The Mopar Performance six cylinder book recommends installing 1/8 inch tall dams in the floor of the Offy intake manifold in front of the #3-#6 runners. Is it really worth it?

Every Engine, Intake and Carb set-up will have it's own distribution needs.
I would not install any "dams" or do any other distribution adjustments until you run your combo of parts and "read" the spark plugs for mixture "richness, or better yet, check exhaust gas temps or O2 reading at each exhaust port ysing a thermocoupler or sensor.
BTW, Most often #1 & 6 are rich and 2 & 5 are lean on a SL6.
DD

Thanks Doug! I haven't run the intake yet, in fact I haven't even got it yet, but I will have it on the van someday. I do have an O2 sensor that I will use to make sure the overall fuel mixture is correct, I just read in the Mopar Performance book that the carb should be mounted with the primaries towards the front and with the dams installed.

Anyay, I guess I will have to set it up the old fashioned way, by careful attention to details and trial and error.

Thanks again!

The 'heated' Offy 4 bbl manifold works pretty good as long as you use a small carb. with vacuum secondaries.
One distribution trick that work pretty good is to use a spacer betweem the carb and manifold. Find one with individual holes instead of an open plentum. Check the Van to see if you have room for a 1 inch thick spacer.
DD

How exactly would you hook up an oxygen sensor for this purpose? Are we talking welding in a port into each exhaust runner? Or in my case, with duals, would I want one in each half going into the collector? Just curious again about if you could do this on a non-permanent basis.

I have also thought about buying one of those gunson colortune kits. Has anyone used them to good success? Again...curiousity

My 86 van and (and any other 80s Mopar with a lean burn computer) has an O2 sensor on the back of the factory exhaust manifold, right below the heat flapper valve. If you get a late model slant exhaust manifold as your core when you make the rear manifold for your dual exhaust then you should have the O2 bung built in. Otherwise I think you need to tap into the head pipe directly after the flange between the exhaust manifold and the header pipe. From what I understand, the closer to the engine you can put the O2 sensor the better. I have seen O2 fittings sold in performance parts catalogs that you just weld into your existing exhaust pipe.

Doug- Thanks for the tips about the spacer and the carb! I have several carbs to try, a Holley 2305 (I know it is a two barrel, but I can run an adapter) and an old Carter AFB 400 CFM carb. I won't be running the four barrel until I install a rebuilt motor with the MP 244 cam, Ford 300 valves, and .030 oversize pistons. I am just gathering info right now.

Thanks guys!

That's why I was wondering what approach would be better, the O2 sensor or getting a Gunson colortune that reads each plug. Since the slant has issues with lean/rich due to runner length, what is going to give you better data? Either way, i guess its not really possible to control individual distribution unless I went with EFI, so the point is moot =/

MJ