Which jets and rods for my Quadrajet?

[MagmaJct]

Short of it:
I have a 1971 C/10 with a 350 and a Carter AFB. Engine and intake are stock/original AFAIK. I acquired a Quadrajet 4MV 17054919 (1973?) when I got the truck. I'd like to try and use this carb instead of the Carter.

I'm in the process of rebuilding the 4MV because it's condition was/is "unknown". I found one of the secondary metering rods is bent at its tip. Because it'll need to be replaced, what is the correct rods and jets (both primary and secondary) is correct for my otherwise stock application?


Long of it:
The PO was my Uncle until he passed away. The PO before him was my grandfather/grandmother before they passed away. At one point, in the 1990s, the original carburetor was stolen. My Uncle replaced it. When I acquired the truck after he passed, it had the Carter AFB installed, and the 4MV was found in his garage with other truck items.

I don't know if this 4MV was the first replacement after the theft or not. I don't know if it was ever run on this truck. The exterior of the carb appears to have a couple years worth of fuel "carmalization" on it, the inside looks immaculate except for the accelerator pump and bend metering rod.

My goal is not performance, my goal is drive-ability first, and economy second. (Grading on a curve here!)

[Greasey Harley]

The thing about a Q-Jet is, they need to be matched to the engine.
Different cam = different tune on carb
different static compression = different tune on carb
different heads/valves = different tune on carb
different exhaust or a .030 over bore could even possibly effect the way a Q jet preforms.
You need ALL this information, to figure out how to properly configure your Qudra-Jet.
There is no ONE setup for a Q-Jet, that is why people hate them.
You could take a Q-Jet off one 350 (where it worked perfectly) and put it on a another 350 (different heads, cam, etc) and it will run like $#!T

...but if you can get it tuned, it is the best thing in the world!!

[enaberif]

Originally Posted by Greasey Harley

The thing about a Q-Jet is, they need to be matched to the engine.
Different cam = different tune on carb
different static compression = different tune on carb
different heads/valves = different tune on carb
different exhaust or a .030 over bore could even possibly effect the way a Q jet preforms.
You need ALL this information, to figure out how to properly configure your Qudra-Jet.
There is no ONE setup for a Q-Jet, that is why people hate them.
You could take a Q-Jet off one 350 (where it worked perfectly) and put it on a another 350 (different heads, cam, etc) and it will run like $#!T

...but if you can get it tuned, it is the best thing in the world!!

Don't matter what carb you run the same principle applies. The only way you properly tune a carb is to invest in a wideband o2 setup so you can see what your engine is actually doing.

Just swapping jets and rods does nothing.

[wbc409]

I know a guy in MN that is very good with Q-jets. He always has a list of questions for the owner.

[special-K]

^^^ This is true for all carbs. I can't tell you from here. Having every spec on your engine and carb is no more than a good starting point

[68Gold/white]

Originally Posted by special-K

^^^ This is true for all carbs. I can't tell you from here. Having every spec on your engine and carb is no more than a good starting point

X2, without doubt.
www.cliffshighperformance.com is who you need to contact. Send an email, he would be on the phone all day if he took all the calls. He can fix you up, get his book also...

[GRX]

Originally Posted by 68Gold/white

X2, without doubt.
www.cliffshighperformance.com is who you need to contact. Send an email, he would be on the phone all day if he took all the calls. He can fix you up, get his book also...

^^ QFT ... the forums on Cliff's website are a good place for questions as well.

[Lee H]

In your situation it's probably best to start with the carbs born with jets and rods.

[wbc409]

I would check the carb # and carb specs of the carb that you currently have with what was supposed to originally be in the truck. I would start with what was supposed to originally be in the truck/ or engine and adjust from there

[D.PASSMORE]

Don't get stage fright, but if you are not mechanically incline, this could rather challenging. First have a good core that will fit your motor (73 Carb is fine). Get a good rebuild kit with an accelerator pump (blue) that can handle the ethanol fuel mixture.

Your carb: Quadrajet 4MV 17054919 was a 1973 GM replacement carb for a variety of vehicles.

Primary rod: 44 / Primary jets: 74 - Secondary rods: DA

A 1971: Quadrajet 4MV 7041211 / CHEV 71 350 SERIES 10 TRUCK

Primary rod: 42 / Primary jets: 74 - Secondary rods: BA

Go here: http://www.carburetion.com/

You can change out the old with the new.

[MagmaJct]

wbc409, you picked up on my goal with this thread. I know enough about the history of this truck (it's been in the family as far back at 1973 as far as I can tell.) Considering what my Uncle had in his possession when he passed, I'm very certain this was the replacement carb after the original was stolen. As for the Carter AFB installed? Well, I can't ask him what's up with that. I know he was a tinkerer who often "gave up" on original carbs in favor of carbs he perceived as "easier to get working". (Based on a conversation we once had over my VW when I was testing a spare carb I picked up at a junk yard back in the 90s!)

D.PASSMORE, you have the information I'm looking for! Considering this is as close to a stock truck as anyone can find still on the road today, I'm confident the original specs installed from the factory will be sufficient for a truck that sees less than 3,000 miles per year.

Other posters, once I have a baseline starting point, if the truck has economy/performance issues, I can move from there. Thank You all!

[MagmaJct]

Thank You all for the helpful information.

But I have run into a bit of a snag. Upon closer inspection, the throttle lever does not have a provision for the TH350 kick-down! With your guy's help, I came across more detailed information on the carb I have in my possession, and I found it was intended for a manual transmission. I had assumed it was just tuned differently, not that the throttle lever was different.

This means I have to make a decision. Use this as a core to get the "correct" application carb for my truck, find a "bolt on" replacement lever, or modify the existing lever. I hate to modify anything that's no longer in production.

We'll see.

--Mike

[D.PASSMORE]

Drill it and put the cable stud on it. It should be fine.

[MagmaJct]

View the link below. The carb I have looks identical to the throttle arm on the left. It really looks like GM sheared it off. Apparently this was done on vehicles with a manual transmission. I could drill two holes and pop-rivit an extension. I could also braze an extension. (The arm is attached to the throttle shaft with a screw.)

http://www.crankshaftcoalition.com/w...hoosing_a_carb

[68Gold/white]

Your carb was designed originally for a TH400 trans, which does not use the cable...