Carrera Alternator Belt Tension

[mwelitzkin]

im having trouble with my belt tension after replacing my alternator.

i have 6 shims on the outside of the pulley, but barely enough room for the nut. I had 6 shims when i took off the old belt. should i move 1 or 2 shims to the inside of the pulley to loosten the belt? I noted that the pulley is wobbling a slight amount when installed with 6 shims? is this beacuse its too tight?

any help is welcome.


mark
mwelitzkin@aol.com
84 carrera
los angeles

[banjomike]

It is correctly tight when with a good effort you can deflect the belt 1/4 - 1/2". I think over the years there were a few different pulleys on the fan side and there may have been diferent shims and nuts on that pulley. Maybe you have the wrong bits on that pulley. Or maybe the belt isn't quite right (if it were too narrow you'd have this problem).

[ZCAT3]

Mark - when you have all of the shims outside the pulley, you have the belt set as tight as you can. So when a belt is old and has stretched, you are likely to see more shims on the outside. Since you just replaced the old belt with a new one, it is natural that you will need to move some shims inside the pulley as the new belt should be tighter than the old one. I would take 3 shims and put them inside. If after you have tightened the nut and turned the pulley a bit to get everything to settle in it is too tight or too loose then move another shim in or out. Mike's test for tightness is a good guideline. The pulley should not wobble.

[djmcmath]

I would only add one thing -- as a second check for tension, put the tranny in neutral and try to turn the engine via that 24mm nut. If the belt slips a lot, it's too loose. If it slips just a little bit, but not so much that you can't move the engine if your'e careful, you've got it about right.

The factory procedure, iirc, says to start out all the way loose (ie, all shims between the pulley halves), then test it by moving one shim at a time until it's right.

Dan

[Wil Ferch]

Make sure you have the correct circumference belt ( 710 vs 725 mm).


Wil

[ricochet]

I replaced my belt a while back, and started with 2 shims inside, 4 out. The tension seemed correct, but I noticed the pulley on mine was slightly wobbling. I kept driving it, then soon, I got the alternator light.
Well, the pulley had come off the CRANKshaft, that's when I found why she had been wobbling, appareantly the 24MM bolt was not tight enough. The results: the pulley was trashed, and the end of my CRANKSHAFT was somewhat scarred up, with the guide pin hole unuseable. I tried, but the new pulley did not seem right. I had a machine shop dress up the pulley end of the CRANKSHAFT, oversize ream the old hole (for a larger diameter hardened pin) after he had drilled a second hole for a new pin (180' over). I now feel confident this will hold. Grab that pulley and see if there is any looseness, also check the pulley to CRANKSHAFTS bolt tightness.
Hope this is not your case, but if I'd read this earlier I'd have not screwed mine up. Just in case

I edited my referrence to flywheel as CRANKSHAFT, I was just in from a long day and too little sleep. I MEANT CRANKSHAFT, I believe you guys get most things right, I misstated this. But I never had ..., yet I got it wrong.

Just look for the 24 mm bolt in the center of your CRANKSHAFT pulley, you'll get the main message and my intent. It happened to me...

[randywebb]

flywheel?

[ricochet]

OOPS!!! Crankshaft. I was in a tight for time and made a mistake (in a hurry). I apologize, meant well. I stand corrected, and will correct my error.
Sorry folks, flywheel was misstated. Thanks fer the question, but ya get my drift? Am a newbie (sorta) but was building engines 30 years back (mostly 2 stroker enduros to start).

BUT I SHOULD UNDERSTAND A CRANK FROM A FLYWHEEL.

[Lorenfb]

Bottomline: It's always better to have a squeaky belt than a bad bearing.

That rear plastic bearing support on most 911s just "love" that extra load.
Most overtighten the alt. belt, especially on 964s, which can snap the shaft
because of the 964's extra long shaft.

[RoninLB]

Originally posted by Lorenfb
Bottomline: It's always better to have a squeaky belt than a bad bearing.

I'm with Loren on this one.
After the belt break-in I'll adjust it loose enough so it's not Flapping if I quickly rev the engine.