Crankshaft cylinder 1

Hi my 2006 2.0 started to burn loads of oil and rattle after 3000 revs.

I’ve put

New valves and valve seats.

Piston rings etc.

On cylinder 1 there is light scaring on the crank shift, can’t feel it with the tip of my finger, crank still feels smooth.

I’m putting normal big end bearings back in, not over sized ones.

If it starts to rattle again what other options do I have, any advice is welcome as this car is draining me very fast.

Cheers
Michael

Hi Michael. It sounds as if it might be alright. It may be possible to very lightly polish the scarred area with very fine emery cloth to get rid of any burs around the scarring. Have you got a micrometer to check the diameter of the affected crank journal and compare it with the others or check whether it is within manufacturing tolerances? If polishing does not recover the situation you could have the crank reground (all journals if high mileage and fit oversize (undersized diameter really) crank bearings or even buy a new crank.

1 Like

I will have a look and measure it, I did rub my finger across the marked area and I couldn’t feel any thing at all, still felt smooth, I will check and keep my fingers crossed. Just trying to keep my little car on the road.

Cheers for the info, much appreciated.

Good luck. Hope you get it sorted.

1 Like

Thank you very much, wish I’d just taken the engine out now, would of been easier , doing my best.

Cheers.

Does anyone know what the thickness of the crank should be, im going to measure all 4 and see if I have any differences.

Or where I can find the tolerances.

Cheers

Here’s somewhere to start a search
https://forum.miata.net/vb/showthread.php?t=608059

1 Like

As I’m at work on my own watching Goodwood and looking on here I thought I would look up the crank sizes for you as I work in an engineering company than regrind cranks as one of our services.
According to the ACL bearing catalogue the big end journals should measure between 46.980mm - 47.00mm or if you are measuring in old money then it is 1.8496" - 1.8504", so those sizes are the upper and lower limits for the standard bearings and obviously they should be round. I hope that helps you.
Chris.

3 Likes

Helps a lot thank you.

Helps a lot, thank you very much.