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charlie coghill
08-21-2005, 07:41 PM
Is any one else building/going to build the .6 crusader that is running in the July/August issue of HSM?

I am having a problem with the dimentions on the top of the crank case. The drawing does not locate the 4 tapped holes very well unless I an missing something.

On the drawing of the crank case that showes where the cylinder will set, it gives the hole location from each other and gives one hole location of .185 from the edge. It does not locate any hole from the back side of the crank case.

Looking at drill jig C the edges are located from the center of the hole.

My thoughts are, that after drilling and boring the cylinder hole on the crank case, I will look at drill jig C and half the diminsions given, ie .940=.470 and 1.190=.585 and move those distances to locate the first hole and the rest would be easy.
Just move the distances between the holes that are given on drill jig C.

Maybe this is the way the author intended for it to be done.

More than likely, I will not make the drill jigs, having a DRO on the mill solves making the jigs.

Do any of you see any other way of doing this?

JCHannum
08-21-2005, 08:13 PM
I will probably try this engine, but usually wait for a couple of issues before starting. I also will not be visiting my aluminum supplier until the end of the month.

It looks like the holes are located symmetrically to the bore. You probably can't go too far wrong by doing that. The location probably is not too critical, especially if using fixture C to locate them. If you wait for the next issue, and see what the cylinder looks like you can drill them then. The main consideration is probably to leave clearance for cylinder mounting bolts.

The tip to mark the fixtures top & bottom to keep proper hole orientation is a good one, if there were minor differences, this would compensate for them.