Setting Up Main Rod and Bearings

By Tom Mason

Originally published in the Austin-Healey Magazine


I have rebuilt my share of engines that have run, and run very well. However, I learned a lot about rebuilding at Quality Coaches.


The first thing to set is the end float on the crankshaft. Normally this will be about .003 to .007depending on your engine. Next, each main bearing should be checked with plastigauge and then torqued. At this time, you should be able to spin the crank easily by hand turning the flywheel. If there is a bind you should stop and investigate the cause. Finally, the pistons should be installed and then the rods torqued and plastigauged. Plastigauge is easy to do, all you need to do is put a little piece on the bearing and torque the cap. You remove the cap and compare the size of the crushed plastic to determine the clearance.


One final thing I learned is that each ring must be inserted in the bore and the end clearance should be checked. If it is too tight the ends of the rings should be cut or filed down until the end clearance is within specs. The Mark I 3000 should be .008 to .013. There is a special tool with a diamond wheel that makes the job easy. Some engines will be just fine and others will be too tight. If the clearance is tight the engine can seize when it gets hot.


These are some of the new checks I learned rebuilding engines. Thanks, and a tip of the hat to Scott and Brian at Quality Coaches.


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