Stock tach is way out - help!

83 Capri 5.0 said:

OK this is the set up, Jacobs Pro Street and an Ultra Coil. When the stock reads 1000 RPM my timing light reads 800, 2000 on the stock, 1600 on the light, 3000 - 2400, 4000 - 3200, 5000 -4000.

So you get the picture, the stock tach shows 200 less for every 1000 RPM. What's up with that? I want to use the stock tach for now. What is the fix for this?

Any help would be appreciated.

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