Okay, I'm doing something wrong here....I've done this before but somehow I'm screwing up this simple step. New Alt/WP belt from Ricambi (201446) Tensioner checked and it spins fine, no slop or wiggle Put the new belt on (Over the WP, around the crank, over the tensioner and around the alternator) Had difficulty getting the belt on, double checked that tensioner was bottomed out on the bracket (it was) but I still couldn't get the belt on. Eventually did but the adjusting bolt snapped. Wrote that one off since I've already replaced the PS and AC tensioner bolts previously. Ordered a new one from Ricambi. When the parts arrived, I pulled the alternator bracket off to get the adjuster out. Removed the broken bolt, cleaned the threads up, lubed the new bolt and reassembled everything. I new it was going to be tight but I eventually got the belt on. Checking tension with the pulley all the way down, tension on the long leg (alt to WP) was in the high 40hz area. Tightened up the tensioner, rechecked it, rolled the engine over, rechecked it again, check to make sure the bolt wasn't bottomed out on the bracket too. Tension was in the mid 50's on the same leg. Went to tighten it up some more....not even half a turn...then SNAP! What am I doing wrong here? I've done this before but I don't see anyway to get the 90 - 100 hz in the WSM... Re-checked the belt and it's the correct number....so Whiskey Tango Foxtrot??? BTW new bolt(s) ordered from Ricambi...again
Nut on the pulley bolt is loose until tension is set? Turning the adjuster bolt counter-clockwise to tension the belt? Surface of the slot and all parts that slide on it are smooth? Maybe bolt the pulley to the bracket off the car and try adjusting it while watching for anything that could be preventing it from sliding smoothly up and down the slot. The belt is a pain to get started. I also scratched my head a little and triple checked the part number. One thing that helped is to pay attention when the pulley bolt has bottomed on the bracket, it angles the bolt up a tiny amount in the direction of tensioning the belt. If you tighten the adjuster to the point that is just before the pulley bolt angles up, it buys you a sliver of extra room to work with. It takes some finesse as it's about 1/16 or less of a turn before absolute bottom where this sweet spot is.
Locknut on pulley loose - yes Counter-clockwise direction - almost positive but the ratchet is still under the car so, I'll double check that later Removed the bracket when I had to change the bolt the first time, polished up the sliding surfaces on the pulley, adjuster, and mount. Slides with little effort without the belt on it. Also liberal coating of anti-seize on the threads. Reached around behind the top of the alternator before the last turn to verify the bolt was not binding against the top of the bracket and I could feel the top/end of the bolt. Had at least one finger width between the top of the bolt and the bracket. New bolts should be coming in early this week so I'll try that last trick you mentioned. Thanks for the suggestions and help.
Following because fasteners are my passion. What size and thread is the one which you stripped? I don't know the 360.
10m x 1.25 snapped at the threaded adjuster. New bolt. Prior bolt had corrosion present. HVAC and PS adjustment bolts were smaller (8m possibly) both with course thread. HVAC bolt broke at the threaded adjuster as well, without any force being applied. PS adjuster was discovered at my first belt service in 2015/2016. This one threads into the bracket and the head was broken off.
Without seeing the assembly, my next step would be getting ARP M10 x 1.25 x (your length). M10 takes a lot of force to strip. M10 x 1.25 is fine thread. You didn't bottom out, you said. And technically you should not even need a 12.9 quality bolt. Are there any markings on the existing bolt head? Corroded of course, creates stress risers. Your M8 (typically 12 mm or 13 mm socket size) looks very much like a 5/16 UNC. Can be confused. But you ordered from Ricambi, which sounds like a reputable supplier. However, with ARP or SPS, you know what you get. With "hz" you mean torque in Nm? Your lbft x 1,4 = Nm. - approx, cos I don't know what lubrication the bolt requires anyway. But if you torqued in lbft you overdid it. It's a shocking amount less torque required when you use lube. Image Unavailable, Please Login
Dominik, you have a lot of good information there but there's a few key details that I didn't mention that have a bearing on this was well. The bolt technically didn't strip but rather snapped at the threaded adjuster. There is no torque value on the bolt since all it it's doing is functioning as a jack bolt to raise and lower the adjuster. The only fastener that is torqued is the one holding the tensioner pulley which locks the threaded adjuster in place, so in this case, lubrication does nothing but help the jack bolt. The bolts were ordered from Ricambi which sourced them from Ferrari / OEM supplier. Coming from the world of drag racing, I know all to well about ARP and SPS. However, this bolt is unique and not easily substituted for an off the shelf bolt. It's not the length or thread pitch but rather the head of the bolt itself and how it is retained in the bracket assy. The Hz I am referring to is Ferrari's method of determining the tension on their belts, in which you "strum" the long leg of the belt to achieve the recommended pitch. Just like tuning a string instrument. Again, there is no Nm value other than the nut securing/locking the tensioner pulley to the threaded adjuster to the bracket.
Did you inspect the belt for cracks? The frequency is essentially a function of stiffness and mass, so if you cant reach the required frequency, it might be an indication that something in your system causes an unexpected lack of stiffness.
I you could, please post a picture of the ends of the broken bolt. Maybe it had a crack already? When I did the belt service on my 360, I found the alternator easy to deal with. The tensioner worked great and I marveled at the simplicity of having that convenient bolt for getting the tension just right. I found the tensioner bolt easy to turn. How much torque was required to turn the tensioner bolt? It should be almost nothing.
brand new belt from Ricambi. 23 date code if i recall Sent from my SM-G998U using FerrariChat.com mobile app
Okay, my best move is not to find a 360 and have a look. I get your expertise and pointing out that the bolt snapped. And not due to bottoming out, or side load. (as in single hear). Also, it seems not to require a torque value as such, merely moving the adjuster. M10 x 1.25 x 50(?) mm is axle shaft and CV joint material. Ironically, a handful of years ago, I suggested to ARP to extend their range and offer them.
