Carburetor Problem

> I believe now that it is a Holley that was made for Ford during that era.
> The part or "list" number is 9510 which is stamped on the horn, which
> means 735 CFM model 4150.

9510 is not a Holley list number. It's a Ford generic designation for
carburetor and may be applied to a series of Holley or Autolite carbs.
For instance, P/N C6ZF-9510-A is an Autolite 4100, while P/N C3AE-9510-BJ
(or BK) are 550 CFM Holleys designed for use on 2x4 barrel intakes. Even
the rare Autolite in-line carbs used a 9510 part number (e.g. DOZX 9510-A).

There's an additional 4 digit list number on Holleys. You're looking for
something like 4345 for a 735 CFM Holley. Holley 735's were unique to Ford
applications and were available in several part numbers (manual and automatic
trans, service replacement, etc.). Mine is stamped with Ford part number
C9OF-9510-H and Holley list number 4345. It came off my dad's 1969 428
Fairlane Cobra Jet which was equipped with a C6 automatic. It was originally
equipped with a manual choke, #66 primary and #78 secondary jets, and stiff
natural color vacuum secondary spring. When I rebuilt it, I updated it with
electric choke, added power valve blow out protection, quick jet change bowls,
and a secondary spring quick change kit. When ordering parts, be aware that
OEM carbs like the 735 are no longer covered in Holley catalogs. They only
cover aftermarket carbs, so you'll need to know what you're looking for when
it comes to buying rebuild kits and tuning or repair parts. When I was
looking into adding the electric choke kit, I called the Holley tech line
but even they weren't sure what would fit or even if they had a kit that
would work. As it turns out, electric choke kit Holley part number 45-223
bolts right on.

> but this one now has a problem that it did not have prior to re-build.
> Idles rough, and a long dead band between idle and about 1,500 RPM.

If it didn't do it before then somehow the fuel-to-air ratio at idle
got fouled up. Check for a vacuum leak first then inspect the power
valve for leakage or early opening. Make sure the throttle plates
are adjusted properly (relative to the slot).

Dan Jones