Whats the best way to set up the choke on my 79,not electric.Seems to take along time to start.
Appreciate any help,Neil.

 

Anyone??

 

Wish I could help...never have been able to make mine work. I have totally, and successfully, rebuilt the qjet. However still no choke, at all.
The various manuals I have tried to follow just do not apply.
Good luck!!

 

First, make sure you have the complete hot air system installed, intact, and functioning: There should be one tube coming out of the intake manifold and going into the rear airhorn area of the carb, and one tube coming out of the manifold entering the front fitting on the choke housing. You should be able to remove the tube attached to the choke housing and blow into it, feeling air coming out the tube that runs into the back of the carb. Once this is verified to be correct and operable, you can set up and check out the choke:

First, you need to make sure that the choke pulloff diaphragm is working - on at least half of the carbs I work on the diaphragm is ruptured. Pull the vacuum hose off the pulloff and install a long piece of vacuum hose on it. Suck on the hose. The pulloff should retract smoothly and evenly, and the pulloff should hold a vacuum once fully retracted. If it does not, you have to replace it in order to get the choke to work properly. New pulloffs are available from NAPA for $15 to $25 depending on carb model - just give them your carb number.

With the pulloff functioning and the engine cold, adjust the round black choke cover so that the line on the cover is 2 notches clockwise from the centerline adjustment position: loosen all 3 of the hold-down screws and turn the cover - don't stick a screwdriving in the slot on the cover and try to turn it as this will break the cover. If the cover is an aftermarket cover and has no line on it, you can adjust it as follows with a cold engine: Crack the throttle open so that the fast idle screw is not touching the choke linkage. Turn the cover so that the choke starts to open. Then, turn the cover the opposite direction until the choke just hits the fully-closed position. Snug the cover screws down.

With the choke in this fully closed position, suck on the vacuum hose that you still have attached to the choke pulloff. The choke should crack open. With the choke cracked open, apply very light pressure to the forward, lower edge of the choke plate to simulate the force of the air that would normally be rushing by it: This will push the choke open up against its stop. In this position, measure the distance between the forward lower edge of the choke and the airhorn wall: The distance should be 1/4". Easiest way to measure this is to stick a 1/4" drill bit down the front of the airhorn. Adjust the distance by turning the screw on the top of the choke pulloff diaphragm arm. This completes your choke adjustment and setup. You can now start the engine and adjust your fast idle speed by turning the screw located under the choke linkage on the passenger side - the screw head faces forward. Adjust fast idle speed to about 1200rpm or whatever you feel is a comfortable cold idle speed for your application.


[Modified by lars, 12:15 PM 8/20/2003]

 

Thanks, Lars. You instructions make sense!
Bill

 

Thanks Lars I was hoping you would chip in :)

 

the heat tube inside the intake heat riser crossover gets covered with carbon and you must remove it from the manifold,wire brush or bead blast off the carbon. the carbon acts as a heat shield and prevents the choke from getting hot enought :chevy


[Modified by clem zahrobsky, 2:28 PM 8/20/2003]

 

Thanks Clem I'll check into that as well.

 

Clem,

Does that mean that there is an openng on the intake into the exhaust passage? I think I was told this a long time ago. And that when converting a Q-jet to electric choke that you had better seal (weld) this hole (or holes?) shut or you would have an exhaust leak.

Is this the case?

Since you may know I'll ask this also: On a square bore intake (use the LS-6 big block for this example), did the Holley's have a similar choke arrangement? Therefore, if you convert to elec choke (or even no choke) are these intakes the same in needing the holes plugged?

Thanks in advance for helping me understand.

Regards, Mark :flag :chevy

 

the heat tube is a loop,the vacuum from the choke on the carb goes in one end and draws air in from the air cleaner and is heated by the exhaust riser crossover in the intake manifold. i have seen cases were this tube was burned thru by the exhaust heat. if you convert to a electric choke and the tube is not burnt thru you need to do nothing with the tube. if you remove the tube unit you must use a block off plate on the hole in the intake or the exhaust will come out there. i hope this is clear.

 

As Clem noted, the hot air choke system is sealed off from the exhaust gasses if the tubes are in good condition, so the tubes can be removed and left unplugged with no ill effect.

The system that Mark may be referring to is the late '60s/early '70s SB and BB carb heat systems: On some cars, there is a curved exhaust passage crossover that runs in the intake manifold just forward of the primary throttle bores. The purpose of this exhaust groove was to pre-heat the carb during cold-weather operations to provide better drivability in cool weather conditions prior to the engine fully warming up. If the incorrect carb base gasket is used, or if the stainless steel heat shield covering this groove is deleted, you will get a massive exhaust leak or exhaust gas ingestion into the intake manifold. This can be solved by using the correct gaskets or by plugging the exhaust crossover holes at both sides of the intake manifold. PLugging the holes results in a cooler-running carb, and is a common performance trick on these cars.

 

you can plug these holes with steel cup type expansion plugs of the correct size. do not tap these holes for screw in plugs as the chips could end up in you cylinders unless you remove the intake from the engine.

 

Clem and Lars,

Thanks for the great info as always!

Regards, Mark