Max Spring Pressure

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learner

Max Spring Pressure

Post by learner »

What would you consider to be the maximum open pressure on a flat cam with out a hardened overlay?


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Valve spring pressure

Post by speedtalk »

I've acutally never found the limit. With a standard core and regular lifters I was never able to try anything wild enough that would require me to test the limits of spring pressure. If they had a flat tappet cam rule they also had a rule that would limit rocker ratio. If the rules were more open they would allow a roller. What are you working on?
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learner

Post by learner »

I've got a large solid in a boat. I'm wanting to run a 1.8 rocker on the intake and i'm having a difficult time finding a spring with the proper or decent closed/open pressures while being able to handle the lift without coil binding. I've looked at crane, isky, comp and crower and so far crower has the closest ones. I actually found a crower number but it has been discontinued. I have an installed height range of 1.85"-2.05" that i could use. I was wanting an installed pressure of around 150-160 that will work with .740" lift. Depending on the spring, it gives me a mid-high 400lbs or even in the low 500's. I've never ran that high a pressure on a flat cam. I'm not sure if it would work for a season without flattening the cam.
How about 144lbs @ 1.95" with 463 open.

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Last edited by learner on Tue Jan 13, 2004 12:33 am, edited 1 time in total.
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Post by speedtalk »

I assume by the rocker ratio it's a BBC? How much RPM? Is the engine going to be dynoed?
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Post by learner »

BBC, max rpm is around 7400. I don't know if the owner will dyno it. Its an iron head motor and they just approved a Dart head. So i think most of his money will go into that motor.

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Post by speedtalk »

You've got your work cut out for you. At that RPM and lift you're either going to bounce the valves or wipe the cam - depending on the pressure. It's going to need near roller cam pressures to control the valves. If you're going to give it a try, get rid of as much valve side weight as possible - titanium, thin stems, lite weight retainers and locks. Oh, and don't forget church :wink:
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Post by speedtalk »

cstraub wrote:1.8 rockers at .700" lift. Engines turn 6K to 9500. I don't let them idle below 1800 rpm and these are wet sumps. I know, scary,
Scary yes. Congrats for getting it to survive though. It's a standard non-welded core? Have you done anything special to get oil to the lobes? Are there any signs of valve float (beat up keeper grooves)?
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Post by speedtalk »

How many seconds is a typical run?
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