Another quadrajet question - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 04-07-2012, 04:14 PM
Supporter of the 4.3 liter V6
 
Last photo:
Join Date: Dec 2010
Location: The Villages, Florida
Age: 21
Posts: 132
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Another quadrajet question

I have one more quadrajet question i need help with. Are the throttle shafts from an M4MC and M4ME interchangeable? Basically the only difference is choke type right? Attachments are no big deal because i have thm400 trans so no kickdown cable.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 04-07-2012, 08:47 PM
richard stewart 3rd's Avatar
Registered User
 

Last journal entry: 351W rebuild
Last photo:
Join Date: Jan 2006
Location: tremont, pa.
Age: 70
Posts: 2,218
Wiki Edits: 0

Thanks: 14
Thanked 15 Times in 14 Posts
Hi
I don't think they interchange, & i don't think the choke parts interchange either.
Rich
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 04-12-2012, 06:54 AM
Supporter of the 4.3 liter V6
 
Last photo:
Join Date: Dec 2010
Location: The Villages, Florida
Age: 21
Posts: 132
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
I just bought a m4mc to use for parts for my m4med quadrajet, and the throttle shafts do interchange, with only slight differences. I decided i'd take the mid section and air horn off the m4mc and ditch mine with the dual capacity pump because i don't need that. So i got my rods and jets and several other useful parts and im in the process of making a custom quadrajet. Also from what i can tell, hot air choke and electric choke off of these two are also interchangeable. Ready to ditch the edelbrock and go back with factory equipment
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 04-12-2012, 08:05 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by ChadGresham
I just bought a m4mc to use for parts for my m4med quadrajet, and the throttle shafts do interchange, with only slight differences. I decided i'd take the mid section and air horn off the m4mc and ditch mine with the dual capacity pump because i don't need that. So i got my rods and jets and several other useful parts and im in the process of making a custom quadrajet. Also from what i can tell, hot air choke and electric choke off of these two are also interchangeable. Ready to ditch the edelbrock and go back with factory equipment
Possible differences in the throttle shaft (primary, I'm guessing) is the throttle/kickdown/TV hook up on the driver side and the choke linkage on the passenger side. If you see the two shafts are compatible for replacing the one you have, no reason not to that I know of.

One thing about swapping the airhorn or base plate onto a different main body is there are various calibrations that are matched to one another- the air bleed number and position can and do vary between carbs, so using the airhorn from one carb on a different body may or may not work. In the case of the throttle plate, there are different sizes of idle bypass orifices used on almost every Q-jet. No sense in matching the bypass orifices to the old throttle plate because at this stage you don't know how much idle bypass air you need- or if you even need ANY.

So if the two throttle bodies (or air horns) are the same type/design, they will exchange physically but the calibrations may not be compatible. You will have a better chance if the carbs are from the same year or as close as possible and the castings have to be similar (there are two main styles as you know). You are swapping parts between "M"-type carbs so your chances of success are better that way.

Hot air choke can be converted to electric choke, no prob. Be sure to NOT use the gasket that's used on the hot air choke; that will keep the electric choke from grounding to the choke housing. Be sure the screws are tight that clamp the electric choke assembly into the housing, if the screws aren't tight the ground can be bad. A lot of guys have run into this when they leave the screws loose so they can adjust the choke. The hot air choke has a small calibrated vacuum "leak" to keep the choke housing free of condensation- this can be plugged when using an electric choke.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 04-13-2012, 06:52 AM
Supporter of the 4.3 liter V6
 
Last photo:
Join Date: Dec 2010
Location: The Villages, Florida
Age: 21
Posts: 132
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Where is this small vacuum "leak" you speak of for hot air choke? I would like to plug that. And the two carbs are very close in year and i looked up part numbers they are almost identical applications as well. Thanks for the information tho, im always learning something new with these quadrajets
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 04-13-2012, 07:06 AM
Supporter of the 4.3 liter V6
 
Last photo:
Join Date: Dec 2010
Location: The Villages, Florida
Age: 21
Posts: 132
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Also last night i discovered in the old qjet i bought, the place where the secondary metering rods go into, one of those is loose. They aren't jets like the primarys, I know you guys already know that but why would that be loose? also is it a problem to leave it loose??
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 04-13-2012, 12:56 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by ChadGresham
Also last night i discovered in the old qjet i bought, the place where the secondary metering rods go into, one of those is loose. They aren't jets like the primarys, I know you guys already know that but why would that be loose? also is it a problem to leave it loose??
The vacuum orifice to the hot air choke has a plastic "nib" (often white) that goes into a hole in the carb body and also goes into a hole in the choke housing. If the choke housing is removed, this will be obvious unless the plastic nib was left off by someone before you got the carb.

For the record, the nib can be left in place and the vacuum orifice unplugged, as long as the nib is not broken or missing. Edelbrock makes no mention of removing it or plugging the vacuum orifice in their instructions for their hot air replacement electric choke conversion kit. I've always gone ahead and tapped a small piece of lead into the hole in the carb body flush w/the boss the hole is in (split shot sinker works well for this) to plug them, YMMV.





I've never had a loose secondary "jet", but you can buy replacements if you need to.

Last edited by cobalt327; 04-13-2012 at 01:01 PM.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 04-13-2012, 10:10 PM
Supporter of the 4.3 liter V6
 
Last photo:
Join Date: Dec 2010
Location: The Villages, Florida
Age: 21
Posts: 132
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Excellent i found that little plastic do-dad there, and i have never had a loose jet either, but im going to remove the plugs from the bottom and tap them for an npt plug so hopefully i can find out why its loose when i do this
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 04-13-2012, 10:46 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by ChadGresham
Excellent i found that little plastic do-dad there, and i have never had a loose jet either, but im going to remove the plugs from the bottom and tap them for an npt plug so hopefully i can find out why its loose when i do this
I'd appreciate a follow up on this from you- that's a new one on me.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 04-16-2012, 06:13 PM
Supporter of the 4.3 liter V6
 
Last photo:
Join Date: Dec 2010
Location: The Villages, Florida
Age: 21
Posts: 132
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
I removed the bottom plug on the side that the loose jet was on but i was unable to see enough in there to understand why it is loose. The hole is angled to where the jet is so i have no idea still why it would be loose or for that matter how Rochester got those jets in there, but im beginning to wonder if it'd be a problem at all. I ordered a book the other day on rebuilding and modifying quadrajets, maybe there will be some information on secondary metering in it. Ill see if i can find anything else out
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 04-17-2012, 09:14 PM
Registered User
 
Join Date: Mar 2011
Location: Kansas
Posts: 20
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Loose sec. disc.

Don't worry about it. They are stainless disc. that are designed to move a small amount.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 04-20-2012, 10:22 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
I'm going to have to disagree w/the theory that they're designed to move. If they were, there would be unmetered fuel passing around the loose "jet", and that would't be anything that Rochester would purposely design into the Q-jet, especially w/emissions and economy being such a concern.

If you look closely at the photo, you can see where the factory stakes or swedges the casting in around the discs to hold them securely in place. The arrow is pointing at the metal that has been displaced from around the hole where the disc was placed to hold it in position. I currently have several (6?) Q-jets in various states of disassembly (don't ask) and none are loose. That all leads me to the conclusion that if any discs are loose, it's from someone tampering w/them or a manufacturing defect. YMMV.

Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 04-20-2012, 06:23 PM
Supporter of the 4.3 liter V6
 
Last photo:
Join Date: Dec 2010
Location: The Villages, Florida
Age: 21
Posts: 132
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Yeah i have two qjets side by side with my cliff Ruggles book in front of me because this edelbrock just isn't cutting it anymore with the rise in gas prices... So unless some one knows, or i can figure out how to tighten this jet back up, i may be leaving that carb on the shelf
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 04-20-2012, 10:05 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by ChadGresham
So unless some one knows, or i can figure out how to tighten this jet back up, i may be leaving that carb on the shelf
Knows what, how to replace or restake the disc? It doesn't look like it was tampered with? If the metal around the circumference is still all there, you could take a hole punch that matches the original size used to displace the metal or if you're careful a center punch w/a dulled tip and restake the disc. I have no idea how a replacement disc would be set in place permanently. I know I wouldn't trust epoxy, but that's me. Wonder what the seller of the replacement discs have to say on the subject?
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 04-21-2012, 06:55 AM
Supporter of the 4.3 liter V6
 
Last photo:
Join Date: Dec 2010
Location: The Villages, Florida
Age: 21
Posts: 132
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
That is true, they must know how to get them in there! I'll try and find some manufacturers and see if they can offer any insight into this situation. Its not super important because all i needed off that particular qjet was the throttle shaft and other small parts. My original qjet doesn't have that problem luckily!
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
quadrajet question jak327 Engine 2 04-24-2010 10:51 AM
Quadrajet question Speakrdude Engine 10 10-25-2009 02:16 PM
quadrajet question? hemi joe Engine 4 10-24-2009 11:34 PM
Quadrajet Question 1979T/A Engine 3 04-21-2008 08:52 PM
Quadrajet Question(s) lardmaster Engine 5 02-08-2004 06:59 PM


All times are GMT -6. The time now is 09:32 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.