#1  
Old 06-24-2022, 06:16 PM
bradrose22 bradrose22 is offline
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Default 78 w72 carb substitute

Hello,
First post on the forum in a long time.
I would like to know what would be a good substitute for my original carburetor. It’s a stock w72. I would like to shelf the carb and get a replacement for driving.
Also an exhaust system and tires for 15x8 snowflakes.
Any recommendations are appreciated.
I would like to get it in driveable condition
To enjoy. Thanks!
Brad

  #2  
Old 06-24-2022, 09:04 PM
Trevor78 Trevor78 is offline
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Shelf the carb? Seek out a regular Quadrajet for a Pontiac if can't find the matching carb, rebuild and rejet to suit your setup. Stock W72 isn't anything terribly fancy, you can easily cover it's needs. But if you have the correct carb already, everything just fits where it should.

  #3  
Old 06-25-2022, 12:46 AM
pippintook pippintook is offline
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Hey Brad, I have 78 TA W72 - I originally rebuilt the stock 400 and used Summit 2801 cam and headers. I used stock intake and stock 78 W72 quadrajet and ran fine. I converted the 400 into a stroker - but kept stock intake and quadrajet. The 78 W72 qjet is 800cfm and a good carb. I would try and rebuild the carb yourself. It is not too hard. The carb can often benefit from a good cleaning and some new parts like float. For parts , I used https://cliffshighperformance.com/ , a bit pricey but the parts are top quality. Cliff also publishes great book on rebuilding - setting up a quadrajet.
.
For tires, 255/60/15 fits nicely and looks good - I have 255/60/15 Yokohamas, though when I replace will likely try Cobras
https://www.tirerack.com/tires/tires...omCompare1=yes
.
For exhaust
https://www.summitracing.com/parts/s...model/firebird
https://pypesexhaust.com/c-702350-gm...-trans-am.html

  #4  
Old 06-25-2022, 03:40 AM
Trevor78 Trevor78 is offline
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Tyres/wheels and exhaust can be a personal taste thing. It can be hard to make suggestions especially if you don't know what you are after. What one person said is perfect, another will hate. Likewise, if you like all 4 tyres being the same or having wider on the rear will at least be a start.

But here's some ideas of tyre/wheel suspension combos:

http://www.transamcountry.com/commun...?topic=83572.0

  #5  
Old 06-25-2022, 07:20 AM
bradrose22 bradrose22 is offline
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Great!
Thanks for all the information and the links.

  #6  
Old 06-25-2022, 08:35 AM
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I have a W72 carb up for sale

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  #7  
Old 06-25-2022, 10:28 AM
78w72 78w72 is offline
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Quote:
Originally Posted by bradrose22 View Post
Hello,
First post on the forum in a long time.
I would like to know what would be a good substitute for my original carburetor. It’s a stock w72. I would like to shelf the carb and get a replacement for driving.
Also an exhaust system and tires for 15x8 snowflakes.
Any recommendations are appreciated.
I would like to get it in driveable condition
To enjoy. Thanks!
Brad
lots of options for a pontiac q-jet that will work for a stock W72, same basic carb on the non W72 firebirds & other big car engines from 76-78, you can find a good core for pretty cheap to rebuild on ebay or other forums & online sources, or check with one of the companies that rebuild q-jets, they probably have a nice stock type carb for a good price. SMI is a good option.

here is probably the best priced rebuilt carb with a cliffs kit out there, & its even a W72#. cant beat the price for this, less than half the price of what some others charge...

https://forums.maxperformanceinc.com...d.php?t=859440

tires: 255/60 are close to stock height but a little wider, 225/70 is factory size. M/T ST radial are a good alternative to BFG & have a higher speed rating & dont have white letter issues that some sizes of BFGs have lately.

exhaust, summit makes a lower priced kit or look into pypes kits. but for basic low hp, a local exhaust shop can make & install exhaust for cheaper than buying a kit & paying them to install it.


Last edited by 78w72; 06-25-2022 at 10:33 AM.
  #8  
Old 06-27-2022, 07:16 AM
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77 Canamman 77 Canamman is offline
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The stock Q-Jet was a good piece, but the fuel curve is lean stock, to satisfy the emission regs of the day. The idle circuit will need some work, and obviously rejet and rods.

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  #9  
Old 07-03-2022, 10:01 PM
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77 TRASHCAN 77 TRASHCAN is offline
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Cliff sells 3 different kit choices. It may be necessary to use the highest end kit. If one is doing much tuning. Cliff put together the lowest price kit to give folks a choice, if they just prefer a “ parts store” type kit.
I’ve always bought the most expensive of his kits. They have parts that almost no one else even sells, or have a clue, what they are or how they work. Cliff supplies service after the sale. eBay does not...

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  #10  
Old 07-03-2022, 11:09 PM
Trevor78 Trevor78 is offline
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Often the difference between rebuilding a carb to stock, even if it was stock on a different engine and setup, or rebuilding it to suit your actual requirements.

  #11  
Old 07-09-2022, 07:51 PM
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Skip Fix Skip Fix is offline
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Generally an early 73 ish Qjet is going to have a little better idle down tube size than the lean 78s, so if any cam upgrade they will idle much smoother and not have main booster "drizzle" with throttle blades open too much to get it to idle.

I put a 73 SD SR carb on mine with a mild cam upgrade and it was a world of difference. Have a 73 "regular" 750 Q jet on the 81 400 and it idles well also.

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  #12  
Old 04-08-2023, 06:09 PM
bradrose22 bradrose22 is offline
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I got a carb for my T/A. Problem is the throttle hook up lever is wrong for my stock w-72.
Also the baseplate is wrong.
Anyone have these parts?

Thanks in advance!

  #13  
Old 04-08-2023, 07:47 PM
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Holley makes studs for the throttle and TH350 downshift cable I have added them on Holleys as well as 73 carbs.

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1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
  #14  
Old 04-08-2023, 07:58 PM
bradrose22 bradrose22 is offline
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Thanks!
My whole lever Assembly is different. The stud doesn’t line up to the lockdown cable. Also the return spring is different. I think the lever assembly is from an olds or Chevy. Not a Pontiac.

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Old 04-08-2023, 08:30 PM
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Carb number and/or picture might help us, help you...

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  #16  
Old 04-09-2023, 08:25 AM
bradrose22 bradrose22 is offline
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Both carb numbers are 17058266.
So the differences between the original carb and the one I want to run on the car are.

1. New carb has a different throttle lever Assembly.

2. New carb has a smaller vacuum port on the back for the brake booster etc.

3. New carb doesn’t have a vacuum port on the front passenger side baseplate for a small vacuum line.

Looks to me the whole baseplate was switched out from another carb.

So is what I’m looking for is the correct baseplate for this carb. And I also need the vacuum fitting for the back if someone has an extra.
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  #17  
Old 04-09-2023, 09:14 AM
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Quote:
Originally Posted by Trevor78 View Post
Shelf the carb? Seek out a regular Quadrajet for a Pontiac if can't find the matching carb, rebuild and rejet to suit your setup. Stock W72 isn't anything terribly fancy, you can easily cover it's needs. But if you have the correct carb already, everything just fits where it should.
Agree^
This is a post builder thread, just get the rite carb, you an get a rebuildable CORRECT CARB at a reasonable price, then rebuild it. There were plenty of carbs at Dayton.

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