Hey all, thought i'd ask around but i'm having issues when slowly raising rpms. What seems to be happening is when I slowly raise the rpm's from idle once I get around 2000 rpms the whole thing tries to die, in that the rpm's drop super quickly and I have to catch it either with the accelerator or the choke. Anyone know what it could be?

My suspicions currently:

1. A valve in the carb isn't opening at the right timing because it's clogged or something like that.
2. After reading some other problems posted here that seemed related it might be my fuel filter?

Any idea's are greatly appreciated! I'll try to answer any questions if people need more context!

 

Have someone do this and take the aircleaner off and see if the primaries are getting fuel. Up to about 2000 rpm its running mostly on the idle circuit. Also does it only do it when you slowly raise the rpms?

 

Yea it's only when I slowly raise it. If I floor the accelerator I can blow right past 2000 rpm and hold it above with the accelerator. But when I apply the accelerator slowly it seems to cut out around that 2000.

 

Alright, took a while, apologies, but I did what you said t_g_farrel! This problem over the last couple weeks has gotten better and I can raise the rpm's past 2k easier now, but it isn't perfect so I'm still digging into this (maybe i'm just used to newer cars?). I also did a couple other checks as I've started reading more about this carburetor and the stock configuration. So I have more info!

1. Got a partner to help, Looks like the primary's are getting fuel, so that's awesome. Although it seems to happen later in the RPM's than I would have assumed? I couldn't see the RPM gauge so this is more of a guesstimate through conversation but it seemed to only fire fuel at just past 2k rpm (2250-2500ish). Question, at about what rpm should the primaries be firing?
2. I don't think the secondary's were opening at all, as I watched a few youtube video's I realized I had disconnected my secondary linkage. Re-hooked that up, but the secondary's still don't open. As I've continued reading I've learned this is vacuum controlled so I took some carb cleaner and sprayed it around the rats nest and other tubing looking for leaks. Nothing immediate but I could probably be more thorough here if I need to revist.

Like I said before though, the whole thing seems better. I haven't tried this under load yet, have the car on jacks after an engine rebuild (didn't do the carb as I remember it working seemingly fine before), but hopefully I can fix this before I do as that 2k rpm would be about the target of me putting it into gear from a stop

Only other thing I can think of through my research to check is maybe my fuel filter? But since gas is getting to the carb I'm assuming that's fine?

 

If it's associated with a constant honking sound (or "ooolooloolooloo") on idle, then it's probably the shutter valve. You can test for this by plugging the hole with your thumb in the air cleaner. I blocked mine off as a "bandaid" (almost ten years later I still haven't fixed it) but still suffer from dying at 2k if I gradually apply throttle. I always have to blip to save the idle. If you don't have that sound, try plugging it regardless. Or soapy water and spray on rubber vacuum lines to test for vacuum leaks.

 

Accelerator pump is bad ... Also secondarys only open under load. Clean the carb using ultra sonic after taking it completely apart.

 

Ok getting back to this project, been busy

Thanks for the suggestions ya'll. I'll check the shutter valve like mentioned. It's not making a constant honking sound on idle but it can't hurt to test it.

I'll also look more into the accelerator pump. I did notice the last time I was messing around with the car it had some freeplay in the accelerator pedal so i'm going to try to fix that first before blaming the pump fully, but ya'll are probably going to be right here. Will try to report back as I can and get things done!