9YaTaH wrote:
drmini in aust wrote:
Clearance is in the valve stems, which are always made slightly U/S.
I use a 9/32" solid reamer.
I've run it to 8,000 a few times since around Wakefield Pk- no worries...
Thanks Doc, does U/S mean Under Size? or did you mean Over Size?
What I mean is should a racing engine have a larger clearance
or are the K Liners so temperature stable that a normal clearance is OK
or do the liners expand a tad with the head?
The valve stems are made a few thou undersize by the factory, so they will have the right clearance in a standard valve guide of 9/32" (0.28125") bore.
The problem is, the guides are made this size, but during fitting (or afterwards) they can shrink in diameter as they are a press fit in the head.
Bronze guides (or K-liners) are the ones to use if running stainless valves as I am. These do not run well with plain cast iron guides. Heat transfer is better with bronze guides too.
K-liners are a thin bronze guide sleeve inserted after boring the guides out. Popular in US as many V8 engines do not have separate guides- their valves run in the head. They would need sizing with a reamer after fitting too.
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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.
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