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Old 09-16-2012, 07:09 PM
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Questions about a QuadraJet

I have a '68 Impala that has a 327 with a QuadraJet 4-barrel. #7028212 etched on it.

It's my understanding that it's a 4MV. I already got a kit, and completed disassembly. I've started cleaning it. I have a question about the piston that has the main metering rods attached. Can I soak that? I don't think I could ever get that little wire back like it's supposed to be if I take it appart?

Also this thing has vacuum controlled choke, it's not electric or that coil thing. There is this red plastic arm/linkage thing on it. It's all cracked and the little teeth on the bottom side are almost worn smooth. What's the name of this and where can I find another?

That's pretty much all for now. Thanks for any insight.

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Old 09-16-2012, 08:57 PM
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my understanding is that is the fast idle (idle-step controler) works off the choke pull-off. Got one on mine, but carb is all apart on my bench. got it w/o choke pull-off canister and most of the linkages, which I will have to find and replace. But, I did see a picture recently somewhere that showed that to be the fast idle. Probably not much help, as I really cant remember where I saw it. but do have a picture of it on the carb before I took it apart. And don't think you are talking about 'main metering rods' think you are looking at the power piston. has two rods with that little wire retainer spring and a brass cylinder with a spring under it. the little wire retainer spring will (just) slide over the rod hanger with very little effort. its spring steel. Am worried more about losing those tiny little pieces than bending them. I just today ordered a inexpensive/junk Q-jet carb from a guy on e-bay for parts, just in case.
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Old 09-16-2012, 09:47 PM
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Well first sorry for posting in the wrong forum.

...according to the diagram those are primary metering rods. But I'll look again to be sure. But what do you think about soaking it?

And yes it helps to have a name to search for instead of "little red linkage thingy".

Thanks for the reply.

Quote:
Originally Posted by fasteddy_1947 View Post
my understanding is that is the fast idle (idle-step controler) works off the choke pull-off. Got one on mine, but carb is all apart on my bench. got it w/o choke pull-off canister and most of the linkages, which I will have to find and replace. But, I did see a picture recently somewhere that showed that to be the fast idle. Probably not much help, as I really cant remember where I saw it. but do have a picture of it on the carb before I took it apart. And don't think you are talking about 'main metering rods' think you are looking at the power piston. has two rods with that little wire retainer spring and a brass cylinder with a spring under it. the little wire retainer spring will (just) slide over the rod hanger with very little effort. its spring steel. Am worried more about losing those tiny little pieces than bending them. I just today ordered a inexpensive/junk Q-jet carb from a guy on e-bay for parts, just in case.
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Old 09-16-2012, 09:51 PM
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Yes you can soak the power piston that has the rods attached to it.
JFYI all quads whether choke stove, divorced or electric choke styles all are vacuum controlled.
Take a pic of your carb and the parts you have questions on. Here's a link for rebuilding it.
Ken's QuadraJet
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Old 09-16-2012, 10:03 PM
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I think you are confusing the secondary circuit with the primary circuit. There are no vacuum controlled chokes on any carbs (that I am aware of). Qjets had electric or thermostatic chokes. The primary circuit has a choke. The secondary circuit operates via vacuum.

I believe fasteddy_1947 has correctly identified the issue here. One function of the choke is to prevent the secondary circuit from opening while the choke is on. This is called the choke lockout. There is also the fast idle cam, which holds the primary circuit slightly open to increase idle RPM's while cold. There are many iterations of the Qjet and many different types of linkages and parts. They do NOT all interchange.

This may help
http://www.crankshaftcoalition.com/wiki/Quadrajet

Cliff Rugles book is considered the Qjet bible. If you are really serious about rebuilding the carb, then you need his book:
How to Rebuild and Modify Rochester Quadrajet Carburetors (S-a Design): Cliff Ruggles: 9781932494181: Amazon.com: Books How to Rebuild and Modify Rochester Quadrajet Carburetors (S-a Design): Cliff Ruggles: 9781932494181: Amazon.com: Books
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Old 09-16-2012, 10:13 PM
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Certainly are vacuum controlled. Choke pull off pot on all of them. Without it the choke plate would stay shut. Choke pull off is there to open the plate enough to keep it running. Also it dampens secondary air valve action.
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Old 09-16-2012, 10:55 PM
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Heck, I been calling it the little red plastic thingy 'til I saw what it was. what I need to do is find picture/diagram of the one I got tore apart on my bench, so's I know what to look for when I try to replace the missing secondary and choke linkages. I soaked the Power Piston and rods overnight with the rest of the secondary metalware, and polished them all up, and then put them back in the bins for later assembly after I find all the right parts. I dropped the rubber tipped needle seat in there too, to keep all that stuff out of the fuel bowl together. I have never seen a carburator kit w/o new needle seat. I'm old and retired, and forget where things came from quickly. Like I said before, bout the worst I can do is lose something, and with this I wouldn't even know it was lost.
Let me ask you question as seems we have similar machinery here. On yours does the check ball well next to the accelerator pump have a lead seal over it, or do you have access to that with a screwed in stopper with a spring (or something)? Mine has a (looks like) poured lead seal over it and I dont believe that is right. Maybe they (last owner) stripped out the threads or something and just sealed it up with (that might be JB Weld too, didn't think of that).
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Old 09-17-2012, 06:21 AM
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Quote:
Originally Posted by fasteddy_1947 View Post
Heck, I been calling it the little red plastic thingy 'til I saw what it was. what I need to do is find picture/diagram of the one I got tore apart on my bench, so's I know what to look for when I try to replace the missing secondary and choke linkages.
The part is the choke fast idle cam. The type of choke you have is called a "divorced choke" (coil assembly that bolts to intake shown below). It has the thermostat coil down on the intake manifold w/a linkage between the coil and the choke mechanism on the carb. The fast idle cam will often still work fine even worn.



Quote:
I soaked the Power Piston and rods overnight with the rest of the secondary metalware, and polished them all up, and then put them back in the bins for later assembly after I find all the right parts. I dropped the rubber tipped needle seat in there too, to keep all that stuff out of the fuel bowl together. I have never seen a carburetor kit w/o new needle seat. I'm old and retired, and forget where things came from quickly. Like I said before, bout the worst I can do is lose something, and with this I wouldn't even know it was lost.
The kit should have included the needle and seat. It usually is in a small bag in w/the rest of the parts. If I understand you right, you didn't soak the needle w/the rubber tip. If you did, you really should replace it. The n&s is available separately.

Quote:
Let me ask you question as seems we have similar machinery here. On yours does the check ball well next to the accelerator pump have a lead seal over it, or do you have access to that with a screwed in stopper with a spring (or something)? Mine has a (looks like) poured lead seal over it and I dont believe that is right. Maybe they (last owner) stripped out the threads or something and just sealed it up with (that might be JB Weld too, didn't think of that).
That accelerator pump check ball is covered by a screw that has an unthreaded extension on the end (shown below w/check ball). So you are prolly right- he lost or stripped the screw and used something else to plug the hole. I don't think that screw is available separately; if the threads are still OK and you cannot find a screw, shoot me a PM and I'll get one to you, gratis.



The wire retainer that holds the primary metering rods looks to be a rubiks cube deal, but w/a photo or drawing, you can easily reattach it and the rods. The wire retainers are still available; parts suppliers are on the page Silver Surfer linked to above. There are two different wire retainers so get the right one if you need one.

Last edited by cobalt327; 09-17-2012 at 06:34 AM. Reason: Add image.
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Old 09-17-2012, 07:54 AM
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First, sorry for helping to hijack this thread- I didn't realize the post I answered wasn't the OP. My mistake.

To clarify a couple things, the fast idle is operated by the choke thermostat as far as the main controlling factor. The further closed the choke coil makes the choke flap, the higher the idle speed, as set by the fast idle adjustment screw and the fast idle cam.

Besides the choke coil/thermostat, there is the choke pull-off, which opens the choke a set amount as soon as the engine starts to let in enough air so the engine will run at a fast idle cleanly w/the engine cold and the choke on.

BTW, saying "main" metering rods is OK- same thing as saying "primary" metering rods, as opposed to "secondary" metering rods.
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Old 09-17-2012, 06:46 PM
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Cobalt327. I thank you for the clarification (I a HS dropout, so I don't word things well and get tongue-tied). I did drop that needle seat in w/the other stuff, rubber tip and all because I do know that a kit will include new one. The stuff in the check ball well was lead. The cap is missing, but the ball was under the lead. I retapped the threads and they appear to be OK. have heard a couple of thoeries of why the check valve was sealed off, my thought now (since the ball was under the lead seal) is they stripped the cap screw out, or otherwise ruined it as will happen on those soft little brass things. But, yes this es79's thread so I'm gonna get off it now. And I thank you again for the clarification, you seem to be the answer man for the Q-jet.
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Old 09-17-2012, 08:34 PM
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Quote:
Originally Posted by fasteddy_1947 View Post
Cobalt327. I thank you for the clarification (I a HS dropout, so I don't word things well and get tongue-tied). I did drop that needle seat in w/the other stuff, rubber tip and all because I do know that a kit will include new one. The stuff in the check ball well was lead. The cap is missing, but the ball was under the lead. I retapped the threads and they appear to be OK. have heard a couple of thoeries of why the check valve was sealed off, my thought now (since the ball was under the lead seal) is they stripped the cap screw out, or otherwise ruined it as will happen on those soft little brass things. But, yes this es79's thread so I'm gonna get off it now. And I thank you again for the clarification, you seem to be the answer man for the Q-jet.
You may well be right about the threads- all I can say is the factory didn't do it that way, but as long as there's no leakage it'll work like that. If the threads are still good (or you made them good), replacing the screw will be the best way to go, obviously.

No problem about asking questions here, in this case it looks like the OP got the answer he needed and has moved on. But if you have more things to ask about, just start a new thread and we can give you a hand there; there are several guys who know the Q-jet pretty well.
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Old 09-17-2012, 09:19 PM
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Whoa, thanks for all the replies. Sorry for the delayed response I've been a little busy today.

Yes, my car has the linkage down into the intake. When I took it apart I studied the linkage a bit it look as though mine wasn't working properly. I don't think it ever worked that well anyway. I recall my great-grandfather always having issues when it was real cold.

I am hoping I can find this broken part. I'm going ahead a replacing everything that I can to give it a fair shot. It's not expensive parts anyway.

I wanted to mention the whole epoxy on the "main well plugs" mine seems to have been done but what ever was used broke down and was a real mess in there, I little scary because if chunks of that somehow made its way though could be bad. I think I'd like to thread and plug them properly. I've read you can do it but no spacifics about what to use?

And I don't care about thread "hi-jacking" makes me feel like I started a decent thread were we all can get some questions answered. By all means just ask and anwser at will.

I will try and get some pictures up too. This thing was pretty dirty. I haven't soaked the big parts yet, gotta get a turkey pan from the dollar store this week.

Thanks again sorry for the long post.
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Old 09-18-2012, 10:02 AM
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Quote:
Originally Posted by es79 View Post
Whoa, thanks for all the replies. Sorry for the delayed response I've been a little busy today.

Yes, my car has the linkage down into the intake. When I took it apart I studied the linkage a bit it look as though mine wasn't working properly. I don't think it ever worked that well anyway. I recall my great-grandfather always having issues when it was real cold.

I am hoping I can find this broken part. I'm going ahead a replacing everything that I can to give it a fair shot. It's not expensive parts anyway.

I wanted to mention the whole epoxy on the "main well plugs" mine seems to have been done but what ever was used broke down and was a real mess in there, I little scary because if chunks of that somehow made its way though could be bad. I think I'd like to thread and plug them properly. I've read you can do it but no spacifics about what to use?

And I don't care about thread "hi-jacking" makes me feel like I started a decent thread were we all can get some questions answered. By all means just ask and anwser at will.

I will try and get some pictures up too. This thing was pretty dirty. I haven't soaked the big parts yet, gotta get a turkey pan from the dollar store this week.

Thanks again sorry for the long post.
Leaky rear well plugs are relatively rare and leaky front plugs almost non existent (later plugs shown below- rear circled, front arrows), even on early carbs. If you have a '69-up Q-jet, it probably will not need anything done. The leaky plugs were the early brass cup-style, not the aluminum plugs that were installed later on.

Unfortunately, some time ago it was written that ALL Q-jets need to be 'fixed' w/epoxy, just to be sure if nothing else. But like you've seen, this fix is all but worthless. Fortunately, the mess doesn't enter the fuel bowl. Ruggles has a kit to replace the plugs if you need it. You can replace them yourself if you have a suitable threaded plug and a matching bottoming tap.

If the later plugs are actually seeping fuel, careful re-peening the edges of the casting where the plugs are installed will often cure any leakage.


Late-style rear well plugs (circled). Front plugs seldom ever leak (arrows).
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Old 09-18-2012, 10:36 AM
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Yeah, mine is a '68. And yeah I believe it has brass plugs. I'll get some pics this evening. What's this "Ruggles" you speak of?



Quote:
Originally Posted by cobalt327 View Post
Leaky rear well plugs are relatively rare and leaky front plugs almost non existent (later plugs shown below- rear circled, front arrows), even on early carbs. If you have a '69-up Q-jet, it probably will not need anything done. The leaky plugs were the early brass cup-style, not the aluminum plugs that were installed later on.

Unfortunately, some time ago it was written that ALL Q-jets need to be 'fixed' w/epoxy, just to be sure if nothing else. But like you've seen, this fix is all but worthless. Fortunately, the mess doesn't enter the fuel bowl. Ruggles has a kit to replace the plugs if you need it. You can replace them yourself if you have a suitable threaded plug and a matching bottoming tap.

If the later plugs are actually seeping fuel, careful re-peening the edges of the casting where the plugs are installed will often cure any leakage.


Late-style rear well plugs (circled). Front plugs seldom ever leak (arrows).
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Old 09-18-2012, 12:00 PM
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Yeah, mine is a '68. And yeah I believe it has brass plugs. I'll get some pics this evening. What's this "Ruggles" you speak of?
First link under 'Quadrajet tuning and repair parts'. Cliff Ruggles is recognized by many to be the "go-to" guy when it comes to quality Q-jet parts and service.
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