All this recent talk about mixture enrichment has left me feeling a
little guilty. I just rebuilt the Qjet on my coach. In fact, I've felt
so guilty that I haven't put the carb back on - just kept looking
forelornly at it sitting on the workbench. Last night my guilt got the
best of me. Gritted my teeth and got the screwdriver out. Discovered
that my carb has 70 primary jets, 50D primary rods and CJ secondary
rods.
Getting out my copy of Roe's Rochester Carburetors left me a little
confused. It didn't seem to correspond to Joe Mondello's "Killer
Gasoline" article. Stepping up two jet sizes was easy enough, but,
according to Roe, the 50D primary rods are "Special rod used in GMC
Motorhome - has 0.036-in. power tip." That itself didn't make sense as
all other pre-1975 primary rods have 0.026-in. tips and I would have
thought that a smaller diameter would have provided more enrichment(of
course - gotta remember that the carb is a system in and of itself).
Well, I called Mondello's shop this afternoon. The tech guy said that
they recommended the 72 jets and not to change the primary rod if you're
using a stock cam. Just what I wanted to hear! Ordered the catalog
and reference book from Mondello and(in the interest of time) called the
local Pontiac dealer I get my GM parts from. I'll have the 72 jets
tomorrow and have the carb back on tomorrow night.
BTW, ordering the jets is easy. All part numbers start with 70319, the
last two digits are the jet size, i.e. 7031972 for the 72 jets.
One last thought - why not start a database of Qjets used on the
motorhomes? The carb model number on each Qjet uniquely identifies it
and all carbs of that number will have the same jets and rods. As long
as you're sure your carb is still original, just check the main jets and
rods while they're out for rebuild and send that info to me along with
the carb number(stamped vertically on the side of the carb). I doubt
that there are more of these out there than model years. Whattayathink?
Patrick
- --
Patrick Flowers
Mailto
atrick
The GMC Motorhome Page
http://www.gmcmotorhome.com
little guilty. I just rebuilt the Qjet on my coach. In fact, I've felt
so guilty that I haven't put the carb back on - just kept looking
forelornly at it sitting on the workbench. Last night my guilt got the
best of me. Gritted my teeth and got the screwdriver out. Discovered
that my carb has 70 primary jets, 50D primary rods and CJ secondary
rods.
Getting out my copy of Roe's Rochester Carburetors left me a little
confused. It didn't seem to correspond to Joe Mondello's "Killer
Gasoline" article. Stepping up two jet sizes was easy enough, but,
according to Roe, the 50D primary rods are "Special rod used in GMC
Motorhome - has 0.036-in. power tip." That itself didn't make sense as
all other pre-1975 primary rods have 0.026-in. tips and I would have
thought that a smaller diameter would have provided more enrichment(of
course - gotta remember that the carb is a system in and of itself).
Well, I called Mondello's shop this afternoon. The tech guy said that
they recommended the 72 jets and not to change the primary rod if you're
using a stock cam. Just what I wanted to hear! Ordered the catalog
and reference book from Mondello and(in the interest of time) called the
local Pontiac dealer I get my GM parts from. I'll have the 72 jets
tomorrow and have the carb back on tomorrow night.
BTW, ordering the jets is easy. All part numbers start with 70319, the
last two digits are the jet size, i.e. 7031972 for the 72 jets.
One last thought - why not start a database of Qjets used on the
motorhomes? The carb model number on each Qjet uniquely identifies it
and all carbs of that number will have the same jets and rods. As long
as you're sure your carb is still original, just check the main jets and
rods while they're out for rebuild and send that info to me along with
the carb number(stamped vertically on the side of the carb). I doubt
that there are more of these out there than model years. Whattayathink?
Patrick
- --
Patrick Flowers
Mailto
atrickThe GMC Motorhome Page
http://www.gmcmotorhome.com
