How to check a crankshaft stroke

David Lee · 06-26-2012, 08:32 PM

Good day,

I was asked by a machine shop that is going to do my offset grind on my crankshaft to check what the stroke is before we do the offset. How would I do this in the block?

Thanks

Tom Turner · 06-26-2012, 09:06 PM

If your crankshaft grinder does not have a stroke checker, request that he gets one or find a grinder that does. You can check it yourself in the block with a long travel (at least as long as your stroke) dial indicator and a bridge (at least as wide a your bore spacing) Run the piston to BDC and zero the dial. Run the piston up to TDC and read the travel. You can do this with a dial caliper (like NHRA does) but a dial indicator is more accurate. Crank grinders tend to setup on existing crank pins and disregard actual stroke. Make sure your guy understands the concept of "grinding on index" and the importance of the stroke being the same on all throws. Another thing.....only take .014.

David Lee · 06-26-2012, 09:16 PM

Thanks Tom, I will ask him if he does. But I would also like to know so I can make sure that the grind was correct. Time to get a long travel dial indicator

kansas stocker · 06-27-2012, 01:21 PM

I use a depth mic and a dial caliper as a back-up.
I shoot for .013.
Pete

06-26-2012, 08:32 PM	#1
David Lee VIP Member Join Date: Oct 2007 Posts: 1,168 Likes: 487 Liked 346 Times in 126 Posts	How to check a crankshaft stroke Good day, I was asked by a machine shop that is going to do my offset grind on my crankshaft to check what the stroke is before we do the offset. How would I do this in the block? Thanks

06-26-2012, 09:06 PM	#2
Tom Turner Member Join Date: Jan 2005 Location: Lake Tapps, Washington Posts: 137 Likes: 0 Liked 0 Times in 0 Posts	Re: How to check a crankshaft stroke If your crankshaft grinder does not have a stroke checker, request that he gets one or find a grinder that does. You can check it yourself in the block with a long travel (at least as long as your stroke) dial indicator and a bridge (at least as wide a your bore spacing) Run the piston to BDC and zero the dial. Run the piston up to TDC and read the travel. You can do this with a dial caliper (like NHRA does) but a dial indicator is more accurate. Crank grinders tend to setup on existing crank pins and disregard actual stroke. Make sure your guy understands the concept of "grinding on index" and the importance of the stroke being the same on all throws. Another thing.....only take .014.

06-26-2012, 09:16 PM	#3
David Lee VIP Member Join Date: Oct 2007 Posts: 1,168 Likes: 487 Liked 346 Times in 126 Posts	Re: How to check a crankshaft stroke Thanks Tom, I will ask him if he does. But I would also like to know so I can make sure that the grind was correct. Time to get a long travel dial indicator

06-27-2012, 01:21 PM	#4
kansas stocker Member Join Date: Oct 2002 Location: kansas Posts: 235 Likes: 479 Liked 249 Times in 48 Posts	Re: How to check a crankshaft stroke I use a depth mic and a dial caliper as a back-up. I shoot for .013. Pete