Crankshaft end-play

[ddrum]

I'm starting to reassemble my l20b and I already checked the oil clearances using plastigage and everything is fine. I put the center main bearing cap and torque it to 40 ft lbs. I pushed the crankshaft forward and my filler Gage which starts at .004 inches, did go in. I pushed it back and the filler Gage didn't want to go in.

 

My brother recently rebuilt his Dodge 318 and the same thing happened when checking end play. Only one side cleared, but he said that was fine since everything was under standard specs on his engine. My crankshaft on the other hand, has been shaved .25mm only on the main bearings.

 

So my question is, does the crankshaft end play have to clear on both ends? or am i going to have to take it back to get machined?

 

Thanks, Erick

[HRH]

Plastigage sucks. Use a dial indicator with a magnetic base. Much much more accurate.

[ggzilla]

Move the crank all the way and check it. Then move it all the other way and double-verify it. It must match.

 

You can use feeler gauges, which is Datsun recommended.

[datzenmike]

L20B end play is 0.004" to 0.007"

[ddrum]

should i move it before torquing it down or after?

[ggzilla]

What does your repair manual say? Do it by the book, so it will be right.

[ddrum]

Yeah I'll double check it thanks a lot. :)

[ddrum]

Yeah it only clears one side with the .004 one, but the book says .002 to .007. I'm going to take it to the machine shop and see what happens.

[ggzilla]

The machine shop will just check it the same way and tell you it's good and ask for $20.

 

Per your book, you don't need it to clear .004. Just make sure it clear .002

 

After you torque all the mains down, use a lever to push the crank forward. See if you CAN slip a .002 in and CANNOT slip in a .007. Then lever the crank the other way. You will get identical readings if you are putting the feeler gauge in the correct place -- and if the crank is moved all the way.

[ggzilla]

Useless, the Nissan factory service manual doesn't say how to check it. But the drawing shows a hammer handle (presumably) used as a lever to move the crank.

 

 

If the thrust bearing is like this center one, you should be able to measure it on either side.

 

But on thinking about it, it doesn't really matter if you measure one side or the other. Just make sure the crank is moved all the way. And it was inspected in that area, along with with the center main & cap faces (there is no burr or damage in the area), you'll be fine.

 

[ggzilla]

The Haynes manual is more helpful:

Temporarily refit the crankshaft to the crankcase having refitted the upper halves of the shell main bearings in their locations. Fit the centre main bearing cap only, complete with shell bearing and tighten the securing bolts to [torque specification] . Using a feeler gauge, check the end-float by pushing and pulling the crankshaft. Where the end-float is outside the specified tolerance, the centre bearing cap will have to be renewed.

[ddrum]

i tried this time with a .002 and it bearly went in, just the tip. can i call it good?

[datsunaholic]

Seems kinda tight. This is endplay, so you can't use plastigage here. I assume you've already checked main bearing CLEARANCE, right? That's done with plastigage with the bearings clean (no oil). The end play needs to be checked WITH oil on the bearings. All of them- you at least need all the main shells in place. Now, me, I torque down ALL the main caps, but for a proper reading you at least need all the main caps on snug and the center torqued down. You then push the crank forward, check the front clearance, then push the crank back and check rear clearance. The crank is supposed to float .002-.007. A .002 should go in easily, a .008 should not go in at all. You actually shouldn't have to push the crank, as the feeler blade itself will move the crank unless you assembled the thing dry.

 

This is on EITHER side of the center main. They should be identical readings as the crank should easily float. Too tight, you;ll burn up the center main. Too loose, you'll have something like my 4X4 (almost a quarter inch free play due to someone putting the bearing in wrong)

[Stoffregen Motorsports]

When I'm building a bottom end I snug the mains up just more than finger tight (5lbs or so) then smack of the back of the crank with a hard rubber mallet, thus pushing the crank forward. This makes sure the center main cap is lined up and also makes sure the two halves of the center main bearing are too. If they are off, you can lose some thrust bearing end play, but just as importantly, the crank will only contact one half of the center main bearing (thrust side). This misalignment can cause premature bearing failure.

 

I check thrust end play with a dial indicator on a magnetic base. But feeler gauges should be fine, as long as you don't jam one in there and scratch the thrust bearing leaving a bur.