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So I'm just getting into tinkering with the carb on 1972 C3. Now that I've got the timing set right, I'm trying to figure out why it still feels like it's gasping for breath, and is very cold blooded.
Here is a picture of my carb set up.
My Rochester Quadrajet carb
See the electrical device in the lower left? It has a short loop of vacuum hose to itself, and what appears to be an open vacuum port on the front.
I don't even know what that thing does, but that vacuum line sure looks wrong. Shouldn't it be attached to a vacuum source?
Can anyone please identify what that part is, what it does, and if that vacuum line is as wrong as it looks to my untrained eye?
Not sure but also looks like you might have manifold vacuum looped and attached to a ported vacuum port with the short piece of hose on the front of the carb.
Hi JJ,
That solenoid is part of the 72 TCS system. (Transmission Controlled Spark).
You can see the 2 hoses' routing and the electrical connection in this photo from the Dobbins 68-72 Fact Book.
I'm not sure why yours is bypassed ? Often people just didn't understand what they were, or how they were intended to function, so the just disabled them.
Ah, is that the gizmo that prevented the spark from advancing until you were 4th gear? I read about that. I won't mind if that kludge is disabled.
I've downloaded all 138 pages for the manual on this carb, and read all the posts I can find here about them. I've also printed the excellent timing and tune-up guide that a member created for our viewing pleasure. It has been a fantastic help.
To that end, I have reset the fuel/air mixture screws (they were set way rich) and adjusted the timing (that was way off). I now have a much more driveable Corvette.
Not sure but also looks like you might have manifold vacuum looped and attached to a ported vacuum port with the short piece of hose on the front of the carb.
I think that's an optical illusion in my first pic.
So my test drive was a success. After adjusting the air/fuel mixture to spec, and then adjusting the now-reduced idle speed up a smidge, the car runs much better. Zippier, more pep, maybe a bit less cold blooded, too.
I test drove it from 5 mph to 80 mph, sustained 80 mph for 20 minutes (God bless Texas speed limits!), and it performed much better.
Most of that carb is still a mystery wrapped in a puzzle inside an enigma, to me -- but I will happily take this small progress!
--
Jay
Quadrajet Carb Question
