2firebirdpals

Well- I thought that a rebuilt Rodchester quad would help my engine BUT sooo far--not to be. I still am not sure BUT I set it up by dialing in each mixture screw and counting how many turns to base totally in---- I counted 4 1/2 full turns from Fully closed(leaned) for each . Isnt that rather a rich setting??? What is the suggested # of turns from based-fully leaned in- that I should Do? PS The car runs like crap at that setting

Restrorob

iTrader: (7)

For proper adjustment you need a vacuum gauge hooked up to port vacuum, Then adjust each side in or out to obtain the highest vacuum reading as possible (normally close to 20")...... There's no set number of turns due to each engine/carb being different......

2firebirdpals

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In the old days- the rule of thumb was to place the carb on with whatever setting was already on the carb then turn the mixture screws until stumbling occurs then turn back ONE full turn. Do this on each side.

But this new carb is wierd--- when I turned IN one mixture screw( which would lean the mixture) the engine never stumbled even when turned IN all the way-Leaned. Now "that" is wierd. Fully leaned IN and the engine never stumbled ??? Something does not make sense.

Restrorob

iTrader: (7)

You have a vacuum leak somewhere or there's issues with the carb, I'm 55 and remember the old days of using a vacuum gauge to "properly" adjust a carb.....

2firebirdpals

I'm 57 and growing up with fellow shadetree mechanics- none of us had a vacuum gauge. And only some of us had a "timing light". - We "gapped" our spark plugs and set points with a feeler gauge. Only a few had vaccum gauges and of course the Shops had everything at their disposal.
Brooklyn in the late 60's and early 70's.

Damon

Can you turn BOTH mixture screws in all the way without the idle slowing or the engine beginning to stumble?

Mixture screws are supposed to be adjusted EVENLY SIDE TO SIDE. Start them both at 4 turns out then go in or out on one of them and immediately repeat on the other. Then assess if there is any change in idle.

I go half a turn at a time for my initial rough adjustment.

five7kid

iTrader: (14)

If this is a computer q-jet, the proper adjustment is 3-3/8 turns out. The idle mixture screw threads were finer on the computer q-jets than they were on the non-computer q-jets.

https://www.thirdgen.org/forums/carb...e-rebuild.html table almost at the bottom of the page, shows the number of turns for the p/n of carb you have.

The final idle mixture adjustment is done with the idle air bleed.

2firebirdpals

Got ya-- I also count 1/2 turns- to be precise---will now need to check the Idle Air Bleed----- never needed to before- Will check the diagrams to locate it. thanks---- I will let ya know- what I find.

Damon

IAB is under the metal plate in the front "tower" of the choke airhorn. Two little rivets, one on each side, hold the plate in place. The big slotted screw head you see underneath is connected to the IAB valve.

A "baseline" setting is ~4 turns up from lightly seated. Same as the mixture screws.

The IAB and the idle mixture screws BOTH affect the idle mixture, but their effects are opposite (in is leaner on the mixtures screws, but richer on the IAB). You really need to be running in closed loop and looking at the dwell readings to get it in the right range. You can go batty adjusting one of them in, the other out.... chasing your tail half of forever.

There's a whole procedure in the service manual.

Camaro86IrocZ

iTrader: (1)

Also depends on who rebuilt the carb.. these days carb rebuild quality is variable.. if from a major rebuild house, could be a mix of mismatched parts all thru out the assembly set up with base tune settings for multiple engine combo's,, Qjets were engine specific from the factory.. Better to start with a virgin core for your application, get Cliff Ruggels and Doug Roe's books, a rebuild kit from Cliff and take your time with it or have someone knowledgeable do the rebuild, Then dial it in..

Chuck84TA

^^^^^^ THIS

I bought a rebuilt carb for $250 off eBay a few years ago. The car ran better than having the original carb, but it still wasn't right.... Come to find out when I rebuilt it last spring with Cliff's HP kit that it had the wrong fuel filter, the throttle shafts were loose, the black cap that fits over the primary metering jets was broken....

I'd get the carb rebuilt or do it yourself, the knowledge gained by that endeavour, no matter how time consuming or frustrating will pay dividends.

Get Cliffs book and Doug Roe's book. Took me awhile, (kinda slow) but I am finally getting a grasp of this carburetor!.... I think..lol

2firebirdpals

WELL---- i checked the IAB valve and found that it was set at the rebuild shop turned all the way IN and backed out "only" 1/8 th of a turn---- hard to believe??? But True! That must be awfully rich - Right? Since -as you said- it's opposite the mixture screws. In is Rich and Out is Lean.
Now-what would you do next--- Dial it out"lean" 4 full turns "correct"?.

2firebirdpals

Also forgot to say----- My idle is running up and down "erratic" between 850 and 1050 in Park. . I really want to post pics of the car for the board to see. But cant seem to get it right.