Hi,

Just talked to a friend that bought a '76 Feather Duster yesterday. He plans to bracket race the car with SB 340. The 225 is in tact, running and I can get cheep.

Whats special about his motor?

Old S.B. mopar guy

Bobby

It'd be the last model year you could get one with a forged crank, it also will have a specially curved distributor and carburator that would help the car acheive it's 36 mpg highway rating... The aluminum intake manifold is also a cast unit (not welded like the later units, and the exhaust pipe is less restrictive...The header pipe would be worth something to someone on here with a stock 70's A-body.

Hope your buddy doesn't have to smog a post-74 car in your area, with rising gas prices, the Feather Duster in even modified trim is still a good fun driver and gets good gas mileage, and my insurance company doesn't scream when I say inline six, instead of V-8 and drag racing....

-D.Idiot

hello DI- enjoy readingyour informational responses to duster and especially feather duster questions since i have had one since 89. with the sl6, od and 2.9 axle you get an unbelievable finaldrive of 2.15 and unless you are going 50mph on the flat, you start to lose rpms and have to shift down. even around town in direct and occassionally od mine gets about 24. on arecent nj- fla trip on 95, it pumped 31 and 32. never got 36 though. a few questions- what do you mean by a specially curved distributor- is it weak springed to advance faster from idle? the light weight aluminum items help but seem to corrode faster. never got clipped but if i did wouldnt be surprised if the bumpers get knocked off fast. think 2.15 final is the highest ratio i have ever seen in a gasoline car. some chryslers used by the coppers years ago had a higher differential gear than 2.9 or even 2.76 but used torqueflites which didnt have od, so the multiplication was probably lower than 2.15. one other q- how is the carb different . looks the same as a small one barrel on millions of a bodies. thanks for our interest and expertise. ps- never adjusted the valves in this one- always runs quiet and smooth. think that would raise the mpg beyond 24/32. regards paladin

The distributor isn't too different spring wise from the standard models, but the governor is meant to work with the 12BTDC initial timing and the vacuum pod is set to come in at highway cruise 'lug' times...

You could get certain V-8 equipped automatic road barges in the early 80's with 2.24 8 1/4" rear gears.... 2.15 is very steep...

My parents never got more than 30 mpg with theirs either...


-D.Idiot

I doubt the distributor vacuum advance comes in at highway cruise 'lug' times. You would have detonation / ping city.

Here... maybe this will help

At highway cruise speeds you're at about 15-19" Hg, the rpms are really 'low' for 2.15 at 65 mph (probably pretty close to 1600 rpm)... the petrochemicals are spread way across the combustion chamber (during cruise under slight load) and need to be lit early to get good combustion (not including help from the EGR)....

so the advance at that moment would be pretty close to:

12BTDC+ 8 (the 3.5-5.5 range @2300) mechanical + 24 degrees @ 8.5"Hg or more(i.e 24" to 8.5") = 44 degrees +/-

vacc. advance goes away at a certain point according to how the 'pod' is set... the one currently in my duster 'fades out' at 12" Hg...since at that point I'm accelerating and am about the open up the power valve...

All the OD equipped Feather Duster's refuse to shift to OD under 50 mph on the clock on flat land, and prefer to stay at 55-65 mph at the least to keep the rpms out of the 'idle' range.

Good reference pic.

-D.Idiot