Tach

[doug2525]

I have a 440 bored over .060, cross-ram intake. According to my axle size 3.73 gears, tire dia. 28 inch and final drive of the trans which is 1. At 60 mph my tach should read about 2900 rpms. I'm reading about 3900 rpms. I have the tach wired in the MSD rev limiter.
I have a new Pro Tach. Any ideas on why the tach is reading a 1000 rpms high and any idea how to fix it.

 

[sleepar]

They should have a calibration... some are 4,6,8, cylinders some have an infinite amount they can go... call the company who sells/made it...

- - - Updated - - -

They should have a calibration... some are 4,6,8, cylinders some have an infinite amount they can go... call the company who sells/made it...
My guess is you look around for a swich and its set up for a 6

 

[Sonny Black]

I have 355's...............60mph/ 2500 to 2600 or so

 

[HT413]

I think sleepar hit it - you have it in 6cyl mode. If it's reading 4000 rpm and should be 3000 (25% less) that's because it thinks there are 25% fewer cylinders.

 

[383man]

I agree sounds like its in the wrong mode. Also is the car an automatic ? Here is what my car turns and the setup. On my 63 Sport Fury bigblock I use 4.30 gears and a 30" tall tire. Its an automatic car with a Dynamic 9.5 converter that will flash to about 4200. At 60 mph cruisin the highway I turn right about 3200 rpm as I drive it at 60 mph all the time. Just something to compare yours too. Ron