Between 6000-7000 rpms on my big block, the power steering belt jumps and flips, by the time I shift into second it jumps off. alignment is incredibly good... the motor is full roller and revs fast... I am guessing load from pump is causing slack on feeding side of belt...

I noticed an old post where someone referred to using a shoulder bolt to keep belt from jumping... I was wondering if anyone had any other fixes for this problem

my thought is to go to junk yard, get a belt tensioner of any old car, make a bracket and then put it atop the belt, to hold it down...but of course its late saturday... and they are closed... I would like to run it hard tonight.

thanks in advance

Ive had really good luck with dayco belts with the cogs on the outside. My alternator belt use to fly off all the time changed to the dayco with cogs on the outside problem fixed. Dunno why it works but it does. Might be something to try. If the alignment is good only other alternative i can think of would be to make or buy a deep groove pulley for it.

Deep grove pulley.Thats what they used in the big HP BB.Thats one way you can tell a 325hp from a 375and up HP motor.

I use the March pulleys on mine. I don't have power steering but I do have an alternator in the stock location with a long style water pump. I shift it at 7500 and I've never thrown a belt in 10 years of having them on.

March underdrive pulley solved all problems.

I'm not trying to be funny, but my lawn mower has a round steel (about 1/4" thick) guide that goes directly over the belt on the pulley that prevents the belt from jumping out of the pulley. There's no reason why one of these couldn't be fabricated to use on a car engine.

Make sure you have the right width belt. I had the exact same problem until I went with a narrower belt that sat down in the pulley grooves correctly.

You can source a cheap BBC serpentine setup for the alt. and w. pump from a junkyard if you are using a long waterpump. It consists of a alternator pulley, water pump pulley and a crank pulley off of a 1986 1 ton 4x4. It does still us a v belt for the P.S though. This eliminated all my belt throwing issues.

Todd

went to the local parts store yesterday... found a 2 1/2" tensioner pulley with roller bearing inside... takes a 13/16" post to ride on... of course its sunday... so as soon as everyone is open I am going to go shopping for a 13/16" bolt... I think I will just make a little bracket, weld a nut to it... and walla... have something easily removable... that will still allow me to change belt... but also hold it down... after I am done I will post some pics.... in the mean time...I will see if I can find a skinnier belt... I don't know that it will have an impact though, the belt stays in its pulley groove... it just climbs in the air and turns before the pulley (kinda like a ripple in a whip)... later it eventually climbs off when trying to right itself...If I pull it tighter than... well tight.... it still climbs on the feeding side of p.s. pulley and turns itself... but at least it doesn't come off.

A couple of things I learned over the years is that first, if you throw a belt and it goes inside out, toss it and replace it, it is now no good and will continue to jump off from then on.

Secondly, like stated above by another poster, is that the belt rides in the sides of the pulley groove, not the bottom, the more contact area you have, the more grip it has. So try to find a skinny belt or a deep groove pulley.

And thirdly, get as much belt wrap around the circumference of the pulley as possible. At least 30-35%, that way as the rpm's climb, and the belt balloons out, there's still a good amount of the pulley the belt is riding on. This is also a reason why the underdrive pulleys work so well, they are smaller in diameter and therefore the belt covers a lot more of the pulley.