I have been running my 89 1 ton, 5 sp 110 miles a day, and have done a few mods, 3200 spring, 1.5 turns on star wheel, fuel screw ? many turns, afc cone, full fuel, otherwise stock, I have been pushing 700* at 75 mph on a flat, and 800* up a 5% grade,,, I just removed the ladder rack which went over the cab to the wind shield, It was the most common aluminum type,,, And now i dropped about 100* across the board, so now i am about at 600* at 75 mph on a flat, I didn't realize how much drag it would cause,,, But now i do and so do you
Just thought this might interest some here.
Peter.

 

I picked up the top speed a few MPH when I removed it, I figured it was because mine weighed 400 lbs though...

 

I think mine is about 200+ lbs,,, ?top speed? MMM i dont know with mine. could it be true, have you run yours till it wouldn't go any faster?
I did without the 3200 spring, it was about 95 mph. I am scared with the 3200 spring.
Peter.

 

That's very interesting on the rack removal. I would think that the change in aerodynamics is the cause of improvements. Though it seems insignificant when you consider the frontal area of the ladder rack, remember that it extends all the way back to the rear. That is it disrupts the entire airflow picture all the way from top of cab to tailgate! The Kamm effect seen as a low spoiler at the back of a van shape made HUGE differences in performance because it dramatically improved that same airflow envelope.

Also we see that mirrors and all exterior components are streamlined nowadays as the automakers wise up on fuel economy. I've wondered many times how much it costs me to listen to the wind whistling past the old fashioned West Coast mirrors on my old fashioned vintage Dodge!? And how much for the full length square tube rack up topside? I think I'll twist a few bolts and find out.... Thanks!

 

I wouldn't be so fast as to say it's just do to the ladder rack. There's a whole donkey cart of variables that can cause a few MPH difference. Maybe my engines just getting broken in at 310,000 miles?

100 degree EGT drop sounds rather severe, however...

 

I have been doing this same run, each day, same time, same road, same speed, no other changes made when rack was removed, and the weather here in pa has been quite constant these past two weeks, as well as my foot, 100# is alot, but what can i do other than read the gauge, i can still hit 1500# when i push the old truck, I also have about 300k on it,
Putting a 4" on tomorrow, Doubt i will see any further change though,
Peter