87 Wrangler stutters under throttle punch

Vehicle specs.
87 Wrangler, inline 6, 20k on rebuild. Header, DUI ignition, not sure of any head or block work, egr isn't hooked up.

Whats a good starting point for base timing?

It's acting like its lacking vacuum ignition advance. runs fine, revs up nicely with light initial throttle. But if I snap the throttle open, it hesitates for just a moment. My first thought was accelerator pump, but I verified that it's working. Another reason I'm pretty sure its timing, is the 1st to 2nd shift. 1st has alot of power up top in the power band, and as soon as I shift, it falls on it's face for just a moment, then comes back.


I took the carb apart, and inspected the accelerator pump seal and cleaned it out, and I checked my signal vacuum for the dizzy, and when I snap the throttle I get 15+ inches of vacuum.


Anyone have any insight on this?

Thanks in advanced timing... Andrew

Is this system modified as I thought this year was fuel injected. Normally on older carburetor vehicles they have a vacuum advance on the distributor.
If this is the case make sure its working properly.
I would start at manufactures suggested timing first.

wow...

Did you read the original post?

I'd think vacuum also...check the condition of ALL your vacuum hoses under the hood.

Since the original timing setting isn't working, I'd suggest this technique:

While the engine is running, rotate the distributor to advance the timing until it starts running rough, then back off slightly until it smooths out. My brothers and I have used this on numerous vehicles with many different engines and cams, and it has worked for all of them. Sometimes it's near the factory setting, sometimes not...depends on cam and fuel.

If you need a place to start, I dredged this (http://www.automotiveforums.com/t910781-timing_for_89_jeep_wrangler_4_2l.html)up from uncle internet. Let us know how it comes out....

If you have a vacuum advance unplug the vacuum hose and set base timing.
Replug the vacuum hose and rev the motor as you watch the timing with a light. It should immediately advance as you rev the engine. If not use a vacuum pump and make sure it moves the distributor pickup.
If you have a vacuum leak as suggested use a can of carburetor cleaner and spray along the edges of the intake. If you hit a leak the engine will smooth out.