Discussion
Cant add more than what Puma has said really. He's certainly a lot more qualified than most to comment
But the report does certainly report no real blame onto you other than the oil ( and his claims about temperature strip readings which arent that bad really ). And blaming the oil is of course BS. I dont think there is an oil available today that would be poor enough to be the problem.
As for the comment about short skirt pistons....I guess they've never worked on any modern engines ?
Short skirts arent exactly uncommon these days even with OEM engines, but they will run much tighter bore clearances than huge skirted pistons.
But the report does certainly report no real blame onto you other than the oil ( and his claims about temperature strip readings which arent that bad really ). And blaming the oil is of course BS. I dont think there is an oil available today that would be poor enough to be the problem.
As for the comment about short skirt pistons....I guess they've never worked on any modern engines ?
Short skirts arent exactly uncommon these days even with OEM engines, but they will run much tighter bore clearances than huge skirted pistons.
Do we have pictures of the piston skirts and a close up of the piston crowns? They look very rich but also show a hint of lean mixture. How was this engine run in? The inlet tracts are nice and clean which is a plus.
Edited by Boosted LS1 on Friday 11th April 22:24
Edited by Boosted LS1 on Friday 11th April 22:31
Just noting one more thing in his report. He says piston top lands contacting the cylinder walls is a primary cause of piston slap type noises. No it isn't.
The top land on a piston of this size will be circa 0.5mm (20 thou) below nominal bore size. This is to allow for thermal expansion in the most extreme running condition of piston crown temperatures reaching circa 300C in race use. Above this temperature aluminium piston alloys lose strength rapidly so it's kind of academic trying to cater for even higher temperatures.
If you put a piston in a bore and rock it you can't make the top lands touch the bore walls or even come close to them. The couple of thou clearance on the skirt won't allow the piston to rock enough to bring the 20 thou clearance on the lands into contact.
In road use the piston crown temps and land expansion won't come close to taking up the bore clearance. That's why you have loads of carbon on the top lands. If they touched the bores this couldn't form. The carbon actually builds up to take up the clearance.
Piston slap noise is caused by the piston rocking from making contact at the top of the skirt on one side and bottom of the skirt on the other to the reverse. Nowt to f**king do with the ring land area.
If the ring lands are touching the bore walls you've got much more severe problems to solve like why are my pistons melting?
The top land on a piston of this size will be circa 0.5mm (20 thou) below nominal bore size. This is to allow for thermal expansion in the most extreme running condition of piston crown temperatures reaching circa 300C in race use. Above this temperature aluminium piston alloys lose strength rapidly so it's kind of academic trying to cater for even higher temperatures.
If you put a piston in a bore and rock it you can't make the top lands touch the bore walls or even come close to them. The couple of thou clearance on the skirt won't allow the piston to rock enough to bring the 20 thou clearance on the lands into contact.
In road use the piston crown temps and land expansion won't come close to taking up the bore clearance. That's why you have loads of carbon on the top lands. If they touched the bores this couldn't form. The carbon actually builds up to take up the clearance.
Piston slap noise is caused by the piston rocking from making contact at the top of the skirt on one side and bottom of the skirt on the other to the reverse. Nowt to f**king do with the ring land area.
If the ring lands are touching the bore walls you've got much more severe problems to solve like why are my pistons melting?
The only photos I was sent of the pistons are slightly out of focus....so useless. Still waiting for photos of the bores.
Engine has a Mark Adams ECU so I would hope fuelling was better than standard!!
Running was Cam Breaking a 2000rpm for 10mins then driven with Auto box in Sport mode.......running through the rev range and good use of engine breaking as stipulated in builders running in instructions
Engine has a Mark Adams ECU so I would hope fuelling was better than standard!!
Running was Cam Breaking a 2000rpm for 10mins then driven with Auto box in Sport mode.......running through the rev range and good use of engine breaking as stipulated in builders running in instructions
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