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Only ONE valve spring? Pics!

Just been having lots of fun getting the heads off my '77 C3. My question is...why have all my heads only got one valve spring? Aren't they all supposed to have two? Or am I missing something here? (Apart from some springs of course!) -M
Old 06-18-2005, 12:26 AM
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All the 911 heads I've seen have had 2 per valve so I'm with you, I thought they all had 2 also. Now I'm curious.
-Chris
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Old 06-18-2005, 03:04 PM
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Perhaps they were rebuilt at some time and either they were ommitted accidentally or are some kind of aftermarket spring?

R/
Dustin
Old 06-18-2005, 06:30 PM
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Many thanks for you replies so far...OK...so I'm missing a spring on each valve. Now for my next inquiry. How do you correctly measure the valve spring height as I'm obviously going to have to get new springs. In first picture you can (hopefully) see the diagram I'm refering to, followed by two possible points to measure the base of the springs from. In the second picture the pencil is pointing at the top of the spring retainer lip. In the third it's pointing at the bottom of this retainer. Which is the correct point? If I measure them from the top of the spring retainer (fourth picture) then my springs are in spec. I'm hoping this IS where you measure from but somehow I've a feeling it isn't! Some clarity on this point would be really helpful. Cheers -M

Old 06-19-2005, 04:09 AM
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Sorry to go on about 'MY' valves! (But they are pretty important..so bear with me!) Anyway...more questions and more pictures. Now...it's all about valve guides and sideways movement. I took these little buggers off in the first place because I suspected leaky valve guides and seals. However..when I give them a wriggle I can feel no sideways movement on the valves (see the next two pics..that's my grubbly little hand trying to wriggle the intake and exhaust valves side to side). Also (if you look at the very first pictures in this thread) my valve seals look in good condition and don't appear to be worn or broken in any way. OK so the valves themselves need a little clean (third pic) but the guides don't feel or look like they need replacing. Just looks like the engine's been running too rich, hence the oily mess. Your views please...am I dreaming in novice cockoo land or do I need to be brought back to Earth with an expensive bump? -M
Old 06-19-2005, 04:31 AM
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Since we are after all, measuring the spring height, measure to the bottom of where the spring would rest in the seat.
BTW: Where are you looking up your spring height spec (what book)? Is the spring height spec for a C3 the same as an SC (34.5mm -.3)?
-Chris
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Old 06-19-2005, 04:33 AM
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I see...so all my springs are 'out of spec' if I measure from their bases...which is kind of what I thought. Bugger! New springs AND shims required. I'm looking at the numbers in the little white 'Technical Specifications' booklet (that's where I got the picture from) It's also the same in Bentley, Haynes and Waynes book...all say 34.5 -.3 spec for both inlet and exhaust on '77 C3. Just out of curiousty...what difference does valve spring height make to overal preformance? I mean this thing used to run OK. -Mark
Old 06-19-2005, 05:14 AM
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looks like some pretty fat wire on those springs, compared to a stock spring.
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Old 06-19-2005, 07:49 AM
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If you are talking about "installed" height it is adjustable with a simple shim under the spring . A spring setup longer than stock spring will have a lower seat pressure but if the spring has been changed to one with a different wire it might also have been setup with a diff installed height.on purpose.
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Old 06-19-2005, 08:19 AM
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Johnsjmc I was thinking that too. In the manuals it says the 'outer springs are tapered and orientated with the tighter coils to the head'. Mine aren't. Why would the PO put different srpings on? Anyone else done this 'modification' to their own engine. Make any difference? Should I keep 'em or bin 'em??-M
Old 06-19-2005, 08:28 AM
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You need to remove one and have it,s spring rate determined. An automotive machine shop has a tool to measure spring pressure at installed height and again at max lift. Then compare to a stock spring. All springs are not created equal and the replacement springs you have may be good ones just different from factory. You can measure them yourself with a drillpress and a bathroom scale. Set the spring under the drill chuck and press them down against a bath scale Note the weight to compress to a known length. John
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Old 06-19-2005, 03:07 PM
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In a situation like this where "upgraded" parts of unknown origin are present the safest course is often to replace them with standard parts. You might want to check the cams as hot grinds frequently require stiffer springs to avoid valve float and these are often sold together as a kit. If you find the cams to be stock, I suggest you replace the springs with the appropriate matched parts. If the springs are too weak valve float is a real possibility, if too stiff premature cam and lifter wear is inevitable.
regards,
Phil
Old 06-19-2005, 04:54 PM
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OK..just taken off the springs and found that my valves have 'significant' wobble on them. They need new guides after all. How much should this cost. I've been quoted 75 per head (that's approx $136). The price includes 'boring out the old guides and inserting new spiral guides'. NOT removing the entire old guide and inserting a new one...which is what I thought should be done. The machine shop recommends this other process as it eliminates the possiblity of the new guide cracking the head. Any thoughts about this? Good idea? Good price? It doesn't include any new parts obviously. Cheers -M
Old 06-22-2005, 12:25 PM
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mingmong

I measured the installed height the way you have in the picture with a dial gauge, all you have to do is also measure the thickness of the top retainer and the 'depth' of the lip on the bottom seat, this is the offset you add (IIRC the depth is greater than the thickness) to your measurement.

I think those springs are aftermarket

HTH

Neven
Old 06-22-2005, 01:13 PM
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Sorry read your later post on guides and no I would not go the spiral guide root, Contact Autofarm or one of the other Porsche Specialists and they will do it for you

Neven
Old 06-22-2005, 01:24 PM
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Neven...I'm inclined to agree with you on the spiral guides issue. I'm also changing the valve springs for stock (not cheap!) but I want these important parts sorted out properly! -Mark
Old 06-22-2005, 02:03 PM
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Mark

With 911 engines nothing is cheap! Also regarding the guides its more important that you use the right material than the method, they are one of the most stressed parts as you can see by Porsche never getting a 4 valve head to work or the tricks they did on the racing engines

Neven
Old 06-22-2005, 02:07 PM
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