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budman k20 · 11-18-2013, 07:30 PM

Cali72K20
The factory tach's are known to be inaccurate that is why I mentioned I have a factory tach. You really need to know what your speed is using a gps source. It is very possible that your truck has 4:56 gears and with an auto the rpms you are reading from the tach could be close. Yours still sounds high but that could be from an inaccurate factory tach. Another possibility is you have a 6 cylinder tach. All the factory tach's I have seen are 5K. It's a popular thing to put a 8K Camaro tach in the truck dash if you have a performance engine.

11-18-2013, 07:30 PM	#19
budman k20 1972 K20 Join Date: Apr 2008 Location: Greenfield MN Posts: 360	Re: 4.11 gears and 287/75/16 Cali72K20 The factory tach's are known to be inaccurate that is why I mentioned I have a factory tach. You really need to know what your speed is using a gps source. It is very possible that your truck has 4:56 gears and with an auto the rpms you are reading from the tach could be close. Yours still sounds high but that could be from an inaccurate factory tach. Another possibility is you have a 6 cylinder tach. All the factory tach's I have seen are 5K. It's a popular thing to put a 8K Camaro tach in the truck dash if you have a performance engine.