Author Topic: Floppy Choke Plate  (Read 125 times)

Offline Brett Slater

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Floppy Choke Plate
« on: May 20, 2020, 01:48:23 PM »
Hey folks,


I've been lurking around for a while and figured I'd see if anyone could offer any insight on my choke issue.

The carb is a '73 800 cfm Buick Q-Jet that was rebuilt by Quadrajet Power back in late 2016 and then basically redone again in 2018 by Everyday Performance. It utilizes a divorced choke and because I'm using an aftermarket intake, I had to kind of wing it and use an OEM Chevy thermostat spring, etc.

I installed the new motor a month ago and ended up having to tie off the choke plate because it was closing under acceleration. In turn, that caused terribly hard starting, so I set it back up correctly today and it fired right up, immediately going to high idle.

Once warmed up, I went for a test drive and it felt super responsive. Probably more than it has the entire time I've used it. As an aside, a subsequent test drive with the factory ram air air cleaner on seemed to make it run like it was previously - lagging and blubbering. That's another story I guess I'll have to deal with later.

When the drive was over, I noticed the choke flap was floppy and not firmly held at a 90 degree angle. This is where I'm at a loss and hopefully someone can offer a tip or two in terms of choke adjustment.

Here is a video of what I'm talking about and thanks in advance!

https://youtu.be/L5zvmkA7kvQ


Offline Kenth

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Re: Floppy Choke Plate
« Reply #1 on: May 21, 2020, 12:46:27 AM »
Chevy OEM bimetal pushes the choke blade open. and Buick OEM bimetal pulls the choke blade open.
Using the Chevy style bimetal on intake takes the whole Chevy mechanism on carb too for proper choke action.
It would help to see the choke side of carb.

Anyhow you may adjust the choke rod to choke valve?
With choke closed (cold engine) place cam follower on second step on fast idle cam and hold against highest step.
Gauge between lower edge of choke blade and air horn wall.
Bend rod to adjust.
With Chevy style choke mechanism on carb .100" and with Buick choke .130".

Offline Brett Slater

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Re: Floppy Choke Plate
« Reply #2 on: May 21, 2020, 03:27:40 AM »
Sorry for the lack of content and thanks for the reply.

After some convos with a couple of my Buick peeps, it was brought to my attention that the secondary choke pulloff is, in fact, missing. Clearly an important piece of my flappy choke blade puzzle.

How a "rebuilt" carb makes it through 2 different builders and no one catches it is beyond me. I bought this carb from a friend who had it rebuilt and I'm sure he had every intention of using the stock '70 intake/divorced choke setup.

I'm beside myself.

Offline Brett Slater

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Offline Kenth

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Re: Floppy Choke Plate
« Reply #4 on: May 21, 2020, 06:56:00 AM »
Looks like you have a 1971-72 bimetal choke unit on intake, this works the same as OEM Buick.
But the choke rod seems to be the short Chevy, Pontiac, Olds style with one bend at middle of rod.
Buick and Cadillac uses a longer choke rod to the blade with two bends that is adjustable at the upper bend.
BTW, you will do fine w/o the secondary pull-off with primary pull-off adjusted as needed.

Offline Brett Slater

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Re: Floppy Choke Plate
« Reply #5 on: May 21, 2020, 10:42:37 AM »
Good to know. Thanks!

Which one of those is for the Buick, the bottom?

Offline Kenth

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Re: Floppy Choke Plate
« Reply #6 on: May 21, 2020, 12:19:29 PM »
Yes, the bottom one is for Buick.

Offline Brett Slater

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Re: Floppy Choke Plate
« Reply #7 on: May 21, 2020, 07:42:07 PM »
Looks like you have a 1971-72 bimetal choke unit on intake, this works the same as OEM Buick.
But the choke rod seems to be the short Chevy, Pontiac, Olds style with one bend at middle of rod.
Buick and Cadillac uses a longer choke rod to the blade with two bends that is adjustable at the upper bend.
BTW, you will do fine w/o the secondary pull-off with primary pull-off adjusted as needed.

How would this novice achieve getting the choke to work properly without the secondary pulloff?

Offline Kenth

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Re: Floppy Choke Plate
« Reply #8 on: May 22, 2020, 03:29:56 AM »
Without the secondary pull-off, which is a part of "choke delay system", i would set the primary pull-off at .250" to start with.
With cold engine close the choke, seat vacuum break using outside vacuum source, rod in bottom of slot at choke valve shaft, gauge between air horn and lower edge of choke valve.

Offline Brett Slater

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Re: Floppy Choke Plate
« Reply #9 on: May 22, 2020, 12:38:55 PM »
Looks like you have a 1971-72 bimetal choke unit on intake, this works the same as OEM Buick.
But the choke rod seems to be the short Chevy, Pontiac, Olds style with one bend at middle of rod.
Buick and Cadillac uses a longer choke rod to the blade with two bends that is adjustable at the upper bend.
BTW, you will do fine w/o the secondary pull-off with primary pull-off adjusted as needed.

You nailed it. Good eye!

I tinkered with it today and added the secondary pull off. Also, tweaked that choke rod and realized even after that it was still too short which makes a lot of sense now.

Just ordered the correct one depicted in the bottom picture you previously posted. Thanks again!