[Carousel72TRed]

Gentlemen,

I have a Rochester Quadrajet 7028269 carb in my toolshed. According to Wallace Racing it is for a 68 Pontiac 350 with a manual transmission. Can anybody tell me the CFM of this carb and if it is worth any $ if I want to sell it?

Carousel72TRed

[JSchmitz]

750 cfm and whatever the market will bear. What is the condition of it?

[Carousel72TRed]

Thank You JSchmitz,

This is either the carb that came with my 69 GTO auto trans when I bought the car in 78 or off of another 69 GTO I bought for parts in the late 80's. It appears to be in good shape and complete. If it is 750 cfm I will probably keep it if I decide to put it back on my car. I have a Holley 750 VS on my car now. I am taking a wild guess it would be worth $100-$200 if I wanted to sell it at a swap meet. What bugs me is Wallace Racing lists it as for a 68 Pontiac 350 and it just goes to show you what you think you have is OEM is not the case. I found out a Ram Air Hood that I thought was a 69 Ram Air Hood was actually a 70 Ram Air Hood thanks to all of you folks at PY Online Forum.

Carousel72TRed

['ol Pinion head]

a nice shape 7028269 ought to be worth 2-3 similar condition 7029268's.

[Carousel72TRed]

Thank You 'ol Pinion Head

Do you know if 7028269 carbs were OEM on 68 GTO's and if this carb was for 68 Pontiacs with manual transmissions and is there a difference between a Quadrajet for a manual transmission vs. one an automatic transmission? I know I am asking a lot of questions but Wallace Racing has this carb listed as one for a 68 Pontiac 350 Manual Transmission and I may very well decide in the future to put this carb on my GTO. I have seen quotes saying a Quadrajet when set up right is a better carb than a Holley.

Carousel72TRed

[Kenth]

7028269 carbs were OEM on 68 A-F*HI PERF M/T 350HO.

[Carousel72TRed]

Thank you Kenth,

Do you know if my Rochester 7028269 carb will work on my 69 GTO with auto trans or if I want to switch back to a Rochester carb I will have to get a Rochester 7029268 which was on my car originally. I do not know much about carburetors in detail. I do not know if the 7028269 has vacuum or mechanical secondaries. I do have an instruction sheet on Rochester Model 4MC-4MV models but don't know what the 4MC and 4MV models mean.

Carousel72TRed

[padgett]

MC has the choke coil on the carb, MV the coil is on the manifold and has a lever to the carb.

Since the actual Rochester 9D-5 manual may be hard to find, I'd suggest getting a copy of Doug Roe's "Rochester Carburetors." (available on Amazon and elsewhere).

[Kenth]

Originally Posted by Carousel72TRed

Thank you Kenth,

Do you know if my Rochester 7028269 carb will work on my 69 GTO with auto trans or if I want to switch back to a Rochester carb I will have to get a Rochester 7029268 which was on my car originally. I do not know much about carburetors in detail. I do not know if the 7028269 has vacuum or mechanical secondaries. I do have an instruction sheet on Rochester Model 4MC-4MV models but don't know what the 4MC and 4MV models mean.

Carousel72TRed

The 7028269 will work just as well as the 7029268 in all respects.

All Quadrajets has mechanically opened secondary throttle blades.
Incoming air is controlled by atmospheric pressure on the airvalves when the throttleblades are opened to intake vacuum.

[unruhjonny]

Originally Posted by Carousel72TRed

Thank you Kenth,

Do you know if my Rochester 7028269 carb will work on my 69 GTO with auto trans or if I want to switch back to a Rochester carb I will have to get a Rochester 7029268 which was on my car originally. I do not know much about carburetors in detail. I do not know if the 7028269 has vacuum or mechanical secondaries. I do have an instruction sheet on Rochester Model 4MC-4MV models but don't know what the 4MC and 4MV models mean.

Carousel72TRed

that carb will be a fine sit in replacement for a missing/original 67-72 Pontiac (non OHC-6) Quadrajet;
It was setup for the fuel requirements of the 350HO, but I'm sure it would work just fine on any 350-400-455 4bbl motor;
No matter the carb, if you want to maximize anything you will have to fiddle with jetting ect.

[Carousel72TRed]

Originally Posted by Kenth

The 7028269 will work just as well as the 7029268 in all respects.

All Quadrajets has mechanically opened secondary throttle blades.
Incoming air is controlled by atmospheric pressure on the airvalves when the throttleblades are opened to intake vacuum.

Thank You Kenth,

[Carousel72TRed]

Hi Kenth,

I have one last stupid question to ask you and it has to do with the term vacuum secondaries. Is that term used to describe the operation of the secondary air valves on a Quadrajet as you described and on a Holley vacuum secondaries?

Carousel72TRed

[Greg Reid]

Originally Posted by padgett

MC has the choke coil on the carb, MV the coil is on the manifold and has a lever to the carb.

Since the actual Rochester 9D-5 manual may be hard to find, I'd suggest getting a copy of Doug Roe's "Rochester Carburetors." (available on Amazon and elsewhere).

The Roe book is excellent but I couldn't make heads nor tails of it until I read Cliff Ruggles book. Illustrations are critical when you don't know the basics.

[Kenth]

Originally Posted by Carousel72TRed

Hi Kenth,

I have one last stupid question to ask you and it has to do with the term vacuum secondaries. Is that term used to describe the operation of the secondary air valves on a Quadrajet as you described and on a Holley vacuum secondaries?

Carousel72TRed

Holley vacuum secondaries uses a port in the smallest diameter of the primary venturi to control the opening of the secondary throttle blades, no mechanical link from primary throttle axle to the secondary throttle axle to open the secondary throttle blades.
As velocity in the primary venturi rises at WOT the secondary throttle valves opens.

The airvalves in a Quadrajet opens, due to the pressure difference between the atmosphere and the vacuum in intake created by the pistons moving up and down under the nearly closed throttle blades, when the secondary throttleblades opens at WOT.

HTH

[padgett]

And the most common problem with QJs is people backing off the secondary opening spring and experiencing a massive bog when they just flop open.

[unruhjonny]

Originally Posted by Greg Reid

The Roe book is excellent but I couldn't make heads nor tails of it until I read Cliff Ruggles book. Illustrations are critical when you don't know the basics.

The older out of print Doug Roe book is much better than the currently available one.

[padgett]

Dunno, mine has a 1973 date. Price tag is $4.75. Have had a long time.

[Carousel72TRed]

[QUOTE=Kenth;6290674]Holley vacuum secondaries uses a port in the smallest diameter of the primary venturi to control the opening of the secondary throttle blades, no mechanical link from primary throttle axle to the secondary throttle axle to open the secondary throttle blades.
As velocity in the primary venturi rises at WOT the secondary throttle valves opens.

The airvalves in a Quadrajet opens, due to the pressure difference between the atmosphere and the vacuum in intake created by the pistons moving up and down under the nearly closed throttle blades, when the secondary throttleblades opens at WOT.

Thank You Kenth,
you have answered the majority of my questions on carburetors and other subjects and I really appreciate it.

Carousel72TRed

[Ponticat68]

Hello,. I am looking for that exact carb for my 68 350 HO, let me know if you would like to sell it. Can't find one for the manual 4 spd cars very often. Thx

[Ponticat68]

Hello,

I am looking for this carb for my 350HO, let me know if it is available.