Grinding a crank

I'm rebuilding my engine this winter and curious about crank grinding. I've read a lot about grinding technique and direction of the grind vs polish. Since all of this is really just the job of the technician doing the work, I'm wondering if there is a difference between grinding a standard crank and grinding the reverse rotating cranks.

I'm asking because I want to know if I need to make sure the technician knows it's a reverse rotating crank or if the polish is good enough that it really doesn't matter.

Find a machinist with graying hair; he's likely to know the details if he does marine engines. Fair warning, some folks you meet may look at you funny.   

Does it really matter what the direction of the rotation is then? The law of averages would be that they be righties

8122pbrainard wrote: Gary S wrote: Does it really matter what the direction of the rotation is then? The law of averages would be that they be righties There is some logic to the grind direction but personally I don't feel it's worth the effort.

I was referring to the method Quinner uses getting his crank ground

I am continuously amazed by the posts on this site. Are you having some mechanical issues or are these just performance enhancements? I ran my 74 all last year, 40 years old and other than fluids and a belt never once took a tool out all summer long.

Bummer. Yup, always amazed at the knowledge here, from mechanical to metallurgy...

As 8122pbrainard wrote in his post the bearings will work better with what is called a favorable polish of the crank to lay down the microscopic face of the crankshaft. Favorable polishing and reverse grinding was adhered to for many years of crank grinding at OEM and in the aftermarket. How much life did it really add to an engine I really do not know but it was said to hold oil better on the face of the crank while operating. I can say that Federal-Mogul came out with Silicon enhanced Bored Aluminum Engine Bearings in the early 2000's and they became the OEM standard because they held oil better. A bored bearing has grooves like those in an old style record used on record players. The bored bearings hold oil better and they live more than double the life of the old school bearings and one side advantage discovered after they were in millions of engines was that the bored silicon enhanced bearing would polish the crank for you. The cranks in those engines equipped with the Bored Aluminum silicon enhanced bearings looked better and measured smoother after 50,000 miles than they did brand new. A new crank might measure an RA of 15, the roughness measurement, run it and it would measure an RA of 8 to 10. Smoother than new. Most bearings will leave the crankshaft rougher than when installed. If it was mine I would run these type bearings and not even think about the direction of polish because the bearing would fix it for you.
FORD OEM had a crank polisher break down on one shift on a very popular engine build and a couple thousand crankshafts were installed on the next shift because nobody noticed they had not been polished yet. These were installed into cars and ready for shipment before anyone figured out they were built with no crankshaft polish done. Ground to size yes, polished smooth no.
Federal-Mogul advised Ford to run them as is and no problem would ever surface. Ford tested two engines with no crank polish and after a simulated 10,000 mile test the engines were torn down for inspection and found the cranks that were installed un polished came out of the test polished better than the standard OEM polish. Ford became believers in the new bearing technology. At that time the material was only tested to stock engine HorsePower ratings but some of those stock engines made 400 HP. ( Ford 351W in the Lightning was supercharged ) this was more HP than most of our boats are exposed to.
If you run the standard copper lead tin bearings which have worked very well in boats for 50 years, make sure the crank is polished and if you can get them to finish with a favorable polish for reverse rotation engines go for it. They could do this for you in less than 10 minutes shop time so not much cost is involved.

There you go, a long winded story about crank shaft grinding and polish work.   

Federal-Mogul called them Bored Aluminum Bearings. They were designated with an A. The standard 350 Chevy Rod brg was a 2555CP the Bored Aluminum A series was a 2555A. or an 8 pack was 8-2555A plus you would add Std, 10,20 or 30 depending on what size your crank was ground to.
The std 350 Chevy Main brg was 4663M For the A series Bored Aluminum main set the part number is 4663MA plus the oversize.
Ford 351W Rod BRG Set 8-3380CPA standard Copper Lead Tin,
8-3380A = Bored Aluminum bearing.
Ford 351W Main Std Set, 5078M copper lead tin.
Ford 351W Bored Aluminum is a 5078MA, A series 1977 to 1997.

The early 351W Main set 5107M is only available Copper lead Tin.

There is nothing wrong with the Copper Lead Tin, they were used for OEM for many, many years, the A series just has some advantages Copper Lead Tin can't offer. I checked this morning and the part numbers listed are the same today.

The basic thought behind using a favorable polish is simple. If you look at the crankshaft with a microscope the surface after grinding and polishing looks a little like a blade for your circular saw. The teeth on the blade all face one direction. Engine builders always wanted those teeth rotating back wards across the face of the engine bearing not rotating with the teeth pointing forwards in the direction of rotation. Most crankshaft grinders followed this practice.