How to measure crankshaft end float

[glynherron 9]

After too many years I'm about to start the rebuild of my s4s engine but will have a few questions for the engine guru's out there.

So how to measure and correct crankshaft end float. I'm guessing that with the crank laying in the block with the thrust bearings in place I use feeler blades and check the tech spec. But if the end float is too much how do I know what size to order. Are they stamped with their original size?

Thanks in advance

[Alex Carter 156]

They are stamped std if standard then If you need bigger it will be plus what ever the gap is it will state in the manual what the tolerance is on my v8 they were standard with 0.3 tolerance after the new shells and big ends it hardly moved at all . Ps I'm not an engine guru just more of a fiddler lol. If in doubt south west are very helpful phill will be able to advise what you need

[Vulcan Grey 251]

I had to do this recently.

 

When you build an engine, you measure crank end float dry, no oil or grease on the crank or the bearings., since the oil would take up some of the clearance.

 

You can measure the end float with the engine together, but it is much more difficult to move the crank...

 

I did my measurement with the engine on a stand, just using new journal bearings, top half of the block, and the crank.

You use a dial indicator on a stand (attached to the engine with a threaded rod or a magnetic base).

 

 

You can see the gap here where the thrust bearings will go, they only go in the top half of the block, one on each side of the first journal. 

 

The thrust bearings

 

They get slid into place.

 

Then you slide the crank back and zero the dial indicator

 

Then you slide the crank forward and read the dial indicator.

 

In my case, I needed the thicker set of thrust bearings.

 

The  proper endfloat spec is .003" - .008".

 

I needed the +.005" thrust bearings to fix my engine.  They also have +.0025" bearings.

[glynherron 9]

Hi Travis. I was hoping that you'd reply. Awesome explanation. On holiday for a week but ordering a dti as u write.

A preliminary test with standard feeler blades on the inside thrust washer showed an easy 4 thou and a tight 5 thou with the original used thrust washers. There wasn't any numerical markings on the backside of them. Maybe I'll be okay with new standards?

[Vulcan Grey 251]

probably be fine with new standard thickness washers.

 

The only reason mine were worn, was that I stupidly installed mine backwards about 6k miles before....  The steel backing of the washers wore down the crank.  Prior to that there really was no wear in 74k miles!

[glynherron 9]

Oh dear. What made you realise? Or was there a teardown for something else?

[Vulcan Grey 251]

I blew the head gasket at the track 6k after the engine rebuild, since there was coolant in the oil, I took the entire engine apart again, and that is when I noticed the thrust bearing was messed up.

[mdw 273]

One of mine had dropped into the sump prior to me buying it. It felt like you could measure the end float with a stop watch. It wrecked the crank but the block was welded and repaired.

[glynherron 9]

How would that happen. Surely it must have been out of place for a long time! Shame you had to find out!!

[Vulcan Grey 251]

One of mine had dropped into the sump prior to me buying it. It felt like you could measure the end float with a stop watch. It wrecked the crank but the block was welded and repaired.

 

 

I've heard of that on another engine (910 in an SE).

[mdw 273]

I knew it had the excess end float before I bought it.  It was all mashed up in the sump when we dropped the pan.

[DanR 69]

Something a lot of drivers don't realize is how accelerated wear occurs by keeping the clutch pedal down while waiting for the traffic to move.

 

The thrust bearing is only lubricated by splash feed so keeping the clutch engaged unnecessarily forces the oil out and increases the wear.

 

Best to engage neutral and release the clutch in those conditions.

[glynherron 9]

Good advice Dan