Optispark Repair

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You can make the LT1
\’92-\’94 Optispark setup more reliable than a �95-�96, even with the
early distributor configuration. Buy a $12 \’96 GM Vette distributor
vacuum harness assy. Buy a $4 clear plastic fuel filter. Buy a $3 tube of
premium black Permatex RTV, because it withstands the highest temps.
Reserve a long day to fiddle around. Here\’s how it all goes together:

1a)Disassemble and clean the inner and outer cap & rotor
assembly with a mild soap like Murphy\’s, Ivory or equivalent and
thoroughly clean off all carbon, soap and dirt residue. Early style top
caps must be drilled in a specific spot and at a specific angle to provide
venting and a piece of vinyl hose will need glued in the hole. You will
have to examine a later style outer cap to see where to drill the hole. It
is at 6 o�clock pointing toward the driver�s side tire. Use masking tape
on drill bit to prevent drilling the small molded spark shield inside.
Sorry, I can\’t describe better. I elected to buy a new early
distributor and also a late distributor cap kit. I removed the early upper
cap and replaced it with the late upper cap. This was expensive but ideal.
You need an odd E5 female Torx socket to remove & install cap.


1b)buy a new later �95-�96 style cap and rotor
assembly. The outer cap that the spark plug wires plug into was revised to
provide a vacuum system connector. It WILL fit the earlier distributors
perfectly. Problem is, the lower cap assy is different on the early and
late distributors and can\’t be purchased separately. I heard the Pep
Boys early cap kit provides the proper early lower cap with a later style
upper cap that has a plug in the vacuum hole. That would be ideal.

2)Use a liberal bead of Permatex to seal the lower cap section
to the aluminum base, top cap to the lower cap and thoroughly cover the
stupid \”shrinking\” white foam seal around the wiring harness area of
the distributor. You may prefer to use a hobby paintbrush to cover seams

3) The fuel filter hangs under the dashboard with the
inlet end open to the air. The outlet end goes to a piece of vacuum line
and feeds thru the firewall or grommet near the upper door hinge into the
engine compartment. This hose must feed to one of the three vent holes in
the distributor base assy closest to the driver�s side by gluing in a
piece of thinwall 1/8\” vinyl emissions control hose in with the silicone
sealer. Form the hose so it routes away from the crankshaft dampener
toward the driver\’s front tire and looping upward with a fairly tight
but not kinked radius of about 3\”. Plug the remaining two holes with the

This vinyl hose in the distributor base must be routed
up the front of the motor between the serpentine belt tensioner and
alternator bracket. You will likely need to see a \’95 or \’96 Vette
to see how they squeezed it in there without pinching or wearing a hole in
it. It is a real snaked route. You can split rubber vacuum hose and cover
the vinyl hose with it to prevent collapsing when you restrain it using
plastic tie wraps . It follows the edge of the aluminum accessory bracket
all the way up to the intake. This 1/8\” vinyl hose in the base gets
routed across the top of the motor toward the battery. I drilled aluminum
bracket to access door hinge area from battery. You can convert to rubber
vacuum hose if you wish and route it through the grommet in the upper
driver\’s door hinge into the dashboard area. You�re done with hose #1.

>>3) Now hose #2. Take the vent hoses from the �96 GM Corvette
OEM Vacuum Harness kit and use the one with the two in-line gizmos in it.
One in-line device is a one way valve and the other is a flow restrictor.
The accompanying bare hose in the GM kit is not used. Remove the plastic
cover off the driver\’s side of the engine intake manifold. You will see
a nice vacuum source going to the EGR valve. Install a tee and plumb the
modified early cap or stock later distributor cap hole to the intake
vacuum source using the \’96 hose with the 2 in-line gizmos. Make sure
it\’s installed with the gizmo\’s near the intake. This hose is routed
from the intake down the accessory bracket following the same path. Hose
length is critical.

>>Conclusion: Low humidity air is sucked
from under the dash and fed into the distributor aluminum base assy, out
of the cap thru the one way valve and restrictor into the intake. This
should be bulletproof, far better than the \’95-\’96 setup that has
similarly poor sealing and draws moist air from the air intake assy. You
should be able to submerge your ignition now. GOOD LUCK.

�95-�96 cars can benefit from Permatex bead sealing of all
distributor cap seals too. Also, moving the vacuum fresh air source from
the gray \”L\” fitting in the Air Intake hose to the cars interior dash
area with the fuel filter method as described above will prevent intake
hose humidity or rain infiltration from condensing in the distributor cap.
This could be a real concern on RAM air modified cars that draw air from a
license plate snorkel/scoop or from the positive pressure radiator shroud

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