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Old 07-20-2011, 01:59 PM
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Balancer bolt problem!

I am putting together a 327sbc.I bought a new harmonic balancer and a new bolt. The balancer wont go on the crankshaft snout and the bolt won't screw in to the crank at all even without the new balancer.The threads on the crankshaft look O.K. so I am wondering if Chevrolet made different size balancer bolts. This crankshaft is your basic 307/327 cast piece from around 1970. Please enlighten me,Thanks B.P.

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Old 07-20-2011, 02:41 PM
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Go to your local parts store and rent a balancer installer. Don`t do anything such as hone the balancer out to size or sand it, it has to have a tight interferance fit otherwise it`ll work loose, break the bolt and the balancer and if your really lucky like I was sheer off the keyway of the crank which ruins it and ended up costing me another $450 clams to fix. As for the bolt as far as I know chevy used the same threads in all the cranks. You may want to inspect the threads in the front of the shaft very carefully as they can be crushed together but look normal to the naked eye. If your sure the bolt threads are correct, Get a high quality thread chaser and go over the threads. if the threads in the crank are damaged it`ll have to be heli-coiled.
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Old 07-20-2011, 02:55 PM
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balancer/bolt

Thanks alot,I appreciate the solid advice....B.P.
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Old 07-20-2011, 03:19 PM
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right stuff

Gr. 8, 7/16"-20 x 2-1/4" long. Mr. Gasket 945G is a good grade 8 washer and bolt package or you can go with ARP's finest.
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Old 07-20-2011, 08:01 PM
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Quote:
Originally Posted by Ballpeen
I am putting together a 327sbc.I bought a new harmonic balancer and a new bolt. The balancer wont go on the crankshaft snout and the bolt won't screw in to the crank at all even without the new balancer.The threads on the crankshaft look O.K. so I am wondering if Chevrolet made different size balancer bolts. This crankshaft is your basic 307/327 cast piece from around 1970. Please enlighten me,Thanks B.P.
The most common thing would be that you have a 1/2" bolt (usually used on aftermarket SBC and most all BBC cranks), instead of the usual SBC 7/16" fine thread bolt.

But there are other possibilities:

There were 327 cid large journal cast cranks made around '68 that didn't have a hole drilled for a damper retainer bolt, period! The damper was pressed on and that was that.

A crank lacking any hole like this could have been drilled out for most any size bolt that someone wanted and could even be a 3/8" fastener, and either fine or coarse thread depending on what tap they happened to have on hand. So before assuming anything, take the time to see exactly what size the threads in the crank are actually for before screwing anything into it.

Also:

There are some damper and crank snout combinations that do not give the required 0.0007-0.0014" press fit (or whatever the manufacturer recommends, if different from this) when used together. This is especially true of some of the offshore dampers- if the internet reports are to be believed.

It takes good tools and good techniques to measure that small of a difference- and it takes precision equipment like used to hone rods to open the ID of the damper if this is needed- you do not want to have at it w/a piece of sandpaper or a flapper wheel mounted in a drill.

And finally:

If this damper and crank snout are compatible w/one another, something that will help the installation is to heat the damper up to 200 F before installing it onto the crank. And by all means, use a damper installer to put the damper on. The damper installation tool looks something like:

And don't forget to use some sealer on the damper keyway to prevent oil from seeping out once the engine is running. It doesn't take much, just a light application. You can apply a light coat of grease onto the crank snout as well.

Good luck.

Last edited by cobalt327; 07-20-2011 at 08:31 PM.
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Old 07-21-2011, 05:30 PM
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balancer/bolt

Thanks Cobalt, I think I have it solved. The cranksnout just needed a little cleaning and some very minor smoothing with light sandpaper(#320),then I rented a balancer installing tool and cranked it on.It was still a tight fit but I think it's all the way on.I have a more experienced buddy coming over to make sure.If I have any more issues I'll be back for more help.Grateful again, B.P.
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Old 10-19-2011, 11:31 AM
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Use caution when using any abrasive material on the crank snout. If you reduce the diameter of the snout, then you are screwing up the press fit of the damper hub onto the snout. This must be a tight press fit in order to transfer crankshaft harmonics to the outer inertia ring to be dissipated.
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