[tostaroller]

i have a 66 289 mustang hard top (one of millions). It came with the stock 2v but i switched it to a 4 barrel holly carb... I'm trying to add a tac but i dont know what the max rpm my engine is... the shop manual for mustangs shows the Brake horsepower at
289 v-8 2v= 200hp@4400 rpm
289 v-8 4v= 225hp@4800 rpm

so if youve added a tac to your mustang can you please help me if you know the highest rpm to shift at without detonating your engine... also if you have any tips for how to avoid detonation id appreciate them

[Glen]

There are no absolutes on Tach set.

But my rule of thumb is to add 500 RPM to max HP or Torque, which ever is higher. Usually HP.

It also depends on how your engine is built. For example, if you made max HP at 6000rpm on a stock aging bottom end, then I wouldn't go as high as 6500rpm.

6000rpm is consider max on stock bottom end. I wouldn't run it past 5500rpm if you can help it.

Taking it to the track and finding it's sweet spot is the my best guage.

Hope this helps