26 replies to this topic

[belche23]

Hello all,

Just started to build my 1275 +60 engine, got to the point where we are measuring float end movement.

We think we are reading the dial right and we have 0.2mm which changes to around 8thou.

So we need +3 washers to bring it to 5thou

Hopefully the video works below-

[belche23]

http://s635.photobuc...t]=1&sort=1&o=0

[Cooperman]

You need 2 x 0.003" thrust pairs to bring it to 0.002" which is the ideal for a new build engine.

[belche23]

Oh ok, every where I read something different.

[Cooperman]

Both the original BMC Workshop manual AKD4061 and Haynes give the end-float as 0.002" to 0.003".
During use this may well increase slightly, but normally the bearings take the wear. Over time it is necessary to fit thicker bearings, usually after a re-grinning of the thrust faves on the crankshaft.
Always aim to start within the stated figures.

[belche23]

Thank you cooperman, I'll be in mini spares tuesday morning

[belche23]

To be honest I can't find any for sale anywhere. Where can you buy them from?

[Cooperman]

Mini Spares part number AEW2136-003

[AlexMozza]

We stock them. Although I think we are getting some more in soon.
Give us a ring on Tuesday morning at Somerford Mini.

[limby2000]

Martin (mra) will make to the size you need, he made me one i could,nt get anywhere.

[Cooperman]

If you have, say, 7 thou end float, you use a pair of +0.003" which would give 1 thou which is below specification. What you do is to linish a bit off the back face of one pair - that's off the steel backing side - until, after repeated trial fits, you have 0.002" float. Actually just under 0.002" float is OK, but not below 0.0015".

With a larger end float, even with a pair of +0.003" both sides, you can buy a couple of pairs of +0.030" and have a machine shop machine metal from the steel backing until the float is correct. Just make sue the measuring is done accurately.

It's the way these thrust bearing wear that means you should never start the engine, especially from cold, with the clutch pushed down, as there can be momentary oil starvation if you do.

[Spider]

The oversize Thrusts aren't per side but in total. So, those marked as +0.003" sets will only reduce the Total Thrust by 0.003", or put another way are 0.0015" per side. In this regards, I'll point to Main & Big End Bearings, these are sized on the Diameter (ie, total) not per side.

 

In your case, with what you've measured (sorry, the video wasn't clear enough here) at 0.2 mm which I work out as you have to the 0.008". Fitting a pair of 0.003" thrusts will bring that down to 0.005".

 

I know what the workshop manual states in regards to crank end float and respectfully note other's experience, in particular Cooperman, but I've found even at 0.003" they are too tight. I generally aim for 0.004" to 0.005" for a road engine. If you're not sure, I'll also add here that there's no consequence from adding a couple of thou here, but there will be consequences if it's even as much as 0.001" too tight.

 

Even ACL's (a bearing manufacturer) advice points to this;-

 

 

 

<Edit: moved to following page >

Edited by Moke Spider, 30 August 2016 - 11:03 PM.

[Carlos W]

Did you use a new set of standard thrusts to measure your end float?

[belche23]

Did you use a new set of standard thrusts to measure your end float?

Yes new pair

[belche23]

Mini Spares part number AEW2136-003

They are the ones I was hoping to buy, but they are out of stock.