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Valve heights in head

ksbundy

Active Forum Website User
VOC Member
I have had the valve seats and valves replaced in the heads and I now find that the valve springs are coil binding. Does anyone have the dimensions for the position of the top of the valve (or circlip grove) in relation to the head (or upper guide). This should allow me to get the seats cut to a position where I will resolve the spring binding and also get the rocker arm movement to where it should be, without resorting to trial and error.
Thanks Ken.
 

clevtrev

Well Known and Active Forum Website User
VOC Member
I have had the valve seats and valves replaced in the heads and I now find that the valve springs are coil binding. Does anyone have the dimensions for the position of the top of the valve (or circlip grove) in relation to the head (or upper guide). This should allow me to get the seats cut to a position where I will resolve the spring binding and also get the rocker arm movement to where it should be, without resorting to trial and error.
Thanks Ken.
Somethings wrong, if the coils are binding, the collar must be positioned wrong, it would normally hit the guide before the springs bind. Maybe the collars loose on the stem, allowing that to happen.
 

ksbundy

Active Forum Website User
VOC Member
Somethings wrong, if the coils are binding, the collar must be positioned wrong, it would normally hit the guide before the springs bind. Maybe the collars loose on the stem, allowing that to happen.
I thought that at first, but the guides are flush with the top of the retaining nuts. The valves are new as are the collars and they are seated on the valve stem correctly. By lowering the valve seat it will give me more clearence between the collar and the valve guide, as well as stopping the spring from coil binding. I have measured the travel and it is correct for Mk 11 cams (.365") If I knew where the valve was supposed to be in relation to the head, I could get the valve seat machined to suit.
 

timetraveller

Well Known and Active Forum Website User
VOC Member
I dont have a measurement but the 30 degree angled valve seat normally needs to have the ground portion extending outwards towards the outer edge of the valve seats by well over half the radial thickness of the valve seat. If they have only been ground to a thin edge they are not gound down far enough. The exhausts should have seat to valve head contact width of about one tenth of an inch to enable heat to pass out of the valve head into the seat. The inlet can be as thin as you like consistent with a good seal and then the inner edge of the seat ground back to aid gas flow. As an aside many racers use a 45 degree angle on the exhaust. As another aside Terry Prince sells valve springs that will allow up to about half an inch of lift without binding but yet give a standard seat pressure.
 

b'knighted

Well Known and Active Forum Website User
VOC Member
What are the chances, with new valves and collars, that the step for the collar is too high, collar too thick or the valve too short making the spring top too low?
 

nkt267

Well Known and Active Forum Website User
VOC Member
I've got 1.388" above the top guide on the inlet and 1.4" above the top guide on the exhaust..I'm still getting my Comet back together..John
 

johnmead

Well Known and Active Forum Website User
Non-VOC Member
I have Terry Prince MK5 cams with 11mm lift and am using beehive springs and titanium retainers/keepers. Since I do not like the stock Vincent keeper design I had a machinist machine grooves in the valve stems to use modern keepers.

John Mead
 

roy the mechanic

Well Known and Active Forum Website User
VOC Member
Hi, the dimension you seek is called "installed height" I went through this a while ago, it appears there's not a spec written for it, or if there is, no one was prepared to let on, What i did was- rig up a degree wheel on the crank, note at how many degrees the coil bind occurs, back it off, remove the tappet adjusters, fix-up clock guage to pushrod, return to the bind point, continue to rotate to find out how much more lift is required (or left togo) to go "over the nose" of the cam. add 25 thou for safety, Hope this helps, Roy.
 

johnmead

Well Known and Active Forum Website User
Non-VOC Member
[FONT=&quot]I use an installed height of 1.475 with the beehive springs.

The seat pressure will be 80 lbs. @ 1.475", 90 lbs. @1.450" and 190 lbs. @ .440 lift. Corresponding nose pressure will be 220 lbs at .440 lift.

John Mead [/FONT]
 

roy the mechanic

Well Known and Active Forum Website User
VOC Member
Johnmead, the numbers quoted sounds like "the bees knees" , please tell where they can be bought. I ended up with springs from a W R C peugeot to acheive similar specs, as the ones supplied with my cams (supposed to allow .500lift) had 390lbs over the nose!and got rejected as soon as tested on the poundage rig! Regards, Roy.
 
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