Our old race motor has about 2-3mm endfloat on the crank.

On pulling the cap and checking the thrust faces on both the crank and the bearing shell there is only relatively minor wear.Certainly not enough to account for this level of end float. On checking another crank with the bearing shell it to produces a similar amount of end float.

This engine is an early A12 with distributor up front.

Question: Are there different bearing sets for the mains to accommodate different production years that accounts for this level of end-float?

There are not different widths of the thrust bearing (center bearing flanged type).

What about comparing your thrust bearing width with that of a new one? Maybe someone here can measure a new one and report the width.

BigE will know for sure, I have seen white metal being added to the thrust bearings to control the end float. I had this done on old 2R toyota cast irn engine in our old MK1 shovel nose Corona 68 vintage

i have not come across this problem with that amount your saying 2-3mm ( thats huge ) 0.07mm- 0.15mm is std endfloat .i measured 3 new sets of main thrust bearings, on there own not fitted in block.
they measured - 1.060'/1.063' or (26.924/27.00mm). hope this helps.cheers

well picked up jmac thanks

It won't be dirt cheap if they aren't available off the shelf (check out ACL brand, iirc they have the option of a thicker thrust bearing for some engines - iirc minis, so at least check just in case) but you can get material added to bearings, or a thick thrust bearing adapted into place. I've seen it done on vintage cars (for example ones where the material is added direct to the con rod itself and then machined to the required size) - so it is definitely possible

It's not all that surprising that this sort of play develops - generally if it's racing, you've got high rpm, but also typically a higher clamping force pressure plate/clutch setup. And when at idle, there's not much oil flow to the thrust bearing area, and a lot of force to push back against the clutch pressure plate force as you hold the clutch pedal down before launch.

If the rest of the block/bottom end has still got a lot of life left in it, no reason not to pursue it imho.

Whereabouts are you posting from? If you were in melbourne, crankshaft rebuilders in blackburn (used to be in Kew) would almost certainly be able to do this, and more to the point have a top shelf reputation for the qualirty of their workmanship/service.

EDIT - Bige - there's a type in your post (and for the record, it's definitely a typo, I'm not suggesting you can't do math or something!) - the mm should be 26.924 and 27.000 not 29.924 and 27.000 :)

Thanks for all of the replies.

Problem is now sorted. To explain. The engine in question was assembled by another bloke and ran a relatively mild cam. We eventually built our own late block with bigger cam, 1400 head etc.

The discussion here has made me aware that the thrust bearing on the crank is the same for both the early and late blocks. Turns out the guy who assembled the old engine put the thrust on the rear main and not the centre main.!!!!!! Hence the excessive end float.

A new set of bearings is in order and the problem will be all sorted. Lesson for young players!

As long as no danger to crank or caps you'll be fine then

That's amazing! I don't know how many engines would even physically allow such a swap to take place and still enable the crank to spin at all!

Amazing indeed.
The only damage done was to the bearing shell itself. The shell inserted into the block suffered the front flange shearing off. I assume this was because the block web is slightly wider on the rear and once the cap was torqued down the block effectively acted as a wedge and split the front flange off. That bit was sitting in the bottom of the sump. Not a mark on the crank!
Amazing little engines.