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Post by endru on May 6, 2013 19:30:23 GMT -5
I'm having trouble wrapping my mind around the concept of 64mm vs. 69mm valves. The problem may simply lie in the fact that I haven't yet installed a BBK or performance head, so I haven't had the chance to see this stuff disassembled. But this is something that's been bothering me and I don't want to mess up when I'm ordering parts. My question is, why does it matter what the valve length is on my stock head? My only guess is that my 69mm head is in fact slightly taller (in addition to longer valves) and therefore going down to a 64mm head would make the crankcase bolts too long and the camshaft chain too long. And for those that have 64mm valves, the opposite would be true - a 69mm head would extend past the crankcase and too short of a cam chain. Is this where the problem lies, or am I way off?  |
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Post by teddy554 on May 6, 2013 19:45:54 GMT -5
You can run 69mm or 64mm on your motor but if you dont have the right rocker arm assembly the rocker cant touch the valve or there is to much contact. basically as long has you have the right rocker arms you cant run either
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Post by teddy554 on May 6, 2013 19:48:24 GMT -5
the valve length does not effect anything with the timing chain or the bolts, or thje thickness of the head
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Post by domindart on May 6, 2013 19:51:37 GMT -5
its not the size that matters its how -wait what?  |
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Post by endru on May 6, 2013 19:54:35 GMT -5
Aha, that solves it, thanks Teddy. I wasn't thinking that you the rocker assembly from the original head. Makes perfect sense now.
So when I was investigating my stock head months ago trying to figure my valve length, it wasn't immediately obvious whether or not the valves were sticking up far enough to be 69mm. I wonder though if it wouldn't just be easier to measure the rocker arm lengths to determine the valve length.
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Post by teddy554 on May 6, 2013 21:44:30 GMT -5
I think i have both ill measure sometime tomorrow for you but until you see both side by side it really is hard to tell
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Post by endru on May 6, 2013 21:52:51 GMT -5
[replyingto=teddy554]teddy554[/replyingto]Yeah I'm about  % sure that I have 69mm valves, just by eyeballing them from the side to see how far above the lip of the head they are. But I like cold hard measurements, so that would really be appreciated. Thanks! |
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Post by triker on May 7, 2013 0:31:26 GMT -5
I have discussed this in another thread. The 69mm valves will measure about 10mm above the head. The 69mm will measure about 5mm above the head. Or you can measure the distance between the valve stems. 69mm valves will be about 77.5mm apart and 64mm valves will 73.5mm apart.  Roy |
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Post by endru on May 7, 2013 20:59:18 GMT -5
[replyingto=triker]triker[/replyingto]Thanks Triker, that's extremely helpful!
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% sure that I have 69mm valves, just by eyeballing them from the side to see how far above the lip of the head they are. But I like cold hard measurements, so that would really be appreciated. Thanks! 
