Need a Few Pointers/suggestions

[Shane]

After stumbling around for the last 3 weeks to a month, and dealing with a ton of minor problems and one major electrical one, My baby is running good...(except for a blown convertible top motor, but i am not thinkin about that)...

I had the bright idea of coming home and setting the cars timing to 0 on the timing mark and on the advance on the timing light....I figured I would go from there....I did so and set the idle to 700 ish and life seemed good! but as soon as I touch the gas peddle, the idle jumps up to 1800-2000 and stays there..If i try to adjust, it stalls out...

I have a 340, not bored out, with X heads, purple cam, 600 double pumper holley, windage trays, headers, msd igniton, everything else stock...

From reading on here is it possible that I HAVE to have a little bit advanced timing for the car to run right?? If so what would be a good starting point?


I am very new to this stuff so suggestions are greatly appreciated!


Thanks,

Shane

 

[edbux]

I'd check your throttle return spring or look for some sort of binding of the throttle. A weak spring can cause what you're describing. I always go with two springs. Also, you might look at the throttle cable, see if needs adjusting. It took me 50 years, but I eventually learned to look at the simple things first.

 

[340sFastback]

Disconnect your vacuum advance if you have one and see if that makes a difference.

 

[C130 Chief]

With your combo, Id try 10 degrees BTDC at idle. Set with the vac advance line removed and plugged.

If you cant get the carb to idle at 850 RPM without a vacuum signal coming from the ported outlet, you will need to open the secondaries a little bit. That is, the vacuum port on the right side of the primary metering block should read zero when you connect a vacuum gauge at idle. (This is the port the vacuum advance should be connected to. If you are getting a vacuum signal here, your throttle blades are too far open.)

 

[Shane]

Ok thanks for the idea...I will have to go tinker around with this for a bit, and will let you know...or ask some other question!

Thanks,

Shane

 

[Shane]

ok i just want to make sure I have the basic ideas right before i spend the afternoon setting the car up...

When you say the vac advance line removed and plugged...I unplug the vac line from the distributer to the carb and plug that line?

Do I also plug the inlet on the carb, or do I leave that off?

If my throttle blades are too far open, how do i go about adjusting them?

 

[yellowdartdave]

Sounds like your partially running on the main circuit as well as the idle circuit to keep it running. Then you barely touch the throttle and it revs way up.
Not getting enough airflow (Vacuum Signal)for a correct fuel/air mixture at idle. To compensate you then crack the throttle plades open a bit for more air and that messes everything up. No matter what you do with the idle mixture screws, it does not help??
Had the same problem on my car. .508 cam, headers and the stock Thermobog. Ended up drilling a small hole (1/8 inch) at the front of each primary throttle blade and it helped a whole bunch. Went up to a 3/16" and it was perfect. Car now idles all day at 800 rpm and when I nail the throttle there is an instantaneous sound of spinning tires followed by the great wail of a Thermobog trying to suck in the hood.
Hope that helps.

 

[C130 Chief]

You can leave the line connected to the carb, and pull it from the dist. Stick a golf tee in the line to plug any possible vacuum leak. No need to plug the advance can on the dist itself.

With the engine doing it's high idle thing, just pull this line from the dist and cap it with your finger tip. If the idle drops, thats your problem.

I bet if you advance to 10 degrees BTDC you will be able to close the primary throttle blades enough to make this problem go away.

Don't even think about drilling throttle blades on a Holley. Thats pure hackery. Holleys have secondary idle stop screws (as well as secondary idle circuits). If you don't have a manual for your carb, go download one from Holley.com. Lots of good info there.