Aggressive cams stock valve spring

[M50aleks]

Hi, im building a rally car Engine
2.5 liters m50 non vanos Engine

I have heard/read that the oem non vanos valve springs can handle 8000rpm ++

Is there anyone in here that have tried this with aggressive cams ? Like the 282/274 catcams ?

Do i need stiffer springs if im turning 8000rpm whit these cams ?

Thanks

[bluptgm3]

There is a someguy2800 here who knows this stuff well…hope he sees this!!


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[someguy2800]

I've run a little over 8000 with similar cams and stock M50nv valves and springs and M52 lifters converted to solid lifter. The stock non vanos springs have about 76-80 lbs of seat pressure. Right now I am using stock outer springs and a higher rate inner spring that raises the seat pressure to 92 lbs and I have ran that to 9000 rpm. I am using Enem 276/276 solid lifter cams and I make my own solid lifter conversion.

[E30s50dude]

I've run a little over 8000 with similar cams and stock M50nv valves and springs and M52 lifters converted to solid lifter. The stock non vanos springs have about 76-80 lbs of seat pressure. Right now I am using stock outer springs and a higher rate inner spring that raises the seat pressure to 92 lbs and I have ran that to 9000 rpm. I am using Enem 276/276 solid lifter cams and I make my own solid lifter conversion.

would there be a need for a stiffer outer spring at some point or does NV spring seem to hold up ok.

[M50aleks]

I've run a little over 8000 with similar cams and stock M50nv valves and springs and M52 lifters converted to solid lifter. The stock non vanos springs have about 76-80 lbs of seat pressure. Right now I am using stock outer springs and a higher rate inner spring that raises the seat pressure to 92 lbs and I have ran that to 9000 rpm. I am using Enem 276/276 solid lifter cams and I make my own solid lifter conversion.

Thank u, I actually have your solid lifter conversion, 👍
Do you think the oem damper is good enough with rpm limit 8000 rpm with 75mm stroke, or is the ati damper or similar a must when turning this high rpm ?
This is NA no boost If that makes any difference ?
Whats your thought on that ?


Thanks

[someguy2800]

would there be a need for a stiffer outer spring at some point or does NV spring seem to hold up ok.

I don’t know at what point that would become necessary

- - - Updated - - -

Thank u, I actually have your solid lifter conversion, 👍
Do you think the oem damper is good enough with rpm limit 8000 rpm with 75mm stroke, or is the ati damper or similar a must when turning this high rpm ?
This is NA no boost If that makes any difference ?
Whats your thought on that ?


Thanks

I have never ran a 75mm stroke and I’ve never ran for long periods of time like a rally car so I do not know what will happen with the stock damper.

[M50aleks]

I've run a little over 8000 with similar cams and stock M50nv valves and springs and M52 lifters converted to solid lifter. The stock non vanos springs have about 76-80 lbs of seat pressure. Right now I am using stock outer springs and a higher rate inner spring that raises the seat pressure to 92 lbs and I have ran that to 9000 rpm. I am using Enem 276/276 solid lifter cams and I make my own solid lifter conversion.

Have You measured the spring Pressure @ 11.5mm lift on the stock springs, and with your setup with higher rate inner springs ?

Where can i buy only the inner springs ?

[someguy2800]

Have You measured the spring Pressure @ 11.5mm lift on the stock springs, and with your setup with higher rate inner springs ?

Where can i buy only the inner springs ?

The stock NV outer spring is 56lb seat pressure and about 178 lbs at 11.5mm lift. Coil bind is at 12mm lift.

The stock NV inner spring is 24 lbs seat pressure and about 58 lbs at 11.5mm lift. Coil bind is also at 12mm lift.

The inner spring I am using is Cat Cams PAC-I92009, but they are not a drop in install. You will need to make spacers to go under the spring seat and center on the valve guide. I made some 4mm thick shims out of some washers on my lathe. With 4mm of spacers under the inner spring the seat pressure is 36 lbs. I did not write down what the spring pressure was at 11.5mm, I didn't write it down.

[M50aleks]

The stock NV outer spring is 56lb seat pressure and about 178 lbs at 11.5mm lift. Coil bind is at 12mm lift.

The stock NV inner spring is 24 lbs seat pressure and about 58 lbs at 11.5mm lift. Coil bind is also at 12mm lift.

The inner spring I am using is Cat Cams PAC-I92009, but they are not a drop in install. You will need to make spacers to go under the spring seat and center on the valve guide. I made some 4mm thick shims out of some washers on my lathe. With 4mm of spacers under the inner spring the seat pressure is 36 lbs. I did not write down what the spring pressure was at 11.5mm, I didn't write it down.

Ok thanks, is the installed height on the nv springs 37.5mm ? I have som spare springs i measured, and they were about 25.5mm at coil bind