Stumble at low rpm in gear.

[Isaac nickerson]

Hey guys, was driving my k10 around today with a sbc 350 with a 4160 carb when it started to stuble after shifting gears. I would start from first, go a little, give it some more gas, then it would bog down. this was not happening last night but started this morning. What do you guys think I should check first?

 

[Camar068]

I'd try the filter first, not knowing holley, may be inline or in the carb. Surely someone else will chime in

 

[Isaac nickerson]

I just replaced the fuel filter so I doubt it would be that. Anyone else have any thoughts?

 

[JeffK10America]

Have you checked your site glasses for proper fuel height .

 

[Backfoot100]

Could be choke setting, accelerator pump setting, idle mixture adjustment settings, timing, tune or any combination of them.
Need more detail.

When was it last tuned? What is the timing set at? What is the idle vacuum reading? What RPM is idle? Is there any slop in the accelerator pump arm? Is it cold or warmed up when it happens? How does it start cold and warm? How far is the choke open when its set? Does the choke open up all the way when warm? How long has the Holley been installed? How long has it been running problem free?
See where this going.....It didn't do it last night doesn't give me a whole lot to go with.

I'd be happy to give some suggestions but I need more info.

 

[potent rodent]

as said before check your float level and mostly your fuel filter how long has it been since u changed it ?

 

[Old60Driver]

If you're sure the filters are clean, I would check choke operation and linkages first. Mainly, cause it's the easiest.

Just my .02

 

[Isaac nickerson]

Just changed the fuel filter 3 months ago. My timing is correct. I tuned it like 6 months ago. My vacuum is 19 hg. Just checked the accelerator pump last night, all good with that. The choke only opens all the way when you hit the throttle. I have not been able to figure out how to stop the idle cam from sticking....

 

[Isaac nickerson]

Oh and the holley has been installed for years. I rebuilt it 6 months ago. the problem occurs when warm.

 

[Kody24]

Is your vacuum still at 19"? I've had small vacuum leaks cause a stumble. Another thing to check would be proper operation of your vacuum advance. Remember most carburetor problems are actually ignition problems. Also, does it stumble with a light throttle or if you really stomp on it or both. There are different causes for each of these.

 

[Backfoot100]

The choke only opens all the way when you hit the throttle.

This is definitely not right. I assume an electric choke?
When it's warm the choke should always be open. Not just when you hit the throttle.
Sounds like choke needs adjustment or the bimetal spring in it is toast and needs replacement.
Make sure its cold and take the air cleaner off. The choke should be open. When you set the choke by pumping the gas, it should close so its only open about 1/8". Just turn the key on but don't start it. An electric choke should then open by itself anywhere between 30 and 60 seconds.
If its not opening with the key on after being set, you need to figure out why.
Check that its getting power with the key on. Also check the adjustment. If its not getting that 1/8" crack when being set it needs adjustment.
Could also have been put back together wrong after the rebuild.
Many times the black choke adjustment cover is not put back together so that it engages with the hook on the end of the bimetal spring after a rebuild.


Check out these things and then report back.

 

[Isaac nickerson]

Thank you. Ill try that as soon as its cold. Also I went to take a look at the fuel filter and noticed this red goo inside it. Like I said i replaced it 3 months again. But could this account for my stumble? Here us a pic. and to answer you question kody24 it stumbles on both.

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[Isaac nickerson]

Is your vacuum still at 19"? I've had small vacuum leaks cause a stumble. Another thing to check would be proper operation of your vacuum advance. Remember most carburetor problems are actually ignition problems. Also, does it stumble with a light throttle or if you really stomp on it or both. There are different causes for each of these.

Also how to you test vacuum advance?

 

[Itali83]

That would be water in your fuel. You can buy a ton of filters and just run it through or drop the tank and drain it out. Anything in your fuel other than fuel will make it run like crap.

ben

 

[Kody24]

Also how to you test vacuum advance?

With a vacuum gauge and timing light. There should be a rapid drop in vacuum when you open the throttle accompanied by an immediate increase in timing. If there is a lag in the timing increase or if it doesn't increase until the mechanical advance kicks in then your vacuum advance isn't working properly. This will cause it to run at whatever your initial timing is set at until higher in the rpm range, which is way late and can cause a hesitation and loss of power when you first get in the throttle. Lots of videos on YouTube that explain it better than I can here.