Valve Spring Pressure for Roller Cam question.

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Jay Bradel
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Valve Spring Pressure for Roller Cam question.

Post by Jay Bradel » 11 Oct 2019, 13:01

What would the valve spring pressure need to be for a roller cam with solid roller lifters and 6500 max RPM .600 lift? Other cam spec's not know yet.

Thank you in advance,
Jay

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PackardV8
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Re: Valve Spring Pressure for Roller Cam question.

Post by PackardV8 » 11 Oct 2019, 21:45

It's not quite that easy. The spring pressure required is a function of the intensity of the roller lobe profile. Some "high intensity" profiles are for drag/dyno racing and have time-to-failure measured in hours. OEM roller cams easily rev to 6,500 and are warrantied for years and thousands of miles.

jack vines

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Mike Van Veghten
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Re: Valve Spring Pressure for Roller Cam question.

Post by Mike Van Veghten » 12 Oct 2019, 00:24

Very short on..."details" in this question. More details ARE required..!

One way to get "close" (as Jack mentions !), go into a cam manufacturers, Comp Cams, Crower cams, Isky Cams, etc., dig around and look for a similar cam to what you have. All of the above manufacturers will recommend a spring to go with that particular cam.

That will provide the pressure that you need. Then...you NEED to know, what installed height valve train you have, E.G., 2.03" (Stude), 1.75, (small Chevy). Are you using small Chevy length valves ?

Another thing to remember...if you are going to be using this engine on the street, look into "endurance/circle track type springs. If it's a drag race only spring, that's pretty easy. If it's a road race type engine, see my first comment.

You also need to be aware of the spring diameter. The Stude head is not like a small Chevy, Ford, etc., there is space limitations you need to look out for.

So...again, as Jack notes, there is much more to buying springs, than JUST...buying springs.

Took me some time to find a spring for my engine. And as it turns out, they AREN'T cheap..!

Mike

Jay Bradel
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Re: Valve Spring Pressure for Roller Cam question.

Post by Jay Bradel » 15 Oct 2019, 08:58

I have a couple Cam Blanks Phil will grind for me but I don't know what cam specs I will use. The set of Lionel Heads I am going to use has dual springs and pressures of only 125#. I think that is too light regardless. I guess I should figure out the cam I want to use and then see the spring pressure required.

This will be for street use. The engine builder I use has commented on the limited resources for spring availability. I believe they are Chevy valves Lionel used.

Thanks for the help will be back with more questions as I progress with this build.

Jay

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Mike Van Veghten
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Re: Valve Spring Pressure for Roller Cam question.

Post by Mike Van Veghten » 15 Oct 2019, 11:30

Correct, 125# is too light for meaningful rpm work.

Most roller cams that the Stude engine would use (.550" to .650" lift) needs springs in the 200# to 250# range for proper lifter control in the 6500 to 7000 rpm range.

Mike

Jay Bradel
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Re: Valve Spring Pressure for Roller Cam question.

Post by Jay Bradel » 16 Oct 2019, 10:20

I have enough clearance cut into the block wall for valve clearance to have .550" lift. I have not CC'd the heads yet. Still lots to do before deciding on cam specs. I want to use the Paxton SN supercharger but have not determined how I will build it and how many PSI it will produce.

More research on valve springs is needed. Hopefully I can find heavier springs for my Lionel heads.

Since these heads flow really good, maybe 10 or less PSI is acceptable for a street engine and still produce decent HP????

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Mike Van Veghten
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Re: Valve Spring Pressure for Roller Cam question.

Post by Mike Van Veghten » 16 Oct 2019, 12:26

With aluminum heads, I don't see why not...but -

I've got a little four cylinder car (2005 JCW Mini Cooper, 211hp) that puts out 14psi currently. I have a larger crank damper/pulley on the shelf that should raise that to 15 or 16psi. This is a street engine with all factory parts.

I would however, with that much pressure, add a "pop-off"/pressure release valve to redirect the pressure when you suddenly let off the gas so the engine will actually...slow down..!

Also, with that much boost, the addition of an intercooler (air to air, water to air, or ice box) of some type will go a long way in making that much pressure actually usable. Hot air at 10 or 15psi is not nearly as efficient as cool air at the same boost levels. That much boost with hot air can actually be harmful...read that..."detonation".
A knock sensor (ignition timing reducer) might also be a good addition at that boost level.

Mike

Jay Bradel
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Re: Valve Spring Pressure for Roller Cam question.

Post by Jay Bradel » 17 Oct 2019, 12:40

Good information, lots of work for me this winter. Thanks all.

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