First Dyno Complete
01-11-2023 | 12:21 PM
#82
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Joined: Dec 2007
Posts: 70
Likes: 23
From: Liberty, MO
Better to be aware of an issue now rather than when it is an obvious and costly problem. If it does cost some time for this season hopefully the pain won't be as bad as it could have been. Now is the time to get the engines right.
01-11-2023 | 12:26 PM
#83
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Joined: Jun 2005
Posts: 8,407
Likes: 797
From: Central IL
So to reach my goal of 500hp using the parts I bought, boring the cylinders was not required and because the bores were in good shape I was able to maintain the standard bore so just a hone. The guy said at my level, forged pistons weren't required. Forged are apparently also heavier(?) and again, just not necessary at my hp level. That was the story.
01-11-2023 | 12:33 PM
#84
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Joined: Aug 2010
Posts: 1,384
Likes: 565
So to reach my goal of 500hp using the parts I bought, boring the cylinders was not required and because the bores were in good shape I was able to maintain the standard bore so just a hone. The guy said at my level, forged pistons weren't required. Forged are apparently also heavier(?) and again, just not necessary at my hp level. That was the story.
Obviously that could be anything typed in.
What pistons do you actually have?
Did you buy 4.250" or 4.280" pistons?
01-11-2023 | 12:59 PM
#87
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Joined: Aug 2010
Posts: 2,227
Likes: 547
From: Cape Coral FL
I would have a hard time believing that you could take a standard bore block with some hours on it, hone it to clean up the cylinder walls and only have .002 clearance on new std bore pistons. It could happen, but I bet you have more piston to wall clearance than that.
I agree that forged pistons would be better, but I personally have a favorable opinion on KB pistons. I built many claimer engines back in the day for dirt track cars and used KB pistons in them. I never saw a piston failure that wasn't caused by something else, usually by a dropped valve or severe overheating. We ran these things hard, 7200+ rpm, lap after lap, night after night and sometimes got them very hot. I do know from experience that detonation or too small of a top ring gap will destroy them in very short order. I personally think that if you have enough piston to wall clearance, the top ring has a large enough gap and you don't have detonation, that the KB pistons will be just fine at 500hp. We made way more hp than that with them in small blocks.
I agree that forged pistons would be better, but I personally have a favorable opinion on KB pistons. I built many claimer engines back in the day for dirt track cars and used KB pistons in them. I never saw a piston failure that wasn't caused by something else, usually by a dropped valve or severe overheating. We ran these things hard, 7200+ rpm, lap after lap, night after night and sometimes got them very hot. I do know from experience that detonation or too small of a top ring gap will destroy them in very short order. I personally think that if you have enough piston to wall clearance, the top ring has a large enough gap and you don't have detonation, that the KB pistons will be just fine at 500hp. We made way more hp than that with them in small blocks.
01-11-2023 | 01:19 PM
#88
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Joined: Sep 2018
Posts: 101
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KB pistons are junk for marine use,maybe will last totally stock 330 HP engine ,cast I think are better in that case. Ask me why I know this ,fell for the argument over cast pistons once ,never again,also look at casting shift in KB pistons ,one skirt is almost twice as thick as other side,good old Mexican quality control.
01-11-2023 | 01:34 PM
#89
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Joined: Aug 2010
Posts: 1,384
Likes: 565
I would have a hard time believing that you could take a standard bore block with some hours on it, hone it to clean up the cylinder walls and only have .002 clearance on new std bore pistons. It could happen, but I bet you have more piston to wall clearance than that.
