Bellhousing Adapter negetive Shimming?

[fourbangerbob]

My adapter has no shims under the bolt ears--these are my readings:

Measured according to the " Les" Bible

top----.005

Bottom--.020

Les says .006 max diff. ---If I shim top, won't it get worse on the bottom?

[Joe K]

If I shim top, won't it get worse on the bottom?

Yes. To bring a "negative shim" you can file some off of the bosses on the engine (or the ears on the flywheel housing)

Fear not, you can always put shims back to bring it back to where it was.

But before you do this VERIFY your distance between the lip on the flywheel housing INCREASES in clearance between the top and the bottom as you do the Les Test.

I usually use the crank itself as my center base for testing. Spin the crank with the arm attached to the flange on the crankshaft. If you attempt to do the test with a stationary crank flange (a la "straightedge" method,) you can get biased readings on account of the flange not being square with the crank axis. This is a more common crank/flywheel defect than many realize.

And it's also possible that the dial indicator may be swinging across a zero indicating the REVERSE of what you might expect - as I say make sure deviation INCREASES as you go from top to bottom.

You may even find passage from top to bottom on the housing will show high spots and low spots. Especially so if your flywheel housing has the typical "mid-line crack." (which I don't consider fatal, but given a better choice I put an intact flywheel housing to an assembly.)

By putting little pieces of scotch tape alongside the bolts (and on the gasket) I was able to get my flange deviation down to about 0.003 - but this is playing around. About 0.006 is probably as good as it needs to be. (lotta flex and unknown inaccuracies in that bell-housing that the free motion at the clutch disk spline/input shaft make irrelevant.)

Hope this helps.

Joe K

[BRENT in 10-uh-C]

Really what needs to happen if have the flywheel housing trued. I would venture a guess that at least 3 out of 4 are out of spect by at least 10 thousandths, ...and some are 20 thousandths.

[Tom Endy]

When taking the measurements you need only be concerned by the top 180 degrees. The bottom 180 degrees will be pulled into position when the bell housing is bolted up. Before the bell housing is installed you can grab the bottom of the clutch housing and actually move it back and forth.

What I do is cut my own clutch housing gasket from .015 nominal thickness of gasket material. This should crush down to close to the thickness of the two .010 metal horseshoe shims. Torque the four bolts that connect to the engine block. Use shorter bolts or install the throttle linkage for the top two and torque. I prefer to use a pair of shorter bolts. The published specs is .006. You should be within this figure with a dial indicator across the top and on the sides.

Tom Endy

[Tom Wesenberg]

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Originally Posted by fourbangerbob

My adapter has no shims under the bolt ears--these are my readings:

Measured according to the " Les" Bible

top----.005

Bottom--.020

Les says .006 max diff. ---If I shim top, won't it get worse on the bottom?

You say "my adapter"..........is this the stock flywheel cover, or is it some special adapter?

I've never had a stock flywheel cover that didn't need to be shimmed to make up for the gasket. Double check your readings and be sure the crankshaft isn't moving forward and rearward as you turn the crank. Of course this is no problem if you are working with the engine in a stand with the front down.