I had a customer (who actually became a friend over all this :0) who wanted
the same thing. A choppy/thumpy idle *with* good driveability.
The only problem was that he had a steep driveway that he would have
to back up right after a cold start in order to go to work. And his car
was carbureted. So a big, thumpy cam was going to make a tough daily-driver
situation much, much worse to live with.
After weighing all the variables, a 327/350hp L-79 'Nostalgia Grind' from
Comp cams was going to deliver decent all-around performance with the
383ci SBC we were working with. (That along with a better matching
slightly-looser than stock torque converter.)
The only problem was that the extra 56 cubic inches were going to tame
the idle so much that the customer's desire for a 'mean idle' were not going
to be met?
The solution (which I've successfully used several times in the past to deliver
solid street driving manners along with a desirable thumpy idle) ...was to
intentionally mis-tune the Idle Circuit on the carb, but leave the main jetting
(& power valve) circuits on the money. If you follow this
LINK I go into the
details a bit and there's a video you can listen to.
With the accelerator pump & everything else dialed in, this worked really well.
On a cold start, the engine fires right up, runs solid on a fast idle, and the
'70 Chevelle backs right up the steep driveway to the street with no issues.
And as soon as the engine warms up and the choke mechanism is out of
circuit the engine thumps like it's at the dragstrip ready to rock. But even
so, just as soon as the throttle is cracked, the 383 responds like a stocker
with a sharp tune. The owner ended up having his lumpy cake & eating it too.
****
So, assuming that this vehicle is no longer subject to emissions laws
that would prevent you from doing the following, a possible solution would
be to have a computer tuner guru (there's a few in this forum) figure out
how to implement a 'too-lean' idle on your truck once fully up to temp.
Combine this with a hard-pulling RV/towing cam, and you end up with
the best of both worlds -- improved DD driveability, along with a nice,
lumpy polyrhythm idle. It can be done relatively easy in carburetor land,
but I'll bet that a sharp EFI dude could brew up the same thing.
Food for thought. And I offer this only because every single time a car owner
talked me into installing a 'way too big' cam for their ride, they were never
really happy with the results on the street. Vehicles that are no fun to drive
end up rarely being driven, and sold way before their time. Don't do that.
