Richard/Ca
Senior Member
Can any body help me. I would like to know if there is any way to measure a crankshaft journal in a model a engine while it is still in the car? I really don't want to pull the engine. Richard
ask one more time.
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George Miller
Well-known member
If you are talking about the rods journals yes. If you are talking about the mains, maybe but you might need special tools. You could come close with calipers, but not the best way
BILL WILLIAMSON
Well-known member
Have you asked a local machine shop for ideas?
They used to make a special micrometer with extended tips for measuring in the block. I haven't seen one in years.
So i guess the answer would be no.
Bill
Tom Wesenberg
Well-known member
I would trust my vernier caliper to measure it, as long as the two points could reach the edge of the main bearing in the block. Even though the mains on the crank can be turned any small amount, and the babbit cut to that size, I think most shops still turn the crank in steps of .010".
Richard/Ca
Senior Member
Sorry I forgot to mention it is the rear journal. I think someone put the wrong cap on it. It looks like a good engine and when I check the rod caps they were in real good shape. And nothing seemed out place.I started and ran real good but then it got water in the oil bad gasket. So when I pulled the pan to clean it that is when I found the broken rear main journal. Would like to make sure of the size before I have a replace made. jax55 I never thought of that I will look and see if I can do that on the rear main journal Thanks Richard
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Richard/Ca
Senior Member
Thank you everybody for all your help. To hot to check it out today.
Loosen the other main caps to let the crank drop down a little so you can get a true measurement of the actual diameter. If you have a Harbor Freight nearby, they have a selection of inexpensive calipers and mikes of various shapes, or if you know an old time mechanic, he may have something from years gone by.
John
Senior Member
I checked my "special in block" mike, but it did not go small enough for the 1.625" or so Model A mains. Any good machine shop should be able to read the cap bore diameter my making a mandrel to fit. I have done this in the past with success. You can also take your shims, the cap, and a small piece of round stock along with a depth micrometer and approximate the shaft diameter to within a thousandth or so.
To do this, take the cap and align any shims as they were when the cap was assembled in the engine. Place the small piece of round stock, say about 1/2" diameter and about 3" long in the valley of the bearing cap. The round stock diameter isn't critical, just smaller than the crankshaft journal. Use a depth micrometer bridged from the sides of the cap including the shims to the round stock in the valley and get a reading of depth from the edge of the cap and shims to the round stock. Add the diameter of the round stock to the measured depth to the round stock from the shims on the edge of the cap. Multiply this total by two as you are reading 1/2 of the total shaft diameter. You now have your shaft diameter.
This is easier to do than to explain. Hope it helps Richard/Ca....
John
To do this, take the cap and align any shims as they were when the cap was assembled in the engine. Place the small piece of round stock, say about 1/2" diameter and about 3" long in the valley of the bearing cap. The round stock diameter isn't critical, just smaller than the crankshaft journal. Use a depth micrometer bridged from the sides of the cap including the shims to the round stock in the valley and get a reading of depth from the edge of the cap and shims to the round stock. Add the diameter of the round stock to the measured depth to the round stock from the shims on the edge of the cap. Multiply this total by two as you are reading 1/2 of the total shaft diameter. You now have your shaft diameter.
This is easier to do than to explain. Hope it helps Richard/Ca....
John