[Mk2] [Turbo] Pist'on broke

[tarmac terrorist]

i am currently running wiseco 87.5mm low comp pistons with ceramic coated crowns & teflon coated skirts i have done 30000 miles on these and at times have seen over 1.6 bar of boost ( poor things) but engine is holding up. only thing the gap between bores & head gasket edges is very close unable to re bore if all goes wrong will have to be a new block

[TBDevelopments]

yeah head gaskets are cut to 87.5mm

To be honest its doing very well, i don't like going above 86.5mm let alone that. Those walls much be wafer thin.

Tim
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[tarmac terrorist]

ye agreed although the vehicle is a rev2 so prob helps a little, hopefully will be seing you in the new year bry reacons your the man for garret turbos still saving me pennys at the mo, had a clutch off you a short while ago and was very inpressed with it thanks

[TBDevelopments]

ok buddy thanks for the kind words, well i'll do my best to help you.

Tim
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[Century Motorsport]

Tim they are glaze busters, not hones. They will NEVER remove metal from a bore, just rough it up.

If you know engine builders using those for hones then you need to stop talking to them!!! The only way to hone a motor is have the block clamped down and level with a machine hone doing the work. Thats the only way its accurate.

There are drill hones - like the one you saw in my unit. But that was only used to clean the bores, not take metal out. Still not the best but was my only option at the time!

Even if you were to use 86.25 you would still need a re bore - unless your bores are that worn that a hone could take out the difference but not likely.

86mm pistons in std bores will never be to tight - the bores only get bigger, not smaller - its just a case of luck if your bores arent worn too much.

Anything up to 7thou clearance will run although it is not advised esp on turbo motors - blow by will occur and it will reduce engine life + performance.

Also Matt, the head doesnt need modifying at all for bigger pisons to go in - only the block.

[TBDevelopments]

the bottom one is a deglazer yes.

If you need to remove that much metal when building an engine its obvious the bores haven't been machined close enough. The hone is only really there to create the cross hatch pattern after boring and spec piston clearances.

Not like your going to be opening them up 0.5mm.

Tim
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[Jimbob]

Tim,

I have to agree with Nathan. The hones you put up pictures of are stone/ceramic based hones which will be a carbide or similar. These are only used for effectively what is cylindrical lapping. With a stone you must also use a paste or slurry usually silicon based with a diamond (or similar) suspension. This slurry holds metal from the lapping process and prevents any particulate from scoring the material being lapped. Kinda like using wet and dry paper.

If you use a carrier or paste this will end up out the bottom of the bore which is ok as long a your sump is off the car, which kinda means its almost as easy to hoik out the engines.

The hones I had pictures of are metallic based not stone based. They actually take out material. As Nathan says honing using stones will take an age, and I am still not convinced that it would be that square to the bore. For a test get a grit of sandpaper equivilent to a stone based hone, i'd guess around 400-600grit, now try and sand .5mm off a lump of cast iron. Then marvel at your 60" biceps.

I may well be wrong on this as engines are not my speciality subject, however I am a mechanical engineer by trade and look after valves and pumps everyday, which includes lapping of seats and faces. Although I don't actually get my hands dirty, just write the specs.

Be interesting to hear other opinions

Jim

[TBDevelopments]

well i did say in the first thread that this wasn't ideal, and i also said this was possible to do with the engine in while just replacing pistons the same spec as standard, ie 86.00mm forged items. This is used as a light hone/deglaze to give the crosshatch pattern needed. It can also be used to open up the tiny cleanance gap if needed. Because this is so small a hand type tool would be ok. You wouldn't need to be square to the engine as its self centralising.

I believe this is what you did nath in you "501.8bhp" engine your so prowd of.

I'll admit this isn't ideal and not something i'd do. Personal i would drop the engine and do a complete build job checking everything while i was going and making sure everything is clean and spotless. Needless to say the method i've described is doable for standard spec forged pistons with the block in the car, you just need to be careful and make sure everythings clean afterwards.

For an overbore the engine will need to be dropped and stripped anyway so a bench hone can be used.

I personally don't like the wet and dry approach by hand as your not maintaining constant and equal pressure in the bores, Although an old hot hod technique was to use wet and dry paper but they would wrap the honing stone assembly as the device will maintain that constant and equal pressure. But like i said thats just an old hotrod technique thats not needed in this age.

Tim
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[Century Motorsport]

You can get a honing machine for a hand tool identical to the centralising tyre pictured above, which does exactly the same job. I know a few engine builders don't even use the bench tool version as they proper the hand tool version of this.

No they dont.

well i did say in the first thread that this wasn't ideal, and i also said this was possible to do with the engine in while just replacing pistons the same spec as standard, ie 86.00mm forged items. This is used as a light hone/deglaze to give the crosshatch pattern needed. It can also be used to open up the tiny cleanance gap if needed. Because this is so small a hand type tool would be ok. You wouldn't need to be square to the engine as its self centralising.

So is it the same tool or not???

I believe this is what you did nath in you "501.8bhp" engine your so prowd of

No i used a hone as i said, not a glaze buster but i also said it wasnt ideal as it was attached to a drill not a machine. I can show it you if you wish.

Both the pics you put up are glaze busters. You will not get a suitable cross hatch pattern off either and trust me, the only metal the top one will remove is ally.

You rely on a crappy little spring to push the stones onto the walls of the bore, which in reality is nothing.

Nathan

[TBDevelopments]

please post up the picture of the hone then nath, If i posted the wrong picture from google i appologise. The point of this debate was that you can get a honing device for the end of a hand-held drill.

Which is what you did.

Tim
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[craig_mr2_mk1]

we have the same tool that you have posted up (the first picture) which we use on the cr250 if it blows up at the circuit. perfect fot removing ally form the cylinder but wont make the bore any bigger. A GLAZE BUSTER

The other one we have is like the second picture jimbob put up but fits into a drill end, which does make the bore bigger if you wanted it too. not a perfect way of doing my any means. A HONE

Nathan used the second one, the hone to do his motor. its on the shelf next to john's car if you wanna go look at it mate.

Best way to do it is get a professional to the motor, Like Don whos doin my motor now.

Craig.

[Fats]

The cross hatch helps lubricate the top two rings by holding a thin layer of oil, preventing a vacuum is utter poo. The deglaze or honing process helps bed the rings in when running in a rebuilt engine

[Jimbob]

Elaborating on Fats elequently put words

is utter poo

The whole idea of honing is that you want as smootha bore as possible prior to starting up your engine. The finer it is the better the rings will seal and the rings basically have to 'rub off' less metal during running in.

I think we have a concensus now and for once I was deemed right

[simmo490]

this thread has made my day, and obviousley educated me

[Century Motorsport]

Fats i hear you have the same turbo as me - will be good to see the results once all plumbed in.

Yeah tim i used a proper hone, one you fit into a drill but they are expensive and not easy to get hold of. It was infact from Craig's grandad so its a bit of an antique but joes the job just the same.

There are many reasons for cross hatching the bores but preventing vacuum isnt one.

Plus it looks pretty

[Fats]

Fats i hear you have the same turbo as me - will be good to see the results once all plumbed in.

Yeah should see a good result, I wont be running as much boost as you though, 1 bar at the most or rotary goes POP. heard you had a problem with your manifold, sorted yet?

[Century Motorsport]

yeah colleted it back today actually. The waste gate runner snapped off - suspicious weld!!!! Still its off the road till end jan i guess now as its out of tax. When you gettin it?

[Fats]

Got it all except for oil feed and return pipe work, need to get some unions and knock up some piping at work, it should be running some time next year. trying to find a decent wastegate about 44mm minimum

[dude541]

Best way to do it is get a professional to the motor, Like Don whos doin my motor now.
Craig.

mine to!

[tarmac terrorist]

(ref to picture of tool with three stones on it)i have built many engines as a toyota tech & have never heard a honeing tool called a glaze buster, i have one of these in my tool box & is used to i admite to remove glace from the bores if the block has been machined at an engineering firm this would be done as part of the process,this is done to create a good sill between pistons & bores