What is the general feeling about valve guide length? The ones (worn out) that I have are cut back to 1 7/8" (11/16" of which is the part on top) This gives a projection into the ports (inlet and exhaust) of only just the rounded off lower end. The new ones I have from S&V are 2 3/8" overall. This seems to leave an awful lot sticking into the ports but suppose it must be OK? Any comments gratefully received! Simon.
One option is to have the exposed section of the guide in the ports tapered if you are seeking to optimise performance in every area possible. Tapering the guides will reduce gas flow restriction.
Janspeed undertook tapering work to one of my heads fitted in my latest J engine as part of the overall head development work.
Simon, I found exactly the same situation and asked a similar question-check he forum. A friend with some sophisticated gas flow software looked into it for a bit of fun and found that the guide projection did not significantly affect the gas flow, probably due to the size of the ports. I find this hard to believe but he flies and says always believe your instruments (but I notice he gives them a tap occasionally) As a compromise I ended up reducing the inlet by 10mm and leaving the exhaust alone as I liked the idea that the guide may help to cool the exhaust valve. It is not a race engine so I am not too concerned. Hope this helps Bernard
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Posted - 26/01/2009 : 18:44:11
