Align Honing the Block

After the crank is installed, what needs to be done if it doesn't spin easily? Align honing!

plastic gauge

The crank was installed, main caps torqued to spec with plastigauge.

- I plasti-gauged the main bearings to verify clearances and found that bearing #1 (closest to the front) had a bad taper of 0.001" clearance at the rear of the bearing and 0.003" at the front. I measured it twice just to make sure that I didn't squeeze the plasti-gauge removing the cap. This means that the block needs to be align honed.

Match the width of the flattened Plastigage with the paper reference to determine the clearance

The crank was installed, main caps torqued to spec with plastigauge. I cleaned up the plasti-gauge and oiled all the journals. Reinstalled and checked to see if the crank by chance would spin easily. Spinning easily are not the words I would use! It definitely needed to be align honed. So off to the machine shop it went.

- At the machine shop, the caps had 0.003" taken off and the block/cap assembly aligned honed. After, the block was washed and once again needs to be painted :-( The shop had told me that I would need a "special" rear main seal that cost $33 because the block was aligned honed. I thought that this sounded pretty fishy as only 0.003" had be taken off which is only 0.0015" play per seal face. So I went looking for 2nd opinions about this.

- After 3 days of discussing this with about a dozen machinists, mechanics and partsmen and on the Internet newsgroups and getting mixed answers from "it was a crock of sh**" to "yes it's needed", I finally found out that it was indeed true and was unique with 400 blocks only.

When I got the block back, I plasti-gauged it again and every bearing was identical at 0.002" clearance and absolutely no taper. Cleaned up the bearings and lightly oiled them then retorqued the caps back on. The crank spun very easily, I'm one happy camper!

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Copyright May 2011 Eugene Blanchard