HouTXCutlass

Hey,

What is the purpose of the alt bracket that connects to the intake, head and main alt bracket? The main bracket is connected to the top of the alt and the bottom connection has the tension adjustment bolt and it seems a sturdy as needed with just that main bracket. I guess GM had their reasons for it but I've seen plenty of other cars with just a bottom and top bracket and no additional brackets for bracing or whatever. Does anyone know the purpose other than just extra bracing? Does it need to be installed?

Thanks,
Rob

joe_padavano

You can rest assured that the bean counters at GM did not approve the installation of an unnecessary bracket. Eyeball engineering is notoriously inaccurate, particularly when it comes to fatigue failure. Yeah, I'm sure someone will post that they've left the bracket off and the alternator hasn't fallen off, but these cars were designed to survive for many years over rough roads and subject to constant vibration. All metals have a fatigue live where after a certain number of cycles at a specific stress level, the metal will crack and eventually fail. The larger the amplitude of the vibration or flexing, the shorter the time to failure. This is the same phenomena that lets you break a paper clip by bending it back and forth. The added bracket reduces the vibration-induced deflections and thus extends the fatigue life of the bracket assembly out to just about infinity. Also keep in mind that it was cheaper to throw metal at the car than to perform detailed analyses and testing or to manufacture the parts to tighter tolerances.

bccan

My experience w/ that bracket is on a/c cars that have most of the time had the a/c deleted or engine being used in another chassis. Under hard rapid acceleration or as rpm climbs insay, passing gear, the alt belt would start to slip & squeal. I think when brkt is not present the alternator gets pulled inboard enough to allow it to slip, especially if you are winding more than 4-5k rpm. I have used that bracket (in modified form due to tall valve cover height) to solve reccurring belt squeal. You may notice that by '72 (not sure about '71) they reconfigured that bracket but the effective support is still there.

If you care or others interested, you can see the modified brkt in engine shots from my post in this thread. Clearly visible on engine in blue car. Blue car has VC spacers, red car has tall covers so stock brkt won't clear them.

http://www.oldspower.com/vb/showthre...ighlight=stray

bammax

If your talking about the rear support bar then GM used that for years across the engine lines. I've seen pretty much every v8 GM made with that brace and never heard of any issues until people started taking them off. On the LT1 engines from the 90's removing that brace would eventaully lead to the primary bracket cracking in half since it was made of aluminum and couldn't deal with the constant flexing.

HouTXCutlass

Ok well, I don't need to hear any squealing of that sort, so on it will stay.
Thanks,
Rob