Author Topic: Should I ditch my current carb on my Pontiac 301 powered 79 Trans Am?  (Read 168 times)

Offline Ponchonutty

  • Garage guy
  • **
  • Posts: 8
So some of you read my long winded potential issues with my current Frankensteined quadrajet in which a Holley reman, warped correct carb was swapped around with an Olds tagged unit.  He suggested to me to get another core to do the build since the original carb wasn't a matching unit and would negate the costs making it right.  The builder used the necessary parts from the reman unit in order to keep the idle up circuit as well as the AC cut off when WOT. 

What prompted me wanting to have the carb that was on my turdbird rebuilt is that I could never get a happy place with idle.  The throttle would stick just off idle and got worse the warmer it got.  Well, I think the throttle shaft was bent slightly because when the Frankensteined carb was installed, I still had that issue.  He had to use the shaft in this carb I have now.  I wonder if something else could be swapped wrong causing excessive lean conditions since 2 totally different carbs were mix-matched together?

I handed my car off to my buddy who owns a carshop and is capable around these carbs but not to the level as many of you on here.  Right off the start he recommended getting another carb and throw it on to see how drastic of a change might be seen.  I got another off of a Pontiac 400 out of a 74 Grand Prix.  I haven't had a chance to talk to him to see if he's been able to do this as of yet.

So lets say the current carb is indeed the issue, what do I do from here?  Should I use the 74' carb or should I find a carb off of a late 70's to 80 301 motor?  Where do I draw a line as to how bad is too bad?  Like this 1980 Pontiac carb here.  It looks crazy nasty however the seller said it's all completely free and it's just covered in dirt from sitting on a shelf for decades.  Also one more thing is that I installed a 2004r in this car and the geometry for the TV is extremely important so as not to smoke it.  It's one of the main reasons I want to stay with a quadrajet versus another brand carb or even fuel injection.

Offline quadrajam

  • Carb lover
  • ***
  • Posts: 147
Re: Should I ditch my current carb on my Pontiac 301 powered 79 Trans Am?
« Reply #1 on: September 06, 2025, 07:18:57 PM »
  I cant seem to be able to zoom in on the pictures....??...??

QJ

Offline Ponchonutty

  • Garage guy
  • **
  • Posts: 8
Re: Should I ditch my current carb on my Pontiac 301 powered 79 Trans Am?
« Reply #2 on: September 07, 2025, 06:53:15 AM »
Not sure why?  I can from my desktop and it says there's been 4 views???

Offline Ponchonutty

  • Garage guy
  • **
  • Posts: 8
UPDATE
« Reply #3 on: September 12, 2025, 05:49:35 AM »
So found a decent carb that has been in storage for a while.  My buddy got it on the car and tried it out.  Ended up with the same crappy running when you floor it.  Buddy is thinking maybe valves are too tight.  Keep in mind I've never done with anything with this motor.  It always started fine so never thought I needed to get inside it due to things looking very clean.  Now, may have to.

Offline Mudsport96

  • Carb lover
  • ***
  • Posts: 198
Re: Should I ditch my current carb on my Pontiac 301 powered 79 Trans Am?
« Reply #4 on: September 13, 2025, 05:49:55 AM »
What do you mean crappy when you floor it? Backfire? Falls on its face? No acceleration?

Offline Ponchonutty

  • Garage guy
  • **
  • Posts: 8
What do you mean crappy when you floor it? Backfire? Falls on its face? No acceleration?

Has a slight miss at idle.  When I floor it it completely falls on it's face.  If I back out of the throttle a bit it will run better and then shift through the gears.  My wideband I has to be off since when I floor it, it will peg at 50.  I hear no pinging.  Actually through most of the rpms it shows its running extremely lean.

Offline Ponchonutty

  • Garage guy
  • **
  • Posts: 8
Got another carb off of a 75 pontiac.  Didn't change a thing in how it behaved.  Buddy is thinking there's a severe leak somewhere but is unsure.  Said he will be smoking the engine and look for leaks.  He thought possibly the valley pan gasket?  That's possible I assume since I have never had it off but I know prior to me owning it, someone has rebuilt or at least gone through the engine.  Had another comment saying to check the cruise control vacuum but if it was leaking from that, wouldn't the cruise fail to work?  I am not certain the wideband is accurate at this moment because when it pegs at 50 during WOT shouldn't I hear severe pinging?  This is the wideband I am using.  Yes, I have calibrated it several times too.  If you squirt starting fluid down the carb while at idle the engine will smooth out and the wideband will go around 12-14 where it should be.
https://www.innovatemotorsports.com/lc-2-complete-lambda-cable-kit-8-ft.html