C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

89 L98 TPI Rev counter not reading over 4krpm

Old 07-11-2019, 07:54 AM
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Default 89 L98 TPI Rev counter not reading over 4krpm

I recently fitted Accel ceramic plug wires to my 89 with long tube headers and the car is running much better. However, at high RPM the tach flicks around 3600-3900ish even though it's obviously revving higher. Could I have disturbed something by the dizzy when fitting the wires? Or is it time for a new coil? Last time I had a similar problem my coil was on the way out.

If it is the coil, is the DUI uprated coil worth it? I'll be fitting a Miniram soon.
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Old 07-12-2019, 10:39 AM
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I wouldn't go with more than a stock coil for a stock engine, but depending on the build for the MR, i'd consider upgrading to other HEI-capable coils. Accel, MSD, etc.

Sounds like you may have a tach filter issue, it wouldn't be the plug wires. A scanner would show what the RPM actually is vs what the dash reads to check.
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