Piston gauge point and engine machining company recommendations?

[Gazhill]

Merry Christmas all.

I am doing my first engine rebuild on an 803cc. Can anyone tell me where to measure the piston (gauge point I think they call it) to work out bore clearance?

Also any other advise anyone can give me on this rebuild. I know I have to get the crankshaft journals reground.

Does anybody know or recommend any particular engine machining company in the Norfolk area.
Thanks all

[oliver90owner]

This will be taken care of by your engine reborer. They will either bore to suit the pistons or select pistons for the bores. Unless you are looking for a highly tuned engine, the 'standard' pistons used for whatever nominal rebore size will be adequate.

[philthehill]

If you are having the engine re-bored leave the bore/piston measuring and the finding of suitable pistons to the re-bore company.
The bores have to be machined to suit the pistons not the other way round.

If the camshaft journals need re-grinding the camshaft is scrap. There are no undersize camshaft journals available.
Only the front camshaft bearing is renewable. The centre and rear bearings are direct into the block metal.
If you mean the camshaft lobes need regrinding (they are on which the cam followers work) then it will be better to fit a new or good S/H camshaft with the 1/2" wide journals as fitted to the 850cc & 998cc mini (Pt No: 8G712 (pin drive)). If you fit another camshaft fit new cam followers (qty 8 Pt No: 2A13) otherwise the cam followers and cam lobes will wear out very quickly.

[Gazhill]

Thanks philthehill. I made an error its the crankshaft journals i need re-ground. The camshaft is really clean with very little wear.

I know this may sound naive and i know a lot of people will say leave it to the company doing the work. But the car was my Grandfathers and so has massive sentimental valve. I don't want a machine shop simply boring it out and charging me for the privilege, when it may just need the glaze taken off and the cross-hatch pattern re-instated, so i was hoping to do the measurements myself.

So if anybody knows of any good machine shops in the West Norfolk (Kings Lynn) area, can you please send them my way.

[philthehill]

Thank you for the clarification.
The only way to accurately determine if the engine needs a re-bore or not is to measure the bores with an internal micrometer or a bore gauge and external micrometer.
A quick way of determining if your engine requires a re-bore or not is to run a finger nail up the bore and if the finger nail is stopped it needs a re-bore.
If the nail is not stopped you may be able to get away with new rings or leave well alone, especially if the engine was not using oil.
Picture of the engine bores would be appreciated and then we could give additional advice as necessary.

It should be noted that pistons are not round but oval and in most cases the gudgen pin is slightly off centre to equalise the loading on the piston crown which goes some way to eliminate piston slap/rattle.
Phil

[oliver90owner]

Ovality is one enemy when considering reboring or re-ringing. Circular piston rings will not seat well in oval bores!

The bores will wear in the ring area and one can use a ring pushed square to the bore to determine the ring gap in the worn area compared to the bottom, unworn, section.

Only, if a lip is metal will it def need a rebore (I thought, initially, my engine was shot, but the lip, on the one apparently dodgy cylinder, turned out to be hard carbon.

[panky]

I recently stripped and re-built my Mini engine. There were marks on the bore but nothing that didn't pass the fingernail test. They were a little glazed though, so I bought a honing tool off eBay and much to the howls of anguish from some member on the Mini Forum I had a go myself. I didn't get perfect cross-hatching but it was better than fumbling about with emery cloth and when I did a gap test with a new ring all the bores were well within spec over the full depth. Best £12 I've ever spent and the engine runs perfect - and no smoke

[Gazhill]

Here are some images of my cylinders and crankshaft.

[philthehill]

Gazhill
Only one picture has appeared in your post and that is not clear enough to form an opinion.

Panky.
There is absolutely nothing wrong with honing cylinder bores and so long as there is some form of cross hatching - which is done to retain some oil - especially beneficial with a new bore.
You were lucky in finding the ring gap to be correct - in my experience the ring gap has to be adjusted to suit the bore and to bring the ring gap into correct spec.

All.
It should not be assumed that all rings have the correct gaps after checking one ring - all rings should be checked for ring gap and adjusted accordingly.
When fitting new piston rings to old pistons the clearance between top of the ring and the horizontal wall of the piston ring groove should be check for tolerance as if excessive the ring can pump oil past the ring.

Phil

[Gazhill]

Apologies I am still new to using forums. Here are the rest of the images.

[les]

It's possible you are holding the camera too close to the top of the bore, the things at the other end of the bore are in focus rather than the top of the bore, so difficult to see the condition. You may have to look for a new crank, one of those journals look pretty grim to me.

[philthehill]

I agree with Les.
Currently the bore pictures tell us little.
The crank will need regrinding if not replacement. Measurement will confirm either way.
I have to say that if the crank journal is in the very poor condition it appears to be it does make me wonder what the rest of the engine is like even though you have already made comment above.
Unless everything is measured accurately - everything is assumption and may be wide of the mark.
Phil

[biomed32uk]

It is hard to see the bore pictures, but as above that crank journal does look rather past its best, and may be indicative as to the general state of the rest of the engine.

I don't know anyone up in Norfolk, I use Towler engineering in Clacton on Sea for machining work that I can't carry out, but thats a fair way for you still.

[philthehill]

http://damico-engines.co.uk/index.html Whilst performance engine builders may be worth a look - but be aware quality costs money.

http://www.edsnorwich.co.uk/ Has good reviews.

http://www.whitmores-briston.co.uk/

If you google 'engine re-conditioners in Norfolk' plenty of sites will pop up.

Even if the above cannot help you they may be able to recommend a good quality engine reconditioning firm in your locality.
Phil
Happy New Year