question about the choke coil spring on a 69 L-46 Q-jet

[Michael L.]

Guys,

I'm trying to sort out the choke on my 69 L-46 Q-jet and my first question is what is supposed to happen to the choke coil spring when it gets hot? Is the spring action supposed to get stronger or weaker to open the choke? I connected the choke and carefully heated the choke spring and it seems to have gotten stronger or tighter as it warmed up, it definitely didn't get softer. I'm wondering if I maybe set it up wrong although I followed the instructions and pictures and it really isn't that complicated but who knows. See the attached pic.

Mike

choke linkage A.jpgchoke linkage.jpg

[Edward J.]

Re: question about the choke coil spring on a 69 L-46 Q-jet

Mike the spring unwinds As it gets hot. I am not crazy about the after market choke coils, if the old is not a factory one I would look for a NOS one. The ones you buy at auto parts store maybe calibrated for a number of vehicles. And some made in China. The factory ones are set up for correct timed operation according to outside temp. Make sure that the coil cannot be installed upside down.

[Joe L.]

Re: question about the choke coil spring on a 69 L-46 Q-jet

Guys,

I'm trying to sort out the choke on my 69 L-46 Q-jet and my first question is what is supposed to happen to the choke coil spring when it gets hot? Is the spring action supposed to get stronger or weaker to open the choke? I connected the choke and carefully heated the choke spring and it seems to have gotten stronger or tighter as it warmed up, it definitely didn't get softer. I'm wondering if I maybe set it up wrong although I followed the instructions and pictures and it really isn't that complicated but who knows. See the attached pic.

Mike

[ATTACH=CONFIG]101920[/ATTACH][ATTACH=CONFIG]101921[/ATTACH]

Mike------


Q-Jet choke thermostat moves the choke rod UP to open the choke valve. Holley choke thermostat moves the choke rod DOWN to open the choke valve.

Last available GM choke thermostat for 1968-70 Q-Jet was GM #3927190. It was discontinued without supersession in 1985.

By the way, your carburetor retaining bolts are incorrect. The GM #187147 bolts were zinc plated, not black phosphate. As they are supposed to be, the original bolts on my original owner, late-build 1969 were zinc plated.

[Michael L.]

Re: question about the choke coil spring on a 69 L-46 Q-jet

Thanks guys. This choke spring is a re-pop and it seems to not be calibrated correctly. When installed on the engine and cold it sits at the 12:00 position, so to engage the choke rod I would either have to wind it more (clockwise from the front of the engine) or unwind it. Unwinding it means the choke never closes when cold, and winding it leaves the spring too tight to allow the choke to open even when hot. I had to disassemble it and move the center slotted spring retention rod to allow the spring to have what appears to me to be the correct tension but I'll have to wait for the car to get cold to check if the choke closes.

A separate issue I'm having is the car runs terrible when he choke is closed on startup, very rough and super rich and I have to force the choke open to get it to run decent, even when cold. I have bent the choke rod so that the choke is open about the width of my pinky finger relative to the front of the choke blade but it stills runs like crap. When warm and the choke off the car seems to run ok. Any thoughts on why it would run so bad with the choke like that?

Mike

[Mark E.]

Re: question about the choke coil spring on a 69 L-46 Q-jet

Mike,

Be sure to set the choke and choke pull-off properly. With the choke completely closed, the fast idle cam should be set on the specified step. With the choke pull-off fully engaged, the choke should be open by the specified amount, as measured with a drill bit. There's also a specific way to set the fast idle speed. Each application is a bit different; check the tune up section of the manual or the instructions for the carburetor overhaul kit.

It's a straight forward procedure but has a series of steps.

[Michael L.]

Re: question about the choke coil spring on a 69 L-46 Q-jet

I'm trying to figure it out but the CSM and various tune-up manuals I have are really slim in their instructions. I don't have a carb overhaul kit, the carb was restored by a reputable carb restoration shop. I'm planning on pulling the carb off and sending it back to them for a look over. I thought I bought a book about how to rebuild and tune the Q-jet carb but I can't find it. I may just buy it again.

[Mark E.]

Re: question about the choke coil spring on a 69 L-46 Q-jet

Section 6M (Engine Fuel) of the 1970 (1969 Corvette) CSM has adjustment procedure for fast idle and vacuum break. Section 6M of the Chassis Overhaul Manual (a separate book) has procedures for adjusting the choke rod, vacuum break, and air valve.

It's odd how these are split across two different manuals for 1969/70.

I also have the 1973 CSM, which shows all of these adjustments.

[Michael L.]

Re: question about the choke coil spring on a 69 L-46 Q-jet

Thanks Mark. I recently obtained the COM so I'll look it over for the info. Either way, I'll send the carb back to the restorer since it has been sitting for a few years after the resto and may have a leaking seal or something. It's also possible that the fuel system may have gotten contaminated with dust and crap since it was out and uncovered for a portion of the resto.

Mike