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I find it really unusual for a Lars rebuilt carb to have any kind of a problem. He's been at the rebuild game for way too long with way too many happy customers. That said, I'd really look hard at something acting on the throttle system. IT's got to be hanging up on something. Even possible the carb pad is warped bad enough when you torque the carb mount bolts it's twisting the carb and making the throttle hang.
Lars did an impeccable job with the rebuild. I think this one is a failed gasket or a poorly fitted gasket causing a huge vacuum leak or a stuck primary or secondary.
I will be working on it tonight!
Man standing on a corner in a trench coat on a dark rainy night. Psssst- psssst. Hey buddy! Come-meer. Wanna buy a Holley? Opens his trench coat and flashes some 4150s (among watches). Go for it Boomer.
I seriously doubt if it's the rebuilt Qjet. Something is binding somewhere else. Maybe the carb base bolts are not evenly torqued causing a problem with the butterfly shafts.
A Holley is not the solution here. Something is not installed correctly.
I guess you are nearly flooring the gas pedal to set the choke on cold start up? I am wondering how it goes to full throttle unless you do that. If the throttle stays wide open after setting the choke, then don't start it, go disconnect from the carb. See if it bounces back. I have seen rod type throttle linkage hang up on plug wires, etc. I can't remember if the 69 Vettes had them.
I fought a similar weird and random situation on my 65 Impala. The rod type throttle linkage was fine. I finally figured out that the pedal was hanging up on the rubber pad that goes around the base of the column at the firewall. I had to cut part it off to keep it from happening.
Last edited by Scott Liggett; 07-09-2019 at 05:18 PM.
A vacuum leak is not going to cause the engine to rev to 5000 rpm. Remove both the throttle cable and return spring from the carb and see what is binding and where. Also, since you have an auto check the kickdown cable for binding or interference. It could also be the throttle cable itself binding internally.
Last edited by CanadaGrant; 07-09-2019 at 06:52 PM.
The throttle is snapping back closed with no springs hooked up and the cable disconnected. There seems to be zero binding or hang-ups with the action. The primaries opened as expected and the secondaries open once the choke was fully opened (as designed).
I took a straight edge to the bottom and it was perfect.
The pictures attached are of the three gaskets. The one with my two fingers COULD be a vacuum breach, as it is a different color. Thoughts????
If you're confident the carb is fine, go ahead a put it back together. Sounds like it is. And it looks fine. You are using three carb bolts and one carb stud? Is that the norm? IDK. I don't have a QJ.
Maybe CanadaGrant is on to something, "kicking" around an idea.
And I vote No on the vacuum breach. I believe that color reflects on how much heat the gasket receives there.
The throttle is snapping back closed with no springs hooked up and the cable disconnected. There seems to be zero binding or hang-ups with the action. The primaries opened as expected and the secondaries open once the choke was fully opened (as designed).
I took a straight edge to the bottom and it was perfect.
The pictures attached are of the three gaskets. The one with my two fingers COULD be a vacuum breach, as it is a different color. Thoughts????
Is the fast idle screw (top right corner) holding the throttle too far open?
Reassembled everything and took a deep breath. Here is the result!
I am a person who likes concrete answers. Found nothing to fully address what was happening. Fingers crossed all is good. Much better than 5,000 RPMs upon start.
That;s true.
But, on the other hand, he had the carb off, and linkage disconnected. Now it's different than it was in the beginning of the problem. Maybe that's all it took. Maybe not.
I will start it again tomorrow and see how she is. If all is good with some rev's in the garage, I will take her out for a spin... with one hand on the key.
07-09-2019, 07:51 AM
