Guest Anonymous Posted August 7, 2000 Share Posted August 7, 2000 For what it's worth, I had a similar prob. in a non-Chev. motor. The problem eventually turned out to be a minor mis-alignment of the water pump & alt. pulley, and (main cause) the main alt. bolt clearance hole & dowel having too much play at the front of the alternator. This would cause resonances on the alternator at certain revs, enough to either snap the main alt. bolt (which is a big bolt!) or throw/break the fan belt. I fixed it by simply shimming where the bolt went thru the dowel on the alternator (with a piece of a tin can from the trash.....). Resonance stopped, problem stopped... Hope this helps, or someone can give you specific Chev advice. Quote Link to comment Share on other sites More sharing options...
John Scott Posted August 7, 2000 Share Posted August 7, 2000 I also had the belt toss syndrome. Agreed, check the alignment carefully. Some pulleys can be out of round, alignment, etc as well as minor diff. in the water pump shaft lengths. Another cause is flimsy alternator brackets. Sometimes by shoring these up you can minimize the flexing. When I changed my alternator braket, the belts quit flying. Seen 8000 rpm a couple of times, ooops! JS Quote Link to comment Share on other sites More sharing options...
SpeedRacer Posted August 8, 2000 Share Posted August 8, 2000 Ditto on the alignment and check the mounting of the alternator bracket. Also check to see if any of the pulleys wobble. They do sell shims for the waterpump if you need one. Summit and Jeg's sell deep grove pulleys that should solve the problem but it will cost you a few bucks. Most of the HPO (solid lifter) SBC engines in the late 60's and early 70's had deep groove pulleys from the factory if you want to check some of the local yards. Quote Link to comment Share on other sites More sharing options...
PaulR Posted August 8, 2000 Author Share Posted August 8, 2000 Since I put a new 350 in my 240Z, I've been having problems keeping the fan-belt on. It often (not always) flys off on hard launches as the rev's hit about 6000 in first to 2nd shift. I am using a stock V-belt set-up with no accessories, ie just the crank pully, water pump and alternator (stock passenger side location). I am not running a fan off of the water pump (electric). I have double checked the alignment and tension and they both look good. Is this a common problem for Chevys? Any suggestions for solutions? Thanks. Paul Quote Link to comment Share on other sites More sharing options...
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