under pressure

iTrader: (13)

In the spirit of being cheap, I purchased a cam from Edelbrock that was supposed to match my single plane intake and carb with the existing valvesprings etc. The cam is advertised as a 230-237 at .050. LSA is 110 and the ICL is 106. The lift is .540-.540. Intake closes at 41* at .050. This is going on a stock LS6 with the factory lightweight valves. Now I am wondering if the DCR is too low to be of any real use or if I should just get a custom grind and buy the correct springs for what I need. These recent posts regarding piston to valve clearance have me wondering if I am in trouble with this duration. Any ideas?

hammertime

iTrader: (1)

DCR is calculated from the Intake Valve Closing point at the seat, not .050" lift. The .050 durations and VE's for that cam are not that bad (part # 2216 according to edelbrock. The problem is their advertised durations (314/322) would suggest a very slow ramp rate off and back onto the seat. Plugging numbers into the DCR calculator with a 10.68:1 SCR gives a pretty low DCR of 7.16:1. The valve is gonna be close to the seat much sooner than that, somewhat influencing the DCR, but only a little. On the plus side, the slower rates could possibly keep the valves away from the pistons, but you would still need to check.

Re-reading your post and seeing that they have designed the cam to work with the stock valvesprings only further reinforces that these are some lazy lobes. You really should plan on replacing the springs when you do a cam swap. Adding 20+ degrees to the duration @ .050 without a spring change could otherwise lead to valve float or bounce.

I'm not going to recommend another cam just yet, let's see what others have to say.

gun5l1ng3r

As a rule of thumb, if you upgrade your cam, you should upgrade your springs even if they are LS6 springs.

hammertime

iTrader: (1)

ttt for the original poster