Valve Spring Pressure

[Don D]

Just a general statement. Do these motors really need as much pressure as we are springing them with? Just read the instructions for a cam customer is running.

The valve springs used with the XXX cams must have a seat pressure of 100 lbs
minimum, and 250+ lbs at the nose, with 280 lbs recommended.

OK I can do that but that is X2 so we are using 200# and 560# respectively to do the job.

Question is does it really take that to control these valves and can the lifters take this much pressure for the rider that will actually ride 10K or more a year?

I have my own thoughts just wanted to get the consensus of others.

[kd]

Would it help to measure a set of OEM performance springs (if available) that are already mounted in an OEM performance head.  I know the TC MVA springs were overkill likely to provide control with the .650 range cams if over rev occurred.  Is it possible the M8 rocker ratio buffers some of the weight effect away on lift? 

Just a couple of things that popped into my head as I read your question.  Disregard if too far off point.

Added later:

The reduced mass of each of the valves "should" require less spring pressure to control them.

[rbabos]

Just a general statement. Do these motors really need as much pressure as we are springing them with? Just read the instructions for a cam customer is running.

The valve springs used with the XXX cams must have a seat pressure of 100 lbs
minimum, and 250+ lbs at the nose, with 280 lbs recommended.

OK I can do that but that is X2 so we are using 200# and 560# respectively to do the job.

Question is does it really take that to control these valves and can the lifters take this much pressure for the rider that will actually ride 10K or more a year?

I have my own thoughts just wanted to get the consensus of others.

Have you compared what v rod uses for springs that take it to over 9k? Mind you, you don't have all the extra component inertia of the pushrods and lifter weights to fight back so they could be lighter in that regard.
Ron

[No Cents]

  George Bryce has been using light weight springs with titanium valves in his M8 heads with pretty good results.

[Don D]

Have you compared what v rod uses for springs that take it to over 9k? Mind you, you don't have all the extra component inertia of the pushrods and lifter weights to fight back so they could be lighter in that regard.
Ron

Interesting enough the V-rod and M8 AV&V springs are the same. The M8 suggested installed height is +.040 but they still suggest maximum lift of .580
I am not going to get into Ti parts to save weight but respect the work of George Bryce a lot.

[rbabos]

Have you compared what v rod uses for springs that take it to over 9k? Mind you, you don't have all the extra component inertia of the pushrods and lifter weights to fight back so they could be lighter in that regard.
Ron

Interesting enough the V-rod and M8 AV&V springs are the same. The M8 suggested installed height is +.040 but they still suggest maximum lift of .580
I am not going to get into Ti parts to save weight but respect the work of George Bryce a lot.

Interesting.
Ron

[Don D]

Ok so we have two very small light valves. How much pressure is needed seat and over the nose? Shouldn't the cumulative total of pressure be less than what we use for the twin cam? The spring pressures used by me on lighter 7mm valve heads has been very successful and is much easier on lifters.