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Author Topic: valve springs  (Read 3109 times)

roberto

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valve springs
« on: 24 August 2014, 17:54 »
hey folks. bit of an odd one this but here goes. does anyone know if it would be ok to mix single and double valve springs in the same cylinder head? my plan was to fit agg exhaust valves/guides and springs in my pb head but leave inlets standard.
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Offline Sgt_Lemon

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Re: valve springs
« Reply #1 on: 24 August 2014, 19:46 »
Why? Firstly the pb head has two springs which is supposedly more than enough for every application other than ridiculous high lift and snappy cams. What are the the aug valve sizes, lengths, diameter (shank and head), and collet groove count. It just seems silly. There are already off the shelf 35mm cutback exhaust valves for a pb head. Rec will do you a set for £90 delivered for all 4 and the springs are plenty good enough. I can dig out the valve number for them if you want.
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roberto

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Re: valve springs
« Reply #2 on: 24 August 2014, 20:19 »
well the thing is. I already have the complete agg valve assemblies and my head needs new guides so with the pb and agg guides costing the same I thought why not put the more streamlined valves(agg) in during the rebuild. valve head is same diameter but with 7mm stems and a less restrictive profile between stem and head. the springs/collets and top caps are not interchangeable so the single agg springs would have to be used. just not sure if it would bother the engine in any way having doubles on inlet and singles on exhaust valves. 90 quid for the 35mm valves then you need the seats to match and the head machined to accept it all. cant justify the cost really.
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Offline Sgt_Lemon

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Re: valve springs
« Reply #3 on: 24 August 2014, 20:32 »
If it's just because you own the other parts already you might as well. It's just going to be virtually unnoticeable in the flow characteristics of a completely standard head.
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roberto

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Re: valve springs
« Reply #4 on: 24 August 2014, 23:46 »
I will be doing some light port work/3 angle seats/decent skim and mild cam. so every little helps :cool:. aiming for 130ish bhp.
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Offline Santiago

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Re: valve springs
« Reply #5 on: 25 August 2014, 09:18 »
The outside diameter of the two types of valve guide is the same, is it?
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Offline Sgt_Lemon

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Re: valve springs
« Reply #6 on: 25 August 2014, 10:09 »
No pb valves are 8mm but if you are doing new valve guides it might work. A valve cutback would be beneficial.
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Offline Santiago

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Re: valve springs
« Reply #7 on: 25 August 2014, 10:53 »
Outside dia of guides.  :wink:
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roberto

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Re: valve springs
« Reply #8 on: 25 August 2014, 14:21 »
Quote from: Sgt_Lemon on 25 August 2014, 10:09
No pb valves are 8mm but if you are doing new valve guides it might work. A valve cutback would be beneficial.
yeah im planning on getting the valve back cut just in from the seat.
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roberto

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Re: valve springs
« Reply #9 on: 25 August 2014, 14:22 »
Quote from: Santiago on 25 August 2014, 09:18
The outside diameter of the two types of valve guide is the same, is it?

yeah the guide o/d is the same on both.
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