New Conical valve springs

Referring to my posts made under Comnoz' topic 'About time for the Spintron' where I ran tests of a standard valve train setup for a Commando 750 cc engine with steel valves, alloy pushrod, beehive valve springs and a PW3 exhaust cam, in Prof. Gordon Blair's 4StHead software.

The difference when substituting a Ti valve for the steel item first used was approx 1000 rpm in favor of the Ti item, which would still just survive without separation or bounce occurring at 9500 rpm, whereas the steel valve reached its limit at 8500 rpm.

I should state here that these tests were done using data measured from components to hand, and are representative only to that set of components. For instance, another cam, a 4S for instance, might give very different results, likewise the same applies for a different valve spring or pushrod.

Brooking 850 said:

Hi Jim, any more video/info to come our way?
Regards Mike

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I recorded about 30 more minutes of video yesterday with the PW3 cam and 3 different valve spring sets. Unfortunately the audio file that was recorded along with the video to show what the clips were failed and now I can't tell which was which.

What I have found was the conical spring I was planning on using for a race setup did not test any better than the conical spring I am using for the street setup. That spring setup has been dropped in favor of a dual spring setup for racing.

I am gong to try to get some video to show what I have been seeing. Jim

Snotzo said:

Referring to my posts made under Comnoz' topic 'About time for the Spintron' where I ran tests of a standard valve train setup for a Commando 750 cc engine with steel valves, alloy pushrod, beehive valve springs and a PW3 exhaust cam, in Prof. Gordon Blair's 4StHead software.

The difference when substituting a Ti valve for the steel item first used was approx 1000 rpm in favor of the Ti item, which would still just survive without separation or bounce occurring at 9500 rpm, whereas the steel valve reached its limit at 8500 rpm.

I should state here that these tests were done using data measured from components to hand, and are representative only to that set of components. For instance, another cam, a 4S for instance, might give very different results, likewise the same applies for a different valve spring or pushrod.

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Snotzo,
I have not been able to get a PW3 cam to work well over 7200 rpm with any of the springs I have tested -using a steel valve and stock pushrod.
The best so far with the pw3 has been a lightweight dual spring setup with about 140 lbs on the seat. [R&D] That spring would stay in contact with the retainer and not spin like a top but even at 7200 rpm the valve bounce was pretty severe.
Now I know why the valves seats in KC's racebike look like they did every time I freshened it up. Jim

Hi Jim C,

As I am running a PW3 in my 850 Sliline racer with Black Diamond Valves and springs, I would be interested to know at wich RPM valve bounce is starting to happen. Surely it would be preferable to stay under that threshold as much as possible?

Thank you very much for your fascinating posts!!

Best from Brussels,

Bruno

Snotzo,
I have not been able to get a PW3 cam to work well over 7200 rpm with any of the springs I have tested -using a steel valve and stock pushrod.
The best so far with the pw3 has been a lightweight dual spring setup with about 140 lbs on the seat. [R&D] That spring would stay in contact with the retainer and not spin like a top but even at 7200 rpm the valve bounce was pretty severe.
Now I know why the valves seats in KC's racebike look like they did every time I freshened it up. Jim
Jim
obviously there are differences between the components you are using in your spintron, and those I measured for input data into 4StHead.
However, I have run the simulation again at 7000 rpm, this time with dual springs that were installed in a Maney engine. The results pretty much tally with what you are finding, severe component separation on the closing flank and severe valve bounce on seating. An additional interesting feature indicated in the 4StHead results is revealed in a Fourier analysis, where conciderable excitation is shown over a wide range of harmonic frequencies, of a magnitude that could cause such things as rotation of springs and collars when the valve train is in motion. Seated pressure of these dual springs was 130 lbs.

In all fairness I must stress that I do not know whether the springs were originals as supplied by Steve Maney for this engine.

Snotzo said:

In all fairness I must stress that I do not know whether the springs were originals as supplied by Steve Maney for this engine.

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For years Steve has used and sold RD VSK-901 N spring kits, so I'd guess that's what was originally in the engine. But those kits use the no. 1005 springs, which only give 85 lbs on the seat at 1.350" installed height. It would take a lot of shimming to get them up to 130 lbs on the seat. Steve did try some RD 1034IRL springs while experimenting with the N480 cam, so it's possible you have those springs. I don't know if he ever used them for customer engines. They were specified at 114 lbs on the seat at 1.400" installed height, so could have been shimmed a bit to get 130 lbs on the seat.

Ken

I have a limited number of spring kits available now.



I also have a few cams. PM me for more info. Jim