Crankshaft grinding 101

[1972ho]

https://youtu.be/VDx7gU-fXcs Just in case you never have saw it done

[miniv8]

Thanks for sharing that

[racear2865]

This indeed is the general idea, but "far" from what has to be done and how to do it. Dont get wrapped up in this video too deep or do a lot more Utubing
reed

[miniv8]

Hence the title... 101

I've never seen such a thing up close.

Grinding cranks would be pretty simple if if all the knowledge, tips and tricks could be compressed into a basic introductory video.

[amc fan]

You can use a large travel dial indicator stroke checker to get the stroke right . The tricky part is indexing the rods on a V8 every 90 degrees accurately. I have seen guys use the degree marking by the chucks , but you have to interpolate the degree setting with the scribed mark. you can also use the dial indicator after you finish the first journal and use that reading to adjust the index but compensating the reading on the dial for the unground diameter, and assuming that the stop is accurate across the table.

[1972ho]

Now I can see why my recently ground crankshaft journal are all over the place in stroke and oil gap.I probably should have waited until Castillo was feeling better.

[PackardV8]

You can use a large travel dial indicator stroke checker to get the stroke right . The tricky part is indexing the rods on a V8 every 90 degrees accurately. I have seen guys use the degree marking by the chucks , but you have to interpolate the degree setting with the scribed mark. you can also use the dial indicator after you finish the first journal and use that reading to adjust the index but compensating the reading on the dial for the unground diameter, and assuming that the stop is accurate across the table.

It is amazing to watch in person how quickly a 20-year-expert machinist can put a crank floor-to-floor and be within tenths on all the journals. However, those who regrind several crankshafts every day tell me most older OEM cranks won't index/stroke at all. Grind the first journal .010" and then find the next one will have to go .030" to bring it in line with the first and then who knows what the next two will do? They won't even try to equalize stroke and index to 90-degrees. Too many cranks would go junk.

[rustbucket79]

Now I can see why my recently ground crankshaft journal are all over the place in stroke and oil gap.I probably should have waited until Castillo was feeling better.

Are the rod journals .010” smaller than how you gave it to the shop? If so, your crank was just as crappy before the grind.

You just can’t change pin timing and stroke all that much, because for every .001” remove on one side of the pin, with a perfect setup you’ll remove that same .001” on the opposite side. If you wanted to add stroke you achieve that by removing more from the underside of the pin, so if you move your chucks .005” it will remove starting from the one side, but the opposite side will be .005” away from the stone now. It’s really tough to mess up stroke and/or index and have it clean at the next underside.

I’ve run 2 different brand crank grinders, there were some differences but both had indexing locks for at least the 90 degree throws.

I’ve ground a number of aftermarket cranks, and despite how perfect the advertising claims, they aren’t that close. At least the offshore stuff from what I’ve seen.

[rebelyell]

https://youtu.be/VDx7gU-fXcs Just in case you never have saw it done

Thanks, but ... just goes to show how no good deed goes unpunished.

[dannobee]

For those of you who grind cranks, is this one closer to how you do it?

https://www.youtube.com/watch?v=snYsCEcu2rk

I've done pretty much all other automotive machining but crank grinding. I left it to those old timers who always had decades of experience doing just crankshafts.

[ProPower engines]

One thing missed here is why the crank is getting machined.
For those that want to start with a still std journal size just well scratched or worn a bit too far to just polish depending on what crank brand GM Ford Dodge etc most times I have seen they can get to within .002 on stroke and 1 degree on index.

Now that maybe just lucky so far but I have seen many cranks that wasted a rod throw and can't be machined correctly.
I have seen as much as .025 stroke increases which really mess's up a 0 deck build when you get the shaft back from being repaired.

It is a dying art for sure and most guys that grind are less then half of a new crank it seems. At least what I see in the US.
Where guys are selling that job for less then $125 just seems to be a waste of talent or time to use.
Up here we pay between $260-$300 depending on the crank and who machines it.

I have only two shops I use to do my cranks and I am willing to wait extra time if needed for either to do them.
But the sizing thing I just do not believe a good crank grinder can't get the journals with in .0001" end to end in size when requested to do so. Yes you pay extra but thats the point it costs money to get the job perfect.
If you just say grind it 10 or 20 or what ever to re-use it then there is a big tolerance they have and most will go to the small side of spec to avoid any issues with too little clearance.

Back in the days of 9/16 stroker cranks for sm blks they just went to a 2" pin and they would be deadly.
Now try to get that done and a new crank is less money.
Crower sportsman crank was just a GM raw forging to start with and I have seen less issues with those then any stock GM crank for cracking or breakage with the same basic part. I know there is lots of different things not done or done between the two suppliers but at one time we had 20+ LT-1 steel cranks in the shop checking to see which would be useable and which needed grinding for a stock crank only class racing deal. That was every replacement crank GM had up here at the time.
We used 0 out of the box as they all needed to be 10/10 and they would come back indexed and to the diameter the journals were requested and still do to this day.

I believe the dedication of the operator has to be there to do the job that well and a well maintained machine to get good results that close.

I will admit I hated grinding cranks because I took too long to get them right and sold my Berco machine 20 years ago and now regret that move for more storage space inside

[1972ho]

What the shops that are just dedicated to just doing crankshaft only are they the better places to get certain type of damage journals worked on and come out with a better sized crankshaft repair.

[MotionMachine]

This guy did a series on every operation that it takes to machine a motor for a complete rebuild. In this case an MGB, which was assembled by another shop and auctioned off with all proceeds going to the Make A Wish foundation, hence the MAW in the titles of the videos. All parts were donated by suppliers and final price was $6K. These are 3 videos on crank grinding, explaining in detail the steps required to grind throws.

https://www.youtube.com/watch?v=7cXBXewS4IM&t=41s
https://www.youtube.com/watch?v=HAcL63coht0&t=93s
https://www.youtube.com/watch?v=q0ZuRAjeTX8

[ProPower engines]

What the shops that are just dedicated to just doing crankshaft only are they the better places to get certain type of damage journals worked on and come out with a better sized crankshaft repair.

One operation that used to be popular with high end crank repairs was hard chroming.
They would hard chrome the damaged areas and re-grind them.
When compared to a new stroker crank back in the old days it was very cost effective. Probably would be today as well.

There used to be a couple shops north of me that have closed up because of the enviro here.
There used to be a place called Chrome-A Shaft in the US but I believe they have closed up shop years ago.
That may still be an option in your neck of the woods

[1972ho]

Chrome a shaft was doing good work in the nineties I sent them a big block high end crankshaft (in Memphis I think they were part Bullet cams )that had a crack in a journal and when it was done I couldn’t tell that it had ever been reworked I don’t really know how the final results were because I sold the crankshaft.