desperate for cold weather quadrajet advice!

[rfoll]

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You need heat for the carb. All of the vortec setups I have used run about 20 - 30 degrees cooler and take a long time to warm up. The only manifolds I have found with this feature are the Performer RPM and the marine stuff. The RPM requires an adapter for the QJ. There should be a fresh crop of frozen and cracked boat motors out there by now.

[rewguy]

As mentioned there is a plug on top in the front of the carb,remove it to. Access the metering rod hanger adjusting screw I am willing to bet if you raise them your problem will go away.These rods control part throttle mixture,just keep raising them a little at a time till 6our problem is gone.I learned this the hard way when as a young buck I rebuilt a quad and had them adjusted way to low the thing idled OK but was lean as heck and wouldn't hardly pull itself. These are the same rods gm added a solonoid to and cycled up and down from rich to lean 60 times a second to get the average a/f mixture they wanted at cruise with the computer controlled qjets.

I don't see any plug on the top toward the front of this carb?

[Tuner]

Have you taken off the top and checked the float level? It depends on exactly which float, but 3/8" to 7/16" is usual.

[Tuner]

As mentioned there is a plug on top in the front of the carb,remove it to. Access the metering rod hanger adjusting screw I am willing to bet if you raise them your problem will go away.These rods control part throttle mixture,just keep raising them a little at a time till 6our problem is gone.I learned this the hard way when as a young buck I rebuilt a quad and had them adjusted way to low the thing idled OK but was lean as heck and wouldn't hardly pull itself. These are the same rods gm added a solonoid to and cycled up and down from rich to lean 60 times a second to get the average a/f mixture they wanted at cruise with the computer controlled qjets.

I don't see any plug on the top toward the front of this carb?

Under the air cleaner gasket, center front.

[superdave2]

Look under the air cleaner gasket." 1/8 double D" screw head under the plug. Turn CCW 1 turn at a time, but you may have to jet up on pri. 4 jet sizes, especially if you are running 10% ethanol pump gas. XX2 on needing heat, add another 2 jet sizes if you don't get heat to it!

[rewguy]

Look under the air cleaner gasket." 1/8 double D" screw head under the plug. Turn CCW 1 turn at a time, but you may have to jet up on pri. 4 jet sizes, especially if you are running 10% ethanol pump gas. XX2 on needing heat, add another 2 jet sizes if you don't get heat to it!

This is off of a 1985 model carburetor....and it will have this plug? I must be dense, because Im not seeing it, lol.

[rewguy]

do you need to take the top of the carb off to get the front plug out?

[rewguy]

i hope someone sees this, lol

[Tuner]

Yellow arrow is the hole, red arrow is the plug removed from the hole.


Below is what you would see if you had the top off the carb.



The red arrow points to the screw. It has a rectangular stem sticking up straight at the camera lens. You can make a tool by progressively driving a 3/16” steel tube over a file tang and flattening it to fit the tang with gentle but persuasive hammer blows. I recall making one by progressively flattening a ¼” tube until it fit snug but I don’t remember if it will fit down the hole so it can be used with the carb top on.

You should probably check the float level anyway.

You can use a small screwdriver or punch (or something similar) and feel down through the vent tube to the metering rod hanger to see how much vertical travel it has against the spring. It if has only 1/8” that isn’t enough, if there is 5/16” travel that is a lot. The more travel, the further down the rod goes in the jet and the leaner it is.

[rewguy]

how do you get the plug out? it is flush with the surface and nothing to grab onto?

[HDBD]

Back in the day there were a whole assortment of spring tensions to fine tune the APT preload. IIRC the vacuum pulls the piston all the way down and it isn't until the vacuum drops that the rods lift. The spring tension calibrates the point this begins. You will be ahead of the game if you get this right, the float correct, and supply heat to the air cleaner. With non-stock manifold vacuum this will affect the APT calibration too and force the need for a lighter spring or the motor will drink fuel. Be sure the accelerator pump circuit is working properly also.

[Tuner]

how do you get the plug out? it is flush with the surface and nothing to grab onto?

Drill into it with a small drill bit, 1/8” or so, and turn in a long enough self-tapping screw so you can get astraddle of it with a needle nosed pliar and leverage the pliar on the vent tube boss to pry it up and out. It should come out fairly easy, particularly if the carb is warm.

You can see in the picture how long it is so be careful not to drill through it.

[barnym17]

I am not sure but I think GM made a heated plate to go between the carb and intake just supply 12 volts and ground, had a grid that heated the air fuel mixture for better distribution.The application would be early to mid 80's vehicle.

[boogie]

I had the same exact problem. I talked to Cliff Ruggles(sp) and he sent me a new step up spring, 77 jets in place of my 76's, his .044 taper primary metering rods, and told me to adjust the APT 3.5 turns up from seated.

ALL MY LEAN STUMBLES ARE GONE! Runs great now, no matter how cold. My carb is a 17058204

[novadude]

I had the same exact problem. I talked to Cliff Ruggles(sp) and he sent me a new step up spring, 77 jets in place of my 76's, his .044 taper primary metering rods, and told me to adjust the APT 3.5 turns up from seated.

ALL MY LEAN STUMBLES ARE GONE! Runs great now, no matter how cold. My carb is a 17058204

If the OP is dealing with an '85 carb it is probably a Single-main-air-bleed. In which case, those jet / rod recommendations won't work, as he needs .036" tip rods. Specific sizes will depend on the size of the main air bleed. Large (.080") air bleeds will pr0bably like a 76 or 77 jet with around a 52M rod as a starting point. Smaller (0.050") air bleeds will want something closer to a 73 jet and 50M rod.

The recommendations above make sense for a 17058204, as they had the large 0.125" air bleeds, which require a large jet. They used the 0.026" tip rods.

Also, check to make sure you have a strong pump shot with any throttle movement, since you said fast throttle movements almost stall it. You may need to reseat the pump check ball, or change accel pumps if there is a lag in pump shot when the throttle is moved quickly. I've not had any luck with the "edelbrock" style pumps that have no garter spring.