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Bored&Stroked · 07-07-2022, 08:58 AM

Hey Chris - you're doing the right thing in tearing it apart. If it was mine, I'd surely ask the dang machine shop why they didn't mic the bearings BEFORE they ground the crankshaft?

You can't rely on standard undersizes on these vintage engines (especially as you're switching over from a babbit setup) - you have to setup the rods/mains and use a precision 3-point dial bore gauge to see what the bearings mic too - THEN you grind your crank to match.

Also, they SHOULD NOT attempt to achieve clearance by polishing the crank - it has to be reground to add the clearance and hopefully they have a good enough crank grinder (equipment and operator) to take off .001 to .0015 off the journals. I'd shoot for .00175 to .002 as a clearance as having it a bit "loose" is surely better than too tight.

On the mains, you should be able to easily grab the shout of the crankshaft and spin the crank over (obviously without the rods/pistons and cam gear on). If you can't easily spin it, then the mains may need increased clearance. The only thing I can't speak too is whether or not the rear main seal setup can cause drag on your particular engine?

Have them check the crankshaft end-play/trust clearances as well.

07-07-2022, 08:58 AM	#1469
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,070	Re: 1932 The Deuce, Dually, Dump Truck Hey Chris - you're doing the right thing in tearing it apart. If it was mine, I'd surely ask the dang machine shop why they didn't mic the bearings BEFORE they ground the crankshaft? You can't rely on standard undersizes on these vintage engines (especially as you're switching over from a babbit setup) - you have to setup the rods/mains and use a precision 3-point dial bore gauge to see what the bearings mic too - THEN you grind your crank to match. Also, they SHOULD NOT attempt to achieve clearance by polishing the crank - it has to be reground to add the clearance and hopefully they have a good enough crank grinder (equipment and operator) to take off .001 to .0015 off the journals. I'd shoot for .00175 to .002 as a clearance as having it a bit "loose" is surely better than too tight. On the mains, you should be able to easily grab the shout of the crankshaft and spin the crank over (obviously without the rods/pistons and cam gear on). If you can't easily spin it, then the mains may need increased clearance. The only thing I can't speak too is whether or not the rear main seal setup can cause drag on your particular engine? Have them check the crankshaft end-play/trust clearances as well.