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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Ds2014 on October 17, 2014, 06:00:06 am

Title: Throwing belts
Post by: Ds2014 on October 17, 2014, 06:00:06 am

I keep throwing belts off? Any suggestions? They come off at about 6 thousand is this normal do I need a serpentine system?

Title: Re: Throwing belts
Post by: Ds2014 on October 17, 2014, 02:19:24 pm

Sorry guys 81 stepside small block 400 th350 2wd

Title: Re: Throwing belts
Post by: jaredts on October 17, 2014, 03:14:14 pm

Check for runout of pulleys and pulleys that are misaligned.  Any particular belt?

Title: Re: Throwing belts
Post by: Ds2014 on October 17, 2014, 04:22:41 pm

The alt comes off and the ac turns inside out

Title: Re: Throwing belts
Post by: Stewart G Griffin on October 17, 2014, 07:24:55 pm

You mean they come off at 6,000 rpm?   That may be your problem......

i think there are some deep grove pulleys available for alternator.  Don't have much time to research now though.

Title: Re: Throwing belts
Post by: roundhouse on October 17, 2014, 10:20:21 pm

I'm surprised the pistons haven't come out of the block if you're revving it to 6K

Do they come off when you drive it normal?

Title: Re: Throwing belts
Post by: bd on October 18, 2014, 12:57:35 am

Quote from: jaredts on October 17, 2014, 03:14:14 pm

Check for runout of pulleys and pulleys that are misaligned.  Any particular belt?

Also, inspect the pulleys for uneven groove wear and groove narrowing (pinching) around their circumference. 

Are you using high quality, name brand belts (Dayco, Gates, Goodyear, etc) and are the belts tight enough?  At six grand you may be enjoying the result of a standing wave developing in one or more belts, or they may be stretching like rubber bands.  An alternator belt isn't tight enough if you can rotate the alternator pulley by firmly grabbing the alternator fan and turning it with your hand while the engine is off.

Once you've inspected, replaced and properly adjusted pulleys and belts, if the problem persists try removing the A/C belt completely to see if the alternator belt still spits off.

Title: Re: Throwing belts
Post by: Ds2014 on October 19, 2014, 06:52:52 am

Roundhouse it's a balanced eagle assembly lol it is scary sounding to hear a v 8 spin 6000

Title: Re: Throwing belts
Post by: Ds2014 on October 19, 2014, 06:53:28 am

Thanks bd, I'm going to check all of the above today

Title: Re: Throwing belts
Post by: VileZambonie on October 19, 2014, 07:56:19 am

Run the large crank pulley and ensure you have proper alignment. An idler can help as well