I talked with a very capable engine builder this past week or so. I have upgraded single valve spings, that I got then when I had a TDO5 20g on my car. I've since went bigger with my setup currently/ planned. I'm making this tread to ask whats the limit with boost and RPM capeability of single valve spings with retainers. I'm currently usining the SuperTech valve spings, retainers, and valves. I'm also using HKS 272 in/ HKS 272 ex cams which are very mild cams. I'm using stock rockers and lifters. To my understanding I thought 8500 rpm, and 35-40 psi relieably without valve float with the single spings and retainers. I was amazed to hear, 8000 and 25 psi. I will also add, I'm not cheap. I believe in checks and balances. I didn't want the dual valve spring from the begining. I had no intrest in a reline higher then 8500 RPM. I'm ready to buy the valve spings, if I have to. I still don't want to deal with the wear/ tear from having a lot of seat pressure.

I can't speak for SuperTech's springs but I have Kiggly Beehives and I've taken my car up to 9,000 on a regular basis without issue.

Pretty sure valvesprings don't have a boost-limit...

Float is going to be based on the springs harmonics and pressure required of the nose of the cam lobes

EclipseOwner95 said:

I can't speak for SuperTech's springs but I have Kiggly Beehives and I've taken my car up to 9,000 on a regular basis without issue.

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Some would say those are argueably the best springs in the market place currently. Although maybe single springs, I'd like to compare thoughts on non-behive springs.

LandSpeed-DSM said:

Pretty sure valvesprings don't have a boost-limit...

Float is going to be based on the springs harmonics and pressure required of the nose of the cam lobes

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It's true, boost can be a variable that could cause valve float.

Considering I have done such (admittedly ill-advised) things as run GM272s to 8500rpm with boost in the mid 30's using stock 1G springs.. I am going to have to ask for documentation/citation/source for that.

I understand anecdote is not data, but that would be an example where the valve springs have a boost limit statement seems to be contrived.

I am entirely open to being educated on this but as it stands I don't see what that would have to do with valve float.

Are you referring to the boost on the intake forcing the spring open? or the drive pressure on the exhaust? Our valves don't have a ton of SA, so its possible I suppose. But you would need to be running a completely inappropriate spring for your cam and a ton of boost, and/or a very poorly matched turbine side.

I could see this being a problem with a 2v head, like the GNX, where the valves are very large.

Crower springs (probably 10 years old by now) & 8500 rpms.

very interesting read.. would like to also hear more about this.

Boost pressure, and exhaust manifold pressure exert a force trying to open the valve based on pressure in psi, and in^2 area of the valve. Say seat pressure of the spring is 60 lbs, the valve is 1 in^2, and boost pressure is 30 psi. This effectively puts the seat pressure of the spring at 30 lbs.

donniekak said:

Boost pressure, and exhaust manifold pressure exert a force trying to open the valve based on pressure in psi, and in^2 area of the valve. Say seat pressure of the spring is 60 lbs, the valve is 1 in^2, and boost pressure is 30 psi. This effectively puts the seat pressure of the spring at 30 lbs.

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I eneded up going with dual valve spings, for what it's worth.

donniekak said:

Boost pressure, and exhaust manifold pressure exert a force trying to open the valve based on pressure in psi, and in^2 area of the valve. Say seat pressure of the spring is 60 lbs, the valve is 1 in^2, and boost pressure is 30 psi. This effectively puts the seat pressure of the spring at 30 lbs.

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100% correct. Valve spring force selection should definitely take into account desired boost level.

Ehh, 99% of the time cylinder pressure is higher than manifold pressure.

I have duals with a small cams and a big turbo. Wasn't worth the risk, given the information provided.

My BCs have been to 9k a couple times. But witht he build coming up im not chancing it. going with kiggly beehives.
Damn, i gotta box that head up and get it out to SIM! so frickin lazy..... haha