I recently discovered that my stock 71 350 4 barrel Rochester carb had a broken front choke pull off. The spring and housing was laying on the intake. Before I ran the engine I plugged that port with a vacuum cap. Outside of proper choke function which I know won't happen until I replace that pull off, is it OK to run with that port plugged? I figure once the engine is warmed up it doesn't matter. But I'm new to this divorced choke concept.
The choke pull-off uses engine vacuum to put the choke plate slightly open against the choke spring so that it will have an air gap and stay running after initial start. If your car runs without it, your choke probably doesn't close all the way to begin with. If this is not an issue, don't fix it.
The primary choke pull-off needs to be in place an operational. It does double duty, unloading the choke quickly on cold starts, and holds the secondary airflaps tightly shut during high vacuum situations. It will dampen the secondary opening slightly to help prevent stumble/hesitation/bog when going quickly to full throttle........Cliff
Choke plate should be held open firmly while driving or it can swing partly shut and cause rich mixture as air rushes into the air horn. Fix it, or wire it open. Never let it swing loose while driving.
I removed it completely from the Q Jet on the Riv. makes her a little cold natured but fine once warmed up.
As Cliff stated, this part performs double duty. When correctly installed, it allows complete control of the air valve when the secondary throttles are requested. Without this set up, I have seen these valves snap open at full throttle, then , when the engine bogged from the suddenly lean misture, they snapped shut, causing significant "changes" to the normal secondary transition. I have seen this situation even with the choke pull-off installed, but defective, and the customer's only complaint was cold flooding. Just a heads up. When this issue was properly addressed, the customer was amazed at how much more civilized the engine performed.
The front pull-off is required to dampen secondary opening slightly. I've seen some folks not use one, and in almost all cases they have to wind the secondary shaft spring WAY too tight, and they still have some noticable stumble/hesitation/bog going quickly to full throttle. We make and sell an adjustable pull-off for the early model q-jets, so the tuner can time the opening rate for perfect transition onto the secondaries. This allows for a lot less tension from the spring, and smooth transition onto the secondaries with good traction (drag racing)......Cliff
Great info everyone I really appreciate it. For moving the car around the garage & driveway I'm alright but I plan on replacing this piece for the road. I found one online for $10 so thinking about ordering that.
Think this will work on my stock 71 350 4v? It says it goes to 1970 but it looks similar. http://www.ebay.com/itm/Carburetor-...ies&hash=item35cba205c4&vxp=mtr#ht_1221wt_647
Thanks for everyone's input. I installed the new choke pulloff, and everything is running smooth now. Tested it this a.m., let it idle until thermostat opened and the choke got "pulled off", took it out for a rip, chirped a few gears, came back, set my idle speed to 850rpm in neutral since it's a manual trans (last spring I was messing with the carb and turned the idle speed screw on the primaries in a little) but now that is set back to what works good. Turned the motor off and it shut off right away, no more running-on!
