what's in a 3a carb rebuild kit?

[dlb]

been slowly working through diagnosing my stock carb's bogging/backfiring on hard throttle when cold. i had checked the float level when i first got the car and it was perfect, but while trying to figure out this problem i checked it again and now the level is so low that i can't see it, even when parked on a decline (nose pointing down). i figured i will have to rebuild this one but want to make sure a needle valve, seat, and float come in the rebuild kit. i tried looking up a list or close up pic of the contents of a rebuild kit but no luck there. can someone in the know tell me if those particular parts come in the kits?

[irowiki]

There's no float valve. What's the needle valve and seat look like?

Here's my kit:








Let me know if you want me to root around for anything specific!

[larry mcgrath]

DLB, the float is'nt included in rebuild kits, it must be ordered sepertly. Carbs have a alumnium tag that is on one of the screws that hold the air horn onto the float boal -it's usualy a triangle shape with numbers that a parts guy can order you the proper float. Irowiki the nedle and seat are the 2 brass pieces in plastic bag on the right. Larry

[Petros]

you always get a new needle valve and seat for the float in a kit. That is what is in the square bag in the picture between the accelerator pump plunger and the base gaskets. it is rare that a float goes bad, it is routine to test it so you know it floats in gasoline however.

DLB, It is possible that your float bowl is over filled and making it run rich, that is why you can not see the level through the site glass. It is more common to have them leak and allow overfilling than to have it stuck shut. If was stuck such and not supplying enough fuel it would not be able to be driven, no acceleration at all. Usually it would just be fuel starved. I suspect it may be over filled if you can not see the fuel level, which would give you a rich run condition.

[dlb]

great, thanks gents. i guess i'll do the rebuild and see if it needs the float then.

i don't think he sight glass is overfilled. i have tested it on level ground, incline, and decline, and can't see any fuel level on any of those. also, the car is bogging and backfiring through the intake on cold, hard throttle but the timing is correct so i think the backfiring points to an overly lean condition. a correlating note is that if i hold the choke closed just a bit when i goose it while cold, it does not bog and backfire. i adjusted the choke but it didn't fix the problem. i replaced the fuel filter and blew the fuel line out with compressed air, and checked all possible sources for vac leaks but the problem remains. i had checked the float level when i got the car and it was fine but now it's gone. my guess is that the float or needle valve and seat are not keeping enough fuel in the bowl for cold, hard throttle conditions so when i goose it then, it runs out of fuel, gets too lean, and backfires. that's my guess but we'll see.

[larry mcgrath]

dlp, my computer wont allow me to access the FSM but it seems to me you can adjust the length of the linkeage to the accelerator pump for a longer stroke,which will add more fuel to the engine ,which will help get rid of your flat spot Larry

[Jarf]

DLB - try crossing #2 & #3 spark plug wires, fire it up and blip the throttle a couple of times.
It'll back fire up through the carb and blow out any crap that is blocking things up, kinda like sneezing.
If it runs good (after correcting the wires), you will know that you have contamination in the fuel system - usually rust silt from the tank.

[dlb]

dlp, my computer wont allow me to access the FSM but it seems to me you can adjust the length of the linkeage to the accelerator pump for a longer stroke,which will add more fuel to the engine ,which will help get rid of your flat spot Larry

thanks larry. since i know the float level is a problem, i'll fix that first but if it still bogs/backfires, i'll look at adjusting the accelerator pump linkage.

DLB - try crossing #2 & #3 spark plug wires, fire it up and blip the throttle a couple of times.
It'll back fire up through the carb and blow out any crap that is blocking things up, kinda like sneezing.
If it runs good (after correcting the wires), you will know that you have contamination in the fuel system - usually rust silt from the tank.

haha, i've got more than enough backfiring as it is! i've already replaced the fuel filter and blown out the fuel line but that didn't change anything. that and ignition timing were my first thoughts but no dice. it's been a tricky devil to track down. i'm confident i'm getting there, though.

[marlinh]

Good luck with your diagnostics, David. I don't think you'll need a float, but if you do, I have several parts carbs around that I could rob.

[Petros]

your low speed idle jets might be cruded up, just rebuild the whole carb and make sure all of the passageways and jets are clean.

[Jarf]

DLB - out of curiosity, have you checked cam timing? I once (and only once) paid a garage to replace my belt (was middle of winter and I got lazy).
Thing wouldn't run worth a darn when I got it back and sounded a lot like the issues your having, in the end, cam timing was off, correcting that fixed all my issues.
My experiences with stuck floats/flooding have usually resulted in stalling at idle.
If it's really running rich, plugs would be carbon fouled and the tailpipe super sooty but am sure you've already checked those out.
Good luck with it, I hate those mysterious types of problems,very frustrating.

[dlb]

hey jarf. i did check the cam timing when i checked the condition of the timing belt, but i haven't checked the spark plugs. i just replaced them so they should be a good indicator. thanks.

little update on this: i was doing some other work on the car today when i looked at the float glass again today. the level was back in the correct range! i started the car up and it idled great. i stomped on the throttle, no hesitation, but then the idle dropped. stomped on it again, bogged and died. got out and looked at the sight glass. empty (or possibly overfull) again. for now i'm just going to remove the carb top and see if there's anything visibly wrong in the float bowl. i have a parts carb i can cannibalize if i just need the needle valve, seat, or float. thanks for the offer though, marlene!

[marlinh]

Maybe you have some fuel starvation problem. Bypass the fuel system by running a fuel line from the inlet side of the fuel pump into a jerry can or something similar. I am sure you replaced the filter, maybe the tank is contaminated...

[rer233]

Old antifreeze jug works real good-position it between the dizzy and booster- you can close the hood and drive the car.

[dlb]

pulled the top off the carb tonight and found the float bowl was full of crud.



cleaned all the crap out and then swapped the needle valve and seat with the ones from my parts carb. the seat came out of the parts carb easily but the one in the project car was a ******* to get out. it was really stuck in there. i wound up tearing the soft brass apart and had to cut deeper slots into the seat with a hack saw to get enough purchase with the giant screw driver. finally got it, or at least the bottom half! the screen at the top was still stuck in there. here the two seats are side by side, good one on the left.



this pic is really dark but you can still see how i mangled the bad seat.



scraped a bunch of corrosion away where the seat was in the carb top and messed around with a tiny screwdriver for a while. finally dug the dirty old screen out.



meanwhile, in the float bowl of my parts carb, a dead bee has been hanging out for a few years, at least. i have no idea how it could have gotten in there.i only took the top off tonight.



i tested the float from the project car carb and it seemed fine. i neglected to check the clearance between its tab and the needle valve ball though. i put the carb back together, started the car, and all was well for a minute. the level stayed in the right spot and the carb didn't bog, backfire, or die when i gunned it while cold. but then it started to act up again, so i looked at the sight glass, and once again i couldn't see the level. i should have checked the float tab before putting stuff back together but oh well. it only took a few minutes to pull the top off so i'll do it again at some point this weekend. or if the fuel level comes back to the sight glass, i'm going to start the car and watch the level while i play with the throttle to see if it goes up or down. this is fascinating.

jarf, i checked the plugs and they're black as night. however, i've only been running the engine for a few minutes at a time and then letting it cool off again, plus i'm pretty much constantly giving full throttle, so i think that makes sense. i've been doing this for a few weeks while trying to beat this issue so i feel like i should wait until i do a bunch of regular driving before using the plugs to diagnose anything. not sure if that's logical or not but it seems like it to me.