secondchance
04-24-2016, 09:48 AM
After the the second 380 rebuild all was great except for irregular tapping noise at idle when the motor was fully warmed up. This noise got even worse with AC running. Eventually a mechanic at Dempsey's shop discovered the tensioner was bottoming out at idle looking at the bottom of the tensioner with the car sitting on a lift - what a relief!
This led to an email discussion with Marc resulting in a conclusion that my alternator ha a L98 pulley - 2.2" as opposed to 2.6" LT5 pulley.
Even with the pulley replaced, this knocking noise persisted. Visual inspection indicated the tensioner was still leaning excessively (close to un-tensioned position) indicating the belt was still too long. At this point I remembered installing new belt use to be tough - barely long enough to get it partially over the power steering belt and I would crank the motor to get the belt fully engaged. However, the new belt would slip on with enough clearance. Hmm...
Marc had told me typical belts listed for LT5 are 80.5" and suggested Dayco 5060800 which is 80". So, I picked up Dayco 5060800 and, sure enough, it would slip on barely with the tensioner fully retracted. This pushes the tensioner so that the tension is increased keeping the belt tighter and keeps the tensioner from bottoming out - fixed!
Further research, out of curiosity, led to a corvette forum discussion regarding the belt involving WVZR-1. It seems original belt specified by Chevrolet is 2037 mm (80.196"). It seems, possibly out of sloppiness or to mitigate owners returning the belt claiming to be too short, belt manufacturers somewhere along the line started to show 80.5" belts as being correct for our LT5s.
There are car to car variations and manufacturer to manufacturer variations. Nonetheless, if you notice unusual clattering at idle and notice the tensioner bouncing around excessively, check how much play there is between the belt and the power steering pulley. There are belts with incremental dimensions and one of these may be a perfect fit.
What I have found so far:
Dayco:
5060800 - 80"
5060805 - 80.5"
Goodyear Gatorback (Continental Elite)
4060801 - 80.1"
4060802 - 80.2"
AC Delco
6K798 -actually for 2012 Corvettes
80.375"
Thought I would share my findings and save other owners from replacing belts and tensioners unnecessarily due to similar situation with unexplained noise.
This led to an email discussion with Marc resulting in a conclusion that my alternator ha a L98 pulley - 2.2" as opposed to 2.6" LT5 pulley.
Even with the pulley replaced, this knocking noise persisted. Visual inspection indicated the tensioner was still leaning excessively (close to un-tensioned position) indicating the belt was still too long. At this point I remembered installing new belt use to be tough - barely long enough to get it partially over the power steering belt and I would crank the motor to get the belt fully engaged. However, the new belt would slip on with enough clearance. Hmm...
Marc had told me typical belts listed for LT5 are 80.5" and suggested Dayco 5060800 which is 80". So, I picked up Dayco 5060800 and, sure enough, it would slip on barely with the tensioner fully retracted. This pushes the tensioner so that the tension is increased keeping the belt tighter and keeps the tensioner from bottoming out - fixed!
Further research, out of curiosity, led to a corvette forum discussion regarding the belt involving WVZR-1. It seems original belt specified by Chevrolet is 2037 mm (80.196"). It seems, possibly out of sloppiness or to mitigate owners returning the belt claiming to be too short, belt manufacturers somewhere along the line started to show 80.5" belts as being correct for our LT5s.
There are car to car variations and manufacturer to manufacturer variations. Nonetheless, if you notice unusual clattering at idle and notice the tensioner bouncing around excessively, check how much play there is between the belt and the power steering pulley. There are belts with incremental dimensions and one of these may be a perfect fit.
What I have found so far:
Dayco:
5060800 - 80"
5060805 - 80.5"
Goodyear Gatorback (Continental Elite)
4060801 - 80.1"
4060802 - 80.2"
AC Delco
6K798 -actually for 2012 Corvettes
80.375"
Thought I would share my findings and save other owners from replacing belts and tensioners unnecessarily due to similar situation with unexplained noise.