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
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.
If this damper and crank snout are compatible w/one another, something that will help the installation is to heat the damper up to 200º 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.