[Holeshot71]

I picked up this carb at a swap meet a while back. Would this be considered a good carb for a performance build? Does it have the good APT set up??

Thanks...

[Jeff Walker]

If it has the aluminum plug in the front part of the air horn where the air cleaner sets, then yes it does have the good APT setup.

[Kenth]

No and no.
It has the auxilary power piston assembly and aux. metering rod/spring assy. and is one of the worst units for a performance build, sorry.
I would look for a 1976-79 Pontiac unit with last three digits 262-278.

[Jeff Walker]

Glad you chimed in Kenth.

I was thinking that was one of the models that had the aux power piston and metering rod assembly but wasn't positive.

The 77-80 Buick and Olds carbs are a pretty good choice too. One advantage these have over the 76-79 Pontiac carbs are that you don't have to modify you air cleaner to fit the large vent hole that is a Pontiac only design.

[JJKJ]

Originally Posted by Kenth

No and no.
It has the auxilary power piston assembly and aux. metering rod/spring assy. and is one of the worst units for a performance build, sorry.
I would look for a 1976-79 Pontiac unit with last three digits 262-278.

Kenth,

I read in Cliff's book that some of the 76 models had the undesirable APT as well. I recently purchased a 17056262 carb that it looks like you're recommending. It hasn't shown up yet, and after re-reading Cliff's book, I got worried that I may have bought a problem carb (I was attempting to avoid only the 75 carbs). This carb has a 0786 build date, do you have any idea on how I might find out if I got a carb with a good APT system?

[Robert Williams]

Originally Posted by Jeff Walker

Glad you chimed in Kenth.

I was thinking that was one of the models that had the aux power piston and metering rod assembly but wasn't positive.

The 77-80 Buick and Olds carbs are a pretty good choice too. One advantage these have over the 76-79 Pontiac carbs are that you don't have to modify you air cleaner to fit the large vent hole that is a Pontiac only design.

Jeff, also the #17080272 off 1980 Pontiac 301" engine, that is why i purchased the (2) that you had for sale, excellent casting with the small vent tube up by the choke plate. I have five of these now, Cliff Ruggles just built me one for a 463"...

[Jeff Walker]

Originally Posted by JJKJ

Kenth,

I read in Cliff's book that some of the 76 models had the undesirable APT as well. I recently purchased a 17056262 carb that it looks like you're recommending. It hasn't shown up yet, and after re-reading Cliff's book, I got worried that I may have bought a problem carb (I was attempting to avoid only the 75 carbs). This carb has a 0786 build date, do you have any idea on how I might find out if I got a carb with a good APT system?

Here's a photo to help identify the difference. The carb on the left has the good APT system Notice the shiny aluminum plug directly in front of the primaries. All carbs with the good APT system will have that.

Now look at the carb on the right. See that there is no plug as with the one on the left. Instead there is a brass plug on the LF corner as the carb is pictured. This carb has the aux power piston and metering rod which is the less desirable setup.

HTH

[Holeshot71]

Wow, thanks for the info!! I guess I won't use the 259 carb right now...Luckly I didnt pay much for it.. I picked up another carb #17058241 off of E-pay last night.. Hopefully this one is a little better..??

[Cliff R]

You may want to "cross-breed" them, as the Buick carburetors often show up with some pretty "goofy" throttle linkage, that hits Ram Air and Shaker bases.

There is really nothing at all wrong with the 259 unit, equal in potential to any other 76 or new later style APT carburetor. They just take a few extra steps and different jet/metering rod combinations as a starting point. I build them frequently here for customers, never had a single complaint about them. Even so, they are my last choice here when building a custom unit for a customer, as they simply take more labor to get ready, and lack the later APT set-up......Cliff