Big Block seems to slow

-

360Duster75

Well-Known Member
Joined
Mar 11, 2012
Messages
267
Reaction score
24
Location
Louisiana
I picked up a 73 Duster that was supposed to be a 440 big block but ended up being a 65 361bb. I was a little pissed at first but got over it because it still runs and drives fine has the 727 and 8 3/4 rear decent interior and body. But my issues have started now. I installed a kick down cable because it would shift to 3rd instantly with the ghetto setup it had. Have to adjust it a little more but now it down shifts when I hit the gas. And I have to adjust the idle to get the correct vaccum for the brakes.

The biggest problem is it seems way to slow for having even the 361bb in it. Tried to launch it but the brakes won’t hold it at all and the tach isn’t working right so have to fix it to know the exact RPM but I go WOT and it just feels like a dog and seems like it’s just going super slow. Not sure what the power output is for a 361bb but can’t be that low. Like it just feels like it’s a 18second car honestly.

View attachment 1715954999

View attachment 1715955000
 
Most of the 361's were 8:1 compression 2 barrel engines. You won't get much out of one.
 
A "good running" 361 with a 4bbl and dual exhaust should be no slouch in a Duster. With a factory 2bbl and single exhaust they listed at 265 hp and 4bbl at 305 hp. I mean, it's not a 440 either. If it feels like 18 seconds, you are in slant six territory and I'd suggest giving the 361 a compression test, tune, make sure the throttle is going all the way open (all 4 barrells). Start with those things...
 
Looks like some aweful big chambers on those heads.

Low compression, low power.

Screenshot_20220712-225755_Gallery.jpg
 
I was never a big fan of 361s from a power standpoint. They might be a great, reliable engine, but not exactly what I would pick for any type of performance platform.
 
Does the gas pedal open the carb all the way
Do the secondaries open
where is the timing, does it ever ping? crank it up!
what rear end gears, 2.76 sucks off the line
What cam, stock small cam? Lumpy and Too big?
How much idle vacuum.

many things to do to wake it up.
 
They'll respond the same to performance upgrades like any other engine. As said, It ain't a 440, but can be very quick in a light Duster, if you go about it right.
 
Looks like some aweful big chambers on those heads.

Low compression, low power.

View attachment 1715955003
That's actually a very small chamber for a big block. Normal open chamber big block heads are in the 90cc range. Those are closed chamber (516 castings probably) and in the 78cc range if memory serves me correctly.
 
I never liked the short stroke of the 361/383s.
I owned 1959 Dodge Custom Royals & 60/61 Darts. The CRs had 361s. The Darts had Poly 318s. All were close in weight, same diff ratio, cast iron TFs. The Poly cars were quicker & the 361s always felt lazy, as in ,'I won't be hurried'.
 
That super tall single plane looking intake isn't doing you any favors for performance. Probably changing it to a dual plane stock intake or a Performer would most likely make it run much better.

Tom
 
Like 318 and Rusty said it should move your duster out nicely.I've been a passenger in a couple of 361 4bbl. Sport Furys and they were not slow.
A lazy tune, tall tires and highway gears will surely produce poor performance.
 
I picked up a 73 Duster that was supposed to be a 440 big block but ended up being a 65 361bb. I was a little pissed at first but got over it because it still runs and drives fine has the 727 and 8 3/4 rear decent interior and body. But my issues have started now. I installed a kick down cable because it would shift to 3rd instantly with the ghetto setup it had. Have to adjust it a little more but now it down shifts when I hit the gas. And I have to adjust the idle to get the correct vaccum for the brakes.

The biggest problem is it seems way to slow for having even the 361bb in it. Tried to launch it but the brakes won’t hold it at all and the tach isn’t working right so have to fix it to know the exact RPM but I go WOT and it just feels like a dog and seems like it’s just going super slow. Not sure what the power output is for a 361bb but can’t be that low. Like it just feels like it’s a 18second car honestly.

View attachment 1715954999

View attachment 1715955000

we had a new one in 1963 , they arent very fast to start with !
A friend had the same 63 ply. , was also red , his was a 318 , and it would eat the 361 for dinner .
 
Does the gas pedal open the carb all the way
Do the secondaries open
where is the timing, does it ever ping? crank it up!
what rear end gears, 2.76 sucks off the line
What cam, stock small cam? Lumpy and Too big?
How much idle vacuum.

many things to do to wake it up.
Well guy said it had a small cam in it but is also the same guy who had a copper tube rigged for a kick down so I’m sure it’s stock. Going to run through the rear gears and compression test today.
 
Single plane intake and the need to adjust the idle in order to get vacuum for power brakes points to a mismatched combination of parts. Too big a cam with too low compression, and an intake that kills the bottom end. I have a 361 with a small cam, dual plane intake and four barrel in a 4000 pound Charger. It is not much off a stoplight with 2.94 gears, but it pulls pretty well once it gets rolling.
 
If you get the rpm's up eg.. drive 1st to 30-40 mph then crush it does it go or still a dog ?
 
A 361 in 58 had the land speed record for a second.
So they like any motor can run.
 
Single plane intake and the need to adjust the idle in order to get vacuum for power brakes points to a mismatched combination of parts. Too big a cam with too low compression, and an intake that kills the bottom end. I have a 361 with a small cam, dual plane intake and four barrel in a 4000 pound Charger. It is not much off a stoplight with 2.94 gears, but it pulls pretty well once it gets rolling.

you're right you know..jpg
 
we had a new one in 1963 , they arent very fast to start with !
A friend had the same 63 ply. , was also red , his was a 318 , and it would eat the 361 for dinner .
yeah, but..... 318's will run :D
 
-
Back
Top