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InläggPostat: sön apr 23, 2017 2:53 pm 
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Blev medlem: sön aug 27, 2006 6:17 pm
Inlägg: 284
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Hi.

Thought i would share a few observations.
Im streetracing a 245 with B234 turbo. It is building 563bhp, 723Nm on pumpgas, Vpower.

It has started giving me a few headgasket failures, despite being oringed. It is running a garrett 60mm turbo off a bus on long headers.

I know from datalogs that there has been sporadic knock now and then, and agree this will kill everything.

I did a leakdown test, and it was leaking badly past the rings, so assumed rings was dead, but they look to be very ok. Instead the cylinderwalls has a black mark from soot next to all bolts, and especially obvious there is a balck soot mark correlating to all cooling passages in the blok, in particular where the headgasket finally blew.

The pattern looks like the cylinder is ballooning close to the top deck where the deck is having the coolant passages. Like the block has deformed plastically there. Is there any experience with this?


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InläggPostat: sön apr 23, 2017 9:58 pm 
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Blev medlem: mån okt 15, 2007 10:00 pm
Inlägg: 5452
Ort: Lund
You need to leave 0,10mm when boring and then hone the block with a torque plate.

Erland


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InläggPostat: lör apr 29, 2017 2:11 pm 
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Blev medlem: sön aug 27, 2006 6:17 pm
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Im still running stock sized pistons, and another question is how much clearance the B230(4) will run before it starts rocking the pistons excessivly.
I can clean up the bores at approximately 96,09mm bore. It seems excessive, but what do you guys think?


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InläggPostat: sön apr 30, 2017 7:54 pm 
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Blev medlem: mån okt 15, 2007 10:00 pm
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I have not seen any problem with that.

Erland


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InläggPostat: tor maj 04, 2017 9:27 pm 
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Blev medlem: sön aug 27, 2006 6:17 pm
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Finish honing now, and with the stressplate it does change the pattern a bit.

Measuring the pistons(used b234f) 12mm down the skirt gives -0,05mm
Measuring the bores after honing they give me +0,12mm, or a total piston-bore clearance of 0,17mm.

I am quite concerned this is too much, and will lead to piston slamming the skirt into the wall too much.

What is considered the max safe clearance?


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InläggPostat: tor maj 04, 2017 11:12 pm 
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Blev medlem: mån okt 15, 2007 10:00 pm
Inlägg: 5452
Ort: Lund
Me and my son have run several engines like that.
There are some advantagets with it, all is not bad.
Last year I lost a freeze plug without notizing until after 2 -3 laps on a track.
I overheated my engine badly and warped the head 0,7mm.
But the high clearance piston and block was just as happy as before.
Fixed the head and put it back in and the engine runs like before.
Some piston noise when cold biut OK when hot.

Erland


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