Just a note regarding my 2bbl conversion and Dutra Duals for my 74 slant six Duster.
Last summer we converted my slant six 74 Duster to a 2bbl Holley 2280 Economaster, with the Dutra Duals for exhaust manifolds. The first Holley had jets problems. That was traded for another rebuilt Holley that worked great ( not uncommon to go through a carb or two in rebuilds). We had some exhaust gas leak problems since the intake and exhaust manifolds were from different cars and years. But after following Doug Dutras web page on exhaust manifolds, we got the manifolds all sealed up tight. The exhaust pipes are 2" off the manifold into a Flowmaster Y connector and back to a 2.25" pipe.
A few weeks ago, we finally put it on a smog machine and tuned it for max efficiency at idle and cruise speed ( ~ 2500 rpm ). It was interesting to note that we got the CO down to almost nothing ( extremely clean at idle ). However this caused dieseling problems when the ignition was shut off. The fender tag on my Duster suggests setting the CO at 5% ( .50 ). After doing this, ( richer idle ), the dieseling problem went away. It would have been better if these older 2bbl carbs had anti diesel dash pots, but they don't. Nice thing with the Holley 2280 is that it has a screw to adjust hi speed mixture as well as the standard ones for idle.
Then for the road test...... WOW..... power to spare. This setup made a lot more power than the old 2bbl and single exhaust. The mileage seems to be as good as the old 1bbl as long as I keep off the lead foot..... hard to do with the fun of that new power.
All I can say is that it is worth the time and "tweaking" that you will have to do to get this setup purring. It makes notably more horsepower you can feel.
( I am also running a MSD 6A, MSD hi output coil and MSD wires. )
Having lots of fun !
Julie Roth
( DusterGirl )
