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Old 07-09-2005, 07:34 PM
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sbc balancer question

I have a motor I'm installing for someone ('89 350) and it was torn apart but I got a bunch of #$@^! with it but I don't know if it's the correct parts. The balancer I got with it is a 6 3/4" size and I was told that it's the correct one if the timing mark on the balancer is at approx. 2:00 at TDC. O.K.,,,, I put the no. 1 piston at TDC and the timing mark is at 2:00 but when I went to the parts house to buy a timing tab, they said a 7" and a 6 3/4 " are the same but when I hold the timing tab up to the motor, TDC is at 12:00 on the tab. Do I have the wrong balancer, and if so am I going to have to change the timing cover again??? The 8" timing tab looks like the one I need, could I just use that one?

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Old 07-09-2005, 09:07 PM
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The timing tab will most likely be different as they are also radiused to conform to the balancer diameter you are using. I say boycott the timing marks on the tab for now. If you can verify that you are at TDC and the distributor rotor is pointing directly at the number one cylinder post, you should be good. Take a look at the timing tab and use the reading to make any future adjustments. For example, if you are definately at TDC and the 0 degree mark on the balancer is at 12 degrees on the timing tab, add or subtract 12 degrees from where you want to be when setting the timing with a light and you should be good.

If the crank has a fine thread tap in it you can use whatever size balancer you want. Older small blocks had a press fit balancer. Mid 60's 327's, etc. for example, had a press on balancer. Your '89 should have a bolt on type.

Someone correct me if I am wrong, but I believe that smaller diameter balancers are normally used on lower horsepower motors and the bigger diameter balancers are used on higher hp motors.

I don't think you will have to changer the timing cover based solely on which diameter balancer you are using.

Like I mentioned earlier, the timing tab will be based on the balancer diameter. They should all be interchangable. By that I mean they should both bolt to the timing cover with no problems. If a 6-3/4" timing tab does not fit outside the balancer, chances are you have an 8" balancer and need a new tab.

Hope that helps.

never mind the smilie...I just think it's funny and had to used it.
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Old 07-10-2005, 05:32 AM
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My timing tab sets at 12:00 (like on a clock) and the timing mark on the balancer is at 2:00 (like on a clock) with the no. 1 piston at TDC. I can't time it like that, the tab and timing mark don't even line up.
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Old 07-10-2005, 05:51 AM
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put a line on the balancer using tire chalk
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Old 07-10-2005, 05:59 AM
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Most any auto parts stores sell the tab you need. I just bolts under two of the timing cover bolts.

Chris
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Old 07-10-2005, 12:54 PM
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If your timing tab has TDC at 12:00 you either have the wrong tab or have it bolted on the wrong two bolts on the front cover. I have a 383 sbc and TDC is at 2:00 position. Joe
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Old 07-10-2005, 07:04 PM
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I was told the small balancer had the timing mark at 2:00 and the larger balancer had the timing mark at 12:00 when the motor was at TDC (which is why I bought the timing tab for the 12:00 position) Obiously that don't appear to be the case. So, if I simply get a different timing tab,, I'm good to go.
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Old 07-10-2005, 08:21 PM
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Chevy made the large and small diameter balancers in both 12 and 2:00 positions. Later engines used the 12:00 position, the earlier engines used the 2:00 positions. Smaller cubic inch and lower HP engines used the smaller balancers. All 350 4 bolt main and HP used the larger dampners. 400's all used the larger dampner but it was not nuetral balanced and can't be used on any other sb. The balancer you have sounds like the ones normally found on 265, 283, 307 and low hp 327's. It will work on a 350 or any other sb except a 400. The larger the balancer is the better it will absorb vibration, but a smaller dampner will rev quicker because of the less reciprocating mass. The balance you have is not off of an 89 engine, it is I'm sure pre 79. Bob
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Old 07-11-2005, 05:59 PM
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To quote the Chevrolet Power book published by G.M., here is what they say about timing marks on dampers:

"Pre-'69 dampers have a timing mark that is two degrees before the keyway centerline; the mark is ten degrees before the keyway centerline on 1969-up dampers."

Although not mentioned in the Chevrolet Power handbook, they made a third style that has the timing mark 40 degrees to the left of the keyway centerline. This was used, I believe, on 1987 and later engines.

All aftermarket dampers, regardless of year, have the timing mark at ten degrees before (or to the left, looking at the front of the engine) the keyway centerline.

The aftermarket timing tabs sold by every speed shop and auto parts store in the world are set up to work with the ten degree location. This is for people who are putting 1969 and later stock dampers, or any aftermarket damper, on a pre-'69 engine.
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