Here’s my situation:
1966, 442
Original engine
Original 4-speed
Car has not run…or even started… in fifteen years
I’ve already dealt with waterpump/timing gears, chain/thermostat. All of that is buttoned up now.
After all of the above I gave it a try…no luck. If I use starter spray, a little pop, but not running. Next, I start with all the fuel system things I can think of.
Removed and cleaned tank
Check all lines…fixed what was required
Previous owner used an electric fuel pump…but, I’ve gone back to a new mechanical pump
Last thing is the carburetor and that’s where my questions are coming from. Carb is not original…it’s a Qjet 7042202…( I think that’s a 1974, and I understand it was off a 350 that was in an El Camino…but that info is sketchy at best). I bought a rebuild kit and have finished that. New idle tubes, float, needle and seat, valve ball…I guess that’s all the usual stuff. Everything went together well except for the choke pull off and associated linkage. (I have this uneasy feeling that I’ve screwed something up with that (more later). One issue is that I have the chassis service manual for the car (66), but not for this specific carb (74). That’s a little frustrating…I did buy Cliff Ruggles book on rebuilding q-jets.
Put the whole package back together. Started up perfect…2-3 seconds and she was purring! Driven about 40 miles (first miles since 2002) and seems pretty good. Starts perfect hot or cold. Idles well…
However, I swear I don’t think it’s ever getting on to the secondary’s. Looks like to me the choke pull off is working and is not holding back the secondary lockout (sorry I’m not sure of my terms here), but after warm up, and sitting in the shop, no amount of throttle causes the secondary air flaps to open?
Lastly, I chose to rebuild the carb because I like the challenge and I love learning about what I’ve got. However, a new/rebuilt carb is always an option. Not sure which way I would head with a new carb. Match the 74 that’s on it now, look for an original from 66, go in a totally different direction?
Sorry for the long post, curious if anyone has any thoughts.

 

Welcome. Your carb number interpretations are incorrect. The third digit is the decade (4 = 1970s). The FOURTH digit is the year (2 = 1972). The last three are the application (202 = Chevy 350 from a multitude of different applications, including Corvettes).

In any case, the Qjet is a VERY forgiving carb. While it won't be optimized, it WILL start and run on your car just fine.

And they won't. More people worry about this unnecessarily than nearly any other problem on Qjets. The secondary air valves are opened by mass airflow through the carb. They will NOT open if you are simply revving the engine in PARK. There isn't enough load on the engine then.

Now, if you really believe the secondaries are not opening while driving, there are a few potential issues. The one I would be most concerned about is the choke linkage. The 66 Olds divorced choke coil is NOT the one this carb was designed to use. It's very possible that the choke is not unlocking the secondary throttle plates. I'm not familiar with this particular carb, but most Chevy application Qjets use a lockout on the actual secondary throttle plates in the throttle body at the bottom of the carb. This is unlike most Olds Qjets from the 60s and 70s, where the choke operated a lockout on the secondary air valves at the top of the carb. Look for a feature like this on the passenger side of the of the carb aft of the choke mechanism. With the car warmed up and the choke plate fully open, the linkage must clear like this.



The other potential problem is an incorrectly adjusted air valve wrap spring on the secondary air valves.

 

Good advice from Joe. I even put a Q-jet on a ford 302 using an adapter plate. It ran like a scalded dog. Better than the Hollie I pulled off and threw away.

 

Morning Joe,
Thanks for your thoughts!
I don't think it will matter but I miss-typped my carb number ... actually 7044202...

Had a feeling the air valves wouldn't open in the garage...thanks for confirming...I feel like such a newbie! And thanks for your patience, I'm getting into places I haven't been befere, no doubt most guys on this site can't remember how confusing that can be.

I'm aware of the lockout..yes, it's definitely on the lower/passenger side of my carb. this is the area of my concern. Just lack confidence that all of the linkages in this area are back where they belong...maybe they are. Is the air valve wrap spring the same as the air valve door spring. I've seen it listed that way somewhere. If this is the spring on the air valve shaft...I didn't remove during cleaning, so I can look at this and check how to calibrate/adjust.

thanks again

steve

 

In that case, yes, that is a 1974 Chevy 350 carb. Note that a 74 carb will be jetted for emissions, not performance. It will also have additional vacuum ports for functions such as EGR and evaporative canister vent. Just cap these, don't try to use them for vacuum advance.

My money is still on the choke and associated secondary lockout adjustment as the potential cause of a problem.

 

Can you post a picture of your pull off linkage? You mention you weren’t positive about the pull off and linkage. We get plenty in our shop that have been installed wrong and the air valves won’t open. That may be your issue.

 

This is last night after warming up.

 

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