Greenlight wrote:You can get the required cam lobe curves from anyone who has a cam checking device such as Cam Doctor, Cam Pro, Dr. Doctor, etc.
Right, harmonics. Inner and outer springs or beehive would be nice but probably not workable in this case.Pumaracing wrote:Hi,
Dave Baker from Puma Race Engines here. Just joined this forum. I can't believe your valve weight of 115 grams. An average length 44mm valve weighs mid 80s to 90 grams. Please confirm before I run valve harmonic calculations because the spring pressures you've just been advised seem very wrong to me.
Pumaracing wrote:Hi,
Dave Baker from Puma Race Engines here. Just joined this forum. I can't believe your valve weight of 115 grams. An average length 44mm valve weighs mid 80s to 90 grams. Please confirm before I run valve harmonic calculations because the spring pressures you've just been advised seem very wrong to me.
I'll run some calcs for you when I get a chance but I'm busy helping someone with his race engine at the moment. I'm sorry but these numbers are a mile out. I design race engines and part of that is obviously the spring forces. From a multitude of actual camshaft data versus rpm and spring forces in real engines I can see that this engine requires much more spring pressure at 9000 rpm than 186 lbs. In any case that's lower than we've already been told for the stock springs at 8000 rpm which should give one a hint.Greenlight wrote:Here ya' go.
The analysis shows that you need a minimum of 186 lbs. of spring force to maintain a stable valve action at 9000 RPM. I normally allow at least a 10% margin (~200 lbs.).
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riff_raff wrote:Looking back over the requirements listed in earlier posts and then considering the force/displacement numbers listed in recent posts, I do not think it is possible to produce a valvespring design that meets all of the requirements. Here are the requirements I gathered from the posts:
Installed spring height- 1.54 inch
Valve lift- .59 inch
Compressed spring height- .95 inch
Spring force at installed height- 82 lbf
Spring force at full lift (9krpm)- 262 lbf
Spring rate- 305 lb/in
Spring coil max OD- 1.26 inch
If these requirements are correct, it would not be possible to design a steel valve spring (even a dual spring) that meets all of the requirements without being greatly overstressed.
That sounds excellent. It never hurts to have a bit more seat pressure than calculations might suggest and it's a very risky strategy to go light in that area. Low seat pressure shows up more quickly as anomalous engine performance than does low full lift pressure. The usual symptom of low seat pressure is an engine that hits a specific rpm and then just won't rev past it like it's hitting a brick wall. I think you'll be very happy with those springs at those pressures for your application.Ferraripilot wrote:I actually sourced a perfect dual spring for this application which has been working very well. The spring has about 97lbs at the seat and 230lbs open. The spring rate is some 312lbs/inch and was an IRL engine design originally. This engines isn't seeing more than 8000-8200rpm and it's been working fine.
Ferraripilot-Ferraripilot wrote:I actually sourced a perfect dual spring for this application which has been working very well. The spring has about 97lbs at the seat and 230lbs open. The spring rate is some 312lbs/inch and was an IRL engine design originally. This engines isn't seeing more than 8000-8200rpm and it's been working fine.
