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Vincent BC&D Valve Spring Data

johnmead

Well Known and Active Forum Website User
Non-VOC Member
Does anyone know or know where to find the following dimensions for the ET39 valve spring:

Free length
Installed height
Seat pressure

Also, is there a "preload" used on the ET39/1 or is it installed without additional shims at the same installed height as the ET39?

I have some "beehive" valve springs from various engines and would like to use them in the engine for my special.

Beehive springs are made to eliminate coil bind when using high lift cams. I am using a set of Terry Prince's MK4 cams and they have a higher lift than the MK2 cams.

John Mead
 

timetraveller

Well Known and Active Forum Website User
VOC Member
Hi John, no shims are required as the top valve guide is shaped to pre-tension the inner spring (ET39/1) However, did you know that Terry provides alternative springs which can take the extra lift without coil binding and yet give the original seat pressures. They are the correct springs to use with Terry's special cams. I checked the profile, timing etc of a set of these cams for a friend some years ago and thought that they would be fairly extreme for road use. Sadly the friend died before the bike was finished so that there was never any feedback as to how they actually performed. I do remember that the cam nose fouled the boss in the timing cover which takes the spindle for the rear valve lifter so check very carefully when you install them as you might have to grind that back a little as I had to in my test engine. Good luck.
 

johnmead

Well Known and Active Forum Website User
Non-VOC Member
Thank you for the information on Terry's valve springs. I noticed them on his list of parts but thought that they were standard Vincent spring types.
 
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