Carb Question

[Dave K.]

Running the stock 2 barrel on my 68 K10s 307. Rebuilt it and it was running well albeit not super super smooth under load. Got the timing dialed in I believe to 2 BTC per the engine bay sticker. Went to recheck the mixture and I could bottom one needle without it starting to die. Getting some backfiring now as well. The problem that prompted me to putZ with it was it would die at a stop sign.

Ignition has been switched over to Pertronix.

Ideas on the carb and mixture?

Thanks, Dave

[toolboxchev]

Insight from the people around here on stock small block lead me to 14 degrees of initial timing, then vacuum advance timing, then total timing.

Then dial the carb.

[LongBox]

Did you bottom out both the idle mixture screws, then back them out an equal amount? It sounds like you have overly rich on one side, and lean on the other.

[geezer#99]

X2 on the timing.
Set your initial at 12 degrees. Unplug and cap off the vac line to the distributor when you set it. THen hook the vac back up.
Then turn down your idle and adjust the mix screws.

[Dave K.]

I turned them in one at a time--the left hand one bottomed out and there was no change in the engine--no bogging down or stumbling. The right hand screw didn't bottom out before screwing it in caused the engine to stumble and spit after which I backed it out. This difference had me curious.

I'll re-check the timing this week but I drove it yesterday first thing and didn't have any problems--later in the day I drove it again and it started dying when I came to a stop. Pull out the choke and pump it and it would re-start. Without the choke it would not start, just cranked. After finding this I started putzing with the mixture screws and found the above mentioned condition with the left hand one (as you look from the front of the truck).

Note that per the original post it never seemed to run super smooth when accelerating. Felt a little rough which made me believe either a timing or perhaps even an overly rich condition....

Note as well no real evidence of the float setting being an issue--at least nothing indicating it was set to high for example.

[LongBox]

OK. With the engine not running, you should screw both mixture screws in till they bottom, then back them out whatever the specification calls for on your application. They should be backed out equally. After that, and with the timing and idle speed set to specs, you do a fine tune on both mixture screws. If you do not have to go through smog check, just set them for highest idle speed, then adjust idle down to speck and repeat the process.

[geezer#99]

Originally Posted by Dave K.

I turned them in one at a time--the left hand one bottomed out and there was no change in the engine--no bogging down or stumbling. The right hand screw didn't bottom out before screwing it in caused the engine to stumble and spit after which I backed it out. This difference had me curious.

I'll re-check the timing this week but I drove it yesterday first thing and didn't have any problems--later in the day I drove it again and it started dying when I came to a stop. Pull out the choke and pump it and it would re-start. Without the choke it would not start, just cranked. After finding this I started putzing with the mixture screws and found the above mentioned condition with the left hand one (as you look from the front of the truck).

Note that per the original post it never seemed to run super smooth when accelerating. Felt a little rough which made me believe either a timing or perhaps even an overly rich condition....

Note as well no real evidence of the float setting being an issue--at least nothing indicating it was set to high for example.

It runs rough due to lack of timing.
And your lack of timing makes Your mix screws not react because you have the idle turned up enough to allow it to idle which totally exposes the idle transfer slot and you're idling on the power circuit. A side effect is it runs rich. Nothing wrong with the float.

[Dave K.]

Thanks everyone. I will revisit the timing once again before putzing with the carb further. I don't have a tach so can't nail down the RPM 100%. Would be great if there was someone in the Milwaukee, WI area who knew their stuff on this front, would save me a lot of hassle but I know I need to perfect skills on this front anyway....