questionable setup,
but it has worked for me for many years without incident.

My problem is that once I installed the new carb, I noticed a poor idle at
slow speed, as if the engine was flooding. When I took off the air cover to
look, I noticed that the volume of fuel is too great and is actually
flooding over the top of the carb onto the intake manifold. YIKES!

The new carb was from a source I won't name here, but was claimed to be
perfectly tuned and adjusted for this application. Being a novice mechanic,
especially when it comes to fuel systems, I was hoping that no adjustments
would be needed, and paid extra to hopefully insure this.

What on earth is wrong here. I don't believe it is a pump problem, as the
set up is identical to that which I used for many miles without a problem.
Could it be a sticking float or something? Any insight would be most
appreciated. As is customary, this comes up just as we are planning to head
south later this week. ARRRRRGGGGHHHHH!

I anxiously await any help anyone could offer.

Sincerely, Tony B.

 

[john wright]

Tony,
My guess is that the floats are set too high and excess fuel is flooding
the engine at low speed. The only question that I would have with the
electric fuel pump what is the fuel pressure? 4 to 6 psig is all that
you should have. Some of the carter pumps are 8 psig and higher that
may be enough to hold the float seats up. The Carter P4070 is the one
that most GMC'er use. You should also have a electric cutoff on your
fuel pump is there is no oil pressure. Several of the GMC Web sites have
diagrams on how to do that. The chance for a fire is very great without
the cutoff.

- --
J.R. Wright
GMC GreatLakers
77 Eleganza II
Michigan

>
> I recently installed a rebuilt carb on my 455 GMC. The old set up was the
> original carb however the fuel pump had been altered. There is no mechanical
> pump on the vehicle, with fuel being delivered via a Carter electric pump. I
> know, from reading other posts that many feel this is a questionable setup,
> but it has worked for me for many years without incident.
>
> My problem is that once I installed the new carb, I noticed a poor idle at
> slow speed, as if the engine was flooding. When I took off the air cover to
> look, I noticed that the volume of fuel is too great and is actually
> flooding over the top of the carb onto the intake manifold. YIKES!
>
> The new carb was from a source I won't name here, but was claimed to be
> perfectly tuned and adjusted for this application. Being a novice mechanic,
> especially when it comes to fuel systems, I was hoping that no adjustments
> would be needed, and paid extra to hopefully insure this.
>
> What on earth is wrong here. I don't believe it is a pump problem, as the
> set up is identical to that which I used for many miles without a problem.
> Could it be a sticking float or something? Any insight would be most
> appreciated. As is customary, this comes up just as we are planning to head
> south later this week. ARRRRRGGGGHHHHH!
>
> I anxiously await any help anyone could offer.
>
> Sincerely, Tony B.