Carb. arrived last week. Excellent shape, all there but the pull-off for the secondaries.Already apart, waiting for a rainy day to clean-up & put together. Question for the carb. guys.: The power piston is on a coil spring & supports two primary metering rods. On the bench the primary jets are wide open. Does vacuum keep them closed, against the spring, once the engine is running?
Yes. At idle, high vacuum pulls the piston down. As vacuum drops (load increases), the piston goes up, enrichening the mixture. It's the power enrichment device.
James, Thanks for the reply. I think I'll order some literature as indicated in an earlier post. I have many more questions. i.e.: the accelerator pump seal sits at the bottom of a well. At the well bottom are a couple outlet tubes going to the primary bores. When the accelerator pump is activated by the linkage I see the rod, the spring & the spring cap moving up & down. The rubber seat seems to stay put. How is the fuel delivered ?
I highly recommend those two above-mentioned books, you'll have a TON of info in your hands with them. If you're budget-tight, get the newer Cliff Ruggles book. There's a checkball under a screw right beside the accel pump well, and another in the bottom of the well. They control the fuel inlet/outlet of the accel pump. The rubber pump seat itself should go down when the throttle is opened, pushing fuel out the nozzles/openings in the venturi bores. There's a spring above the seat because fuel doesn't compress, so that you can slam the throttles open without breaking something. If the seal isn't going down into the bore, look for a burr or something hanging it up. Dry, it should go smoothly from top to bottom without hanging. With fuel in the well, it should also go smoothly down, just not as fast as the shaft does. (Hope this makes sense.)
Got it James, thanks again. I was trying to picture the pump action without the fuel. I was not aware it will not compress, hence the spring as a damper. I've got some reading to do.
i have a 7040244 all rebuilt ready to go for a 70 350 buick, if you or anyone is interested. its currently on my 69 riv and runs great, but am replacing with correct #carb. email me if intersted. price will be right!
