by George Lyle and Jim Thompson
George Lyle writes:
Fan Belt substitutions: If you need a belt out in the boonies, a 10mm by 930mm belt will replace the standard 9.5mm by 905mm belt if you put all of the shims between the pulley halves.. The former belt can be found at NAPA distributors and is a lot easier to find in Wyoming than the OEM Continental belt. In the future I'll carry a spare Continental belt, as I like its fit better. I'm also going to get a few more pulley shims to get a wider range of adjustability.
If you're unfortunate enough not to have a spare belt and need one in an unknown town, this info might of benefit to other "Upright Engine" Folks:
The 9.5x905 is just a hair over 35 1/2" long. Gates is a popular & quality belt maker that seems to be everywhere. Although Gates lists their PN 7355 as a replacement, I have found that it to be just a little too tight, being 10mm (or more) in the width. Better choice is a PN 7360 which is 36 inches (914.4mm) long, fits and adjusts better. The factory supplied 8 shims for adjustment, but like Lyle, I always carry at least half a dozen extras, just in case. (And I always carry two spare belts - I'm just a little more paranoid I guess). 36 inch belts are used on an enormous amount of rice-burners and are easier to find.
The 9.5x905 belt is also available at the Volvo dealer under PN 973547 as a last resort too. A Mercedes model (don't know which) uses a 10x910mm (37 3/4 inch) belt as another option - PN 006-997-02-92
When installing a new Continental 9.5x905 Belt, I've usually found that 5 shims between the pulley halves is best at first. After 100 miles, I check it and in most cases, remove at least one shim to re-tension the belt correctly.
This of course applies to stock crank pulleys & stock OD degree pulleys --"your mileage may vary".
Jim Thompson writes:
The way I was shown by several knowledgeable Vee-dubbers (and it's worked for me for over 30 years) is to have the outer portion of the belt just inside the pulley groove area (about 1/8 of an inch) than to having it ride on the top of the groove. If the belt is placed lower within the groove area of the pulley, the belt tends to cause the pulley halves to work back and forth, cutting and wearing out the center shaft area of the inside pulley half. Most VW people (to include myself) know what the resulting noise sounds like when a pulley explodes (or is getting ready to) because the belt was not properly positioned and tensioned. I've seen people with the belt riding high where the belt enters the pulley on the left and then cuts severely through the two pulley halves and exits out the right - not the proper way to have your belt running.
Optional belts mentioned in my last post are for TEMPORARY use only to get you out of a jam and until you find and install the genuine Continental 9.5x905 which still works the best.
You effectively reduce your fan speed, by increasing the size of your
generator pulley. As volume is increased or decreased as a function of
fan speed, this is one more factor to examine if you feel your engine
may run hot."
"This is excellent information. It did however jog a thought (ouch).
The stock pulley/belt setup should give a 1:1.9 ratio of crank to
generator. This info is for the 1500/1600 class, upright engines.
If you run a worn belt, or one that requires the pully be adjusted so
the belt runs out at the rim of the generator pully, you reduce your
You effectively reduce your fan speed, by increasing the size of your generator pulley. As volume is increased or decreased as a function of fan speed, this is one more factor to examine if you feel your engine may run hot."
Starting about 8 years ago, Continental began changing their belt production to what they called "world standardization". This means 12.5mm becomes 13mm, 9.5 becomes 10mm. Almost all of the 9.5 belts I'm getting from Conti are 10mm now, with the notable exception of the 905mm belt (40HP, 1300/1500/1600 applications), but I've been hearing that soon this will only be available from Conti in a 10mm width as well. Volkswagen already lists the 111-903-137D belt as a 10x905mm in their parts database. Oh well.