degreeing cams
05-14-2007, 08:03 AM
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degreeing cams
I am just finishing a build on my F20C and i am hearing word that I should be degreeing the stock cams. I have milled the head down to 12.3:1 compression, using JDM pistons and still runnign stock cams. Using something like skunk2 cams or toda would require to degree the same to the recomended setting, but would the settings I have require me to adjust the stock cams?
05-15-2007, 09:25 AM
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Yeah, I asked a similar question a while back when troubleshooting issues w/ my Toda cams. Milling the head enough to increase your compression that much will have an effect on cam timing, but the important question is: How much? I never got an answer to that, but in your case, I suspect it might be a couple of degrees.
If you're raising the compression, I assume you're planning to maximize the output of the engine. To do that, you probably need to degree the cams and/or put it on a dyno and tweak the cam settings to find the power curve you're looking for.
If you're raising the compression, I assume you're planning to maximize the output of the engine. To do that, you probably need to degree the cams and/or put it on a dyno and tweak the cam settings to find the power curve you're looking for.
05-15-2007, 11:59 AM
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I've never seen official lift/duration spec's for our stock cams (unless you want to believe the numbers on Brian Crower's website), much less any of the remaining "cam card-type" data (INT opens @ ___ crank degrees, EXH opens @ ___ crank degrees) needed to degree the cams. Do you have these spec's? If so please share.
Delayed cam timing might shift powerband a bit towards hi rpm, but I would be more concerned with basic mechanical issues caused by milling the head.
Did you leave enough head deck thickness to prevent warping? How many thousandths did you mill off? Did you CC the chambers before and after head milling to see how much the chamber volume dropped? CCing the chambers will also verify that head was milled flat and level. Or is your 12.3:1 CR ratio an estimate? Stock USDM 0.030" thick head gasket?
Enough piston-to-valve clearance? I would verify that the pistons have deep enough valve relief cuts to avoid valve contact when VTEC cam lobes are at full lift.
Also, do you now have too much slack in the timing chain? I would read thru the timing chain tensioner posts in UTH. There seems to be some evidence that milled heads cause the TCT to "over-stroke", thus lose plunger spring tension, and cause problems.
Delayed cam timing might shift powerband a bit towards hi rpm, but I would be more concerned with basic mechanical issues caused by milling the head.
Did you leave enough head deck thickness to prevent warping? How many thousandths did you mill off? Did you CC the chambers before and after head milling to see how much the chamber volume dropped? CCing the chambers will also verify that head was milled flat and level. Or is your 12.3:1 CR ratio an estimate? Stock USDM 0.030" thick head gasket?
Enough piston-to-valve clearance? I would verify that the pistons have deep enough valve relief cuts to avoid valve contact when VTEC cam lobes are at full lift.
Also, do you now have too much slack in the timing chain? I would read thru the timing chain tensioner posts in UTH. There seems to be some evidence that milled heads cause the TCT to "over-stroke", thus lose plunger spring tension, and cause problems.
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