cam upgrade

Do you know what the installed height of your springs are now? You need to look at the pressures ON YOUR ENGINE, rather than in any book to know for sure. I rana few numbers quickly here. For installed at 1.80, 1.85, and 1.9. I think stock should be 1.850 but I am going off an iffy memory. So using those heights you could be as far as 34lbs light at max lift and as low as 50lbs on the seat with 926s for the .510 lift cam. With faster rate cams, low pressures are not good. Think of it this way... If the cam survives break in and use the rpm potential will be lowered by at least 10% and because the negative affect is not linear, but a function of rpm, it could be much lower than that. The 911s are the recommended single spring option. They would be heavier on the seat intalled at 1.85 than the dual spring 925s, and would be heavier at max lift, but will not last as long. The reason there is a premium choice is because that is really what the cam needs to live well long term. Again, will it work? (shrugging)Maybe. I don't think it working as designed is any better odds than 50% with 926s. If it were me, I'd step up the springs to at least 911s. That requires no head work. 925s would require the spring seats and guides be machined.