Question about 37lb springs.
- Thread starter oneman
- Start date
1fasttiller
Member
You have other issues if you can't hit 8500rpm with 37lb springs... there are plenty of guys doing that with less. Heck, our stock clones with legal 18lb springs will run 7200-7400.
Engine configuration: 70mm Wiseco piston, ARC connecting rod, 27.5 25.5 valves. Titanium valve plates, Pushrod, Chrome Moly, Rocker champion HD. Standard clone camshaft with reduced base, +1mm lift. Carburetor B&S World Formula pz26.
I started noticing the Mychrone RPM max 7800 per race. I changed the carburetor, changed the jet, lifted the needle, adjusted the valve clearance, and checked the ignition. But the turnover did not go higher than this. Then I put springs from a Chinese bike 45-50lb, they fit the Clones. And after that I felt 9000 rpm.
But the springs from the chinese bike limit the valve lift, they are lower and thicker, so I think the maximum lift will not be higher than 0.280-0.290". So I thought I could try to put washers in and increase the 37lb preload of the springs.
I started noticing the Mychrone RPM max 7800 per race. I changed the carburetor, changed the jet, lifted the needle, adjusted the valve clearance, and checked the ignition. But the turnover did not go higher than this. Then I put springs from a Chinese bike 45-50lb, they fit the Clones. And after that I felt 9000 rpm.
But the springs from the chinese bike limit the valve lift, they are lower and thicker, so I think the maximum lift will not be higher than 0.280-0.290". So I thought I could try to put washers in and increase the 37lb preload of the springs.
mike97760
Site Supporter
They only limit the lift if they are binding. I will take that back, if the lifter is bottoming out against the block but you have such a small cam I doubt thats whats happening. 37 pounds isnt doing you any favors, it is robbing power from you. As stated abouve, #26 or #32 springs would be better. Springs need a lot of energy to compress.
Dougherty#39
Member
10.8 lbs springs. 18s are illegal, but that makes your case even better.
That's why I put 37lb springs instead of Chinese 50lb, I was sure that they would last up to 8500 rpm. I read about it here. But I only got 7800.
We look at the engine speed on the telemetry of Mychron 4, I selected 8600 rpm, then I dropped the gas, but it was checked on a stand, not on the go.
here is a photo from the RS2 software, this is last year on Chinese 50lb springs.
Attachments
Are the Titanium valves stock length? If not and they are longer the valves springs aren't installed at the correct height. you will have low valve seat pressure. I only know about the 10.8 springs and the rules that apply to them. But when i raced cars we had to shim our springs to achieve proper seat pressure.
telemetry is set correctly, I checked it, here are 2 photos, one with 37lb springs, the other with 50lb. nothing else has been changed, only the springs.
I used this camshaft last year to run 8300 rpm in races. I myself am surprised by this problem, before that there was nothing like it. I only changed the springs and the revs were lower.
sorry, I was wrong, titanium retainers are not valves. the length of the valves seems to be standard, but I will try to check it.
I think the problem may be in the valve keepers, I have a middle groove installed. and the spring is decompressed. I'm thinking of installing High groove keepers and a shim under the spring.
Yes, here's the order
