Replacement carburetor

[jim kanomata1]

We are here to help and assist.
At my old age of 77, it is very easy to say things that will offed others
and I do apologize.

On Sun, Aug 4, 2019 at 11:35 AM James Hupy via Gmclist <

> Todd, sometime, perhaps when we are both in the same place at the same
> time, I will relate to you several examples of my own learning experiences
> with carb swaps. Nearly all turned out no better than the OEM provided.
> Jim Hupy
> Salem, Or.
>
> On Sun, Aug 4, 2019, 11:05 AM Ken Henderson via Gmclist <

>
> > Todd,
> >
> > I don't pretend to be a carb expert at all; never even liked fooling with
> > them. And, in fact, I no longer even run an Olds engine, having
> converted
> > to a Cad500 with GM/EBL TBI. But I have been a GMC owner for 20+ years
> > now, always active here on GMCNet. So, I've heard a lot of folks'
> > experiences. Most importantly, I've heard Dick Paterson (MR. GMC CARB)
> > discuss several times his efforts to replace the GMC carb. Even
> replacing
> > the GMC-specific model with one from a Toronado proved unsatisfactory --
> > there are different air passage, the needles are different, and probably
> > other variations that mean nothing to me. The point is that if Dick,
> with
> > all his GM Technician background, GMCMH experience, racing experience,
> and
> > test equipment can't make it work well, I personally wouldn't even try.
> > Now converting to a user-programmable GM 7712247 ECU with the EBL
> > enhancements, that's a whole 'nother question -- especially for someone
> > with an extensive computer background.
> >
> > Another point: When I bought the GMC in '98 it had the raised engine
> cover
> > necessitated by the Edelbrock Performer manifold with which it was
> > equipped. We HATED it! Finding the cracks in the Edelbrock's exhaust
> > crossover was almost a blessing since it was another excuse to go back to
> > an old iron manifold.
> >
> > I'm sure you'll have fun with an Edelbrock or other carb. Please keep us
> > posted. Oh -- and don't be annoyed by any negative comments you may
> > receive; I can assure you that they're meant to be helpful, even when not
> > worded diplomatically.
> >
> > Ken H.
> > Americus, GA
> > '76 X-Birchaven w/Cad500/Howell EFI & EBL,
> > Manny Brakes & 1-Ton, Troy-Bilt APU, etc., etc., etc.
> > www.gmcwipersetc.com
> >
> >
> > On Sun, Aug 4, 2019 at 12:22 PM Todd Snyder via Gmclist <

> >
> > > Huh, I would have thought this was a fairly straightforward topic.
> > >
> > >
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502

 

[russell mehlenbacher]

Todd,
I haven't been keeping track of this whole thread, but the response you
made:

> 'symptoms are very poor running, hesitation on acceleration, would only
> run decent at WOT.'

This is/was my coach behavior. I have a cracking intake manifold. It
worsens with time and temperature. Anytime you do anything with the
throttle... bog. WOT is just fine. I have block off plates on the ends of
the exhaust crossover and now I have a block off on the choke stove hole. A
fairly effective band-aid until I get the Toro manifold cleaned and
painted. It remains to be seen if I'll still desire FI quite so badly.
Good luck,
Russ

>
>

 

[jim miller]

> Jim H, only reason I'm thinking about this is b/c the qjet is 43 years old. Spending 100's on a rebuild, to me, makes about as much sense as spending $10k on surgery for a 16 year old dog

…based on that logic (ie "its old”) I would ask why you are spending money on a 40 year old RV in the first place?

I learned to fly in a 45 year old airplane (a carbureted one at that) and not once did it turn me into a lawn dart or leave me upside down in a farm field. What, pray tell, does age have to do with the viability of a QJ for its intended purpose as long as it is properly maintained? Good cleaning and replacement of just a few wearout items is all that is needed to make one run just like it did when it came out of Detroit 43 years ago. Dick Paterson and several others know additional tricks that will make it work even better especially considering modern alcohol-adulterated fuel that didn’t exist when our GMCs were being produced..

> As to not listening, Im trying to make an informed decision by asking here on this forum if that’s ok? Maybe I'm in the wrong place?

You are most certainly in the correct place and will get far more accurate answers here compared to GMC forums on other platforms. The people that have replied to you so far are legends and have extensively investigated alternatives for every conceivable system on the GMC and know from experience what works and what does not.

—Jim
Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH

 

[johnny]

Todd, have you looked for crack(s) in the intake manifold?
Jim, I >have< had the carb on a J-3 put us on the ground, though fortunately about 600 feet off the runway on takeoff.. enough to get around and back
on the runway - with the prop stopped. Two beer story.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

 

[tmsnyder]

Yes, I looked and did find the crack in the intake manifold, unfortunately. Saw it when reinstalling carb.

With the carb rebuilt it's running much better since the primary power piston was stuck, the accelerator piston cup was torn, and the accelerator
piston return spring was found on top of the intake. Just a couple more of those things that make you say "hmmm, someone has been here....."

The crack has caused me to add intake blockoff plates to my to-do list, but is it too late? How bad can the crack be before the manifold is ruined?
Right now it's just a fine crack between the secondaries but I haven't seen the underside of the intake manifold.

And what are the options for a replacement intake?
--
Todd Snyder, Buffalo NY
1976 Eleganza II

 

[Ken H.]

Todd,

If you only have cracks between the throats, I wouldn't worry about it --
just think how little vacuum differential there's likely to be between them
and how tiny are those cracks.

Now, if there are cracks into the exhaust crossover, that's a whole 'nuther
ball game. About the only hope there is to fill the crossover ("Mondello
Zinc" is what I've used). Some have reported using melted pistons. Others
have used the compound used by dragsters. I don't know the results of
those, but I had good luck with the zinc ('tho' I didn't have any cracks).

Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, Troy-Bilt APU, etc., etc., etc.
http://www.gmcwipersetc.com

On Mon, Aug 19, 2019 at 1:36 PM Todd Snyder via Gmclist <

> Yes, I looked and did find the crack in the intake manifold,
> unfortunately. Saw it when reinstalling carb.
>
> With the carb rebuilt it's running much better since the primary power
> piston was stuck, the accelerator piston cup was torn, and the accelerator
> piston return spring was found on top of the intake. Just a couple more
> of those things that make you say "hmmm, someone has been here....."
>
> The crack has caused me to add intake blockoff plates to my to-do list,
> but is it too late? How bad can the crack be before the manifold is
> ruined?
> Right now it's just a fine crack between the secondaries but I haven't
> seen the underside of the intake manifold.
>
> And what are the options for a replacement intake?
> --
> Todd Snyder, Buffalo NY
> 1976 Eleganza II
>
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