well one day my tach decided to stop workin, then it would work after i drove around for awhile, i have takin it out to put the needle back at zero, it wrapped out to 7000 some how lol, and when my car is running it usually sits at 2000-2500, and when i rap my engine up to like 4000 it shoots down to zero really fast, then goes back to 2500
any help would be appreciated, its auto trans, but i still like to watch my tach since im gonna have a 300hp+ motor heh

 

Check the tach wire that leads to the distributor.

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'86 IROC T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
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ACCEL HEI DISTRIBUTOR
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3:73 Posi Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite

 

trust me that was the first thing i checked, its somethin different than that

 

you are getting interpherence somewhere

 

Sounds to me like the tach is fornicated. Just get another one at the boneyard. Make sure you get the little circuit board on the back of it, and that you get one out of a car with the same # of cylinders as yours.

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