new carburetor needed- 72 GMC K15 350

[michaely31]

Any opinions on what I should buy?

I don't need concours but would like to maintain the GMC air filter assembly.

Would prefer quality.

Performance over Fuel economy.

Dont know if being at elevation should effect choice?

Thanks

-Michael

[SS Tim]

Might look into a Q-Jet rebuilt by a quality rebuilder like Ruggles to get it operating correctly and dialed in for your engine/altitude. Q-Jet will give you plenty of performance.

[LockDoc]

-
With Tim. Hard to beat a Qjet that is set up correctly...

LockDoc

[michaely31]

thanks,

dumb question- is the factory stock carb a Q-Jet?
should I have rebuilt?

(As you likely know, Ruggles is 12 months out to rebuild)

-Michael

[Mike C]

Yes the factory carb is a Q-jet.

I'd buy a JET stage II or a Summit rebuilt electric choke carb. I've done both. Have a JET on my Jimmy and a Summit on my K30. Both work well and are an "order it today get it in 3 days" proposition.

[leftybass209]

Quadrajet is the most logical choice. Switching to a Holley or Edelbrock would cause you to modify fuel lines, possible carb spacers, air cleaner spacers, and an eddy will definitely require a fuel pump change.

[StingRay]

If you can find a good 1980 ish core prior to anything electronic you get better fuel metering than the older ones and the electric choke. When rebuilt and tuned they are a really great all around carb.

[mechanicalman]

Originally Posted by StingRay

If you can find a good 1980 ish core prior to anything electronic you get better fuel metering than the older ones and the electric choke. When rebuilt and tuned they are a really great all around carb.

X2 on that, toss the old divorced choke in the rubble and enjoy much better carb than the original.

[mechanicalman]

Originally Posted by michaely31

Any opinions on what I should buy?

I don't need concours but would like to maintain the GMC air filter assembly.

Would prefer quality.

Performance over Fuel economy.

Dont know if being at elevation should effect choice?

Thanks

-Michael

This is what I prefer:
80-89 Chevy/GMC trucks with electric choke, compatible with EGR not computer controlled. Pick-ups, Suburbans and Vans up to 1 ton. IMO, the best of the traditional Quadrajets.

795 CFM, great for performance and works great on variety of engines due to the inherent design of the quad with the adjustable secondary air valve. And, as all Quadrajets, the power piston travel is adjustable. I like to remove the upper carb cover (air horn) and drill/pipe plug a hole directly in line with the adjustment screw so you can adjust the part throttle fuel metering spring load/limit without dis-assembling after that.

This is what an old Edelbrock 1904 actually was, darned shame they quit reproducing them!

Being at elevation does not necessarily affect carb choice, but it does affect carb jetting no matter what carb you select. But if you jet for high altitude, and drive it in low altitude, you go lean. Jet for low altitude, drive in high altitude, you go rich.

UNLESS you can find a Quadrajet (Quintojet) with an axillary jet, a rare beast, they only came on high altitude applications. I had an EGR capable one on a 75 Camaro that was originally purchased at a Flagstaff Arizona dealership (7,000 feet).

I have one now on my 72 that came off an 85 Monte Carlo SS 350 (yes, they made them for Mexico) that originally came from Mexico City (7,382 feet). The number off the carb does not even show up on the list for repair kits here in the states. It's not EGR compatible and the stock iron intake that the engine had was cast for EGR but not drilled. Rare in these parts, best darned carb I've ever had for fuel economy. Got the primary circuit dialed in when I had it rolled on the dyno thanks to good old Arizona Emissions only $20.00 for every 2 rolls.

What's nice about the Quintojet is that the axillary jet compensates for altitude no matter where you drive and even keeps fuel metering stable regardless of altitude density.

IMO, one of the reasons, if not THE reason the Quadrajet was re-designed from the old divorced choke style is the forward part of the casting in front of the fuel bowl was originally in place for the brass bellows/needle assembly that meters fuel through the axillary jet. That part of the carb was eventually taken over for the MC solenoid on the computer controlled carbs.

Note: Artistic license taken by the author on the naming of the "Quintojet".

[Coley]

Originally Posted by mechanicalman

795 CFM, great for performance and works great on variety of engines due to the inherent design of the quad with the adjustable secondary air valve. And, as all Quadrajets, the power piston travel is adjustable. I like to remove the upper carb cover (air horn) and drill/pipe plug a hole directly in line with the adjustment screw so you can adjust the part throttle fuel metering spring load/limit without dis-assembling after that.

Interesting...I've heard of this....do you have any pics of this MechanicalMan?
(note: sorry...don't mean to hijack anything here.)
Thanks
Coley

[geezer#99]

Originally Posted by Coley

Interesting...I've heard of this....do you have any pics of this MechanicalMan?
(note: sorry...don't mean to hijack anything here.)
Thanks
Coley

Some of the newer carbs have a plug in them you pop out.
Then tap for a plug.
Here's some info.
http://www.crankshaftcoalition.com/w...4MV_carburetor

[mechanicalman]

Originally Posted by geezer#99

Some of the newer carbs have a plug in them you pop out.
Then tap for a plug.
Here's some info.
http://www.crankshaftcoalition.com/w...4MV_carburetor

Geezer-that's a great article, thanks. I didn't know about the spool type one, just the aneroid one, nor did I know the aneroid was adjustable.

[mechanicalman]

Originally Posted by Coley

Interesting...I've heard of this....do you have any pics of this MechanicalMan?
(note: sorry...don't mean to hijack anything here.)
Thanks
Coley

If you are talking about the plug and the power piston adjustment, here it is....
courtesy of Geezer.

[mechanicalman]

Originally Posted by Coley

Interesting...I've heard of this....do you have any pics of this MechanicalMan?
(note: sorry...don't mean to hijack anything here.)
Thanks
Coley

Coley, BTW: Don't ever worry about highjack with me you can ask me anything anytime you want. I enjoy this.

[SierraMtns]

Originally Posted by mechanicalman

This is what I prefer:
80-89 Chevy/GMC trucks with electric choke, compatible with EGR not computer controlled. Pick-ups, Suburbans and Vans up to 1 ton. IMO, the best of the traditional Quadrajets.

795 CFM, great for performance and works great on variety of engines due to the inherent design of the quad with the adjustable secondary air valve. And, as all Quadrajets, the power piston travel is adjustable. I like to remove the upper carb cover (air horn) and drill/pipe plug a hole directly in line with the adjustment screw so you can adjust the part throttle fuel metering spring load/limit without dis-assembling after that.

This is what an old Edelbrock 1904 actually was, darned shame they quit reproducing them!

Being at elevation does not necessarily affect carb choice, but it does affect carb jetting no matter what carb you select. But if you jet for high altitude, and drive it in low altitude, you go lean. Jet for low altitude, drive in high altitude, you go rich.

UNLESS you can find a Quadrajet (Quintojet) with an axillary jet, a rare beast, they only came on high altitude applications. I had an EGR capable one on a 75 Camaro that was originally purchased at a Flagstaff Arizona dealership (7,000 feet).

I have one now on my 72 that came off an 85 Monte Carlo SS 350 (yes, they made them for Mexico) that originally came from Mexico City (7,382 feet). The number off the carb does not even show up on the list for repair kits here in the states. It's not EGR compatible and the stock iron intake that the engine had was cast for EGR but not drilled. Rare in these parts, best darned carb I've ever had for fuel economy. Got the primary circuit dialed in when I had it rolled on the dyno thanks to good old Arizona Emissions only $20.00 for every 2 rolls.

What's nice about the Quintojet is that the axillary jet compensates for altitude no matter where you drive and even keeps fuel metering stable regardless of altitude density.

IMO, one of the reasons, if not THE reason the Quadrajet was re-designed from the old divorced choke style is the forward part of the casting in front of the fuel bowl was originally in place for the brass bellows/needle assembly that meters fuel through the axillary jet. That part of the carb was eventually taken over for the MC solenoid on the computer controlled carbs.

Note: Artistic license taken by the author on the naming of the "Quintojet".

Is this the edelbrock carb you are talking about? WOW...price seems a little high for a used carb.

http://sfbay.craigslist.org/eby/pts/4835460528.html

[mechanicalman]

Originally Posted by SierraMtns

Is this the edelbrock carb you are talking about? WOW...price seems a little high for a used carb.

http://sfbay.craigslist.org/eby/pts/4835460528.html

Yes it is, and yes it's WAY OVER-priced. I've bought used ones as cheap as $25.00 and $15.00.

Exactly the same carb that comes off 85-89 Chevy and GMC pickups and Suburbans up to 1 ton.

Easy pickings at the local U-Pull-It, Pick-Your-Part, or equivalent. Get one with a tight throttle shaft that does not look like the front two mounting bolts have been over-tightened and digging into the lid and you are likely good to go with a repair kit. If you put in in the 283 it may need some calibration.

[michaely31]

good with me, I'm learning

[geezer#99]

I think the ad has one extra zero. They weren't even that much new.
If you access your apt just use a schrader valve tool to adjust it. The larger one for big truck tubes works.
Here's an example.
https://store.snapon.com/Diagnostic-...e-P664425.aspx

[michaely31]

talked with mr. ruggles today
nothing but a class act and he is soon to be a colorado resident- p/t

will try to find a denver area shop to rebuild with the kit and parts
thanks