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Well even in the rain I can tinker in the garage. So yesterday I was tinkering with the carbs, dual Carter AFB.
When I slow down, down shift for a corner and then step on the gas once around the corner I have a big "Bog". Like nothing happens and then it jumps. I suspect it is an accelerator pump issue. I have rebuilt both carbs and then found 'Mike's Carbs in Chehalis, Wash' who helped me with several accelerator pumps to try but still no good.
When I open the throttle I don't get any squirt until nearly half throttle. Now that's not right. I thought about changing the linkage on the pump to allow the pump to be further down at idle to be closer to the spot where the squirt starts but then the pump bottoms out before I get to wide open throttle and stops the movement.
Is the "S" linkage that goes between the pump and the arm on backwards? Can't tell from the picture. It'll go either way but the wrong way will make it bind up if I remember right.
Yes, it goes a certain way.... this shows how it should be oriented, yours looks fine to me:
Many times the bog from cruise is secondaries opening too soon, however the fact you don't get an accel pump shot until half throttle tells me there is a problem in that circuit. IF in fact the carb is getting the FULL stroke then either the plunger has gone bad, there is an issue with the check ball valve or a passage possibly clogged.
You shouldn't have to dick with the plunger height at all... Whenever you let off the throttle the check ball floats up and a metered "charge" of fuel is drawn into the pump cavity from the fuel bowl....when you accelerate the plunger forces the check ball shut and you should IMMEDIATELY get a shot of gas out the squirters to add fuel to the temporarily overly lean fuel mixture...until the air/fuel ratio stabilizes... Pretty simple.
Last edited by Frankie the Fink; Sep 30, 2019 at 02:25 PM.
I have no idea if it will make enough difference, but it sure looks like that arm needs to be turned upside down and flipped over so that the short arm part of it is at the bottom like in the picture from Frankie.
Here is a pic of my 3721SB AFB, a VERY popular service replacement carb for several years of Corvettes:
Which matches the graphic first pic in my post #3 exactly...
But, I think the later AFBs with the multiple holes for adjusting the rod "throw" are connected as the OP shows, here's another one:
Wouldn't hurt to tighten down the air horn lid either, there are fuel stains at every screw head...
Last edited by Frankie the Fink; Sep 30, 2019 at 04:11 PM.
I've had the top off a few times probably causes the stain.
Interesting, I remember replacing the check ball in the pump cavity. I wonder if it were the wrong size or something and wasn't completely closing off the hole and delaying the squirt?
I think you can do it on an AFB but you definitely can on a WCFB....you can remove the lid and with gas in the bowls operate the accel pump plunger by hand withing the range it would have with the lid on and observe things....the plunger should draw in the metered accel shot of fuel and when at its specified height and pushed firmly IMMEDIATELY start discharging through the squirters...
If your check ball is not seating you might see gas pushing back into the bowl and that is your problem...
Thanks Frankie. I did try the other pumps I got from Mike's Carbs. They were to large and wouldn't go all the way down. This pump, which I played with, like you said with the top off, appears to be the right size. I'll check on the check ball once I get the car down off my lift.
Carter AFB problems
