oamhmad

iTrader: (1)

Chevy Goodwrench 350, Edlebrock intake, new Holley 600 CFM carb, vacuum advance distributor.

I've got about 19" of vacum at idle but the gauge needle drifts between 18 and 20. Vacuum gauge is hooked up to a full-manifold vacuum port on the carb. All other vacuum ports to the carb and manifold are plugged when I'm testing this. I have not unplugged and isolated the PCV port yet though.

This is on a new crate motor with less than 5,000 miles on it. It always did this right from the very first time i started it up. I chalked it up to an intake gasket leak since the intake I used during the swap was old and didn't have the best sealing surfaces, and I was starting to notice oil around some of the intake bolts.

Well, I bought and installed a new intake and gaskets and absolutely nothing changed. (no more oil though)

I also have an AEM wideband hooked up and it also fluctuates quite a bit. At idle it's between 13.2-13.8 with a spike to 15 or so every now and then. If I set the idle mixture to 14.6 then the spikes are more frequent and get up to 16.5. It really sounds like its misfiring randomly at this point and if I let it idle like this long enough it eventually dies. So I've got the idle mixture screws set rich to about 13.2.

Timing is set at 15 degrees initial and 36 total (with advance disconnected), all in by 2700 rpm. I'm testing the vacuum with the vacuum advance disconnected and plugged. The timing is dead steady and does not fluctuate.

The vacuum only fluctuates at idle. Anything above idle and it's rock steady and acts completely normal. The plugs all looked normal when I pulled them, just slightly tan.

I haven't bought new plugs, wires and cap yet because all this stuff was brand new when I installed the motor and it had the problem even then.

Any ideas? this has me stumped. I thought the new intake would take care of the problem but it didn't. I'm not sure if this is a vacuum leak or an ignition problem.

Here are some videos:

Vacuum Gauge: http://www.youtube.com/watch?v=LT14D...2&feature=plcp

Air Fuel Gauge: http://www.youtube.com/watch?v=-pYVg...1&feature=plcp

paulo57509

This might help you.

http://www.classictruckshop.com/club...ts/vac/uum.htm

oamhmad

iTrader: (1)

Installed new 8.5MM MSD wires and new cap and rotor. Seems to have improved a little bit.

It reads between 20 an 21 at idle with the needled kinda quivering. I guess its not normal for the needle to be absolutely still.