throwing belts

i have been having a problem throwing off my alt. belt at a high rpm, 6500 ? maybe when shift its a early 70s lower righthand alt. mount ,no pwr st.... just alt and water pump i have heard that the Cj style alt. pully was deeper and larger diameter ? have evan thought about a serpintine belt conversion any suggestions

Bad belt, bad pulley, misalignment of pulleys, incorrect tension, can all cause these problems. I'm running a March crank pulley on my engine, and it's been over 7200 and haven't tossed a belt yet.

I had to go with a Moroso 5 inch pulley on my alternator until I went to underdrive pulleys even with perfect alignment and high price belts it would throw belts over 6500. No problems with the underdrive set-up now.

If everything the other guys told you is good then buy a dayco belt there v-belts are far superoir than anyone else.

strokedmyford wrote:If everything the other guys told you is good then buy a dayco belt there v-belts are far superoir than anyone else.

Thats what I used to run and I would throw those just as easy as the cheapies until I put the moroso pulley on it. I found a smoking deal on an underdrive crank pulley and alt pulley and swapped and had no problems with that set-up either.

What part number are you using now?

I switched to a narrower belt and mine stopped throwing them off.

BigBlockRanger wrote:What part number are you using now?

switched to a narrower belt and mine stopped throwing them off.

x2
ive have spun mine to 6800 on spray with no problem i think its a 13mm

I was using the stock replacement length don't recall the part number but I believe it was the 1/2" wide belt.

thanks to all. i will try the alt. pully first and go from there

I haven't thrown a belt since I switched to serpentine in 1990.

1fatcat wrote:thanks to all. i will try the alt. pully first and go from there

I'd try the crank pulley first.

Im using a single crank pulley from DSC motorsports and a factory alt pulley using a gates 7340 belt and never threw it once in over 3 years even at 7k, Dennis makes a nice custom pulley.