Major Belt Slip Problem. HELP!!!!

[Badass_Forever]

Alright, built a brand new engine, Whipple 3.4 on top, aftermarket dual BB idlers, stock caged lower, RR manual tensioner, RR 4" upper. I have tried both Gates green belts, and Gatorbacks.

I can't get consistent, not-dropping off boost to save my life.

Either it peaks to 18psi, and RAPIDLY drops off to 9 or 10, or it starts at 10 and goes to 9. That's all with the 4" RR upper.

Then I put the 3.5" Whipple upper on just to rule out any weird surface issues with that, and same thing starts at 10psi, immediately falls to 9psi.

I put a small fortune into this thing and I haven't even been able to do a full 18psi pass yet (aiming to be doing 20psi once I get this sorted) and I'm starting to get pretty pissed off.

As for the manual tensioner, I'm putting WAY more tension on it than I feel safe just to rule that out. Video that kinda demonstrates tension level (I'm pushing/twisting pretty hard): https://www.youtube.com/watch?v=l-ZQ76Ocg9s I do intend to switch to a manual spring assist tensioner.

Picture of engine being mocked up: https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/t31.0-8/10264187_10100768522312731_2323012308845009776_o.jpg

 

[01yellercobra]

I'm gonna guess your belt is too long. I can't twist mine as much as you're twisting your's. I have a Thump tenisoner. So I can't adjust it. Plus, dropping a half inch in pulley size without changing the belt will cause the issue you saw. Especially if the belt is on the long side to start with.

Also I don't know if you have room for it but you might want to consider a snub idler. The more belt wrap the better.

 

[Badass_Forever]

just to be clear, the snub idler will not fit with the 4" pully, thats why i went down a size and did add the snub.. it didnt make a difference. would it be to much trouble to ask if you could make a quick video of your belt? I personally feel that i am already putting an extreme amount of tension on this belt already. I dont want to break anything.

 

[01yellercobra]

I'l try to remember to make a video. But the rule of thumb is you should only be able to twist the belt about 45 degrees. Is there a torque spec for tightening the tensioner on the belt? How easy is it to get that belt on?

The reason I think it's your belt is I had a similar issue with an old set up. The boost would build then fall off. I went to a smaller pulley and had the wrong side belt. The boost would shoot to 15 then drop down to 5.