Read my spark plug...

[GasSavers_Erik]

Ported vacuum fittings are usually low on the carb right down by the base plate because these ports in the carb bore are just above the throttle butterfly valve.

[theholycow]

On further thought, the purpose of the yellow thing is startlingly obvious: It allows both vacuum sources to operate the distributor vacuum advance but does not allow them to interfere with each other.

What would happen if the two different vacuum sources were connected? I imagine it would run pretty bad.

Tomorrow I'm going to try setting up direct manifold vacuum to the distributor, eliminating the carburetor's vacuum and the yellow thing.

[GasSavers_Erik]

If they were connected, it would act like you had a vacuum leak and lean things out since the port in the carb would "leak" manifold vacuum under most conditions. Perhaps the yellow thing is a one way valve to keep this from happening when manifold vacuum is higher than ported vacuum.

[bowtieguy]

maybe it would create a lean burn situation

[add|ct]

Originally Posted by Jay2TheRescue

Here's a good cure for purchasing Autolite:

From the makers of the infamous "Orange Can Of Death" comes Autolite spark plugs! If they think they can cut corners and use hot melt glue to manufacture an oil filter, what makes you think they can make a quality spark plug? Besides, even with your 30,000 mile history with them in the truck, the OEM Platinums will go 100,000 and beyond.

Find the OEM plugs on sale, and in the long run not only do you save money, but the pain of changing the plugs. Especially the #6 cylinder. That's a true pain on old Buicks as the A/C unit protruding from the firewall makes it darn near impossible to get a socket wrench in there and be able to move. I had a stubby extension about an inch or 2 long. It was the only way I ever found to do it and not take hours to get the last plug changed.

I couldn't tell where you went from sounding like a lame salesman to making great points, good post!

[theholycow]

Originally Posted by theholycow

Tomorrow I'm going to try setting up direct manifold vacuum to the distributor, eliminating the carburetor's vacuum and the yellow thing.

I decided not to wait...I did it in the parking lot at work before leaving.

What a difference!

Before I had to try very hard to avoid making it buck, and had only limited success...it was pretty likely to buck severely on any hill climb or acceleration, and I certainly wouldn't drive for 10 minutes without it happening, no matter how gentle I was.

After I made the change, I drove 38 miles home without it bucking a single time. I was able to accelerate harder and use all of my throttle.

The bad news is that I was able to cause what I'm pretty sure is detonation, but of course all I have to do to avoid it is not beat on it that hard...well that's how it is when you don't have a knock sensor!

[Jay2TheRescue]

Originally Posted by add|ct

I couldn't tell where you went from sounding like a lame salesman to making great points, good post!

Its a gift!

[Jay2TheRescue]

HC, sounds like you either need to adjust your timing now, or switch to a higher octane.

[theholycow]

I hadn't considered changing something, but I could certainly experiment with those ideas. Wouldn't retarding my timing be bad for fuel economy?

I can get decent acceleration now without knock. It's not bad, I just am not used to being able to cause a problem with a low-RPM high-throttle condition.

However, I suppose it makes sense to experiment with timing after changing so many other things (transmission, distributor vacuum control). I'll have to do some research, I have no idea how it's done. I'll try high octane first.

Before I do any of that I'll drive a couple tanks like this and see what my FE looks like.

[Jay2TheRescue]

Changing the base timing as is simple as loosening the distributor clamp, and rotating the distributor. I never set my timing with a timing light, I just adjust it by feel. I advance it till it pings and back it off a hare.