Home » Public Forums » GMCnet » [GMCnet] CAD 500 QUADRAJET?
| [GMCnet] CAD 500 QUADRAJET? [message #252387] |
Tue, 17 June 2014 16:14  |
James Hupy
Messages: 6806
Registered: May 2010
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Who is running a Quadrajet on a Cad 500 in a GMC motor home that knows the
combination of jets, needles, etc. close to correct for this application?
We are in Joplin, Mo at the airport by the side of the road. Tow truck
coming for a tow to Oklahoma City to camping world. They put a reman for a
368? Cid that was 2 years newer than the engine which is a 76. Correct part
number would be helpful also as I am flying blind here without reference
books, etc.
Coach belongs to John and Deb Harper
Jim Hupy
Route 66 road show.
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| Re: [GMCnet] CAD 500 QUADRAJET? [message #252391 is a reply to message #252387] |
Tue, 17 June 2014 17:50  |
cbryan
Messages: 451
Registered: May 2012
Location: Ennis, Texas
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James,
Maybe the Cad500, the old Cad Company. (fivohfiv) 8tootree-9tree4Oh They say call 24 hours a day. They have carbs, too. I would say Paterson, but he said, I think, that he never had a 500 to examine, yet.
Good time for him to get started. The guys at Maximum Torque Specialties in Albuquerque can also help, I am sure. 76zero tooforzeven 25doubletree. Pardon the spelling. I will keep looking for discussions of the jets for the 500. Whether there have been detail changes over the years that would make trouble for your conversion, I don't know. In this circumstance, it appears that putting a carb on designed for the 500 would get you on the road without too much R&D. Especially if it won't run at all. Seems like if no valve has been swallowed, that it would run somewhat. But you are towing it?
I found some specs quoting a fellow who replaced a 403 with a 500 with quadrajet but having problems with a rich idle. I suspect he had float level problems causing the rich idle. He gave some specs and I quote:
I'm using a 1984 carb of a P30 454 MH. #17080212, second line,1444CPW.
Cam. Comp 202 int. 212 ex. on a 110 ctr. line (should have orderd on a 112 or 114)
Idle tube .037
Idle down channel .046
Lower idle air bleed .056
Idle bypass air .110
Mixture screw holes .064
Main air bleeds .052
Idle air bleeds .067-.068
Main jets 72
Primary rods (from a 72 cad 500 qjet): 41B .026 tip
Interesting information is that for the MH Oldsmobile 455 quadrajets, recommended main jet numbers are 70 minimum, on up to 74.
HTH.
Carey
Carey from Ennis, Texas
78 Royale, 500 Cadillac, Rance Baxter EFI.
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| Re: [GMCnet] CAD 500 QUADRAJET? [message #252393 is a reply to message #252391] |
Tue, 17 June 2014 18:26 |
Sammy Williams
Messages: 522
Registered: August 2010
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Would an Edelbrock spread bore work in a pinch to get you going?
S. Williams
On Tue, Jun 17, 2014 at 5:50 PM, Carey Bryan wrote:
> James,
>
> Maybe the Cad500, the old Cad Company. (fivohfiv) 8tootree-9tree4Oh They
> say call 24 hours a day. They have carbs, too. I would say Paterson, but
> he said, I think, that he never had a 500 to examine, yet.
>
> Good time for him to get started. The guys at Maximum Torque Specialties
> in Albuquerque can also help, I am sure. 76zero tooforzeven 25doubletree.
> Pardon the spelling. I will keep looking for discussions of the jets for
> the 500. Whether there have been detail changes over the years that would
> make trouble for your conversion, I don't know. In this circumstance, it
> appears that putting a carb on designed for the 500 would get you on the
> road without too much R&D. Especially if it won't run at all. Seems like
> if no valve has been swallowed, that it would run somewhat. But you are
> towing it?
>
> I found some specs quoting a fellow who replaced a 403 with a 500 with
> quadrajet but having problems with a rich idle. I suspect he had float
> level
> problems causing the rich idle. He gave some specs and I quote:
>
> I'm using a 1984 carb of a P30 454 MH. #17080212, second line,1444CPW.
> Cam. Comp 202 int. 212 ex. on a 110 ctr. line (should have orderd
> on a 112 or 114)
> Idle tube .037
> Idle down channel .046
> Lower idle air bleed .056
> Idle bypass air .110
> Mixture screw holes .064
> Main air bleeds .052
> Idle air bleeds .067-.068
> Main jets 72
> Primary rods (from a 72 cad 500 qjet): 41B .026 tip
>
> Interesting information is that for the MH Oldsmobile 455 quadrajets,
> recommended main jet numbers are 70 minimum, on up to 74.
>
> HTH.
>
> Carey
> --
> Carey from Ennis, Texas
> 78 Royale, 500 Cadillac, Rance Baxter EFI.
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] CAD 500 QUADRAJET? [message #252395 is a reply to message #252387] |
Tue, 17 June 2014 18:58 |
cbryan
Messages: 451
Registered: May 2012
Location: Ennis, Texas
Karma: 3
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Jim,
Chris from Cadco has responded:
Maybe you can pass along the info -
1 - 368 engines are '80-'85. Not enough CFM, and some were electronic carbs
(without the computer, they will not run right). There is no combination of
jets and rods that will make a 368 spec carb (computerized or not) really
run right.
2 - '2 years newer' would be a '78 425 spec carb, which is functionally the
same thing as a '76 spec carb. If it doesn't work, it's not because it's the
wrong carb.
3 - There are many dozens of Q-jet numbers that are 'correct'.
4 - The fact that it doesn't work right could have nothing to do with
whether or not it is a 'correct' carburetor for that engine.
5 - It could also be because it wasn't set up correctly upon installation -
idle adjustments, and / or choke adjustment or setup (there is a video
walking you through all of the initial setup adjustments on a Q-jet on our
Facebook page, also linked from the tech page of our website). None of that
stuff can be set up properly 'on the bench' - it is set to a base
calibration, but MUST be adjusted for the engine the carb was put on, after
it's on the running engine. Always. The base calibration is often close
enough to be marginally drivable, and many people just bolt them on and
assume that's good enough. That's why many people have the misconception
that a carb can be 'bench tuned' by a good carb guy so it runs right on the
engine, with no further adjustments. Sometimes, it can seem 'good enough' to
drive, but still be far enough out to wipe out the bottom end of the
engine...
6 - If it ran well enough, long enough, to leave them stranded (i.e. get to
where they were stranded at), then I suspect it's not a problem due to
having a completely wrong carburetor (or it was completely wrong, and they
drove it until it took out the engine). It's much more likely that there is
a different problem, either unrelated to, or caused by the carburetor, and
_just_ fixing / replacing the carb is not going to fix the problem.
Chances are, the mechanic there won't even see it until the morning. If they
need help diagnosing it or finding parts, they can give me a call in the
morning.
Chris
Cad Company
Home of the world's fastest Cadillac engines
505-823-9340
8333 Jefferson St NE
Albuquerque, NM, 87113
Carey from Ennis, Texas
78 Royale, 500 Cadillac, Rance Baxter EFI.
[Updated on: Tue, 17 June 2014 19:36] Report message to a moderator |
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| Re: [GMCnet] CAD 500 QUADRAJET? [message #252398 is a reply to message #252387] |
Tue, 17 June 2014 19:31 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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James Hupy wrote on Tue, 17 June 2014 15:14Who is running a Quadrajet on a Cad 500 in a GMC motor home that knows the
combination of jets, needles, etc. close to correct for this application?
We are in Joplin, Mo at the airport by the side of the road. Tow truck
coming for a tow to Oklahoma City to camping world. They put a reman for a
368? Cid that was 2 years newer than the engine which is a 76. Correct part
number would be helpful also as I am flying blind here without reference
books, etc.
Coach belongs to John and Deb Harper
Jim Hupy
Route 66 road show.
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If you are just trying to get going, why not use any big block GM carb such as the GMC 455, Chev 454 or a Pontiac 455. Not sure if you need a side or straight fuel inlet but you have 2 choices.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] CAD 500 QUADRAJET? [message #252406 is a reply to message #252398] |
Tue, 17 June 2014 20:31 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Ok guys thank you for the help. The GMC is currently "on the hook" and
headed for Camper World in Oklahoma City. John and Deb are set for the
night with motels and rental car. Less than 30 days ago, Camper World in
Tuscon, Az. replaced the faulty carb original to the Cad 500 with the
current carb in question. What started this whole thing was a no start
condition with fuel flooding over the top of the engine. When I removed the
bowl cover, the float was sitting on the bottom of the float bowl. When
removed, it was found to be full of fuel. I unsoldered the weep hole,
drained it, and resoldered it. When I leak checked it, 3 more holes were
found. Fixed those, ran for a couple of days then sank again. We limped to
Randy VanWinkle's and replaced the float with a new one. Today on the road,
it was snotty rich, so I took it apart along the road, re adjusted the
float to 13/32" as per specs I had with the kit, and replaced the inlet
needle and seat, because the needle in the carb was flat instead of
pointed. Better, but still rich. Finally stopped in Joplin, Mo. Called
Camper World. They agreed to order another carb. That is where we are
presently. Apparently a short distance from there is a Rochester guy that
will look at it. I will forward these specs to Deb, and she will give them
to him.
Jim Hupy
On Jun 17, 2014 7:32 PM, "Bob de Kruyff" wrote:
> James Hupy wrote on Tue, 17 June 2014 15:14
>> Who is running a Quadrajet on a Cad 500 in a GMC motor home that knows
> the
>> combination of jets, needles, etc. close to correct for this application?
>> We are in Joplin, Mo at the airport by the side of the road. Tow truck
>> coming for a tow to Oklahoma City to camping world. They put a reman for
> a
>> 368? Cid that was 2 years newer than the engine which is a 76. Correct
> part
>> number would be helpful also as I am flying blind here without reference
>> books, etc.
>> Coach belongs to John and Deb Harper
>> Jim Hupy
>> Route 66 road show.
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
> If you are just trying to get going, why not use any big block GM carb
> such as the GMC 455, Chev 454 or a Pontiac 455. Not sure if you need a side
> or
> straight fuel inlet but you have 2 choices.
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] CAD 500 QUADRAJET? [message #252654 is a reply to message #252387] |
Thu, 19 June 2014 16:34 |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
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Just like engines, just because it is rebuilt doesnt mean it is rebuilt right.
I take it you have the brass float rather than the phenolic one, which can get fuel soaked and sink. Also make sure the suspension is free on the float, and the phenolic baffle isnt catching on it
Agree that a "368" [CID? What IS that?] carb would not be right but it should at least run. I have run 350 carbs on a 454 big block in a pinch and it would get you home. Q jets are pretty flexible up to a point.
BTW, you can modify the baseplate of the sealed idle late Q jet to adjust the idle mixture by cutting Vs on either side of plugs on the bottom of the baseplate and knocking the plugs out. Some have soft plugs you can drill and pull with a screw, later ones are hardened it seems. You will need a special tool to adjust them , or you can rig extentions with crimepd and epoxied tubing and your chouce of screw.
76 Glenbrook
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