I just added performance items listed in sig. I have a large "slide-in camper' on the truck. My GCW is 13200 lbs. In 4th or 5th gear, if I try to accelerate to hard around 1600-1700 rpm, the clutch will slip.
Is the clutch bad, or just not designed for the added power?

 

Not designed for that much

The stock clutch is only good up to about 280hp, you should be around 375 or more hp

 

My stock clutch wouldn't even hold a 10 plate FF when it was empty. You did pretty good with the plate and injectors with that much weight.

 

My 10 plate is in the middle position. I just put a turn on the star wheel to reduce low rpm torque. I was hoping to get better mpg with the mods, but wound up losing instead, and at lower rpm to boot.

Any idea what my optimum rpm should be to get best fuel economy?

 

My best came at 1700-1800. Now with your 4.10s, thats gonna be awfully slow.

 

with the 12 valve motors the lower the rpm the better the mpg down to about 1500 rpm.

Biggest thing that will help your mpg is reset the pump timing to about 15-16 degrees, other than that its all about driving style, just remember more boost means your using more fuel. Also those 4.10 gears are gonna be your worst hang up for milage, depending on speeds I ganied 2-5 mpg when I switch from those to 3.54

 

Totally correct.
Most folks don't realize that the plate, it's position and the star wheel don't do anything at all until you floor it or are under heavy load.
If you're easy on the throttle mpgs stock or with mods are about the same.
Timing is the exception, most folks gain at least 2 mpgs bumping the timing up to 15-16.

 

My truck had 26,000 miles on it when I got it and it was bone stock. With just a #11 plate installed and no other power mods it would slip the stock clutch in 3rd, 4th, and 5th. That was with no load in the bed at all and my fairly light 185lb butt in the seat.

John