Although not as bad as you I have the same problems with a 350 MAG MPI. Make sure the vent screen in the bottom of the distributor is clean. I have also started using the NAPA Echlin caps with aluminum terminals. It seems to last longer than the copper ones. The crab style cap is also know as the "crap cap"do a google search for "350 crap cap". There is a lot of info on them. Improvements to NAPA Echlin GM 6 & 8 Cyl. Caps
The Problem
For a long time GM has admitted a design
problem with the ignition systems that use
the RR207 and RR253 distributor caps.
These GM distributor body design flaws
have led to premature corrosion of the cap
& rotor and ignition system failure due to
improper ventilation.
Remember, this is not a NAPA Echlin product
problem but rather an original equipment
design flaw. In fact, GM has released a volunt
ary consumer return notice in addition to
numerous TSBs relating to
this specific problem.
The Solution
NAPA Echlin has made the following
improvements to compensat
e for the faulty OE
design. Both the RR207 and RR253 will now
be manufactured with aluminum terminals.
Due to the OE distribut
or flaws and corrosive
environment, in these in
stances, aluminum will
actually provide a long
er service life than the
brass. Additionally, both numbers will now use
a special formulation manufactured from a
polyester base plus a unique blend of mica
particles and glass fibers. This improvement
results in superior performance due to the
higher dielectric strength of the cap.
Product Differentiation Between NAPA Echlin and Mileage Plus
Although both the NAPA Echlin and
Mileage Plus will use aluminum
inserts, the NAPA Echlin
caps (RR207, RR253) contain 35% mica-glass content in the plastic as compared to 30% for
Mileage Plus (RR207SB, RR253SB). Th
is results in a 31% improvem
ent in dielectric strength
for NAPA Echlin! Higher dielec
tric strength means less voltage
leakage, greater part durability
in adverse conditions and extended service life. See comparison chart.