Understand the springs for the IRL application were designed to rev upwards of 11k rpm albeit with a lighter valve combination, I'm obviously not revving nearly that high nor using as aggressive a cam ramp speed and I'm pretty certain the IRL cam lobe of the day were running nearly .5" lift. The cams I'm running as outlined at the beginning of the post have about 10.75mm lift.riff_raff wrote:Ferraripilot-Ferraripilot wrote:I actually sourced a perfect dual spring for this application which has been working very well. The spring has about 97lbs at the seat and 230lbs open. The spring rate is some 312lbs/inch and was an IRL engine design originally. This engines isn't seeing more than 8000-8200rpm and it's been working fine.
Did I miss something in your previous posts describing the spring requirements? From your most recent post, the rate of your spring pair would be 364 lbs/in based on the .59" lift number you previously noted, and not 312lbs/inch.
You also stated that your valve was 44mm diameter, which is probably much larger than any IRL engine ever used. So I can't imagine a dual valvespring designed for an IRL engine with much smaller valves and valve lift requirements providing the .59" lift you said was required. Those IRL engine valvesprings are probably designed for less than .4" inch of valve lift, and your 44mm intake valve should have at least .49" of lift for good performance.
So far so good, this engine ran at Road Atlanta not long ago and never missed a beat. I know of one Daytona Competizione running these springs as well as is this 312 engine per my recommendation:
https://www.youtube.com/watch?v=vgihUHAHJPQ