I have 98.5 3500 and am looking to put a Pyrometer on it but don't don't entirely know where to put it. I found two spots on the exhaust manifold that stick up and are already threaded part way and was wondering if i could drill them the rest of the way and tap the rest of it.

 

The closer to the #6 hole the better as everyone seems to think its the hottest. I put mine on the hump as close to the back of the manifold as I could drill. If you already have a spot started no reason you couldn't use it and re-tap it.

 

I think the best location is where the exhaust leaves the manifold. If you place it in #6, then that is all you will see. In the event of a problem with any cylinder, you first need to be aware of a problem. Secondly, you need to discover where the problem is. Monitoring #6 only will not help you if the problem is in one of the other 5 cylinders.

 

Most people place the probe pre-turbo on the rear port right before the flange to the turbo. Don't drill the center of the manifold, thats were the divider is, drill centered on the front or rear port.

Farmboy, the spots that are threaded that you speak of are probably mounting bosses for something else. Like the heater lines.