Being Choked to Death - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

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post #1 of 6 (permalink) Old Jun 20th, 00, 06:06 AM Thread Starter
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Location: Monument, CO, USA
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I've been spending the last few weeks fixing little things on my 69Z. My current problem is with the choke. The choke plate would not close when cold and I discovered the thermal choke spring which mounts in the intake was shot. I found a replacement at Napa Auto Parts and thought my worries were over. The choke plate now snaps shut with pressure from the cold spring. However when I start the engine it runs terrible due to the fact the choke plate stays mostly closed. The vacuum break diaphram does activate but it only opens the choke about an additional 1/4" from closed. When I open the plate by hand another 1/2" the engine starts to run better.
What is the spec for how far the choke plate should open when the engine starts cold? How is this adjusted?
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post #2 of 6 (permalink) Old Jun 20th, 00, 09:37 AM
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Location: ohio
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Usually when cold the the 1/4 inch sounds about right. Both choke adjustments are made simply by bending the actuating rod. Take two pair of pliers and straighten or put more bend in the rods to get the opening, with the pull off, and the time of choke operation from the bimetal spring on the intake. Note, that the intake must have the heat passages open and it helps some, not totally necessary, to have the heat riser in the passenger side exhaust pipe at the manifold.
(I'm assuming a Quadrajet? If this is a Holley it may still work the same, haven't seen one in quite a while, but I think they are similiar in this regard)

[This message has been edited by tom3 (edited 06-20-2000).]
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post #3 of 6 (permalink) Old Jun 20th, 00, 02:59 PM
Join Date: Aug 1998
Location: Waldorf Md. USA
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This wont fix the problem, but I just thought I would let you know you are not alone. My 73 Z-28 has the same problem. My brother purchased the car new and it has had the problem since headers were put on in 1974. I think the lack of backpressure is keeping any heat from getting up to the choke spring. He wired the choke open about 25 years ago and lived with it. I bought the car from him a couple of years ago and have been trying to figure out a fix but to no avail !
Good luck with yours,

Bill Koustenis
Advanced Automotive Machine
Waldorf Md
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post #4 of 6 (permalink) Old Jun 20th, 00, 04:54 PM
David Pozzi
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Most all Qjets are set at 3/8" use a 3/8" drill bit and place it to the rear of the choke blade.
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post #5 of 6 (permalink) Old Jun 20th, 00, 05:35 PM
Join Date: May 2000
Location: Carrollton, GA, USA
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I've always just loved a Manual choke. There when you need it. Can't go wrong. What's one more hole in the firewall. For that matter, there are several holes in the firewall already.

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post #6 of 6 (permalink) Old Jun 21st, 00, 05:16 AM Thread Starter
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Location: Monument, CO, USA
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Thanks for the replies.
I have a Holley 780CFM and headers.
I adjusted the vacuum break lever so it will pull the choke plate open about 1/2" instead of the 1/4". This made all the difference in the world upon a cold start. However, I am seeing the problem where it takes a long time for the choke spring to heat up. I'll be playing with it some more. However, I am close to point where I will just disconnect the choke lever.
Note this is a 69 Z28 with original engine and components. The only change has been the headers. A manual choke would solve my problems but I am reluctant to make such changes.
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