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Schleprock
Join Date: Sep 2000
Location: Frankfort IL USA
Posts: 16,639
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If you have the ability to install the new guides for 8mm valves, I say go for it. Anything you can do to lighten the valvetrain is an improvement as long as it doesn't compromise strength/durability. I doubt there's any downside to the 8mm valve stems since that's the size the 993 valvetrain uses?
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Kevin L '86 Carrera "Larry" |
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04-03-2013, 07:49 AM
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Puny Bird
Join Date: Nov 2002
Location: Port Hope (near Toronto) On, Canada
Posts: 4,566
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Quote:
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'74 Porsche 914, 3.0/6 '72 Porsche 914, 1.7, wife's summer DD '67 Bug, 2600cc T4,'67 Bus, 2.0 T1 Not putting miles on your car is like not having sex with your girlfriend, so she'll be more desirable to her next boyfriend. |
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04-04-2013, 04:42 AM
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Straight shooter
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Playing devils advocate on smaller valve stem - there will be less area for the valve to contact the guide and to conduct heat away from the body and head of the valve. If you're looking at stainless then you will need to know your EGT to ensure it doesn't often surpass the failure point of stainless around 1500F.
In reality I imagine you would be fine with stainless and smaller stem with the correct guide spec unless you were pressing into the most extreme conditions...and even then you may not see 1500F EGT without a power adder. Good info on valve materials - http://www.manleyperformance.com/dl/custom_valves.pdf
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“Of the value traps, the most widespread and pernicious is value rigidity. This is an inability to revalue what one sees because of commitment to previous values. In motorcycle maintenance, you MUST rediscover what you do as you go. Rigid values makes this impossible.” ― Robert M. Pirsig, Zen and the Art of Motorcycle Maintenance: An Inquiry Into Values |
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04-04-2013, 07:15 AM
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Puny Bird
Join Date: Nov 2002
Location: Port Hope (near Toronto) On, Canada
Posts: 4,566
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I don't have a EGT tester but I do have a wideband.
Thanks for the info Instead of custom I can use stainless steel 993 valves, they have a short tip, so I'd have to shim up the springs depending on type. Cutting the head to stock size OD is no issue except for a small back-cut.
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'74 Porsche 914, 3.0/6 '72 Porsche 914, 1.7, wife's summer DD '67 Bug, 2600cc T4,'67 Bus, 2.0 T1 Not putting miles on your car is like not having sex with your girlfriend, so she'll be more desirable to her next boyfriend. |
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04-04-2013, 07:27 AM
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Puny Bird
Join Date: Nov 2002
Location: Port Hope (near Toronto) On, Canada
Posts: 4,566
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I have a message to Walt Frickle, he did this and hopefully he'll chime in on his experience.
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'74 Porsche 914, 3.0/6 '72 Porsche 914, 1.7, wife's summer DD '67 Bug, 2600cc T4,'67 Bus, 2.0 T1 Not putting miles on your car is like not having sex with your girlfriend, so she'll be more desirable to her next boyfriend. |
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04-04-2013, 09:38 AM
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P911
