Getting smart on carbs- GMC vs. Toronado

D

dave silva

New member
Oct 2, 2009
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I think my next project on the Revcon will be rebuilding the carb.

I'm starting from scratch. Other than a lawn tractor I have not touched a carb in decades.

Mine is stock Toro. What is the main difference between Toronado and GMC Carb?

I'm not making any changes. The Revcon folks tell me the stock configuration works pretty well.

THe car guys around me and online tell me the Quadrajet can be intimidating.

What is the most likely thing an amateur will screw up?

thanks
--
Dave & Ellen Silva

1972 Revcon Olds 455, toro drive train. All Stock
 
Wrong parts.

Need to find the kit that matches your carb number.

A 75 gmc motorhome carb kit for quadrajet is different then a 78 gmc motorhome carb kit. 97% is the same. But there are differences. Like the
78 carb has a apv (adjustable power valve). The 75 does not.

I know the 78 kit top gasket was not a match for my 75 carb too.

--
Jon Roche
75 palm beach
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
I think of myself as a handy guy. I watched the utube videos. How hard can it be? Well, if you have not done one in the past and you are only going to do one in your life......Don't! Try NorCal Carburetor and pay the $300 or so to have it done by someone who does this every day.

>
>
> I think my next project on the Revcon will be rebuilding the carb.
>
> I'm starting from scratch. Other than a lawn tractor I have not touched a carb in decades.
>
> Mine is stock Toro. What is the main difference between Toronado and GMC Carb?
>
> I'm not making any changes. The Revcon folks tell me the stock configuration works pretty well.
>
> THe car guys around me and online tell me the Quadrajet can be intimidating.
>
> What is the most likely thing an amateur will screw up?
>
> thanks
> --
> Dave & Ellen Silva
>
> 1972 Revcon Olds 455, toro drive train. All Stock
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Quadrojets are not hard to rebuild just follow the directions in the rebuild kit and make sure the float is set correctly. Use the carb part number
on the housing to get the correct rebuilding kit.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
Personally I’d go EFI and never look back. New models of EFI fit right on
the original manifold and fit under your stock air cleaner. If a product
offers improved performance and less headache I have no problems with
putting it on.

Sammy Williams
1999 American Eagle
 
> I think of myself as a handy guy. I watched the utube videos. How hard can it be? Well, if you have not done one in the past and you are only
> going to do one in your life......Don't! Try NorCal Carburetor and pay the $300 or so to have it done by someone who does this every day.

Probably good advice but not my style. The carb is the only part of this machine that I don't have my head around. I'm thinking a i might buy a used
one on ebay for $40 and rebuild that first.
--
Dave & Ellen Silva

1972 Revcon Olds 455, toro drive train. All Stock
 
> Personally I'd go EFI and never look back. New models of EFI fit right on
> the original manifold and fit under your stock air cleaner. If a product
> offers improved performance and less headache I have no problems with
> putting it on.

Maybe down the road. This coach is in remarkable shape with low miles. I am approaching it like car restoration. The goal is to make it run exactly
as it did from the factory and then maybe change things from there.

--
Dave & Ellen Silva

1972 Revcon Olds 455, toro drive train. All Stock
 
Dave:

I like your style! When I was getting back into the car thing about a decade ago, it was the first thing I did as well (a Holley on a different vehicle)

There is plenty of sage information around regarding the Quadrajet, and if you start with the right one, it might be like so many other vehicle projects, you’ll eventually get it right and learn something doing it!

Onward.

Dolph

DE AD0LF

Wheeling, West Virginia

1977 26’ ex-PalmBeach
Howell EFI & EBL, Reaction Arms, Manny Transmission

“The Aluminum and Fiberglass Mistress"

>

>> I think of myself as a handy guy. I watched the utube videos. How hard can it be? Well, if you have not done one in the past and you are only
>> going to do one in your life......Don't! Try NorCal Carburetor and pay the $300 or so to have it done by someone who does this every day.
>
> Probably good advice but not my style. The carb is the only part of this machine that I don't have my head around. I'm thinking a i might buy a used
> one on ebay for $40 and rebuild that first.
> --
> Dave & Ellen Silva
>
> 1972 Revcon Olds 455, toro drive train. All Stock
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
> > Personally I'd go EFI and never look back. New models of EFI fit right on
> > the original manifold and fit under your stock air cleaner. If a product
> > offers improved performance and less headache I have no problems with
> > putting it on.
>
> Maybe down the road. This coach is in remarkable shape with low miles. I am approaching it like car restoration. The goal is to make it run
> exactly as it did from the factory and then maybe change things from there.

Good luck getting it to run 'exactly' like it did from the factory. It just ain't gonna happen with today's fuel formulations. I can understand trying
to keep it all original but technology has moved on and if you plan on really enjoying your rig you may have to bend a little. I know there are many
that drive with the old school carbs with today's fuel but it is at best a compromise and not like it used to be.
It's your rig, do as you please of course but the reality is what it is.
Hal
--
1977 Royale 101348,

1977 Royale 101586, Diesel powered,

1975 Eleganza II, 101230,

1974 Eagle Bus 45',w/slideout,

Rio Rancho, NM
 
> Good luck getting it to run 'exactly' like it did from the factory. It just ain't gonna happen with today's fuel formulations. I can understand
> trying to keep it all original but technology has moved on and if you plan on really enjoying your rig you may have to bend a little.

It's not a commitment to historic accuracy. It's more about not screwing it up. I'm a marginal mechanic. The safest thing to do is establish the
baseline of ALL STOCK and then make incremental changes.

I could put EFI on and I'm sure it would work great but how do know how great if i didn't have a well running carb system to begin with?

--
Dave & Ellen Silva

1972 Revcon Olds 455, toro drive train. All Stock
 
Plus if you buy into the horror tales, the carb will keep right on running when the EMP wipes out the injection.

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
 
By putting in a rebuilt kit, your not rebuilding the carb, but replacing
some parts. There is a reason why the true Rebuilt units are expensive. Lot
of you are not aware of what Dick Paterson or our carb guy does to make the
carb perform like new.

On Mon, May 20, 2019 at 12:05 PM Sammy Williams via Gmclist <

> EMP will kill the HEI ignition and the electrics on the coach, so your
> still stranded anyway. (nerves are ticking now..) lol!!
>
> Sammy
>
> On Mon, May 20, 2019 at 11:57 AM Johnny Bridges via Gmclist <

>
> > Plus if you buy into the horror tales, the carb will keep right on
> running
> > when the EMP wipes out the injection.
> >
> > 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
> >
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
I used some parts from my 1972 Revcon carburetor to rebuild my 1975 GMC carb.
They are very similar. I think the jetting might be different (the primary rods
and jets).

The vacuum break from the Revcon fits my 1975 GMC. The conversion to electric choke
requires blocking the choke heater tube inlet. And no gasket is used on the electric
choke thermostat. You have to carefully align the primary rods, accelerator pump
and choke linkage as you put the air horn back on top of the main body. The fuel
bowl float seat needs to be tight so it won't leak. But you have to be careful
not to strip the threads. And the accelerator pump linkage pivot is easy to snap
off if you use too much force. The threads on the fuel filter are also easy to
strip if you over tighten the nut.

The secondary air valve cam usually has to be replaced. And the air valve spring
has to be adjusted a certain amount, otherwise it might bog when you stomp on it.
Assembling the choke is not too difficult. But you need to adjust the vacuum break
linkage to open the choke when manifold vacuum reaches a certain level.

If you've never rebuilt a carburetor before, it can be challenging.
In that case, it would be good to pay a professional to rebuild it.
--
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
 
EMP will kill the HEI ignition and the electrics on the coach, so your
still stranded anyway. (nerves are ticking now..) lol!!

Sammy

On Mon, May 20, 2019 at 11:57 AM Johnny Bridges via Gmclist <

> Plus if you buy into the horror tales, the carb will keep right on running
> when the EMP wipes out the injection.
>
> 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
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Here is an excellent source for quadrajet parts.

https://quadrajetparts.com/

Place your carb number in the search box.

On Mon, May 20, 2019 at 4:55 PM Bill Wevers via Gmclist <

> I used some parts from my 1972 Revcon carburetor to rebuild my 1975 GMC
> carb.
> They are very similar. I think the jetting might be different (the primary
> rods
> and jets).
>
> The vacuum break from the Revcon fits my 1975 GMC. The conversion to
> electric choke
> requires blocking the choke heater tube inlet. And no gasket is used on
> the electric
> choke thermostat. You have to carefully align the primary rods,
> accelerator pump
> and choke linkage as you put the air horn back on top of the main body.
> The fuel
> bowl float seat needs to be tight so it won't leak. But you have to be
> careful
> not to strip the threads. And the accelerator pump linkage pivot is easy
> to snap
> off if you use too much force. The threads on the fuel filter are also
> easy to
> strip if you over tighten the nut.
>
> The secondary air valve cam usually has to be replaced. And the air valve
> spring
> has to be adjusted a certain amount, otherwise it might bog when you stomp
> on it.
> Assembling the choke is not too difficult. But you need to adjust the
> vacuum break
> linkage to open the choke when manifold vacuum reaches a certain level.
>
> If you've never rebuilt a carburetor before, it can be challenging.
> In that case, it would be good to pay a professional to rebuild it.
> --
> Bill Wevers GMC49ers, GMC Western States
> 1975 Glenbrook - Manny Powerdrive, OneTon
> 455 F Block, G heads
> San Jose
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
 
The real deal is the formulation of today's gasoline, compared to what is
made today. First, there is no tetra-ethyl lead or several other long chain
hydrocarbon molecules present in today's gasoline. Today, fuel relies upon
high pressure and tiny, tiny holes in injector tips to atomize the fuel.
Our quadrajet carburetors relied upon light weight, highly volatile
aromatic compounds that vaporized by pressure differential (vacuum) in the
venturi of the carburetor. Those compounds have been omitted in today's
fuels, the result being that incomplete vaporization occurs in a carburetor
(any carburetor, not just quadrajets) You can not adjust or "tune" your
carburetor for this. You just have to live with what comes out of that pump
nozzle. It sucks, but that is the reality of what the EPA stuck us with.
Jim Hupy

On Mon, May 20, 2019, 3:55 PM Bill Wevers via Gmclist <

> I used some parts from my 1972 Revcon carburetor to rebuild my 1975 GMC
> carb.
> They are very similar. I think the jetting might be different (the primary
> rods
> and jets).
>
> The vacuum break from the Revcon fits my 1975 GMC. The conversion to
> electric choke
> requires blocking the choke heater tube inlet. And no gasket is used on
> the electric
> choke thermostat. You have to carefully align the primary rods,
> accelerator pump
> and choke linkage as you put the air horn back on top of the main body.
> The fuel
> bowl float seat needs to be tight so it won't leak. But you have to be
> careful
> not to strip the threads. And the accelerator pump linkage pivot is easy
> to snap
> off if you use too much force. The threads on the fuel filter are also
> easy to
> strip if you over tighten the nut.
>
> The secondary air valve cam usually has to be replaced. And the air valve
> spring
> has to be adjusted a certain amount, otherwise it might bog when you stomp
> on it.
> Assembling the choke is not too difficult. But you need to adjust the
> vacuum break
> linkage to open the choke when manifold vacuum reaches a certain level.
>
> If you've never rebuilt a carburetor before, it can be challenging.
> In that case, it would be good to pay a professional to rebuild it.
> --
> Bill Wevers GMC49ers, GMC Western States
> 1975 Glenbrook - Manny Powerdrive, OneTon
> 455 F Block, G heads
> San Jose
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
I ran the carbureted 23' on non alcohol gas without problems. It ran well. The few times it had to deal with alcohol laced gas it wasn't happy. The
26' current coach has a TBI. It has had drive-ability problems, but I suspect they are because the TBI hadn't been sorted out when I bought the coach
according to the PO. I think given some time to fiddle with it I can get it to run on what passes for gasoline these days. There's nothing to be
done about the 6 - 10% loss in MPG, the alcohol laced gas burns with less energy.

--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
 
The Qjet on the MH used unique tripple tapered primary mettering rods not found in any pass car application. That's the missing link
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Back in 1984 there was a GM engineer in Sacramento that knew all about
these carbs and he called out the only cores that would work .
That is why we use those bores to be rebuilt, not just refreshed like what
most people are doing

On Mon, May 20, 2019 at 8:30 PM John R. Lebetski via Gmclist <

> The Qjet on the MH used unique tripple tapered primary mettering rods not
> found in any pass car application. That's the missing link
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
> By putting in a rebuilt kit, your not rebuilding the carb, but replacing
> some parts. There is a reason why the true Rebuilt units are expensive. Lot
> of you are not aware of what Dick Paterson or our carb guy does to make the
> carb perform like new.

At only 25,000 miles, am i correct in thinking I don't need a "real rebuild" ?

I'm thinking replacing gaskets and a good cleaning should et me pretty close.

--
Dave & Ellen Silva

1972 Revcon Olds 455, toro drive train. All Stock
 
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