Just changed my belt to a 67.5'' gatorback after finding out RPMoutlet.com sent me the wrong size belt with the pulley. It is still only hitting 9lbs of boost. What else could be wrong?????
Is there a boost dump feature i'm not aware of that dumps it at a certain LB other than the Boost by pass? What diameter should a 4 lb lower be?


MODS:

4 LB Lower? or mabye not
Predator
FTVB
BBP
New belt

happened to anyone else here?

 

It doesn't sound like a boost dumping problem. If it was dumping boost you wouldn't see 9lbs and your truck would just fall on it's face so to speak. Are you using the stock tensioner? If so that could be part of the problem. I think the stock tensioner is set for 8 or 9 pounds so your belt may not have enough tension to prevent it from slipping with the larger pulley. I think the 4lb pulley should measure 8.5" but I'm not certain. I'm sure someone that has a lot more knowledge than me will chime in or you may just get a bunch of search button posts. Whatever the problem is I hope you get it figured out.

 

Sorry Jim, that sucks monkey a$$

Lower Pulley Sizes

2# ~ 7.90"
3# ~ 8.17"
4# ~ 8.50"
5# ~ 8.75"
6# ~ 9.00"


Upper Pulley Sizes

Stock ~ 2.93
2# ~ 2.80


Could you have trouble with the actual boost dump control ?
Some have had a simular issue when swaping S/C's ???

 

i'm going to measure it in the morning.....i have never taken the S/C apart or off. Coming home tonight from work at like 2 am (Bouncer) it was about 55 and perfect. Hit 10 lbs at WOT at the end of 3rd gear, dam this sucks. anything else it could be?

 

Def measure the pulley, if they sent the wrong belt,
then I guess the possibility is there, they sent the wrong pulley too.........

If it's not pulley, belt, or tensioner related, then the only other thing I can think of is the Vac Lines, or the Boost Control itself, but as you said you haven't touched that.

I guess you have no choice but to go over the vac lines,
and especially your boost by pass set up, then check the linkage on the control and make sure you can open and close the butterfly.

What a schitty problem, sorry....

 

thanks rob. i'm heading out right now to check it all. i'm hoping they just sent me the wrong pulley. be back in a few.....

 

they did send me the right pulley. dammit! is there any way i could have put the pulley on wrong? it looked pretty straight forward but i guess its worth a shot. Also could it be whatever line or guage reads PSI could be malfunctioning and i could actually really be seeing 12-13 lbs?

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edit

i just went out there and squeezed the belt together right below the blower snout. I thought if you got the belt to touch with just simple hand pressure it meant the tensioner was bad. anyone have any input on this?

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Jim:

Two things come to mind.

First, you list no intake mods whatsoever. I have to assume you're using the stock airbox, in unmodified form. Especially if you have a 1999 or 2000, the fender hole is silly small. It is barely able to support breathing at stock boost levels. You're going to pull a big vacuum at the fender hole with an overdrive pulley. Even a 2001-and-up doesn't have a big enough hole. Mod the box (preferred in my opinion) or get a conical.

Second, what sort of gauge are you quoting readings from? This could be very well gauge related. If it's the stocker, all bets are off. If it's an aftermarket gauge, swap the stock pulley back on and report differences.

It is very unlikely that the boost bypass is involved. If the thing is capable of closing the butterfly in the bypass passage, this can't possibly be a factor. So unless your actuator is WAAAAY out of whack, forget it. How does your actuator setting/function look?

 

Jim,
You should not be able to squeeze the belt together with simple hand pressure. It sounds like your tensioner may be worn out. Here are some posts discussing worn out tensioners.

https://www.f150online.com/forums/sh...ight=tensioner

https://www.f150online.com/forums/sh...ight=tensioner

I hope this helps.

 

the truck is a 03 and the airbox is modded. somehow i think it has to do with the tensioner. i took it out on the highway today and hit close to 12.....built like 8 at half throttle and then slowly climbed to 12. I tried it again and it only made 9 max so i'm hoping its tensioner related and the belt is slipping. I also have a autometer boost guage so it has to be relatively accurate. that stock pulley was a bitch! to pull off so i can imagine putting it back on.