Learning2race
Expert Class
Posts: 138
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posted August 29, 2011 10:06 AM
Head milling question
My head took a hard hit from a piston after breaking a rod. In order to get the head flat so as to achieve a gasket seal, it would need to be decked 0.012" - more likely 0.014" to ensure enough material past the gasket edge. Visually this looks like I would be cutting into the valve pocket and possibly the valve seat itself.
Wondering if anyone else has had this happen and what thickness can be safely removed?
Thanks
  
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smokinZX14
Needs a life
Posts: 10197
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posted August 29, 2011 10:52 AM
You can go 30 no problem ... I would have them cut it 20 and call it a day ... At 20 the cam timming will not need to be reset .. Roy and i checked this and cutting 20 will only move cam timing less than 1 a deg ...You will never feel a 1 Deg change ... It will raise CR close to 13.1 but will still run fine on pump gas .. You will get a good bump in power with a 20 cut ..
____________
Smokin Performance Cycles..
Tampa Bay , FL .. Brocks Performance Dealer ..
Gen 2 ZX14R Best ET 8.43 , Best MPH 164.95
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Learning2race
Expert Class
Posts: 138
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posted August 29, 2011 11:27 AM
At what point do I have to worry about valve/piston clearance. I've got aftermarket cams (nothing wild - no requirement for milling inside the head to make them fit)
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smokinZX14
Needs a life
Posts: 10197
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posted August 29, 2011 11:43 AM
quote:
At what point do I have to worry about valve/piston clearance. I've got aftermarket cams (nothing wild - no requirement for milling inside the head to make them fit)
If you have after market pistons you will not have any problems ..That doesn't mean you just bolt it togetter , you must check the clearance ... If you have stock pistons you need to check the valve clearance !! If you don't have clearance with stock pistons you can move the cam timing to get the needed clearance .. ..
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Smokin Performance Cycles..
Tampa Bay , FL .. Brocks Performance Dealer ..
Gen 2 ZX14R Best ET 8.43 , Best MPH 164.95
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Y2KZX12R
Needs a job
CompetitionCNC.com
Posts: 3762
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posted August 29, 2011 12:39 PM
If the head took a hit from a piston it usually only takes several thou to clean up but in some extreme cases it may take .010"
If it takes more than 3-4 thou then you better check the valve seats. The distortion very often effects seat run out. If you have excessive seat run-out then you need a valve job.
If you need a valve job then you have the opportunity to sink the valves a little to regain some piston to valve clearance.
If your running stock pistons then P to V clearance is always a concern. Like Lee said if your running aftermarket pistons then not so much, but still check it.
If you have any doubts we can check the head out for you.
____________
Y2KZX12R
CompetitionCNC.com
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