Q-Jet jets (was:Exhaust Manifolds)

[mark grady]

Tom --

> old carb, reformulated gas, lean mixture, exhaust manifolds
> warped, exhaust
> manifolds at Cinnabar, empty your wallet. close?

Taking into account reformed gas, alky gas, cheap gas, gas from beans and
co-pilot gas, what jets are required for the 403 (and 455) to prevent this
wallet deflation?

Too little gas in engine = too little gas in wallet, eh?

Primary jets *and* secondary rods. I may open 'er up before gas hits $3 a
gallon, and I don't want to be too lean.

Inquiring minds want to know!!

Mark Grady
'77 K (miles and year)
original carb and jets

 

[ron & gina]

Now I'm new at this RVing but during our test drive of our 73 Pumpkin-Rose,
Ruth the previous owner was telling me that she had an inline fuel pump
installed and had the gas tanks checked, due to carb/lean mixture problem
where I believe they found a restricted part but not sure that was causing a
lean mixture which she belives caused the replacement of the 455 motor, and
after the replacement she has had no problems. Like I said I'm new at this,
Will ask her about it again when we pick-up our Pumpkin-Rose and will post
if theres any merit on this subject.
Ron&Gina
73 Pumpkin-Rose
Fort Mohave,AZ
- -----Original Message-----
From: Mark Grady
To: gmcmotorhome
Date: Tuesday, April 27, 1999 9:52 PM
Subject: GMC: Q-Jet jets (was:Exhaust Manifolds)

>Tom --
>
>
>> old carb, reformulated gas, lean mixture, exhaust manifolds
>> warped, exhaust
>> manifolds at Cinnabar, empty your wallet. close?
>
>Taking into account reformed gas, alky gas, cheap gas, gas from beans and
>co-pilot gas, what jets are required for the 403 (and 455) to prevent this
>wallet deflation?
>
>Too little gas in engine = too little gas in wallet, eh?
>
>Primary jets *and* secondary rods. I may open 'er up before gas hits $3 a
>gallon, and I don't want to be too lean.
>
>Inquiring minds want to know!!
>
>
>Mark Grady
>'77 K (miles and year)
>original carb and jets
>
>

 

[thomas g. warner]

If you have the original jets etc Mondello says go up 2 sizes.

>Tom --
>
>
>> old carb, reformulated gas, lean mixture, exhaust manifolds
>> warped, exhaust
>> manifolds at Cinnabar, empty your wallet. close?
>
>Taking into account reformed gas, alky gas, cheap gas, gas from beans and
>co-pilot gas, what jets are required for the 403 (and 455) to prevent this
>wallet deflation?
>
>Too little gas in engine = too little gas in wallet, eh?
>
>Primary jets *and* secondary rods. I may open 'er up before gas hits $3 a
>gallon, and I don't want to be too lean.
>
>Inquiring minds want to know!!
>
>
>Mark Grady
>'77 K (miles and year)
>original carb and jets
>
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
"The beautiful Mohawk Vally"

 

[mark grady]

Tom --

1) Does Mondello sell replacment jets? (Or anyone else for that matter?)

2) Any research on the stock sizes so I'd know what size "two over"
represents?

Mark

> -----Original Message-----
> From: owner-gmcmotorhome
> [mailtowner-gmcmotorhome]On Behalf Of Thomas G.
> Warner
> Sent: Wednesday, April 28, 1999 7:22 AM
> To: gmcmotorhome
> Subject: Re: GMC: Q-Jet jets (was:Exhaust Manifolds)
>
>
> If you have the original jets etc Mondello says go up 2 sizes.
>
>
[snip'd]

 

[blank]

> 1) Does Mondello sell replacment jets? (Or anyone else for
> that matter?)

Doug Roe, who wrote the definitive work on Rochester Carbs, sells them. The
address is in the back of his book. I'll look for it tonight. Also, I
think Cinnabar has them, but I'm not sure they'll sell them without doing
the exhaust gas analysis.

> 2) Any research on the stock sizes so I'd know what size "two over"
> represents?

I hope Phil Stewart picks up on this soon, as I seem to remember that Wes
gave him an indication of a "starting point" when he was having carb
troubles. Also, a Joe Mondello article was in GMCMM last year, called
"Killer Gasoline" or something like that, and I think he might have
mentioned a specific number. One more thing to look for when I get home.

Patrick

 

[richard waters]

I assume that Cinnabar sells them since they might be
installing new jets my carb to correct a too lean condition. Before
they do that however they want to see if a broken vacuum
"T" fitting that they replaced corrects the problem. They are
using their "portable five-gas analyzer" they installed in my
coach to detect the carburetor problems. This sure sounds
expensive to me.
Richard Waters

>
> > 1) Does Mondello sell replacment jets? (Or anyone else for
> > that matter?)
>
> Doug Roe, who wrote the definitive work on Rochester Carbs, sells them. The
> address is in the back of his book. I'll look for it tonight. Also, I
> think Cinnabar has them, but I'm not sure they'll sell them without doing
> the exhaust gas analysis.
>
> > 2) Any research on the stock sizes so I'd know what size "two over"
> > represents?
>
> I hope Phil Stewart picks up on this soon, as I seem to remember that Wes
> gave him an indication of a "starting point" when he was having carb
> troubles. Also, a Joe Mondello article was in GMCMM last year, called
> "Killer Gasoline" or something like that, and I think he might have
> mentioned a specific number. One more thing to look for when I get home.
>
> Patrick

 

[philip l. stewart]

>
>
> > 2) Any research on the stock sizes so I'd know what size "two over"
> > represents?
>
> I hope Phil Stewart picks up on this soon, as I seem to remember that Wes
> gave him an indication of a "starting point" when he was having carb
> troubles.

Patrick,Sorry, the only thing I know about this for sure is that you do not want
two air horn gaskets sandwiched together in your Quadrajet. That's "two sizes
over" that causes big problems. I don't know what the jet or metering rod
sizes are in my carb. I think there is is enough variability in these 25 year
old carbs by now that they need to be tuned each individually to get the right
combination of parts.

Phil Stewart
'76 Transmode, TN

 

[mark grady]

I used to have Doug's book, but it turned to ash. I see Amazon.com still has
it available.

Hmmm... Perhaps an Electromotive EFI/DIS is justified?
Can't get rid of the steel wheel blues, maybe this as a project?

I'll get out the big binder that is GMCMH too.

Thanks!

Mark

> -----Original Message-----
> From: owner-gmcmotorhome
> [mailtowner-gmcmotorhome]On Behalf Of
> Patrick.Flowers
> Sent: Wednesday, April 28, 1999 7:48 AM
> To: gmcmotorhome
> Subject: RE: GMC: Q-Jet jets (was:Exhaust Manifolds)
>
>

>
> > 1) Does Mondello sell replacment jets? (Or anyone else for
> > that matter?)
>
> Doug Roe, who wrote the definitive work on Rochester Carbs, sells
> them. The
> address is in the back of his book. I'll look for it tonight. Also, I
> think Cinnabar has them, but I'm not sure they'll sell them without doing
> the exhaust gas analysis.
>
> > 2) Any research on the stock sizes so I'd know what size "two over"
> > represents?
>
> I hope Phil Stewart picks up on this soon, as I seem to remember that Wes
> gave him an indication of a "starting point" when he was having carb
> troubles. Also, a Joe Mondello article was in GMCMM last year, called
> "Killer Gasoline" or something like that, and I think he might have
> mentioned a specific number. One more thing to look for when I
> get home.
>
> Patrick
>

 

[david sandford]

I spent a fair amount of time last fall researching the Q-Jet carbs that
were used in the GMCMH, and came to the conclusion that each model year had
it's own carb, and needle configuration. This corresponded to the
variability in carbs in Buicks and Oldsmobiles of the same period.

The reason behind this was the observation that the Carb in a 73 Sequoia,
was configured differently than one in a 77 Birchaven, two metering rods
vrs. four. Our observation was that the 77 was easier to tune than the 73,
and seemed to develope more power, and exhibited better fuel economy to
boot. The upshot is my father ultimately replaced the carb in the 73 with a
carb from a 77 Oldsmobile. Power seems to be improved, as well as economy.

Granted it is easy to revert to the original config. Besides unless i'm
mistaken you already have a good carb in your unit. I'm referring to Phil
Stewart, with the 76 transmode.

My advice, go through your ignition system make sure it is in tip top shape,
then tackle the Carb. Generally that's the last thing you fiddle with
anyway, at least in my experiance. For the record I used to own an MG
Midget with twin SU carbs, so i might be a bit more conservation when it
comes to messing with carbs than most. The SU's were good carbs, just a bit
odd and finicky.

- ----- Original Message -----
From:
To:
Sent: Wednesday, April 28, 1999 06:25 PM
Subject: Re: GMC: Q-Jet jets (was:Exhaust Manifolds)

>
>

>
> >
> >
> > > 2) Any research on the stock sizes so I'd know what size "two over"
> > > represents?
> >
> > I hope Phil Stewart picks up on this soon, as I seem to remember that
Wes
> > gave him an indication of a "starting point" when he was having carb
> > troubles.
>
> Patrick,Sorry, the only thing I know about this for sure is that you do
not want
> two air horn gaskets sandwiched together in your Quadrajet. That's "two
sizes
> over" that causes big problems. I don't know what the jet or metering
rod
> sizes are in my carb. I think there is is enough variability in these 25
year
> old carbs by now that they need to be tuned each individually to get the
right
> combination of parts.
>
> Phil Stewart
> '76 Transmode, TN
>
>
>