| [GMCnet] Newfound Power... [message #89236] |
Sat, 19 June 2010 14:06  |
kelvin
Messages: 608
Registered: February 2004
Location: Eugene, OR
Karma: 0
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Senior Member |
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I'm a happy camper this morning...
Just to set the stage...
A '73 230 with the 455. This coach had a '76 vintage Caddy Q-jet on it
when I got it 9 years ago. It worked but certainly not well. It had
been upgraded to HEI at some point but that was probably from the same
Caddy. One of the first things I did was install a Patersen HEI. Nice
improvement in how it ran right there.
I then tried to find the correct Q-jet (after I learned they were
special) but only came up with a warped one. I ended up buying an
Autozone rebuild and swapping as many GMC parts into it as possible. It
worked better and the mileage went from 5-6 to 7-9. Got 10mpg two times
with a pretty stead tailwind. Pretty much what everyone says to expect
from a GMC.
The motorhome has always had lousy secondary actuation. Falls on it's
face really bad and just seems to be less than optimal across the
board. Not great at pulling hills by any means and I know it should
work better. Merging into freeway traffic is slow and painful. Really,
really need a rebuildable GMC Q-jet but they just aren't out there.
A new friend of mine knows Q-Jets pretty well. He'd never got to sit
on the step of a "rolling dyno" GMC and watch the carb work and was
excited to try it. He came over this morning and we took it for a
spin. Him playing with the carb while I floored it told him a few things.
So we took the top off the carb and fiddled around with various piece.
He didn't like how the metering rods were moving (not getting open fast
enough) and a couple other things. We also changed the spring rate on
the Secondary Air doors and replace the GMC metering rod "lifter" with
the one that came off the Autozone carb. He liked the location of some
holes in that better.
I gotta tell you. I think we have it pretty close to right. The coach
just gets up and goes when I floor it. And it's actually better over
the whole range of operation even though nothing we did should have
improved the Primary circuit. It's truly night and day from just a few
hours ago.
And for the first time in EVER I can break a tire loose from a
standstill. A motorhome that can burn rubber is freakin' awesome.
There goes the fuel mileage...
Later,
Kelvin
'73 23' in Eugene, OR
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| Re: [GMCnet] Newfound Power... [message #89238 is a reply to message #89236] |
Sat, 19 June 2010 14:17  |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Kelvin,
Nice report -- and I am sure you made notes of the part numbers you have in use now :)
Good to see you back on the GMCnet -- while you were away I borrowed regularly from your photo album for reference.
Dennis
Dennis Sexton
73 GMC
Germantown, TN
USA
-----Original Message-----
From: Kelvin Dietz <kelvin@datsuns.com>
To: gmclist@temp.gmcnet.org
Sent: Sat, Jun 19, 2010 2:06 pm
Subject: [GMCnet] Newfound Power...
I'm a happy camper this morning...
Just to set the stage...
'73 230 with the 455. This coach had a '76 vintage Caddy Q-jet on it
hen I got it 9 years ago. It worked but certainly not well. It had
een upgraded to HEI at some point but that was probably from the same
addy. One of the first things I did was install a Patersen HEI. Nice
mprovement in how it ran right there.
I then tried to find the correct Q-jet (after I learned they were
pecial) but only came up with a warped one. I ended up buying an
utozone rebuild and swapping as many GMC parts into it as possible. It
orked better and the mileage went from 5-6 to 7-9. Got 10mpg two times
ith a pretty stead tailwind. Pretty much what everyone says to expect
rom a GMC.
The motorhome has always had lousy secondary actuation. Falls on it's
ace really bad and just seems to be less than optimal across the
oard. Not great at pulling hills by any means and I know it should
ork better. Merging into freeway traffic is slow and painful. Really,
eally need a rebuildable GMC Q-jet but they just aren't out there.
new friend of mine knows Q-Jets pretty well. He'd never got to sit
n the step of a "rolling dyno" GMC and watch the carb work and was
xcited to try it. He came over this morning and we took it for a
pin. Him playing with the carb while I floored it told him a few things.
So we took the top off the carb and fiddled around with various piece.
e didn't like how the metering rods were moving (not getting open fast
nough) and a couple other things. We also changed the spring rate on
he Secondary Air doors and replace the GMC metering rod "lifter" with
he one that came off the Autozone carb. He liked the location of some
oles in that better.
I gotta tell you. I think we have it pretty close to right. The coach
ust gets up and goes when I floor it. And it's actually better over
he whole range of operation even though nothing we did should have
mproved the Primary circuit. It's truly night and day from just a few
ours ago.
And for the first time in EVER I can break a tire loose from a
tandstill. A motorhome that can burn rubber is freakin' awesome.
There goes the fuel mileage...
Later,
elvin
73 23' in Eugene, OR
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MCnet mailing list
ist Information and Subscription Options:
ttp://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Newfound Power... [message #89241 is a reply to message #89236] |
Sat, 19 June 2010 14:34 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Now put on a Limited Slip diffy.
You'll leave 2 strips of marks, not one.
On Sat, Jun 19, 2010 at 12:06 PM, Kelvin Dietz <kelvin@datsuns.com> wrote:
> I'm a happy camper this morning...
>
> Just to set the stage...
> A '73 230 with the 455. This coach had a '76 vintage Caddy Q-jet on it
> when I got it 9 years ago. It worked but certainly not well. It had
> been upgraded to HEI at some point but that was probably from the same
> Caddy. One of the first things I did was install a Patersen HEI. Nice
> improvement in how it ran right there.
>
> I then tried to find the correct Q-jet (after I learned they were
> special) but only came up with a warped one. I ended up buying an
> Autozone rebuild and swapping as many GMC parts into it as possible. It
> worked better and the mileage went from 5-6 to 7-9. Got 10mpg two times
> with a pretty stead tailwind. Pretty much what everyone says to expect
> from a GMC.
>
> The motorhome has always had lousy secondary actuation. Falls on it's
> face really bad and just seems to be less than optimal across the
> board. Not great at pulling hills by any means and I know it should
> work better. Merging into freeway traffic is slow and painful. Really,
> really need a rebuildable GMC Q-jet but they just aren't out there.
> A new friend of mine knows Q-Jets pretty well. He'd never got to sit
> on the step of a "rolling dyno" GMC and watch the carb work and was
> excited to try it. He came over this morning and we took it for a
> spin. Him playing with the carb while I floored it told him a few things.
>
> So we took the top off the carb and fiddled around with various piece.
> He didn't like how the metering rods were moving (not getting open fast
> enough) and a couple other things. We also changed the spring rate on
> the Secondary Air doors and replace the GMC metering rod "lifter" with
> the one that came off the Autozone carb. He liked the location of some
> holes in that better.
>
> I gotta tell you. I think we have it pretty close to right. The coach
> just gets up and goes when I floor it. And it's actually better over
> the whole range of operation even though nothing we did should have
> improved the Primary circuit. It's truly night and day from just a few
> hours ago.
>
> And for the first time in EVER I can break a tire loose from a
> standstill. A motorhome that can burn rubber is freakin' awesome.
>
> There goes the fuel mileage...
>
> Later,
> Kelvin
> '73 23' in Eugene, OR
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Newfound Power... [message #89245 is a reply to message #89236] |
Sat, 19 June 2010 15:44 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""And for the first time in EVER I can break a tire loose from a
standstill. A motorhome that can burn rubber is freakin' awesome.
""
Kelvin--I love these stories and owner experiences. Once again it dispells the fact that the GMC carb is so special that it is the only one that will work, Agreed, you did swap internal tuning items, but those are readilly available. I continuously read how special our carb is with special passages and all kinds of anecdotal BS. We all need to be aware that there are many great solutions out there that don't fall within the accepted expensive and self serving lore.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Newfound Power... [message #89248 is a reply to message #89245] |
Sat, 19 June 2010 16:22 |
kelvin
Messages: 608
Registered: February 2004
Location: Eugene, OR
Karma: 0
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Senior Member |
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On Sat, Jun 19, 2010 at 1:44 PM, Bob de Kruyff <NEXT2POOL@aol.com> wrote:
>
>
> ""And for the first time in EVER I can break a tire loose from a
> standstill. A motorhome that can burn rubber is freakin' awesome.
> ""
>
> Kelvin--I love these stories and owner experiences. Once again it dispels
> the fact that the GMC carb is so special that it is the only one that will
> work, Agreed, you did swap internal tuning items, but those are readily
> available. I continuously read how special our carb is with special passages
> and all kinds of anecdotal BS. We all need to be aware that there are many
> great solutions out there that don't fall within the accepted expensive and
> self serving lore.
>
Dunno, Bob...
From past research those GMC metering rods aren't available from anywhere
else. I believe Dick P when he says that the bodies are different, too.
This new carb-tuning friend of mine says GM did all sorts of custom stuff
depending on application.
If I could have found a rebuildable carb for a 455 GMC I would have sent it
off to Dick. As it is I'll get to check the performance of this carb on a
1100mile trip next week. Should give me pretty good data (power and
mileage) to decide whether I need to keep pursuing that GMC-specific carb or
not.
And as for what base carb and extra parts are in this carb, Dennis? I
haven't the slightest. I bought the carb for some vintage Tornado and we
ended up with a mix and match of Autozone and GMC parts. Who knows...
Kelvin
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| Re: [GMCnet] Newfound Power... [message #89270 is a reply to message #89248] |
Sat, 19 June 2010 21:19 |
Larry C
Messages: 1168
Registered: July 2004
Location: NE Illinois by the Illino...
Karma: 0
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Senior Member |
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From past research those GMC metering rods aren't available from anywhere else. I believe Dick P when he says that the bodies are different, too.
This new carb-tuning friend of mine says GM did all sorts of custom stuff depending on application.
_________________________________________________________-
Hey, I just went through a nightmare that finally ended with the carb, about 3 years worth.
My mechanic and some of his race car techs struggled over the carb for quite a while, ended up replacing it with a rebuilt. Found out the numbers did not match a GMC MotorHome carb.
The mechanic wanted to know the difference and found that the body is deferent, affecting performance and the rods are different, I think he said they are a larger diameter, it is all a performance factor.
You sound like you have yours fine tuned and performing well. Reason and from the info from my mechanic and the racing techs makes me think if you had the GMC MOTORHOME Carb, you might have gotten a bit more.
Great job, you'll be ready visit the campgrounds soon.
LarC ( It seem that the secret is in the carborator )
Gatsbys' CRUISER  08-18-04
74 GLACIER X, 260/455-APC-4 Bagg'r
Remflex Manifold gaskets
CampGrounds needed, Add yours to "PLACES" />
http://www.gmceast.com/travel
_
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| Re: [GMCnet] Newfound Power... [message #89374 is a reply to message #89248] |
Sun, 20 June 2010 21:54 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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Senior Member |
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[quote
Dunno, Bob...
From past research those GMC metering rods aren't available from anywhere
else. quote]
i got rods an jets from Cinnabar.
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: [GMCnet] Newfound Power... [message #89464 is a reply to message #89236] |
Mon, 21 June 2010 21:59 |
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tha sounds exactl like what happened when I put on my holley street avenger carb, I have a vid on youtube of the front pealing rubber. I should check the number on the old Q-jet, as maybe it was a different unit, but the coach was gutless like yours till I popped on the holley...
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: [GMCnet] Newfound Power... [message #89696 is a reply to message #89464] |
Thu, 24 June 2010 08:47 |
RickOH
Messages: 29
Registered: December 2006
Location: Coshocton OH
Karma: 0
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Junior Member |
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Can you give more info on the Holly Street Avenger carb?
Installs without an adapter ?
Hehght compatable for engine lid of GMC ?
Any improvement in fuel milage?
Any specific model # ?
In my experience Holly was always a little better on performance but not neccessarily great for mileage.
Rick Little 78 Royale
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