Allowable Crankshaft & camshaft run-out?

[chrislandy]

Hello,
I am just starting a build on a Rover T16 turbo engine originally from a Rover 220 Coupe which will soon be fitted to my Shelsley T2 hillclimb kit-car. I have measured the cranshaft runout at 0.07mm, I cannot find any data to check this against, so as a general rule what should the maxium allowable crankshaft runout be?

Also, I have yet to measure the camshafts (TOHC) but again, as a general rule what should the maximum runout be?

Thanks in advance
Chris

[Guy Croft]

Which region are you referring to Chris?

Centre main or flange where FW bolts on? The latter is more usually expressed in terms of runout at dia on FW.

I assume centre main?

G

[chrislandy]

Sorry Guy,
Yes, this was measured on the centre main and supported within the block using the front and rear mains.

I hope I have got my terminology right as it's the first time I've had to measure up this sort of thing (usually get an engine builder build the bottom end)

I was trying to measure whether the crankshaft is bent or not.

Chris

[Guy Croft]

It sounds like it's bent. is it tight to turn?
Typically on a centre main journal of about 2" diameter I'd want to see max 0.03mm preferably a lot less. Check the flywheel flange because if the crank is bent it may show up there too. At about 35mm radius from crank centreline I would not want to see more than 0.02mm runout.

I would also want to have a look at the amount of runout on the thrust faces which I think (from memory) are located on the center main. The reason is that you should get the crank reground - or at least checked by a very competent crank grinder to assure your measurements between centres. If the crank is badly bent it can scuff the thrust washers, never mind scuff all the bearings as it rotates, and the thrust faces can (and sometimes need to be) reground according to the availability of oversize thrust washers. The total additional thickness from a new pair of oversize thrust washers, just for ref, will typically be 5, 10 thou or 20 thou" and end float on that unit wants to be 2-12 thou".

Furthermore, I would crack test it by dye penetrant method before any remedial ops. Those cranks (unless yours is a special steel one) are cast iron and of course - if overstressed - can crack.

GC

[chrislandy]

Thanks, I haven't bolted the crank in yet to check whether it spins freely as I have not got the bearings yet - I have an old set but the block is in for boring/honing and decking at the moment so I can't check. I was thinking of getting the machine shop to check the crank to make sure I measured it right while it was in for a polish, but I am confident I measured it correctly.

Thanks for the tips on the other meaurements to take, very useful.

Yes, they are cast cranks as standard, and it looks like I'll have to get hunting for another one as I am aiming for slightly over the standard power.

Chris