Real world acceptability of crankshaft end float

[daverclasper]

Hi. This is related to my Vitesse. I know the WS manual tolerances for end float, that would have been for cars, maybe clocking high mileage in the day.

I'm aware this is a "how long is a piece of string?", type of question, though as my car does low/gently driven mileage, can I assume that a few thou, higher than factory spec, is probably ok?.

Cheers, Dave

Edited February 20 by daverclasper

[JohnD]

How much slightly pregnant would you not like to be, Dave?

[daverclasper]

Well john, I've only done fairly crude measure, though maybe around 3 thou over spec, or are you saying that anything over is not good? 

[johny]

I'll stick my neck out Dave and say from what Ive seen a few thou more isnt going to be a problem. However remember that each block is different so you can never know externally how much thrust bearing wear is needed before they can slip out of place...

[DanMi]

From what I have seen they are more than a few thou over before they fall out, 3 thou over means that they are wearing and need to be monitored

[Pete Lewis]

you say its only a crude measurement   at +0.003"    is neither here not there 

if it was +020"  then youre heading for troubles 

getting the sump off on a vitesse is a good faf , you need to raise the lump a lot to get the sump pan

to clear the oil pump 

at +003"    i would sleep easy 

Pete

 

[johny]

I would keep an eye on it Dave, dont ride the clutch and then change the thrusts when you do the next crank bearing change😁

[thescrapman]

I was always told, as you Pull and push on the crank,  if you can hear it, it is starting to wear, if you can feel it, getting bad, if you can see it move, too late, about to drop, or already dropped.

[johny]

Actually I dont think it would be too difficult to work out as the manual gives the rear journal width and thrust bearing thickness so we just need the width of a main bearing cap to work out how much wear is needed to give enough clearance for the thrust to drop out...

Also I note that curiously the manual says acceptable end float when 'new' is 6 to 14 thou and 6 to 8 is only the recommended figure🤪

[dougbgt6]

Once upon a time I didn't know what end float was, I could push my crank back and forth "donk donk, donk donk"  Is that bad I thought? It felt like 1/4"  but probably not that much, although bad enough to have damaged the bores. The bearings tried to hold the con rods and pistons vertical and the bores started to wear into an elongated "S" shape. Bad enough for my first re-bore. 

Don't worry Dave, it'll be fine. 

Doug

[daverclasper]

Thanks so much guys, really helpful

[JohnD]

Dave,

That you have that much end float shows that the thrust washers are worn.   The risk is that they will fall-out of the groove in the block main bearing housing.   That was machined so that they would not fall out, as long as they did not wear more than a certain amount.   An amount defined in the wear limits in the manual.

So "a few thou more than the limits"  risks that the washers will fall out into the sump.   Is that a problem?   No, unless the crank then bearing on the naked block surface and wearing that and itself worries you!   Once that happens, the crank and block are scrap.

No, Dave, and NO dougbgt6, it will NOT be fine!

As soon as you, can get the thrust washers replaced.  Oversized washers, +5 and +10 are available, and may used combination to get the end float back within limits. Custom extra-sized washed may be ordered from the US.

The job involves removing the main bearing cap.   It's possible,but difficult on the Vitesse,  because of the long sump, with the engine in the car.  Better done with engine out.

Good luck!

John

PS shame on you, doug, for such misleading advice.

[johny]

If somebody can mic up a main bearing cap axial width for me I should be able to give a pretty good estimation of how much tolerance there is....

[johny]

I suspect, as Doug indicated previously, Triumphs end float limit is more to do with minimising conrod to piston misalignment than stopping the thrusts from falling out....  

[dougbgt6]

13 hours ago, JohnD said:

PS shame on you, doug, for such misleading advice

 Dave is a friend and knows full well, that was a joke. But not you, obviously.

Doug

[JohnD]

9 hours ago, dougbgt6 said:

 Dave is a friend and knows full well, that was a joke. But not you, obviously.

Doug

Maybe so, Doug.    What about anyone else who doesn't know you, looks at your post records and that you are an AO, and thinks, this guy knows what he's talking about!  I can leave my worn through thrust bearings a while longer if he says I can.    And another boat anchor is made!

John 

[johny]

To be fair John this request from Dave was for our opinion and experience - we can all just read the manual for Triumphs recommended figures and of course theyre the best to stick to but this is not always feasible.

Then as always the replies given can vary, and horrors sometimes even be wrong. so its down to the reader to weigh them up and come to their own conclusion with no come backs....

[dougbgt6]

3 hours ago, JohnD said:

Maybe so, Doug.    What about anyone else who doesn't know you, looks at your post records and that you are an AO, and thinks, this guy knows what he's talking about!  I can leave my worn through thrust bearings a while longer if he says I can.    And another boat anchor is made!

Grow up John.

Else I resurrect some of your old posts!  

Doug

Edited February 22 by dougbgt6

[DanMi]

The bottom line is the factory specs are for what the endfloat should be at rebuild. This will of course increase with wear and after some time will be out of factory tolerance, but factory tolerance is for a new engine, so yes if I have the engine in bits I would set within factory specs but on an older engine a few thou outside is to be expected

[Works Spitfires]

The problem is once crank end float goes out of tolerance wear is accelerated, and the inevitable lost washer, and subsequent main bearing cap, and crank damage happens.

 

Ignore any excess crank endfloat at your peril, it can have very expensive consequences all for the sake of a couple of quid new thrust washers.

[johny]

Why do you say that wear is accelerated? Is that wear of the thrust bearings or somewhere else?

[Wagger]

Let's get back to being Engineers.

As wear increases, so does the 'Endfloat' of the crankshaft. In the extreme, the conrods and small end clearances are compromised. They will be out of alignment. The cranks will wear conically and, if the thrusts drop out, it will be so bad that something wil snag, seize or break.

Some 'Engineers' pin the thrusts in place so that they cannot drop out. However, the pins will wear grooves in the crank unless they are soft or well below flush with the bearing surface. This problem is not uniique to Triumph engines. I have seen it on BMC engines too.

My crank is moving by 0.008 inch. (8 thou). When it gets to 12 thou the engine is coming out to fix that and other issues.

[JohnD]

12 hours ago, dougbgt6 said:

Grow up John.

Else I resurrect some of your old posts!  

Doug

Go on then, I could do with a laugh.

John

[Pete Lewis]

until Dave manages to give a accurate endfloat this is all hear say 

Dave  feels its +0.003" more than what ,     which specification are we working on here ???

with the variation in specs in the data its quite possible this is perfectly fine

I repaired a 1300 fwd with dropped thrusts , welded replacement lugs on the brg cap reground the crank and it went from stalling with the flywheel fouling the back plate to a life of over 100k till the body fell apart ,   not all make for a scrap block 

Pete

 

 

[johny]

He says factory spec and that recommends 6 to 8 thou so reckon hes up to around 11...