Discussion
As you may or may not know my Mini has been smoking on the over-run for a while. I have taken a week off of work to sort it out. I have cleared the Garage and got all my tools together ready for the rebuilt, well just check that the rings are ok and not cracked as I (we) suspect.
While I have the engine apart I am going to check the big ends and bearings, even though the engine has only don’t 9000 miles since it was built. My question is what size do the bearing journals have to be to get them reground? Its on STD at the moment so what are the measurements that I would need to take to check this? If it needs grinding to +10 thou what size does the machine shop go to? Is it just +10 over standard? What are the clearances?
So many questions I know but I want to get this right. I will post some pics as I get the engine apart.
Cheers,
Nick
While I have the engine apart I am going to check the big ends and bearings, even though the engine has only don’t 9000 miles since it was built. My question is what size do the bearing journals have to be to get them reground? Its on STD at the moment so what are the measurements that I would need to take to check this? If it needs grinding to +10 thou what size does the machine shop go to? Is it just +10 over standard? What are the clearances?
So many questions I know but I want to get this right. I will post some pics as I get the engine apart.
Cheers,
Nick
If the crank is in excellent condition you may just want to fit a set of bearing shells. I take it you know it's std/std on mains and big ends. Alternatively a micro-polish may be all that is needed.
My recommendation is to grind to -0.010" if necessary.
Before re-assembly ensure that you remove the oil gallery plugs and wash the entire block out properly, and fit new gallery plugs (the early solid type if you can get them).
Fit a new oil pump and timing chain irrespective of previous use or apparent wear. Time the cam in properly with offset woodruff keys.
Check the cam bearings as well and fit new cam followers.
A good machine shop will just go to -0.010" and all you need to do is purchase the bearings. I do always check the final machined size before assembly, just to be on the safe side. Make sure you check the crankshaft end float and always fit new thrust bearings. Ideally the float should be between 0.0015" and 0.004". Thrust bearings are available in std and +0.003" sizes, so you 'mix & match' to get the right end float. If necessary you can linish the back fact of the bearings to get the float right - that's what I do, but it can be a long job.
If fitting new rings don't forget to hone the bores or the rings will never bed in properly and the engine will always smoke on the over-run!!
If you are wanting to really rev the engine I recommend fitting new ARP big end bolts and nuts and, on a non-'S' block, a centre main strap (you get the main cap machined to take this).
Once you get into it it's all quite easy, and don't forget we are all here to help.
Only other advice is to buy the top quality parts, like bearings, oil pump, etc. I personally recommend Mini Spares if you can get to one of their shops (Potters Bar and Harrogate). They are very knowledgable and helpful.
I hope this helps,
Peter
My recommendation is to grind to -0.010" if necessary.
Before re-assembly ensure that you remove the oil gallery plugs and wash the entire block out properly, and fit new gallery plugs (the early solid type if you can get them).
Fit a new oil pump and timing chain irrespective of previous use or apparent wear. Time the cam in properly with offset woodruff keys.
Check the cam bearings as well and fit new cam followers.
A good machine shop will just go to -0.010" and all you need to do is purchase the bearings. I do always check the final machined size before assembly, just to be on the safe side. Make sure you check the crankshaft end float and always fit new thrust bearings. Ideally the float should be between 0.0015" and 0.004". Thrust bearings are available in std and +0.003" sizes, so you 'mix & match' to get the right end float. If necessary you can linish the back fact of the bearings to get the float right - that's what I do, but it can be a long job.
If fitting new rings don't forget to hone the bores or the rings will never bed in properly and the engine will always smoke on the over-run!!
If you are wanting to really rev the engine I recommend fitting new ARP big end bolts and nuts and, on a non-'S' block, a centre main strap (you get the main cap machined to take this).
Once you get into it it's all quite easy, and don't forget we are all here to help.
Only other advice is to buy the top quality parts, like bearings, oil pump, etc. I personally recommend Mini Spares if you can get to one of their shops (Potters Bar and Harrogate). They are very knowledgable and helpful.
I hope this helps,
Peter
guru_1071 said:
the block plugs are not avalible at the mo' so be prepared to have to make your own from a lump of brass!!
You can use soft aluminium for these if you wish.I keep meaning to do a proper drawing and get 100 off turned up in brass. Those pressed brass ones are nasty little things and I did once have one leak at the front of the block. You find out when you have just re-fitted your lovely new engine and then have to strip out the rad, front pulley, timing cover, alternator and front plate to get at the bloody thing.
Extra 300 Driver said:
Dear all,
Thanks for the replies. How do you check the end float? DTI and push the crank??????
Before removing the crank, but usually after you take out the rods & pistons, put a dti onto one end of the crank, put a screwdriver blade between one of the crank end flanges and the block and set the dti to zero. Remove the screwdriver and force the crank as far the other way as it will go, then read the dti - the figure is the end float with the old bearings.
Remember, this float will be reduced by the new bearings and I normally fit a new set the same thickness as the old set and re-measure. Then you can choose the new sizes which, usually, will be the same as the old set.
Whilst the block is out you can get the block deck machined to make the pistons level with the deck at tdc. This is a really good thing to do to improve 'squish' in the combustion chamber.
Email me if you need any further help.
Peter
Cooperman said:
the block plugs are not avalible at the mo' so be prepared to have to make your own from a lump of brass!!
You can use soft aluminium for these if you wish.I keep meaning to do a proper drawing and get 100 off turned up in brass. Those pressed brass ones are nasty little things and I did once have one leak at the front of the block. You find out when you have just re-fitted your lovely new engine and then have to strip out the rad, front pulley, timing cover, alternator and front plate to get at the bloody thing.
I've always drilled/tapped mine out and fitted BSPT hex drive plugs...never ever had any leaks.
Bit of an update,
The engine is now out and in bits. Crank is perfect as are the big ends. Pistons are good with no sign of a cracked ring anywhere. The block has been to the engineers to give it the once over and fit new cam shaft bearings. I am collecting the new rings tomorrow. Only damage so far is a very, and i mean very, slight score in the cylinder, but that will hone out.
The engineers say that the bores looked glazed and will just need a hone.
Will post some pics when I can.
The engine is now out and in bits. Crank is perfect as are the big ends. Pistons are good with no sign of a cracked ring anywhere. The block has been to the engineers to give it the once over and fit new cam shaft bearings. I am collecting the new rings tomorrow. Only damage so far is a very, and i mean very, slight score in the cylinder, but that will hone out.
The engineers say that the bores looked glazed and will just need a hone.
Will post some pics when I can.
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