Valve Spring Advice
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Cruiser
Joined: Aug 2012
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From: CT
Valve Spring Advice
I am building an 80" evo with an EV27 cam, crane adj. pushrods, and some other stuff, but my main concern is the valve springs. I am installing kb .030 overbore pistons with 9.5:1 compression, and polished up heads and valves. Do you think I need to upgrade the stock valve springs? I'm on a junk drawer change type budget also. I know I could, but do I have to? Any advice is appreciated. Thanks, Glenn.
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Cruiser
Joined: Aug 2012
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From: CT
Each head and valve was polished up with some porting done to the heads. The springs were just professionally disassembled, cleaned and inspected. Then reinstalled with new collars, seals, and keepers. The springs should last as long as the bike then correct?
Seasoned HDF Member
Joined: Dec 2010
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From: Coromandel Peninsula New Zealand
Pretty much, none of the work you have done actually affects the need for a spring rate change.
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Cruiser
Joined: Aug 2012
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From: CT
I am glad to hear that. I just have others telling me different. I read, before ordering the cam, it was for basic or performance motors. Bored .030 over jugs and 9.5:1 comp pistons doesn't really define "performance" in my opinion. Lets say in the future I added an ignition module and some other crap. Would it still matter?
Seasoned HDF Member
Joined: Dec 2010
Posts: 7,736
Likes: 1,524
From: Coromandel Peninsula New Zealand
Nope, its cam lift and rev limit that determines the need for a spring change, any cam that is a "bolt in" (and EV27 and 46 are both bolt in) is just that, no need for other mods. If ya go to wild, wild cams then you'll need fancy springs and collars to cope with the increased lift.
If you increase your rev limit to 8K rpm then you need your head testing, as well as fancy springs and collars :-)
If you increase your rev limit to 8K rpm then you need your head testing, as well as fancy springs and collars :-)
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