21 replies to this topic

[Chappb]

I'm fitting a centre main strap to my build but thought i'd get a proper opinion on this matter, when i've had the centre main cap machined flat and the strap installed, does it need line boring? I can't see it being beneficial myself because it's not like the bolts are being relocated. Thanks.

[MRA]

Yes it does, well more of a check and hone, maybe if its bad it will need a line bore.

The reason that it may become out of round is due to internal stresses changing after the machining operation, I have had a couple that have maintained integrity after machining, and a lot more that haven't, its a risk that is not worth taking.

[Chappb]

righty o, will have to find a decent machine shop then...cheers

[ACDodd]

I check mine, before and after, only machine if needed.

Ac

[Chappb]

ok cheers AC

[MRA]

As most people will not have a decent bore gauge or bore mic the best option is to get a decent machine shop to do the job for you.

[Chappb]

thanks for the help guys

[MRA]

This is a job that is not easily measured, you need to make sure that the bore is inline with with the other 3, that it is round and not tapered.,

Any issues and you will lose power, this is one of many areas where a professional engine builder will make the difference to your power curve and all these small increases make a big difference.

[MRA]

PS it cannot be done with a verier caliper !

[Chappb]

can i get something to measure it or is it better to just get it to m/c shop

[ACDodd]

You need to be able to measure the diameter and alignment;

Edited by ACDodd, 09 March 2013 - 10:43 AM.

[ACDodd]

In order to work at the accuracy you need this is best left to a competent machinist to make the required measurements.

AC

[MRA]

You can but they are not cheap, a fairly standard bore gauge can be purchased for about £100 but these may not be long enough to actually get in to the centre bearing, a much better solution would cost over £1000.

Unfortunately a lot of the time we hear "its only a mini" and the care and attention seems to go out the window, it is this detail that increases reliability and often power / torque

[Chappb]

ok no worries, thanks ac.

[Chappb]

You can but they are not cheap, a fairly standard bore gauge can be purchased for about £100 but these may not be long enough to actually get in to the centre bearing, a much better solution would cost over £1000.

Unfortunately a lot of the time we hear "its only a mini" and the care and attention seems to go out the window, it is this detail that increases reliability and often power / torque

I probably better leave it to the experts then!

You need to be able to measure the diameter and alignment;

Just out of interest, How are you checking alignment with that straight edge? using feeler gauges between it?