Re: Henry's 55 Constellation

Posted by Owen_Dyneto On 2010/12/15 9:48:03

okay, what would help me determin if i need standard size main and rod bearings? the motor only had 47k on it supposidly and i didn't see much wear on the bearings that were in there, but i'm no expert obviously.

I think you should start by reading a really good book on the general principals of engine rebuilding including evaluation and measurement. To me one of the best was Glenn's but it's long out of print, though no doubt there are others. Generally this will give FAR more information than you'll ever find in a shop manual.

But you could start by dropping the oil pan and using plastigage to measure the clearances of the rod and main bearings as they presently are. When the bearing saddles are down (do one at a time) to insert the plastiqage, take time to examine the crankshaft for smoothness and absence of defects. If the clearances are within specification are the bearing and crank surfaces are in good condition, determine by part numbers on the current bearings if they are standard or undersize and replace with the same size.

BUT at least on the rod journals, a better suggestion would be to buy a good micrometer and measure the journal top-to-bottom, left-to-right, in several places and compare your measurements to the original crankpin diameter specifications. This will tell you if the rod journal is worn out of round enough to not hold a new bearing properly and will require crankshaft removal and resizing. 0.001 out of round is probably about the limit. A bit tougher for the mains as with the crank in the block, you won't be able to get an easy measurement. Anyway, that's a starting point and I'm sure others will come along and elaborate.

For the rings, remove a piston, examine the ring grooves for wear, giving special focus on the top one. Measure the clearance between the ring and the land and compare to general guidelines for clearance. If the groove has become tapered and you will reuse the piston, cutting the groove oversize and using a spacer with new rings will be one alternative. But I'd certainly remove the pistons, clean them and have them dye-checked for cracks, and plan on replacing the piston pins and bushing.

If you want, PM me with your USPS address and I'll photocopy some pages from Glenn's for you to read.