I just got a new Tach for my truck because I got new gears 4.11 put in and since I run 31" tires, I wanted to see if my RPMs were getting too high on the highway. Anyway, this thing can be set for V4, V6, or V8. I have a 4.9L I6 engine with 5-sp manual transmission. I hooked the new tach to my MSD ignition tach output. However, when I set it to V6, the readings look a little fishy. When I set it to V4, it looks more realistic. Unfortunately, I do not have a V4. And to make things worse, since I've never had a tach in this truck, I don't know what to expect. I would like any feedback from Ya'll. Here is some info I collected.

Setting
6CYL
Ave. RPM. b4 Shiftin'
2k
RPM@65MPH 5th Gear
2k
RPM@75MPH 5th Gear
2.5k

Setting
4CYL
Ave. RPM. b4 Shiftin'
2.5K-3K
RPM@65MPH 5th Gear
3k
RPM@75MPH 5th Gear
4k

I would also be interested in hearing what anyone thinks my red-line point would be. Thanks. I appreciate ANY feedback.

 

does it have to hook up through the MSD ignition?

 

I don't see why it would have to go through the MSD but I don't have a clue how to do it. When I read I could send it straight from the MSD, I was psyked cause I didn't have a clue.

 

Your tach should have 4 wires: red, black, green and white. Run the black to ground, the red to a power source that only comes on when the key is in the RUN position, the white wire to a dash light source, and the green wire to the negative side of the coil. That should work.

On a side note, why did you install the MSD box? Is your truck pre-1992? Just curious, because the '92 and newer factory ignition is better than MSD or Crane.

Take care,
-Chris

 

31/10.50-15 tires roll at about 680 revs/ mile. At 65 mph with 4.11 gears you should be turning about 2450 RPM in 5th and about 2825 at 75. Niether of your tach settings is right.

 

Thanks for all the helpful information guys! PKR - Was your comment on the quality of the MSD ignition a personal opinion or is it something that's widely agreed on? Just curious. I noticed improvements in acceleration and mileage.

Also, could someone tell me about where this engine would redline? Thanks

 

Both. It's been my personal experience, but I do this for a living. I have found that in both Mustangs and F150's, that the ignition system installed by the factory, since 1992, is as good or better than the MSD 6 series, and the Crane HI-6. I tried the HI-6 in my '95, and found the factory much better. I have replaced my coil with a PS 91, but the box itself was better from the factory. It is widely accepted that the factory ignition is good up to about 325-350 hp. After that, it will still work, but gains can be detected with an aftermarket box.

As far as the redline is concerned, what has been done to it? In my truck, I won't take it past 4000 rpm. I usually shift at 3000 rpm, but when I'm in a hurry, 3500 rpm.

Take care,
-Chris

 

"Redline" means what to you? Are you asking for max RPM before shift or are you asking for max RPM before you seriously reduce engine life?

The HP peak on the 300 is about 3500 RPM, rev it much higher than that and all you are making is noise. The WOT shift point with the 300/E4OD is 3600 RPM, no reason the manual tranny version would rev any higher. A stock 300 is probably OK to 5500 RPM without hurting anything, but why would you bother?

 

what is the peak hp on a 302 my auto tranny shifts at 4600