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post #1 of (permalink) Old 04-30-2002, 11:01 AM
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harmonic balancer

Is there a specific model of harmonic balancer for each engine type, or can/should different ones be used depending on the appilcation?

I have a '75 Blazer with a 350 that may be developing a vibration issue that I've been told could be the harmonic balancer. However, the motor is not original and based on the engine numbers appears to be out of a '70 Impala. The motor has been rebuilt before I owned the truck, and generally runs strong. I use it to tow a 5000# boat/trailer regularly. Other than gas mileage (never above 9mpg), I've had no complaints about the way it has been running for several years until it started throwing the belts 6 months ago. As part of diagnosing that problem, the suggestion has been made to check the balancer. However, the balancer currently on the engine is a bigger diameter than the one the Chevy dealer identifies as the correct one for this engine, which supposedly would also be the same part as for the original 350 the Blazer would have come with.

Anyone have any experience dealing with the balancers?

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post #2 of (permalink) Old 04-30-2002, 11:14 AM
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Re: harmonic balancer

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<font color=green>I believe the only oddball is the damper for the 400, since it is an externally balanced engine. The rest of the engines should be able to use the same damper.
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post #3 of (permalink) Old 04-30-2002, 11:56 AM
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Re: harmonic balancer

There are a few different sizes. But they all work the same, and will inter-change. The only thing to watch out for is that you have the correct timing cover for the balancer. The smaller diameter balancer has a lower timing mark guage tab thing on the cover. I've seen a few balancers that have "work out" for lack of a better description. The rubber between the two sections is worn out and shakes a little. Not a big deal to change, and they are all basically the same. Having a different size just means that someone has had it off before.
One of the things you might want to check (not sure if you have already) is the pulley to the balancer. Sometimes the bolt holes get stripped and the pulley will sit crooked. I've had to change a balancer because of that before.
Hope this helps. Good luck!
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post #4 of (permalink) Old 04-30-2002, 02:58 PM
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Re: harmonic balancer

In my short existance, I've seen six different harmonic balancers for 305-327-350. I'm sure there's more.

I'd just find one that your pulley will bolt to. That's always been my problem.

I usually stick the biggest/heaviest balancer I can find on it. I'd rather have a low idle than throttle response on my truck.
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post #5 of (permalink) Old 05-01-2002, 03:15 PM
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Re: harmonic balancer

My 79 Jimmy came with a 350 with an 8 inch balancer on it. The timing chain had worn through the cover and I had to buy a new one. The timing mark one the original cover was no where near the one for the aftermarket cover. Make sure the balancer you get has the timing mark relative to the keyway in the old balancer or the timing will be way off.
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