Alternator Belt Tension

Jac123

.
Apr 19, 2019
48
Catalina 30 Forked River
I had dust from the alternator belt all over engine. Read the post here and removed light rust from pulleys installed new belt and so far (2 trips) no dust. The belt has needed to be tightened after each run.Used engine about 1-1/2hrs each trip. Is it normal for the belt to stretch the first couple of times? I bought a cheap tension guide -anyone have a tension number they use? Thanks
 
Oct 22, 2014
20,993
CAL 35 Cruiser #21 moored EVERETT WA
Morning @Jac123
I use the old mechanic’s technique of 3/8 inch (approx) deflection over the long gap, or less then 90 degree twist of the belt on the long gap.

Of note most dust issues come from out of alignment of the pulleys or improper alternator install. Use a straight edge to check the alignment. Be sure the through bolt on the alternator is the right size and the alternator does not wobble. You may need a spacer or shims/sleeve to get this right. Be sure the bolts are all properly tightened. It also helps to buy a good quality belt.

@mainesail had advise on alternator installation where he identified these important elements.

It is up to the installer to account for:
 Correct pulley to belt alignment
 Proper pivot bolt diameter
 Adequate belt adjustment range
 Correct bolt diameters, threads and lengths
 Proper torques and thread depth engagement
 Locking washers or nyloc nuts
 Correct belt & length
 Adjuster arm fitment, length or spacers”


There will be a little stretching of the belt. Not a lot. Proper install of alternator and you should get good service from your belt.
 
May 7, 2011
281
C - 30 # 3573 Lake NormanNC formerly Bflo NY
JA

It is normal for a little stretch but depending on what belt. What belt (mfgr and p/n) are you running?

Your alternator could also be slipping if you have the OEM bolt/washer.

Do not over tighten the belt. It will cause stretch (and you’ll need to replace your water pump and rebuild your alternator (bearings wear.)
The C34 forum itself also has many posts describing belt issues and “recent” ones with good pix on aligning and the bolt issues. It’s a great resource - many have the same engines in there as the C30.
 
May 7, 2011
281
C - 30 # 3573 Lake NormanNC formerly Bflo NY
The Dayco Top Cog belt is what my Wb distributor recommends because it has more surface area in contact, it dissipates heat better, and the cog being on top is better for the smaller size pulleys we have, like on the alt. If you experience any slip or wear I would go with that, I have for 20 years.
 
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Dec 5, 2015
114
Oday 272LE Louisville, KY
I'll second the Dayco top cog belt. It solved 95% of my belt dust problem on a M 12 engine.
 
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