DI, can you tell me more about the dual stage power valve?

They are spendy and not for "power" (i.e. performance).
They are meant to be used on big vehicles (more weight to power ratio) to assist in keeping the primary jetting down by allowing the power valve to tip in sooner, but not the full power valve opening (they use the small PVCR type of opening-not the picture window PVCR).

Anyhow, they are rated by two numbers the first is the initial tip-in and opening for partial enrichment, then they have a second number for the rest of it (a 10.5/5.5 will tip in at 10" tip the rest of the way at 5", but still won't flow as good as a normal 10.5....).

I use it on mine when detuning for mileage...I'm running the 10.5/5.5 one now, and may swap in the 12.5/5.5 one next as the 10.5 doesn't tip in soon enough to help out as I'd like.

It'll take the nuts out of your build (in my case it has as much acceleration as my wife's 4.0L Grand Cherokee, but keeps the mileage on the highway respectable...).


-D.Idiot

Thanks for the info. Unless I can manage to pull more idle vacuum out of my engine, I'm going to drop to a 5.5 (maybe 4.5 ) PV when my secondary metering block gets in (since I'll have the carb off anyway) and was wondering what exact uses the dual stage PV had. Sounds like it is not what I am after.

After some fiddling I have a steady 14 in-Hg vacuum at idle in park/neutral, but it drops to 10-11 in gear, and about 10 seconds later begins it's "wild ride" sometimes fluctuating all the way down to 5-6 in-Hg, which is likely getting me into the rich/lean feedback loop mentioned earlier in the post.

As far as I can tell my timing at idle is rock solid, but I have not set it for total yet (I do not have a dial back timing light, will be marking my dampener every 10° up to 30° this weeked to get an idea, and try setting total around 28-30° )

Will post back. Thanks for the suggestions.

Have you tried disconnecting all vacuum line one at a time, vac advance, power steering, pcv etc and try to see if you have a leaky line or ?? Have you sprayed the carb and base with carb cleaner?
Try increasing idle speed to find where it starts giving consistant vacuum numbers. This may tell you about which circuit need tweeking. Also, is your squirter snug against its linkage OR depressing it at closed throttle? A bad vac advance pod on the distributor gave me a similar problem you are having. A pcv valve would do the same I would imagine.
Hope this helps.