Question for Q-jet users - Team Camaro Tech
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post #1 of 7 (permalink) Old Jan 1st, 01, 07:19 AM Thread Starter
Join Date: Aug 1998
Location: Waldorf Md. USA
Posts: 3,280

First of all,
Happy New Year !!!!

Now, I have a question that covers a particular situation only. My 73 Z-28 is 100% stock except for Headers. I cannot get the choke to fully open on the Q-jet. The car has been in my family since new, my brother bought it new in 73, and I bought it from him a few years ago. The motor and everything else is bone stock except like I said the headers. My theory is that the lack of back pressure is not allowing enough heat to get through the exhaust crossover in the intake, thus never opening the choke, which is the divorced type. I have installed a new choke coil, etc etc. The choke linkage is very free...just will not open all the way.
My main question is...does anyone else have this problem or is it just me. I just ned to know if it is normal with headers so I dont waste a bunch of time troubleshooting. At present I have the choke wired open, but really would like to get it back to normal operation. The only other possibility I can think of is the exhasut crossover being carboned up, but it is doubtful.
Thanks in advance,

Bill Koustenis
Advanced Automotive Machine
Waldorf Md
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post #2 of 7 (permalink) Old Jan 1st, 01, 10:59 AM
David Pozzi
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Location: Central California, USA
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Any chance the choke rod ruinning from the choke blade down inside the carb body is hooked on the wrong hole?

On some Qjets, I think there are two holes in the little choke arm inside there and the link might be hooked in the shorter hole which would make for less choke blade movement and less choke opening.
It could easily happen if the carb has been rebuilt, as you can't see in there easily.
It's a long shot.

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post #3 of 7 (permalink) Old Jan 1st, 01, 02:59 PM
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I don't think Headers has much to do with your problem. I also have a 73 Z28 (original owner) and had a similar problem. I had an Aluminium Intake on mine for the longest time. When I restored the car I could not find my original Choke Assembly so I used one that looked correct from a Year One Catalog. Well I had the same problem basically. The choke worked fine when the car was cold but never did open up all the way when it was hot. I tried bending the rod to make it longer (its designed that way) but that did not work. Drove me nuts. Eventually a friend of mine found a 73 Z28 that was being parted out and still had the original Choke Coil on it. He sent it to me and I put it on mine and it works perfectly now. The coils look identical but they function differently. That may be your problem also. The solution for me was to find an original. The good news is that Intake was also used on the Vette Thingy and many other Chevrolet Cars in 73 and 74. So you shouldn't have too much of a problem finding an original and it just may solve your problem also. The only thing I used from the Choke Coil from Year One was the little Cover Box, other than that all the other parts are from the Donor Z28.

Hope this helps,

Bob R

1973 Z28 Original owner
1971 RS Z28 in Restoration
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post #4 of 7 (permalink) Old Jan 1st, 01, 03:11 PM Thread Starter
Join Date: Aug 1998
Location: Waldorf Md. USA
Posts: 3,280

I did the carb and I am pretty sure it is ok...I have probably done a hundred q-jets. I really think it is a heat related thing. Just need to figure out how to fix it. It is just one of those things that will bug me until I get it fixed to my satisfaction.

Bob, That is interesting...I got the choke coil from the parts store, it is not GM, but I have never had problems with them before. Guess I am calling the local Chevy store on Tuesday morning to see what I can get. Will keep you posted. It wont be the first time a non-GM part has screwed things up ! Bob, its nice to find another one owner 73 Z-28. My brother bought this one new and he was going to sell it a few years back due to a new family etc. I didn't want to let it get out of the family so I bought it from him. I also have a 71 Chevelle Heavy Chevy that I bought new in 1971 ! I have been thinking about selling the Z lately, I will see how my finances are this spring. if I can keep it I will, I can't help thinking that my brother will be kicking himself for selling it in a few years when his son gets old enough to get intersted in cars !

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

[This message has been edited by BillK (edited 01-01-2001).]
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post #5 of 7 (permalink) Old Jan 1st, 01, 09:08 PM
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Location: Monroe, WA, USA
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hey bill there are 2 or 3 choke coil's for the devoriced set has to do with how far they move and the way that they move. i bet you got the wrong one..most after market lumped them into a all in one part and some tim's it dose not work..been there with my 74 chev 4X4 with a 350 in it..i used a edlebrock rinaly to make it work.. good luck.
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post #6 of 7 (permalink) Old Jan 2nd, 01, 06:36 AM
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Location: Ontario, Canada
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Hi Bill Had the same problem with my 68, Q-Jet, Bought a new coil, Found that it worked backwards, actually pulled the choke closed as it warmed up. Pulled it apart and reversed the coil, it worked for a while but never opened all the way, I have a cleaned out intake with the proper restrictor and heat riser all in working order on a cast Iron manifold. Played around with the length of the rod as well, Have come to conclude the coil has to be wrong, compared it to a coil from a two barrel and it is different again,
Who Knows?????????
I went back to a wired opened choke and pumping the throttle 101 times to start.
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post #7 of 7 (permalink) Old Jan 3rd, 01, 07:01 AM
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When orig manifolds removed, you removed the heat riser valve which helped heat the carb for warm-up and help open the choke. Remove this, remove heat, choke doesn't open fully.
One may adjust the choke to fully close when cold, and then attach pennies(?) to "weight" the plate open as eng heats up. Put the coins on the very bottom edge&side of the plate. I've used about four, two per side of plate, drvr side & pass side.
Everett 68/350/PG/11.90
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