Rochester Quadrajet 4MV Carburetor: Removal, Disassembly, Rebuild (Rookie Level) - Page 9 - Hot Rod Forum : Hotrodders Bulletin Board
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  #121 (permalink)  
Old 03-31-2011, 04:18 AM
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Here's a pic of my 76 door jamb.
Looks like you had a large plate like mine before unless all the cabs came with pre punched holes and they used different VIN plates for special applications.
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  #122 (permalink)  
Old 03-31-2011, 05:15 AM
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Quote:
Originally Posted by lt1silverhawk
There is no VIN on the dash, nor any holes where it should be at.
Likely not even supposed to be one there- which points to my lack of knowledge on these C20's-and larger trucks. I'll stay in the background on this all until there's something concrete I can offer.
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  #123 (permalink)  
Old 03-31-2011, 09:42 AM
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Thank you guys for trying so hard.

To keep this thread from getting any longer and deviating from its original topic of rebuilding a carburetor, I have created a new thread. This will hopefully attract other forum members with more knowledge in this issue who may not come to this thread because its title doesn't mention factory smog equipment.

For anyone else reading this, the carb rebuild was completed by page 7.
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  #124 (permalink)  
Old 03-31-2011, 11:22 AM
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rochester throttle shaft

before you spend money on a q-jet, check the throttle shafts for wear. usually worn out. lots have been dissassembled and re-bushed with success. just get the right guy to do that for you so the shaft actually stays centred where it was originally. otherwise idle set up can suck.
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  #125 (permalink)  
Old 03-31-2011, 12:41 PM
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Hey dsraven,
Quote:
Originally Posted by dsraven
before you spend money on a q-jet, check the throttle shafts for wear. usually worn out. lots have been dissassembled and re-bushed with success. just get the right guy to do that for you so the shaft actually stays centred where it was originally. otherwise idle set up can suck.
Going by the recommendation of some forum members, I chose to do my rebuild without re-bushing. But I'm glad you brought it up for anyone else who may need to do it.

The thread is still open to tips, pointers, cautions, warnings, procedures, etc.
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  #126 (permalink)  
Old 04-20-2011, 08:51 AM
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Quote:
Originally Posted by willys36@aol.com
Trottle spring orientation is critical to the life of your primary shaft bushings as mentioned above for any carb installation. Design yours like the 'best' picture below and your shaft busings will last forever.

Hi, I want to change my setup to the better setup, but I am looking for people and pictures that already did this on a Quadrajet.

HEre's some pics of mine.
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  #127 (permalink)  
Old 04-20-2011, 09:19 AM
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Quote:
Originally Posted by kikkegek
Hi, I want to change my setup to the better setup, but I am looking for people and pictures that already did this on a Quadrajet.

HEre's some pics of mine.
No photos showed in your post.

While the "Best" set up shown above may well be the best, the "Better" image shows a set up that is (IMO) 90% as good as the Best set up. It's easier to do, and only requires that the return springs be attached forward of the throttle cable/linkage attachment point.

Always use a dual return spring- a "spring inside a spring" as used by many OEM's is an excellent type of return spring to use.

Below is a simple $9.00 spring and bracket sold by Mr. Gasket (P/N 720-19) that might work in your situation, and shows the type of spring to use:


Last edited by cobalt327; 04-20-2011 at 09:24 AM.
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  #128 (permalink)  
Old 04-20-2011, 09:24 AM
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oops, sorry here the pics.



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  #129 (permalink)  
Old 04-20-2011, 09:34 AM
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Quote:
Originally Posted by kikkegek
oops, sorry here the pics.
Actually, the way you have it- while crude- is actually not too bad as far as wear on the throttle shaft goes. That said, it's "unsanitary" appearing and the one spring behind the throttle shaft offsets some of the advantage of the forward-mounted spring. Not to mention using the hose to mount the spring- you need to use a solid mounting point rather than tie wrapping the return spring to the hose.

I would suggest you mount a bracket forward of the shaft as shown above and use the dual spring. You will need to improvise how the bracket is made and mounted, to have the spring in line w/the throttle cable (not at an angle, like if the spring were mounted to a small bracket attached to an intake mounting bolt) so the pull of the spring is in the same plane as the pull of the throttle cable.
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  #130 (permalink)  
Old 04-20-2011, 11:44 AM
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Glad you asked about this kikkegek. I've wondering about how to set this up myself.




Quote:
Originally Posted by cobalt327
No photos showed in your post.

While the "Best" set up shown above may well be the best, the "Better" image shows a set up that is (IMO) 90% as good as the Best set up. It's easier to do, and only requires that the return springs be attached forward of the throttle cable/linkage attachment point.

Always use a dual return spring- a "spring inside a spring" as used by many OEM's is an excellent type of return spring to use.

Below is a simple $9.00 spring and bracket sold by Mr. Gasket (P/N 720-19) that might work in your situation, and shows the type of spring to use:

Hey cobalt327,

Does the bracket mount in a specific place or does a hole have to be drilled in a specific place to install it? Or if that's too much work, would the setup pictured below be a better choice? It is a manifold-mount universal set up (attached are the installation instructions in pdf). I couldn't find one that was Q-Jet specific on Summit.

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  #131 (permalink)  
Old 04-20-2011, 02:56 PM
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I made a custom bracket myself tonight and mounted it to the brakcet of my A/C pump. The springs are still not puling hard enough for my setup. I will have to fine tune it. I'll takes some pics tomorrow.
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  #132 (permalink)  
Old 04-21-2011, 04:02 AM
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Quote:
Originally Posted by kikkegek
I made a custom bracket myself tonight and mounted it to the brakcet of my A/C pump. The springs are still not puling hard enough for my setup. I will have to fine tune it. I'll takes some pics tomorrow.
To add to the information. It seems that only when the engine is warmed up, I have the high idle problem, because the throttle linkage last bit has extra resistance. So the last 1-2 mm before it hits the idle screw feels heavy. So heavy when warm, that the springs dont pull it back to full idle, making it idle at about 1000-1100 rpm.
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  #133 (permalink)  
Old 04-21-2011, 08:59 AM
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heavy throttle

check the throttle shaft bushings for wear. that is common problem. the throttle shafts bind because the butterfly valves never end up in the same place twice. thery also leak vacuum so it is hard to adjust the idle mixture. also check all the rest of the linkages and pull offs on the carb. some are affected by the choke so if the choke is still on a little that part of the linkage isn't operative. like the 4bbl lockout won't owrk if the choke is active. grab some carb cleaner/lubricant spray at the parts store and do a little clean up of all the rods etc. if you have a little extra cashola, get a new aftermarket carb and some new distributor weights and springs (recurve the distributor) at the same time. that will perk it up. have to spend a couple hundred though.
good luck,
dsraven
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  #134 (permalink)  
Old 04-21-2011, 01:36 PM
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OK,

heres some pics of my forward "better" spring setup. Its hard to take pics, but here they are.

I noticed that in my setup my spring was about half an inch shorter stretched in "idle" position then in the carbs original setup.

So today I drilled two more holes too stretch it a little more. I'll take a drive tonight and report back on it.




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  #135 (permalink)  
Old 04-21-2011, 01:39 PM
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Hey kikkegek,

That looks pretty good. Where did you mount the bracket to?
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