Belt for Delco alternator conversion on an '82 928
10-11-2019, 12:17 PM
#1
Belt for Delco alternator conversion on an '82 928
Folks - I am doing the Delco alternator on my '82 928. The instructions I found on this site recommended a Goodyear Gatorback 4050345 or Dayco 5050345 belt. I bought the Gatorback only to discover my old belt had 4 grooves and the new belt had 5. Oops! I went back and looked at the instructions and the guy was working with an '84, so I am guessing that there must have been a change since my car's MY.
The old belt was a Contitech 4 pk 858 and I will need something a little shorter. Has anyone done this to an older 928 - can you remember what belt you used? I would rather not modify the belt tension bracket if I can help it. Thanks!
The old belt was a Contitech 4 pk 858 and I will need something a little shorter. Has anyone done this to an older 928 - can you remember what belt you used? I would rather not modify the belt tension bracket if I can help it. Thanks!
10-11-2019, 01:15 PM
#2
Pro
Based on the "how to read the number on a serpentine belt" on Gates' website (https://assets.gates.com/content/dam...tt001-16.pdf):
The original belt would be a 4 rib, Metric belt, with a length of 858 mm.
I found the Dayco 5050345 is also known as 5PK875, which would be 5 ribs, 875mm length.
I couldn't find a direct interchange PK number for the Goodyear belt, but with the same *50345 in it's part number, it's likely the same belt.
It sounds like they were going the wrong direction in length, based based on the numbers, as well as it being one rib too wide.
As to which belt you should buy, make a best guess as to how much shorter you want to go, and look for an appropriate belt?
As an example: if your current belt maxes out the tensioner motion, and you want to pull it back ~1", buy a belt that is ~50mm shorter, such as a 4PK820 or something near that.
The original belt would be a 4 rib, Metric belt, with a length of 858 mm.
I found the Dayco 5050345 is also known as 5PK875, which would be 5 ribs, 875mm length.
I couldn't find a direct interchange PK number for the Goodyear belt, but with the same *50345 in it's part number, it's likely the same belt.
It sounds like they were going the wrong direction in length, based based on the numbers, as well as it being one rib too wide.
As to which belt you should buy, make a best guess as to how much shorter you want to go, and look for an appropriate belt?
As an example: if your current belt maxes out the tensioner motion, and you want to pull it back ~1", buy a belt that is ~50mm shorter, such as a 4PK820 or something near that.
10-11-2019, 02:42 PM
#4
Former Sponsor
As Porsche increased the output potential of the 928 alternator, they had to make the belt wider and wider, to keep the belt from slipping/burning up. You may find that you need to do the same thing.
10-11-2019, 06:25 PM
#5
The winning belt wound up being a Gates K040332. With the original 928 alternator pulley, slightly smaller than the Delco one, it fits with plenty of adjustment room to spare.
Thanks for the heads up. If it does start to slip I will try the Delco pulley first so as to get a little more mechanical advantage on the alternator. I hope I don't have to put a new pulley on this thing. All I've done is wrench on it since I bought it home! New ball joints, new power steering hoses, new alternator... the list just keeps growing!
10-11-2019, 07:30 PM
#6
Pro
The winning belt wound up being a Gates K040332. With the original 928 alternator pulley, slightly smaller than the Delco one, it fits with plenty of adjustment room to spare.
Comparing it to the original 4PK858, it sounds like it's only 17mm shorter, which sounds like it wouldn't do that much. That said, if it works, great!
10-11-2019, 07:49 PM
#7
For some reason, the new belt seems a lot shorter than the old one. You are right, 17mm does not sound like much.