18 replies to this topic

[Mad Max]

Hi

Just been out in the bitter cold to measure up all my bores in my 998 and they are all still with tolerance with regards to the haynes but the bores are very glazed. So i was going to rehone and get some new rings.

I've got one of the tools that fits in a drill and i get the theory of creating an up and down movement while rotating slowly.

Any other tips?

[Pigeonto]

Is that the tool with 3 stones on arms or abrasive paper.I've only ever used the stones type and apart from what you say I apply plenty of paraffin/home heating oil all the time to keep the stones clear of metal particles going round with them

[grahama]

Hi,

I have to say that I have done that with mine and so far it looks fine, (after initial fire up). Can't show you any before and after pics because photobucket is down at the mo. If there are no major gouges on the bores or ridges then all should be fine in my opinion, but I am no engine building expert lol.

If you could put up some pics of the bore condition it will help the experts' opinions. Also how many measurements of the bores did you do as they need to be measured by internal gauges in many places to ensure they are indeed the correct shape through the entire length.

Will put some pics up later if I can.

Graham

[Sam Walters]

Dont bother. Thats one quick way to ovalate and taper the bore.

Some will tell you otherwise. Including some "experts".

But put it this way. Professional shops will spend thoudands on machine to do this. They wouldnt bother if you could do it with a 20 quid tool and a hand drill.

[Vipernoir]

Without a proper bore-gauge I wouldn't suggest even attempting this, and even then I suspect there is a higher probability of ballsing it up than getting it right first time...

[Mad Max]

Thanks for your replys. My dads an engineer so used proper Mics. There is a little step of .01mm at the top of the bores but they are all in good nick. How much would a hone normally cost to have it done properly

[Sleepy Stu]

Think mine was like £50 the last time I had it done?

[Cooperman]

Those so-called 3-legged honing tools are really only for glaze-busting on otherwise good bores, not for honing to 'true-up' slightly worn bores.
Of course, worn bores require re-boring, final honing and new pistons at the next size up.

[MRA]

Did you use a 2 leg or 3 leg bore mic ? If it was a 3 leg was one of the legs offset ??

I use bore gauges when I do rebores and I use calibrated setting rings, a set like tis would normally retail at about £1700 and would need to be accurate and repeatable to 0.002mm or 0.0001"

A reasonably decent bore honing machine will cost anywhere from £5000 second hand upto £50+K

I would never use the glaze busters as they are NOT hones, they will follow whatever the cylinder is now shaped like, be it oval, tapered or possibly even hexagonal..

A proper Honing machine is designed to take out materialand make the bored cylinder round, irrespective of what mess the boring machine does, it will also take out tapers, the glaze buster will not.

Glaze busters if used incorrectly can also be a little bit dangerous, they should NOT be spun at high speed, 100 to 300 rpm being about maximum RPM.

[crock]

I don't advise it because the ring step you felt with your thumb nail will crack your new rings. If you can't get rid of the ring step you are doomed. The car will run but never make any power.

[Mad Max]

So a proper honing machine will take the lip out? thats good, a new set of pistons with machining won't see much change out of £400 which is quite a pinch for a 998

[Cooperman]

If there is a big lip, when the bore is honed to not only remove the lip, but -re-circularise (is that a word) the rest of the bore it can easily go over-maximum tolerance on diameter. Then it will never run properly, even with new rings. That is false economy.
With a well-worn engine the only solution is a re-bore and new pistons. In fact it is not unusual to spend money on keeping a classic car on the road and re-building is part of classic car preservation, the money spent being a part of the steady increase in value over the years, which we have seen with all classics, especially the Mini.

[MRA]

Lets put it this way, a race engine develops high power primarily by revving, but also due to slight decreases in internal friction, for instance we add a small amount to the road going spec, which means that the blow by is increased and piston slap, oil consumption are all increased, none of which are desired for a road car, your block will need to be rebored to get the best out of it.

If as you say the lip is 0.01mm per side and the cylinder is not worn more than this then you may be able to hone it out to size, however, I can't think of anyone I know with a Honing machine that would bother, this has a lot to do with how it will wear the stones as well as the potential for failure, it just may not clean up, then its down to their reputation....

I think you have 3 choices, get a bike, bore and new oversize pistons or another engine

Whilst choice 1 will keep/help make you fit, hopefully its working on me anyway
Choice 3 is an unknown and you may well find yourself in the same situation
Choice 2 is the best except on cost as it will cost you a few pennies...

[Shifty]

Its time like this I miss 'cord' ridge hopper piston rings???!!!

I'm sure the older peeps on here remember them? Piston rings intended to cobble together old engines. The top ring actually had a step in it to avoid the ridge left by a worn bore!!

Happy memories!!

[Cooperman]

Its time like this I miss 'cord' ridge hopper piston rings???!!!

I'm sure the older peeps on here remember them? Piston rings intended to cobble together old engines. The top ring actually had a step in it to avoid the ridge left by a worn bore!!

Happy memories!!

I remember them well, Shifty, although I never used any, not even on my old Ford V8 Pilot.
They were a real 'bodge' although a lot of 'engine re-builders' used them. But people still ask "How cheaply can you build me an engine?" The answer is that it's not possible to build a cheap engine and gget a good result. I look at some of the prices for re-built engines 'on exchange' and wonder at how few man-hours have been spent doing them. Thorough and accurate build quality -if you like!
I don't know what others have experienced, but it seems to me that over 50% of those who put 2nd habd un-tested engines into their cars end up with big problems after a short while.
Old engines, like the Mini engine, don't last like modern engines and with classic cars engine re-building to a good standard is necessary.