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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Alan
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Re: Valve Spring Pressure for Roller Cam question.

Post by Alan » 24 Jul 2020, 22:39

Iskenderian 305D-806S combo. works up to 7,000 rpm. Stone used valves made special for him by PEP of Las Vegas, they are longer than Chev. valves. That is why so little pressure on the seat.

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Tom Osborne
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Re: Valve Spring Pressure for Roller Cam question.

Post by Tom Osborne » 20 Oct 2020, 10:46

If using Chevy or Ford valves you will require shorter rocker arm shaft towers. Lash caps .080" , then you need custom pushrods to get your correct geometry set. Comp cams Chevrolet or Ford beehive springs for street or custom 350 lb or more open and 150 lb closed for aspirated springs, for supercharged applications you need serious springs if you want the valve train to survive 7000 rpms and more. A 6500 RPM range roller cam still needs to as stable as higher lifts. Running Harland sharp 1.6 ratio rocker arms will add more lift and duration. Running weak valve springs is not an option. As under boost they will pop on you and likely ruin your motor. Spring retainers need to be titanium and locks need to be very strong isky ones. Scrimping on parts is your worst nightmare. Factory long valves is the best starting point and you can use all high end parts without any trouble. High end Nascar type valves are 3 times the price of good stainless ones. 6500 rpm needs them. Valves should be moved .060" further apart when going to 1.60 diameter exhausts. Most studebaker builds do not require over .500" lift . many pull very strong at .450" lift remember that back in 1962 some cams were only up to .478" lift. In solid cam form. 175 mph was nothing to scoff at. A roller cam that is moderate lift with easy on parts profile would be my choice.
"First by far with a post war car"
TOM-O-HAWK STREET/STRIP Project

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

Post by Mike Van Veghten » 20 Oct 2020, 15:24

I'd never run 150lbs on the seat with a .550" lift cam.
Unless you hold the rpm to about 5000/5500rpm. Then the whole thing would be a waste power wise.

Back when I ran my small Chevy powered Anglia (540" / 565" lift), I knew I was late on my spring maintenance when the rpm would drop for no reason.
And I was running 220-225lbs on the seat. new springs...back to a solid 7500 rpm.
Even at say...6500 for a Stude, I'd still run a more powerful spring. The spring maintenance would be a lot less as the spring would go farther before loosing it's pressure, so a better spring is still a viable item.

I've got "good" springs for my (and a friend) 299 Stude build, so this isn't isn't just off the top of my hat.
Check the recommendations for spring pressure in the cam catalogs, per your lift and duration...

Don't shortchange a proper spring, the power lost...could be yours.

Mike

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Jeff Rice
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Re: Valve Spring Pressure for Roller Cam question.

Post by Jeff Rice » 25 Oct 2020, 08:47

Some generic info from Summit Racing:

https://help.summitracing.com/app/answe ... lid-roller
(copy)

Valve Spring Pressure - Solid Roller

Recommended Spring Pressure
Engines with solid roller cams are usually performance, race engines. They use aggressive Lobe Profiles and usually run at high rpm. Because of this, they require the highest spring pressure of all the engine types.

Seat Pressure Guidelines
Seat pressure is determined by valve/retainer weight, rpm range, and desired life expectancy of the valvetrain.

The table below gives some seat pressure guidelines:

Camshaft Type Seat Pressure
Mild Performance 165 lbs. minimum
Moderate Performance 180 - 200 lbs.
High Performance/Circle Track 220 - 250 lbs.
Professional Drag Racing 340 - 370 lbs.

Open Pressure Guidelines
Open Pressure should be the minimum pressure needed to control the valve as the lifter goes over the Nose of the Cam Lobe. Too much open pressure puts a lot of stress on other valvetrain parts. This can lead to Valve Float and broken pieces.

The only way to really find the right open pressure is through experimentation and track testing.

This table lists some starting points for your open pressure tests:

Engine Usage Open Pressure
Street/Strip Performance 340 - 350 lbs.
Circle Track, Bracket Racing 450 - 600 lbs.
Pro Level Drag Racing, Short Distance Circle Track 600 lbs. or more

Notes
Most manufacturers recommend valve springs to go with each cam they make. We recommend using these springs, or a spring with similar specifications.

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