View Full Version : got my bhj damper today and.....

08-04-2002, 04:34 AM
i got my bhj damper today and was looking at the paper work that came with it. it said something about having the inside diameter honed to where there is only like 0.001 to 0.0015 of a difference between it and the crank. i guess my question is do i have to do all that or will it just bolt right up with no prob? supposedly if the gap is too big it will ruin the keyway and too small and the damper could weld itself to the crank. oh yeah, and the stock pulley and damper were both balanced separately or neutrally right?

MIKE 38sc
08-04-2002, 06:33 PM
Yes you will need to check the clearance and if it is not in spec. you will have to have the balancer honed out. Apparently there is such a variance in the production tolorences of the crankshaft that it was impossable to machine the balancer to where it would perfectly fit every crankshaft. Its really a shame Ford got so slopy with the production tolorances, you wouldnt beleive some of the crap I found while blueprinting my engine. Theres really no excuse for it.

08-05-2002, 09:48 AM
What does blueprinting an engine involve? Is this just
measureing all clearances and stuff?

j. :eek:

08-06-2002, 01:51 AM
Blueprinting is taking all the spec's to the prefered tolerance.

This would include as an example but not be limited to:
All bearing clearances the same and set for the prefered oil.
The decks flat and square with the crank and same height.
All combustion chamber and piston volumes the same for CR.
Rods, pistons, and crank checked for length dimensions and balanced.
Rockerarm on valvestem geometry verified.
Block cam and crank bearing bores alignment verified.

All this work increases the labour needed to rebuild an engine to an insane degree. Most of it is just checking and verifying but if things are out you have to be able to do something about it.

Many general rebuild shops are not able to hold the tolerances to do this work and those that can will charge heavily for it. An example would be planing the heads to square them and balance the chamber volumes to the desired depth. Most shops plane heads with a large grinder much like a belt sander. It takes off around 0.010" where ever the operator pushes hardest. The prefered method for a blueprint would be a milling cutter or a surface grinder that could precisely remove from 0.002" to 0.100" from whatever corner you wished, and leave a perfect surface finish.

Steve Best

MIKE 38sc
08-06-2002, 08:06 PM
Yes and so much more.;)