Sf2 head number of fins / valves and guides

martymoose

martymoose

Hero member
Location
Sydney, Australia
All sf heads are supposed to have 8mm valves, 1974 sfc heads have 7 mm valves.  Well, my sf head has 7mm valves, and oil seals on the inlets. 

I remember reading somewhere the number of fins on the various heads, can someone point me in the right direction please. 

Cheers
Marty
 
Here's some interesting info Marty, regarding the 1974 SFC from Marnix's excellent book......
 

Attachments

  • SFC 1974 fin count.jpg
    SFC 1974 fin count.jpg
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My SF2 heads had inlet guide seals but not exhaust seals. The 7mm SFC guides I once had fitted also had inlet guide seals. My race SF has 8mm valves, never been a problem, 6C cam in it.
 
I need to find new valves, inlet 42.5mm head, 95.5mm length.  Exhaust 35.8mm head, 95.5mm length. Do i stay with 7mm, or bore out the guides to 8mm? 

Are the head sizes standard for sfc valves?
 
martymoose said:
Thanks pat knew id read it somewhere. Green book says 8mm but marnix's book contradicts "all".  Interesting.
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Wouldn?t say so. The street models always had 8mm stems, but the new 16 fin head came when the 17 fin heads phased out.
You can recognise a 1974 SFC head by the 7 mm guides, yes, but also the diameter at the inlet was 36mm instead of 34mm for the SF123. Much more time was spent on the flowing of SFC heads too.
 
MarnixSFC said:
You can recognise a 1974 SFC head by the 6 mm guides, yes,
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You mean 7mm, Marnix.

I'd leave the 7mm valves in and just source SFC valves, Marty. I sourced OS inlets and std size exhausts from red for my SFQ head but had to machine up bronze alloy guides because they valves are stainless steel. My SF head I fitted SFC valves, guides and ported to 36mm. If the guides on yours are cast iron, you'll need to source non-stainless valves. I reckon hotted up Kwaka 9 two-valve motors might have used pretty big inlets - certainly had 7mm stems. Could be cut and tipped?
 
Paul Marx said:
Yup, and 36mm inlet.  8)
More coffee in the morning.

Paul
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You might want to check and see if they make these in PHB ......

Jim

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I used to have the 7mm inlet valves made - up to & Inc 44mm and the exhaust up to 36mm. Got a set left for my own bike - but none to spare ATM. - Regards - Phil
 
It didnt stop Eades for a good while doing it i bent 2 valves 600ks away from Sydney on my first ride after thay rebuilt my head doing exatly that
 
Piranha Brother 2 said:
Aren't they stainless, Red? Or is that only for the OS 44mm ones? If Marty's bike has cast guides he won't be able to use stainless.
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Cast? Stainless? Do you know anything about valve construction?

I suggest you let folks who know contribute before you add anything more. I sure as hell know little but I am thinking I know more than you.

Jim
 
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