Q-jet carb help pleease

[BCOWANWHEELS]

I had a fella clean and put a kit in my 72 c10, 350 4bbl q-jet. He didnt check the adjustment screws settings before dissasembly. Best my old memory serves me is initial starting points are 4 1/2 truns out. Can anybody be of help please.
Thanks
bob

[rsavage]

I start out with 1 1/2 to 2 turns out.

[Richard2112]

Recently rebuilt Q-jet. Started with 3 1/2 turns out then adjusted with vac gauge. These carbs seem to be rather forgiving when it comes to starting with mixture setting. On a guess, I'd think that anywhere between 1 1/2 to 4 1/2 should work for starting.

[LockDoc]

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I initially set mine to 1-1/2 turns out.

LockDoc

[HO455]

Qjet idle mixture screws come in two varieties, course and fine threads. The course threaded ones use 1 1/2 turns and the fine ones use 3 1/2 as the starting point. Earlier carbs came with the courser threads. I don't remember the year of change over.

[BCOWANWHEELS]

thanks fellas , don't know why this fella didn't check so it could be set back to stock specs

[RustyPile]

Originally Posted by BCOWANWHEELS

thanks fellas , don't know why this fella didn't check so it could be set back to stock specs

"this fella" didn't check because there is no "stock spec" for the settings.. As the carb ages and internal build-up starts to occur, the "sweet spot" setting will change.. That's why the screws are adjustable.. After the cleaning/rebuild, that setting will change.. Over the years when I worked as a driveabllity tech, I never "counted the turns" during disassembly.. During re-assembly and preliminary adjustments, I used 3 turns for a starting point.. Every engine is different, every carburetor is different.. The final setting will be where each particular engine runs best.......

[BCOWANWHEELS]

SO what is the best poor man way to set the carb

[RustyPile]

Originally Posted by BCOWANWHEELS

SO what is the best poor man way to set the carb

By "set the carb", I assume you mean idle mixture settings?? This setting is the last one to do.. Carb must be correctly assembled, internal settings -- float level, etc during the assembly.. If you have bad or leaking vacuum hoses, now it the time to clean all that up, as vacuum leaks, even small almost undetectable ones, have a big effect on carburetor adjustments..

Mount the carb, be sure the choke is properly adjusted along with the choke pull off. Use a hand vacuum pump in adjusting the choke pull. These settings/adjustments should be covered in the instructions that came with the kit..

Once the choke is adjusted, start the engine and allow it to warm up while watching the choke "release progress".. Make fast idle and other choke related adjustments during this time.. Once the engine is warmed and the choke is FULLY released, adjust the curb idle and ignition timing..

Here's where a trained ear and experience come in. Personally, I've never used a vacuum gauge for making carb adjustments.. That doesn't mean it's wrong to use one... I use what I call "RPM roll off".. It's a way of cleaning up the idle emissions.. Alternating from side to side, rotate the idle mixture screws counterclockwise, searching for the highest idle RPM.. Try to maintain a balance of turns on each side.. Once you have found the highest RPM setting, re-adjust the curb idle speed screw to bring the engine back closer to the spec'd idle speed. Then rotate the idle mixture screws clockwise, each an equal amount, until you obtain a 50 RPM drop in idle speed.. If the idle is smooth, STOP right there.. If the idle is rough, add about 1/8 turn counterclockwise to each idle mixture screw.. Re-adjust the curb idle speed and you're done......

[demian5]

Originally Posted by RustyPile

Mount the carb, be sure the choke is properly adjusted

Ha! That's a post on its own!

Don't forget the secondary butterflies spring tension adjustment or you will get the Q-Jet "bog > cough > spit > backfire > accelerate" issue.

I usually bench set it all up at 1.5 turns and the choke it the middle setting with fairly tight butterfly tension.

[rsavage]

I believe most of our 67-72 trucks would have a divorced choke if it is correct.

[demian5]

Originally Posted by rsavage

I believe most of our 67-72 trucks would have a divorced choke if it is correct.

Yes, I agree, and hence the "entire post" comment.

You actually bend the rod for that one. Its about a 3 morning ordeal to get it decent.

[Coley]

Something that has to be added into this is prior to any carb adjustments and settings...what is your timing? (Geezer will add to this I'm sure....he is up on timing stuff!!)
You absolutely have to do this first and confirm it....never attempt to adjust the carb without getting your timing right on....timing is job no. 1.
Lots of comments about where this should be....but I think a lot of guys set their base timing up at least to be 10° or 12° for fairly stock engines +/- ...noting that the factory 8° is a little low and mostly for emissions purposes.

Once the timing is done you will have your initial idle speed to work on next.
Remember for timing, you need to plug the vacuum to the distributor, set the parking brake...put the truck in gear and attempt to get that idle rpm down....and only afterwards adjust this idle on the drivers side of the carb (not the choke/fast idle side).
If you end up with an idle speed of 1000 rpm...you will be defeating the idle circuit of the quadrajet.

If you do get the idle down (in gear) to say....650rpm? ....then, finally you can adjust those idle/jet mixture screws for best running.

Next....setting the choke circuit on the passenger side, is a completely different task....to be discussed later.

Anywhooo....that is my take on this....guys feel free to weigh in if your experience of knowledge is different or better!

All good
Coley

[BCOWANWHEELS]

carb guy should have recorded all spec,s and when reasembled it should have been set to those specs as it would be a excellent real close starting point. this carb guy knows I,am crippled and I feel he took advantage of me...............

[demian5]

Originally Posted by BCOWANWHEELS

this carb guy knows I,am crippled and I feel he took advantage of me...............

He may have, but if he is a good carb guy and has a shop, or even works out of his house, part of the deal should be that after you get it installed, to dial it in and set the timing etc....

Did you call him and ask?

I charge quite a bit to rebuild carbs, but I see it through to the end.