Question about my Tach
 

I just put a new tach in the truck, and I'm not completely sure if it's accurate or not...

I did a WOT run in the truck, and according to the tach, it shifted first to second at 4000 RPM. Shifted from second to third at 4200 RPM.

Here's the engine I have...
http://www.jegs.com/webapp/wcs/store...55609_-1_10763

Now either the tach is inaccurate, or it's shifting too early, because the specs on that engine show 290hp at 5200 RPM, and I'm about 1000 below that according to the tach. I've got it hooked to a main power source in the fuse box, and I've got the actual RPM wire hooked to the "tach" terminal on the dist. cap. It also shows it's idling at about 500rpm in gear, which I think is a little lower than it actually is. I could be wrong though..

Re: Question about my Tach
 

Is this an aftermarket tach or a factory one? If it's an aftermarket, it should have a switch on the back of it for a 6 cylinder or 8 cylinder. It may be on the 6 cylinder setting and just need to be changed. I used to have a Sun tach in my 82 years ago and that's how that tach was.

If it's a factory tach, it's very likely that it came out of a 6 cylinder truck, and that's why it's reading off as the 6 cylinder and V8 tachs are different. ...Joe

Re: Question about my Tach
 

If you put in a factory tach, do this. Turn your ignition switch to on, don't start it; your tach should read 0. If it dosen't, your tach is off/bad. I have one good tach in my truck, but have three more that are off/bad :( David

Re: Question about my Tach
 

It's an aftermarket sun pro tach, and I already made sure it's on the 8 cylinder setting, but I guess it wouldn't hurt to double check that

Re: Question about my Tach
 

I think I am missing something. Why would the specs on the engine determine when your tranny will shift? Wouldn't the tranny control the shift points? How does a tranny decide when it will shift?

Re: Question about my Tach
 

The transmission doesn't care what your engines power band is. Wide open throttle shifts are going to happen whenever they are set to in the transmission.

Re: Question about my Tach
 

I know all of this.

What I'm getting at is that if the tranny is set to shift at 4200rpm, well then, the engine is capable of much more than that.