The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 12-05-2018, 11:04 PM   #1
justaburbn
Registered User
 
Join Date: Aug 2014
Location: priest lake idaho
Posts: 14
81 GMC K35 454 Carbwork/New Selection?

Okay, so I have a stock BB. Carburetor appears to be original Quadrajet. Starts rough but idles out kinda, once warm. Choke issue? Maybe, but it doesn't act like the Qjets I remember. Secondaries are not working. No Master QJet Rebuilder in my area that I know of. Bought a re-manufactured Qjet from local auto parts store and it arrived with damaged parts and looked nothing like what I have so I returned it.

My options as I see them are go with Holley, Edlebrock or keep searching for a local builder who has proper equipment and expertise.

But how do I know which one. I have been on Holley's site. Way too many options for me to decipher.

Somebody help me out here. I'm just a carpenter. I can change parts just fine. I'm afraid all the truly good ole mechanics I grew up around are all gone now and have left me to fend for myself.
justaburbn is offline   Reply With Quote
Old 12-05-2018, 11:21 PM   #2
geezer#99
Registered User
 
geezer#99's Avatar
 
Join Date: Aug 2009
Location: Bowser
Posts: 10,063
Re: 81 GMC K35 454 Carbwork/New Selection?

Could be your choke is set up wrong or needs a minor adjustment.
I assume it’s an electric choke.
Pics of your carb would help.
The secondaries are also controlled by the choke. Again pics help.
You can buy an excellent replacement carb for what it’ll cost for an eddy or Holley.
Look here.

https://www.smicarburetor.com/
geezer#99 is offline   Reply With Quote
Old 12-06-2018, 03:47 AM   #3
akart
Registered User
 
Join Date: Sep 2014
Location: Manley Hot Springs Alaska
Posts: 187
Re: 81 GMC K35 454 Carbwork/New Selection?

Go w/an Edelbrock. The holleys are way too complicated for me and they always require tuning, and look at all the fiddley stuff they sell for them. Stuck an ED on my 82 K20 adjusted the the idle circuit as instructed and that was it. Also bought the kit for about 60 bucks which has all the rods jets and springs to tune it, if needed. Like to lean it out (check plugs). Good easy instructions and recommendations on this forum. I'm happy with it . I'm an old carpenter too in Alaska and am up-grading this truck on my own. Heads and headers next.

Last edited by akart; 12-06-2018 at 04:00 AM. Reason: SP
akart is offline   Reply With Quote
Old 12-06-2018, 06:40 AM   #4
Wgesnerjr
Senior Member
 
Wgesnerjr's Avatar
 
Join Date: Jun 2015
Location: Atlanta, GA.
Posts: 260
Re: 81 GMC K35 454 Carbwork/New Selection?

try and find a specialist you can send the carb to.

http://thecarbshop.com

https://quadrajetpower.com/rebuild-services/

truck may be down a while, but you may get a better rebuild from a specialists.
__________________
Jay Gesner
Atlanta, GA
1985 C10 Long Bed 4X2
LS 5.3, 4L60E
Father/Daughter Project
Wgesnerjr is online now   Reply With Quote
Old 12-06-2018, 11:59 AM   #5
justaburbn
Registered User
 
Join Date: Aug 2014
Location: priest lake idaho
Posts: 14
Re: 81 GMC K35 454 Carbwork/New Selection?

Quote:
Originally Posted by geezer#99 View Post
Could be your choke is set up wrong or needs a minor adjustment.
I assume itís an electric choke.
Pics of your carb would help.
The secondaries are also controlled by the choke. Again pics help.
You can buy an excellent replacement carb for what itíll cost for an eddy or Holley.
Look here.

https://www.smicarburetor.com/
I really don't think the choke has anything to do with the Secondaries.

I can send pics later.

Have you heard of http://www.nationalcarburetors.com/contactus.aspx
They are so much cheaper than anyone else. Claim to have the best reputation and have been in the Carb business since 1954. Also they build to order and supposedly engine test every Carb
justaburbn is offline   Reply With Quote
Old 12-06-2018, 12:08 PM   #6
justaburbn
Registered User
 
Join Date: Aug 2014
Location: priest lake idaho
Posts: 14
Re: 81 GMC K35 454 Carbwork/New Selection?

Quote:
Originally Posted by akart View Post
Go w/an Edelbrock. The holleys are way too complicated for me and they always require tuning, and look at all the fiddley stuff they sell for them. Stuck an ED on my 82 K20 adjusted the the idle circuit as instructed and that was it. Also bought the kit for about 60 bucks which has all the rods jets and springs to tune it, if needed. Like to lean it out (check plugs). Good easy instructions and recommendations on this forum. I'm happy with it . I'm an old carpenter too in Alaska and am up-grading this truck on my own. Heads and headers next.
Thanks, did you replace the intake as well?
justaburbn is offline   Reply With Quote
Old 12-06-2018, 12:11 PM   #7
Wgesnerjr
Senior Member
 
Wgesnerjr's Avatar
 
Join Date: Jun 2015
Location: Atlanta, GA.
Posts: 260
Re: 81 GMC K35 454 Carbwork/New Selection?

Not sure on Chevy Quadrajets, I only have experience with Pontiac ones. But, the secondaries are not "controlled" by the choke, but locked out by the choke. Once engine is warm and choke is off, secondaries are unlocked.

I have found there is a small lock out that can be "bent" out of the way. But why someone would you want to use the back barrels before the engine is warmed up sounds foolish to me.

Also, if it is an electric choke, there is a vacuum pot called "choke pull off" that can go bad and the choke will not turn off. Again, not sure if Chevys use it but it caused all kinds of hell when it went bad on my Catalina.
__________________
Jay Gesner
Atlanta, GA
1985 C10 Long Bed 4X2
LS 5.3, 4L60E
Father/Daughter Project
Wgesnerjr is online now   Reply With Quote
Old 12-06-2018, 12:13 PM   #8
justaburbn
Registered User
 
Join Date: Aug 2014
Location: priest lake idaho
Posts: 14
Re: 81 GMC K35 454 Carbwork/New Selection?

Quote:
Originally Posted by Wgesnerjr View Post
try and find a specialist you can send the carb to.

http://thecarbshop.com

https://quadrajetpower.com/rebuild-services/

truck may be down a while, but you may get a better rebuild from a specialists.
Thanks. That would be my preference. I was thinking of buying another reman to put on and then send the original out to someone I can meet face to face.

Know of anyone in North Idaho?
justaburbn is offline   Reply With Quote
Old 12-06-2018, 12:21 PM   #9
justaburbn
Registered User
 
Join Date: Aug 2014
Location: priest lake idaho
Posts: 14
Re: 81 GMC K35 454 Carbwork/New Selection?

Quote:
Originally Posted by Wgesnerjr View Post
Not sure on Chevy Quadrajets, I only have experience with Pontiac ones. But, the secondaries are not "controlled" by the choke, but locked out by the choke. Once engine is warm and choke is off, secondaries are unlocked.

I have found there is a small lock out that can be "bent" out of the way. But why someone would you want to use the back barrels before the engine is warmed up sounds foolish to me.

Also, if it is an electric choke, there is a vacuum pot called "choke pull off" that can go bad and the choke will not turn off. Again, not sure if Chevys use it but it caused all kinds of hell when it went bad on my Catalina.
Well, that all makes sense. I have a lot to learn about Qjets but I'll get there. I guess I should start with the s# and see if I can find out if it is even the original one. Some say it matters and some say it don't. Not that I am trying to keep it original, this is a plow truck and I need it to be reliable more than anything else.
justaburbn is offline   Reply With Quote
Old 12-06-2018, 01:09 PM   #10
Dead Parrot
Registered User
 
Join Date: Aug 2012
Location: Oklahoma City, OK
Posts: 1,089
Re: 81 GMC K35 454 Carbwork/New Selection?

Quick check for choke. Should be closed on first cold start. Should start to open within a few minutes. Needs to wind up fully open when engine hot.

A lot of times, they wind up being set rich, meaning they don't open all the way or open later then the engine needs as it warms up.

If all the choke linkages are working, when the choke is open enough, the secondary throttle plates will work. Until then, they are locked shut. Don't confuse the throttle plates with the top plates(forget the proper name). The top plates open by air pressure as the lower throttle plates open. The top plates via a small hanger, pull up the secondary rods and allow more fuel to flow to the secondary holes.

Early Q-jets had a metal stove mounted on the passenger side of intake. PITA to adjust. Later versions had a heat tube that ran from the intake to the control unit on the passenger side of the carb. Even later versions replaced the heat tube with an electric heater. Both of the later versions can be adjusted by rotating the black cover. (May have to drill out rivets and replace with screws, several threads on topic).

Check your timing. A lot of idle problems are really timing related.

If yours has electric choke, make sure the wire(IIRC some version of green) is connected and has power with the engine running. IIRC - a lot of these also run to the oil sender so the choke heater doesn't pull juice when the motor is off.

2nd the call for some good picts.
Dead Parrot is offline   Reply With Quote
Old 12-06-2018, 01:12 PM   #11
geezer#99
Registered User
 
geezer#99's Avatar
 
Join Date: Aug 2009
Location: Bowser
Posts: 10,063
Re: 81 GMC K35 454 Carbwork/New Selection?

Quote:
Originally Posted by Wgesnerjr View Post
Not sure on Chevy Quadrajets, I only have experience with Pontiac ones. But, the secondaries are not "controlled" by the choke, but locked out by the choke. Once engine is warm and choke is off, secondaries are unlocked.

I have found there is a small lock out that can be "bent" out of the way. But why someone would you want to use the back barrels before the engine is warmed up sounds foolish to me.

Also, if it is an electric choke, there is a vacuum pot called "choke pull off" that can go bad and the choke will not turn off. Again, not sure if Chevys use it but it caused all kinds of hell when it went bad on my Catalina.
Controlled or locked out is the same thing.
All quadrajets have a choke pull off. It doesnít matter whether itís electric, hot air or divorced type.
And the pull off also Ďcontrolsí the secondary air door.

Your carb likely only needs a little maintenance to keep it working.
geezer#99 is offline   Reply With Quote
Old 12-06-2018, 07:45 PM   #12
akart
Registered User
 
Join Date: Sep 2014
Location: Manley Hot Springs Alaska
Posts: 187
Re: 81 GMC K35 454 Carbwork/New Selection?

Quote:
Originally Posted by justaburbn View Post
Thanks, did you replace the intake as well?
Yes I did put on an Edelbrock esp manifold but you don't have to do that. EDL makes a spread bore to square bore adapter maybe 20 bucks. I'm thinking you may want the 750 cfm carb for the 454 (might check that) Also I went w/the manual choke to simplify things. I do recommend the Edelbrock fuel pump which puts out 6 lbs pressure which is what the EDL's want as the EDL's do not like more and stock is more and could flood the carb,(common problem).
akart is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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

Forum Jump


All times are GMT -4. The time now is 07:08 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Copyright 1997-2013 67-72chevytrucks.com