Engine: 2 bbl carb and/or distributor fix???

[sals54]

I've got a friend who has 64 Lark, 259 Auto, which has a stumbling problem on initial acceleration. Its a high mileage car with other troubles, but I need to help him without spending too much. I know the carb and distributor could both use a complete rebuild, but with limited funds, he's looking for the easiest fix. I have suggested a carb rebuild, but he's hesitant to spend too much on a professional rebuild. He says when disconnecting the vacuum advance, it runs a little better. ( as I wrote this, I just realized I need to check the diaphragm on the advance... duh ) But assuming that its OK, I'm wondering about a simple carb kit rebuild without having the shafts done. I suppose a kit would help regardless, but which is going to help the most? Carb or Dist? I would like to give him the most bang for the buck. Thanks in advance.

[jlmccuan]

Maybe just popping in a new accelerator pump. Should be in a basic carb kit. Pictures as you take apart. Carb cleaner in a can and back together may get him going.

Hope this works as I owe you one.

[mapman]

Sometimes it will clear a plugged passage if you just take the mixture screws out and blow them out with a little compressed air. I think you are on the right track with the accelerator pump and distributor vacuum advance too.
Rob

[sals54]

Thanks guys, those things would certainly be done with a carb kit, but I guess my main concern is being as sure as I can that the carb and not the distributor is the place to start. I suppose the carb would be my first guess, but its not my money this time. He's a great old guy, just a bit persnickety.

[Dan Timberlake]

I'd use my timing light and mity-vac to test the vac advance on the car.
I'd go thru the tune up procedures in the shop manual. Lots of check, clean, and adjust, and not too many R&Rs
I'd look down the carb throat while slowly working the carb throttle linkage and watching for an immediats squirt of gasoline when the throttle is opened from idle

[Clem64]

Does it still have its original Prestolite distributor? How many miles are on the engine? Many of those Prestolites were troublesome in 63-64. The mechanical advance system was well worn at 30K and shot at 60K. Find someone with a distributor machine and spin it up to look for irregularities. From your description, that's where I would begin troubleshooting. Good luck.

[BobPalma]

Check the PCV system, too, Sal. Cheap and easy to correct if the valve is plugged (high miles, you said), vacuum line broken, internal ports in the carb base plugged up, etc. The engine needs the proportion of air that is supposed to be coming from that system. BP

[Mike Van Veghten]

Hey Sal -

Sounds like it could use a good carburetor cleaning in any case. The "kit" shouldn't be too expensive, but the proper cleaner could be a little costly. Split the cost with him and keep the stuff.
As others have mentioned, sounds like ....
1. bad accelerator pump
2. incorrect idle mixture setting
3. low float setting
4. low initial timing (the vacuum advance isn't working to a positive manor during acceleration..!)
5. plugged (partially plugged) passages in the carburetor
6. corroded plug wire connections, corroded tips inside the cap...

Good luck.

Mike

[gordr]

What the others said. A stumble on acceleration, if it can't be traced to a weak or missing accelerator pump shot, is often caused by the vacuum advance unit not working. If you have an advance timing light, you can check initial advance, total advance (mech. + vac.), and mechanical alone (check at 2500 RPM with the vacuum line disconnected.

Wouldn't hurt to check engine compression and vacuum first. This is a tune-up issue, and you can't do a good tune-up if the engine is unsound internally.

[sals54]

Thanks again guys. Its pretty much all of the above. I checked the vacuum advance and its very stiff. Does not move unless extreme pressure is on it.
While reading the timing light, the advance does not even move until rpms jump to almost 2000.
The accel pump is not being actuated until the throttle rod is moved almost half an inch. The accelerator pump is also barely pushing fuel into the throat when activated. The linkage is very sloppy. It acts as though its sucking air through the shaft cuz when the throttle linkage is moved slightly, it already bogs before the accel pump can even be activated.
We're going to get together again this week and see if we can free up the advance weights, tighten up the accel pump linkage, and see if I've got a vacuum advance to swap out for him.
I'll report the results later this week.
Again, thanks guys. I hate working on other peoples cars during the troubleshooting phase. I would just replace the carb with an Edelbrock, switch to cable throttle linkage, and shop out the distributor for a good working one. Not so easy with someone else's money.

[jlmccuan]

Sounds like the advance plate in the distributor is sticky. The accel pump is definately out of adjustment. Do you get any fuel sprayed in when it does take up all the slack?

[sals54]

Jim
Yeah, it gets a small amount of fuel, but not nearly as much as it should. I'm certain the squirters are clogged a bit. All the holes in the linkage are oversized from excessive wear, so at 4 different places in the accel pump linkage, they're all sloppy. I'm hoping that a band aid will help make the car more enjoyable to drive for him. He's starting to have health problems in his age, so driving this would be nice therapy for him.