I have driven my GMC CCKW about 30,000 miles since I bought it in 1980. It
has the original 270 cid 103hp (on a good day going down hill) engine
pulling 11,000# of truck. According to the manual, the engine would be
replaced at 10,000 miles and sent to be freshened up. Having 3 times that
many miles plus some unknown number of miles before I bought it, I have not
seen any negative problems with the lack of lead. I was very concerned after
seeing the EPA's own test of a Chevy 6 cyl run at 75% load. Having a CCKW,
the gas pedal spends about 3/4 time buried in the floorboard.
About 4 years ago I had the head rebuilt by a racing machine shop to the
tune of $650. I had the Chevy 350 valve conversion installed (refer to Reg
Hodgson article in Army Motors). I wanted to make the head 'bulletproof' and
they did that for me even modifying the head to add Teflon seals to the
valve guides.
I noticed no positive difference when I reinstalled the head. Actually, I
think it ran a little rougher, but the power was unchanged as far as I could
tell.
As far as I can tell from the Reg Hodgson article with his claim of
improvement with this change, he had one sick engine before he started...
So I guess that my experience has not been as negative as I had expected w/o
lead. Now my Chevy Bomb Truck must be run with the choke out some to prevent
popping back through the carb. This indicates to me that there is a bad
valve in there and with only about 10,000 miles, this is a completely
different situation than the CCKW cargo truck mentioned above.
Your mileage (and valve life) may vary
Dr Deuce
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