Newby 69 C10 stepside

[sfcharr]

Need some advice. I recently purchased a sweet 69 stepside with a 283 SBC from a 67 chevelle. I'm having drivability issues with either the Holley carb or the HEI vacuum advance. I set the idle and adjusted the fuel mixture on the carb. It doesn't seen like I'm getting any vacuum for the distributor from the carb. any ideas?

[68anniversary]

Have you tested the vacuum port with a gauge? If you are getting vacuum at the carb then maybe the advance diaphragm is bad? Make sure you have the line connected to the right port on the carb.

[VA72C10]

also maybe the power valve in the holley?
what's the advance at idle with it unplugged and then with it hooked up and revved up?

[Dads69C10]

Welcome. Once you figure out the problem be sure to post some pics of your truck

[68Stepbed]

Keep in mind that carbs have ported and nonported(full vacuum) vacuum ports. The ported vacuum is what is used for vacuum advance distributors. There won't be any vacuum at idle. The port you should be hooked to is on the side of the metering block a little over halfway up on the passenger side.

Does the truck run ok, or is there a problem?

[sfcharr]

Jeez, thanks for all the responses! Yea the vacuum is hooked up to the port on the metering block. I messed around with the idle mixture screws a little the other day and it improved the driveability a lot. I need to get the vacuum gage and maybe a vacuum pump to check the advance. The truck seems to fall over itself at part throttle. It idles fine, and sounds real healthy when you hammer it. But that's not the way to drive this old truck.

[68Stepbed]

Does it have a very rich idle? If so, check the power valve. It sounds like you have a lean condition. Yes, get a vacuum guage. Most Holleys come with a 6.5 power valve. That works fine on a cammed up engine with low vacuum signals, but not so good with stock engines. Find out what your highest vacuum reading is, divide by half and get the power valve closest to that number. For example: 20" of vacuum divided by 2 = 10. That means you would need a 10.5 power valve.

The power valve opens during vacuum signal loss. The higher the PV number the sooner it will open and enrich the transition circuits.

Also, buy some literature for Holleys. They are invaluable when tuning a carb.

[sfcharr]

Ok, what i discovered is that # 3 plug is not firing. Wire checks out fine, plug checks out fine. It has a HEI distributor. any ideas how to trouble shoot this distributor. I have a multi-meter.

[68Stepbed]

Could just be a bad terminal in the cap. Also, a wire can somtimes show to be good, but it may have a weak section in insulation and grounding out. I would try a new cap first though.

[VetteVet]

Here's a great holley site---http://www.67-72chevytrucks.com/vboard/showthread.php?t=230964

[sfcharr]

Turns out the contacts in the cap were burned up. I believe this was interrupting the spark. I will know for sure Saturday when I replace cap and rotor.

[jim zag]

Turn the idke mixture screws in until they bottom out and then turn out 1 1/2 turns. This is a rich starting point. I usually end up at 1 1/4 turns out. Adjustment less than one turn out usually results in off idle lean condition. Make sure the accelerator pump cam arm adjustment has no slop at idle.