Was building up the Ka lump with the GF and she handed me this whilst removing the old rings...





Poor little lump has seen some Det in it's time

If anyone has a spare piston hit me up please!

Cheers!

 

for turbo karl?

 

what size piston? standard comp?

 

Sorry yes RST standard Size and comp! lol

 

looks pretty fooked karlos

 

How easy is it to swap the piston over, do I need to press the pin out and in again?

Yeah it is James! lol

 

Karlos, IMO its a cunt to change the piston only, and i've got a press in the shed. You need to properly support the piston whilst you press out (then in) the pin otherwise you crack the skirt. You could try heating the piston and tapping out the pin i guess??

Pistons with rods (standard) come up on the bay a fair bit for next to nothing, and if one piston is like it i would deffo check the others VERY carefully lol.

PS, cleaned the block today mate and it all looks good, cheers off to the machinist on friday


Rob,

 

having removed standard cast pistons from rods, and then fitted new 1s, i will be the 1st to say its a mare of a job lol

as said, needs supporting a lot, a punch or press the same size as the pin, plus a lot of heat from a blow torch!

obviously removing isnt a massive issue as if the skirt cracks, its scrap anyways, but refitting the new 1 needs to be perfection, and making sure the pin goes through the rod square, whilst its all red hot, its great fun

id go the route of buying a piston n rod complete on ebay, but if u want a standard piston on its own, i think 3 of my 4 old 1s survived intact, just stuffed up the loft destined to do nothing

 

lol

 

Ok, sounds like a ball ache!
Glad your happy mate, be nice to get your engine built up I bet!

I'll speak to my local engineer see if he will swap it over for me for free, I know him fairly well so worth an ask, if you dont mind posting me one for a beer or two plus postage mate?

If not then ebay it is or someone else on here of course!

Should be plenty kicking about as 99% of rebuilt RST's have to go at least 0.5mm oversize because of bore wear.

 

i will go up the loft and dig them out and sort out the best of the lot for ya, there was nothing wrong with them, i just bought all new, and they were used in an unbored block, so are standard size and compression. if u cover postage and wana sort me a beer token, then thats very cool with me, pointless keeping 3 pistons that are now too small for my block lol

will drop u a pm later dude

 

Your a star thanks mate!

 

The crack in the ring land is more to do with boost pressure than dett.
Very common on high boosting std piston CVH's.

If you dont have any luck there is a std set for sale on another forum.

 

What would you call high boosting Jano?
Stock pistons have been skimmed and used up to 300bhp so I'm suprised you say it could be boost pressure.

 

I binned a standard rod and piston the other day, DOH!!

 

i had that on my cosworth nms said det id the culprit and stu said so in FF too iirc

 

lol
Go get it out then!!
Yeah i've only ever seen it caused by Det, dont really understand why boost pressure could cause it? Too much fuel/air mix creating too much power maybe, but that would normally hole the top of the piston, cracked ring lands AFAIK is a classic sign of Det

 

Thats the problem, when you skim them they lose alot of the stregth on the crown.

I dont skim my std pistons as they will take more boost for a longer period before they fail.

Companys spend lots of time and money developing the best CR for the std cast type pistons, change them and you will no doubt change the characteristics of the design.

Anything above 16psi is high boosting for stock CVH pistons. At this point its down to how well the engine has been built and how good the piston material is from the factory.

 

yea, companies also spend a lot of time and money choosing the correct turbo, management, cam, port shape/size, inlet manifold design etcetcetc....

then we come along and change it all....

anyway my point is, that by changing the things we do fords original cr calculations for economy, reliability, fuel type etcetc, aren't really relevant any more. I don't think they were particularly scientific in the first place, compared with say a CAD modelled zetec....

Rob,

 

ouch! have you got a spare piston yet mate? i might have one lying around ..

 

Skimming will make the piston more likely to hole at the top, not crack the rings lands IMO.

I still dont see how boost can crack a ring land, it's the shockwave from Det that does it, and after all boost is only relative to the engines VE.

Thanks fella but got one sorted now!

 

i'd put it down to a big burst of boost, seen quite a few like that, det normally leaves more marks. As Rob said, check the other pistons very carefully, last one i was had broken all 4 pistons!

 

Did a bit of reading earlier, bad ring gaping (too small a gap) can cause the above damage, so can too large a piston to bore tolerance as the piston slop creates a side load on the ring/ring lands cracking and thus breaking them..... and looking at where its broken that could be it....

Cylinder pressure was also mentioned as a possible cause as most force (from combustion pressure) is exerted on the ringland under the first ring, however, knowing how chocolate rst rods are i suspect they would be damaged to???? det was also mentioned but this should be obvious on the piston face too.

High rpm was also mentioned as a possible cause... so essentially every thing lol....

I guess you won't really know for sure... had the engine ever been rebuild?


Any way bugger all this Karl, i reckon your missus dropped it on the floor when you were making the tea

Rob,

 

Fair play! Could indeed be any number of things then..
Dont think it had been rebuilt ever no mate.

 

Ah... you can probably omit ring gaps and bad piston to bore tolerance then..... so maybe over revved, too much boost for too long? det lol

And i edited by last post with the most likely reason

 

Behave Rob.... she knows better than that lmao

 

Never mind all that, your bird was stripping the engine down with you? where did you find one like that? congratulations my bird wont even step into the garage

 

lol mines threatening to castrate me if i don't finish my car soon and take her on holiday..... little does she know the next project is lined up

 

It's her project she's doing the rebuild mate! I'm just supervising
One in a milllion mate!
hehehe oh dear Rob!!