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Valve Clearance


bmetcalf

Well Known and Active Website User
VOC Member
From: https://www.hotrod.com/articles/measuring-setting-valve-piston-clearance-advanced-guide/

This article advocates checking valve piston clearance by using light checking springs and a dial indicator, rather than clay or play dough. They say that “The tightest clearance between valves and pistons does not occur at maximum valve lift, but instead at two places during the piston travel. The intake valve is closest to the piston in the vicinity of 10 degrees after top dead center (ATDC), while the exhaust valve rides closest roughly 10 degrees before top dead center (BTDC). “ I’m sure positions outside that are worth checking, too.
 

stu spalding

Well Known and Active Website User
VOC Member
Hi Bruce, I've found that Plasticine etc is very useful in determining side clearance between the valve head and valve pocket in the piston. Even when there's plenty of room for valve travel it can still be tight for side clearance, so I use both methods, just to be sure. Cheers, Stu.
 

timetraveller

Well Known and Active Website User
VOC Member
Quite right. Max lift is nowhere near the minimum clearance. Stu is right and as a precaution I always take a little off the side of the valve cut out on the pistons to ensure the radial clearance is sufficient.
 

roy the mechanic

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VOC Member
Years ago Syd Lawton told me he used to blue-up the heads of the valves, touch them on the piston and scrape the pocket so the whole head was at the same angle. The theory was, if you had a light touch on a down shift it would try to compress the valve and not bend it.
 

timetraveller

Well Known and Active Website User
VOC Member
Problem with that on Vins is that the cut out only covers a small part of the valve face. It might work on a Manx with huge cut outs but on a Vin, even with 10 : 1 s, there is nowhere near the whole valve face covered.
 

vibrac

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VOC Member

Marcus Bowden

Well Known and Active Website User
VOC Member
Years ago Syd Lawton told me he used to blue-up the heads of the valves, touch them on the piston and scrape the pocket so the whole head was at the same angle. The theory was, if you had a light touch on a down shift it would try to compress the valve and not bend it.
Syd Lawton was in partnership with Pat Wilson as he was the Vincent dealer and the main mechanic was an ex works engineer Mike Creamer who eventually went off on his own when Pat W moved to Plympton Devon.
Mike produced several Creamer Shadows from Rapides and they were sort after because of their quick nature.
bananaman.
 

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