Having trouble "dialing it in" HELP!

[nejeff]

Hi,

I'm a novice at these things but I pride myself at figuring these things out. Can't do it this time. Here's the story:

Put 307 in my 72 and did the following:

Changed plugs .035, New wires + cap, condenser, rotor + points new, rebuilt 2-barrel out of the box.

I set the dwell at 30 and the timing at 8 btdc but it is still acting like it's getting too much gas and feels like it's just a screw turn or something away from running good. It feels like it's being held back some. Some hesitation and a little backfiring.

I have adjusted only the idle screw on carb.


What's the proper way to get this baby tuned? What am I missing here?

Thanks guys

[ddsmith]

If you feel the distributor is adjusted correctly and you said the carb is a rebuilt 2 Barrel. I would suggest adjusting the idle mixture screws on the carb. Try using the info at this link for the adjustment. http://www.gmcpauls.com/Tech%20Tips1.htm go to the page where it talks about vacuum gage use then read down to the part about idle mixture adjustment.

[Locutus]

I notice he says 17-22 is normal. I assume this applies to stock motors? What about a 284 duration cam what would be normal?

Mike

[ddsmith]

If you look at the information it says that a reading that is steady from 10-16" may be caused by a big cam. Low vacuum reading are an expected outcome of a big cam and I think it is the overlap that causes the low vacuum at low rpms.

[cdowns]

i'd go with a little more dwell 32-34 and open the plugs to 38-40