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Username Post: 81 GMC c2500        (Topic#280361)
free_bird49221 
Contributor
Posts: 218
free_bird49221
Loc: Adrian, MI
Reg: 04-29-12
04-29-12 09:22 AM - Post#2220221    

I just purchased my first full size gm truck. Engine was rebuilt along with the trans a few years back. Truck is pretty clean as far as rust goes. worst rust is the rockers of the doors.
My problem is the truck has a stock 4 barrel carb that is not running right. I'm thinking there is something wrong with the choke or linkage to the choke. I know carb's are not to hard to adjust however i just don't have experience with tweaking a carb.
Any one know of a good site that can help me adjust the jets and the choke. I'm looking at the likely hood of getting a rebuild kit for the carb and giving it a good cleaning.
any advice i can get on this before i jump in is greatly appreciated. times like this is when i wish my single mother of 3 would have let me take shop in school.
This truck will be my daily driver and a working project for my family and I. The wife and I see this as a truck I can run and tinker on with my sons and her.
Truck has a 350 m code vin. it is a stock Rockwell carb i believe, with a 700 trans.
Ande
81 GMC c2500
06 Chevy Malibu
80 Olds cutlass


 
technitom 
Contributor
Posts: 248
technitom
Age: 46
Loc: Near Cincinnati, OH
Reg: 12-01-11
04-29-12 10:45 AM - Post#2220243    
    In response to free_bird49221

a pic is worth a thousand words... did you mean rochester quadra jet?

Words are a lot like toothpaste... Once its out of the tube,
there's no getting it back in...


 
81_C2500 
Forum Newbie
Posts: 7

Loc: Northern Calif.
Reg: 11-27-10
04-29-12 10:50 AM - Post#2220245    
    In response to free_bird49221

Welcome! That carb would be a Rochester. You can purchase full manual for it at this link:

http://www.carbkitsource.com/manuals/carbmanuals/C ...

If you want to really get into info in it, Loads of Rochester info is also available at this link:

http://www.digitalcorvettes.com/forums/showthread....

The transmission that originally came in that truck would be a Turbo 400 , THM400.

Jim P
81 GMC Sierra C2500, LB, Fleetside, 350, TH400, 14 bolt, 8,600+ GVW.


 
gchemist 
Senior Chevytalk Moderator
Posts: 21865
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
04-29-12 04:42 PM - Post#2220356    
    In response to 81_C2500

Welcome to the site. Checkout all the carb links on this page http://www.73-87.com/7387garage/garage_dri vetrain....

How to read a vacuum gauge: http://www.secondchancegarage.com/public/186.cfm

How to tune with a vacuum gauge: http://www.centuryperformance.com/tuning-with-a-va...

'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
free_bird49221 
Contributor
Posts: 218
free_bird49221
Loc: Adrian, MI
Reg: 04-29-12
04-29-12 06:40 PM - Post#2220415    
    In response to technitom

yes i would be the quadra jet. thanks for the links see what i can come up with. would put these pics up if i knew how.
Ande
81 GMC c2500
06 Chevy Malibu
80 Olds cutlass


 
free_bird49221 
Contributor
Posts: 218
free_bird49221
Loc: Adrian, MI
Reg: 04-29-12
05-01-12 10:06 AM - Post#2221126    
    In response to free_bird49221

http://i1066.photobucket.com/albums/u407/free_bird ...

http://i1066.photobucket.com/albums/u407/free_bird ...

http://i1066.photobucket.com/albums/u407/free_bird ...

sorry for the links but only way i can find to get pics up so far.
Ande
81 GMC c2500
06 Chevy Malibu
80 Olds cutlass


 
Vaughn 
"12th Year" Gold Supporting Member
Posts: 15397

Loc: Colorado Springs, CO
Reg: 08-08-04
05-01-12 06:14 PM - Post#2221298    
    In response to free_bird49221

The Quadrajet is a really good carb.

However, there are VERY FEW people out there that know how to properly set up a Quadrajet (even VERY EXPERIENCED mechanics hardly ever get it right) - and a simple rebuild RARELY addresses the driveability issues that come up. Since your truck has an unknown carb rebuild history, it is a fair bet that it has been fiddled with - and this almost always results in a poorer running carb.

The best thing you can do is to send it to a specialist in Quadrajet carbs, and have it rebuilt by them. I suggest SMI induction:

http://www.smicarburetor.com/

No, it isn't a cheap way to go. It will cost about $300 to get it rebuilt and recalibrated properly. However, it will be the best money you've ever spent on a vehicle. Tell them you need a driver carb (what they call a Stage I rebuild) - and be VERY THOROUGH about answering all their questions in their questionnaire. They will ask you things like what cam was used, what your altitude above sea level - all of which are critical when setting up a carb. If you don't know the answers - find out.

They can do a quick turn around, but it is a little more - and you have to specify it when ordering.

One of the first things most people do - is to ask "why can't I just get a rebuilt or new carb from the parts store? It will cost less." The problem with that is that those carbs are RARELY calibrated properly for your application. Often those new/rebuilt carbs don't run any better than the carb you currently have on the motor.

The carb you will get back from SMI will work MUCH, MUCH BETTER than what you will get from the parts store.

 
gchemist 
Senior Chevytalk Moderator
Posts: 21865
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
05-01-12 07:24 PM - Post#2221337    
    In response to Vaughn

For costs, you may consider a new one too.
http://www.nationalcarburetors.com/

If don't need to meet emissions, install a dual plan intake and a new carb. The rebuilt engine will like a new combo.
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
free_bird49221 
Contributor
Posts: 218
free_bird49221
Loc: Adrian, MI
Reg: 04-29-12
05-03-12 06:52 AM - Post#2221898    
    In response to gchemist

I am looking at national carb. From the pics i have can anyone tell me if i have a electric, air or divorced choke.
Ande
81 GMC c2500
06 Chevy Malibu
80 Olds cutlass


 
gchemist 
Senior Chevytalk Moderator
Posts: 21865
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
05-03-12 08:29 AM - Post#2221935    
    In response to free_bird49221

Your second carb picture indicates two things. It has an electric connection. It also has a hose. Follow the wire. Where does it go? It looks like air with the wire activating something.

I would convert to electric.

The EGR valve is removed and plugged.
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
free_bird49221 
Contributor
Posts: 218
free_bird49221
Loc: Adrian, MI
Reg: 04-29-12
05-03-12 11:02 AM - Post#2221986    
    In response to gchemist

messing around today it looks like some seals are blown. when its running for a few it gets gas build up on right side by the throttle linkage. National carb is looking better and better. the other company that was suggested might do better work setting it up but problem is i have no idea on if engine was truly rebuilt and what was used. along with no way of finding who had it rebuilt. Love cleaning up others mess with no clue as to how they messed it up in first place.
Ande
81 GMC c2500
06 Chevy Malibu
80 Olds cutlass


 
gchemist 
Senior Chevytalk Moderator
Posts: 21865
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
05-03-12 11:49 AM - Post#2221999    
    In response to free_bird49221

Do a compression check. Stock motors will have low compression. Plus you get a good idea on engine condition.
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
free_bird49221 
Contributor
Posts: 218
free_bird49221
Loc: Adrian, MI
Reg: 04-29-12
08-08-12 10:35 AM - Post#2257140    
    In response to free_bird49221

God i feel like a little kid right now. Just ordered a carb for the gmc.
http://www.nationalcarburetors.com/lookup.aspx?par...
Had the pour thing sitting in the drive sense i bought it in April waiting to get the money to get the carb and fire it up. Just got the money and in time too. National Carburetor was really helpful and friendly when i called to make sure i was looking at the right part. Cant wait. Don't think the ole lady will be to thrilled but o well she will get over it i have.
Ande
81 GMC c2500
06 Chevy Malibu
80 Olds cutlass


 
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