So I just recently installed a new scx upper and scx -2 lower blunt nose style on my '29 VR-1 from having a XR upper and standard sportmaster lower, and I seem to lost 10mph if not more, the boat handles horrible and the prop slip is threw the roof, can anyone help me out on what they think I need to do to get back where i was? You think standard SC with the SCX upper is the way to go? I'am currently running a P5 32 done by b-blades, I ran it up to 88gps at 6000rpms and got nervous so backed out , slip was like 26.5% , I should mention I'm running a 8inch stellings box as well, I was running a tad over 100mph with my old set-up , any help would be greatly appreciated, I just got sick of replacing the XR's .

I would definitely work back toward your previous x-dimension using drive spacers. Single engine Velocities have very mixed results with shorty drives and -2" clearly seems too short given your results. Good luck.

I agree. Sounds like you need to go back to the original height. Can you try a couple different spacers? Maybe drop it down 2" and work back up 1/2" at a time.

The scx lower is a lot of the problem. Swap the lower and you should see some speed return. The scx upper and lower uses a lot more power than standard xr. Seen it tried on a SVL and a big Fountain same result lost 8 mph.

Thanks guys, Im gonna order a SC standard Imco, and see where my cars fall. Stay tuned

Quick update date, we did the Sacandaga Fun Run this past weekend, I had a chance to put my sportmaster standard lower back on with my IMCO SCX upper , and Im back in business again, I learned that my VR1 absolutely hates the -2 shorty along with the blunt nose scx lower, so I think the end result, is I will be just putting gears in my lower sportmaster every 70-90hrs rather than sacrifice 12 mph lol, I spent to much money to get where Im at to lose that much speed, 2-3 mph I could deal with , but not 12, we ran 101mph in the run Saturday with a full tank of gas, so that is where Im as of now, just in case anyone was wondering my X dimension is 3.5 below and that seems to be the sweet spot for my boat My X was only half inch below with the shorty, anyone else wanna share there sweet spots?? Please feel free...

Nice update!

Curious what you are running for power to run that mph.

Nice to see you got that 2" back, now can you see over the dash? Sorry Mike had to say it, your boat looked good

I have a booster seat Rock haha

Im running a Saris built 825hp , basically a 525 with a whipple, little different cam and a little lower compression, as whipple instructed.