Phil
I agree with Patrick, and not knocking the carb overhaul job, but it
certainly sounds like incorrect disassembly & assembly procedures may be
part of your problem. The Q-jet is of a good design, and will perform well
if maintained properly. I have done the disassembly & reassembled of the
GMC carbs, and they do have their own "quirks" to look for. Some of these
are: Use the AC-Delco rebuild kits, some of the over-the-counter kits are
incorrect (ie. the gaskets were not punched for the air-bleed tubes);
Always install a new, correct float; Do not use the foam pad to correct the
leakage of the plugs, use a hi-temp epoxy on the plugs to seal them.
Replace the power piston spring; Here are the AC-Delco numbers for these
items. For all the 455 engines, both Fed & Cal. Carb Kit # 76057; Float #
7046301; power piston spring, # 7036019. For all the 403 engines, both Fed
& Cal, Carb Kit # 76031; Float # 7046300; power piston spring # 7036019.
We have a member in our local club, the Greater Midwest Classics, that
bought a coach with a 500 cid CAD engine in it, that had the factory Bosch
fuel injection. He had quite a few problems with the FI, so he changed it
over to a carbureted engine. I help to gather up the items needed for the
changover, as he obtained a carb for it from the CARBURETOR SHOP at
Ontario, CA. They will build the Q-jet to your spec's, and bench test it
also. They will also rebuild your carb, if you send it to them, the last
contact I had with them. For info on this, call 909-947-77444 or
909-947-9722.
I have run the Holley TBI for five years now, and have had excellent
results. It has the closed-loop system for automatic fuel ratio changes. In
the five years of running, I had an injector go bad, and Holley replaced
it. It also had a few "quirks" to look for, as the early models did not
have the correct gasket for mounting unto the intake manifold, at least the
one shipped to me did not. I used the correct carb gasket, it works fine.
Bob
I agree with Patrick, and not knocking the carb overhaul job, but it
certainly sounds like incorrect disassembly & assembly procedures may be
part of your problem. The Q-jet is of a good design, and will perform well
if maintained properly. I have done the disassembly & reassembled of the
GMC carbs, and they do have their own "quirks" to look for. Some of these
are: Use the AC-Delco rebuild kits, some of the over-the-counter kits are
incorrect (ie. the gaskets were not punched for the air-bleed tubes);
Always install a new, correct float; Do not use the foam pad to correct the
leakage of the plugs, use a hi-temp epoxy on the plugs to seal them.
Replace the power piston spring; Here are the AC-Delco numbers for these
items. For all the 455 engines, both Fed & Cal. Carb Kit # 76057; Float #
7046301; power piston spring, # 7036019. For all the 403 engines, both Fed
& Cal, Carb Kit # 76031; Float # 7046300; power piston spring # 7036019.
We have a member in our local club, the Greater Midwest Classics, that
bought a coach with a 500 cid CAD engine in it, that had the factory Bosch
fuel injection. He had quite a few problems with the FI, so he changed it
over to a carbureted engine. I help to gather up the items needed for the
changover, as he obtained a carb for it from the CARBURETOR SHOP at
Ontario, CA. They will build the Q-jet to your spec's, and bench test it
also. They will also rebuild your carb, if you send it to them, the last
contact I had with them. For info on this, call 909-947-77444 or
909-947-9722.
I have run the Holley TBI for five years now, and have had excellent
results. It has the closed-loop system for automatic fuel ratio changes. In
the five years of running, I had an injector go bad, and Holley replaced
it. It also had a few "quirks" to look for, as the early models did not
have the correct gasket for mounting unto the intake manifold, at least the
one shipped to me did not. I used the correct carb gasket, it works fine.
Bob
