On Tue, 27 Jun 2006 07:44:22 -0400, DSK wrote:




.... It had an early and feeble
attempt at emission control but I left it all off when I changed a
head gasket and the truck was much more efficient without it.

Doubt it very seriously... you probably had a clogged line
or vacuum leak long before you took it all off. Those
systems were actually quite good when working properly. They
were a bit on the fragile side though.


I don't know. It had the pre catcon system that injected air into the
exhaust manifold just south of the exhaust valves, looking for a post
cylinder burn. Had a air pump that was belted off the crank pulley.

That system seemed to rely partially on a retardation or dwell of the
throttle dump. When you took your foot off the pedal it would not
immediately drop but slowly come down. Made it a little tricky to
shift a manual. Additionally, it had a tendency to backfire
excessively on deceleration. All of this from day one. Others
complained of burned exhaust valves

When I took it off (or more accurately didn't put it back on when I
chaged the head gasket and did a valve job), it ran so much smoother.
Immediate throttle dump, no more backfiring and no hesitation. Gas
mileage increased by about 5 percent. So it ran more efficiently as I
stated, but I can't comment on the relative emission effectivity.

They didn't use that system for very long.

Frank