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broken ones!!! lol.

what sort of pistons are they???

I just had a thought,
You're running sidedrafts right, could there have been a carburation problem with the venturi that feeds number three cylinder?

The rings arent fixed in place, they can move alittle.The rings are pushed against the lands during piston movement. You give something a good rattle and the weakest part will eventually fail.

thats what i mean,i know detonation is violent, so if it was detonation ud think there would be damage on the top where the detonation occurs not on the lands, and i would think it would occur in more places other than this one small spot plus, thought it would do damage to the rings. this is the only damaged piston and the rings on all pistons werent touched, im no expert but i think detonation would occur on all the pistons not just one.... ohh wlel at the end of the day doesnt matter the engine is blown next time i wont be doing the same again. it will be tuned by a professional with proper equipment.

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It doesnt have to show marks to say lean out. Detonation is violent.
Think about cylinder compression pressures and add detonation. Thats a lot of hard banging going on.
Now think about all the things that can contribute to causeing detonation.

This has been linked here before, but...http://www.mototuneusa.com/break_in_secrets.htm
I found this lnk ages ago when surfing. I followed this method when I broke in my new engine. Because my new motor A15, is bigger than the old a14, (129cc's) I jetted it really rich.
I towed the car out to the countryside, and let rip.
Once it was warm, I pushed my brand new engine, up to 105mph. (On the clock) Being towed home, I phoned the tow car driver to check my speedo, and it turned out it was reading slow by 15%. So I had pushed my BRAND NEW engine to 120mph @7PSI.
No problems. That was holding back a bit too!
It sounds like your engine builder should know his stuff. Did he bore some extra clearance into the bore? My machinist gave me an extra three thou, to allow the piston to grow a bit more from boosted tempratures.
The suggestion of a gas anyliser is a good one. I recently borrowed from a mate a broadband air/fuel ratio meter. I put a boss on the tail pipe to fit a five pin bosch O2 sensor. You plug it in, and tape it up the boot and in the window. Then the remote plugs into the cigarette lighter socket. It's got a digital display which tells the a/f ratio.
It told me I was running rich as. I used it to diagnose why it goes flat at 6000.( Leaning out, not a spark problem)
If you can get a hold of one of these, you'd find it most helpful.

l18b110, Quote:
when i said the lands were broken i shouldve specified, the lands were broken below the first ring and below the seond ring ill take a photo.
dizzy is electronic stock a15 import one, has been regraphed to i dunno what specs as i dunno what they do.... jeff says its regraphed for turbo but i dunno what that means. i didnt have vac avance conectted to manifold. boost was only 7psi, comp ratio was around 8-8.5 to one, again this is what i was told by jeff taylor as i dont know how to check.... although a fair amount has been removed form the piston so i belive it would be around that.no further material than the stock depth was removed only the dish was made a larger diameter pics below.


ok this pic shows the lands where theyre broken, notice theres no yellow or white spots to show white hot lean out.... only thing that worries me is the scuff marks on the skirt i dont know whther i did this when taking it out or whther there is tighter clearance there, maybe the lands caught the bore? surely rings would go before that happened???


the small crack looking thing on the left isnt a crack is just dirty part or something. notice theres no damage only a few tiny little pin-dot marks from detonation ( i was told thats what it is) theres also no spots that would show lean out. the sides above the rings of the piston are completely black same as this.

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I must have missed the part where you said the rings were OK. I assumed they had broken and then cracked the headlands.

but I disagree about the lack of damage to the piston tops -you did say the headland were broken! factory A series pistons don't stand up well under boost. it doesn't take much detonation at all to crack them.


what have you done to the dissy?

how much boost?

what CR?

this is a weird sutiation in that all the main thing that would cause this dont match up, it wasnt the rings, in a sense that they hadent bedded in, i ran 5-600 k's with stock carby, and it had heaps of comp before going. also it doesnt seem like it was caused by detonation, because the way i see it if it was detonating that bad to break the lands and not the rings, then there would be damage on the piston tops....also the rings like i said werent damaged. the reason jeff says its the reason he did is beacuae when the car came on boost it trailed massive amounts of black smoke, i cant see it being lean with the amount of smoke???
i know everyone says efi is the best way to go and it is, but i really wnna get this setup to work properly, the lotus' used the same setup and theres no way they wouldve run them for the amount of years they did with them running like ####. sux because even people that know the lotus setup tell u its exactly ther same sept for the mods ive done so must have something to do with the combination of parts i have inside the carbs ......... oooohhh the fun continues