cams
#2
01-21-2006, 08:19 PM
#11
01-25-2006, 10:46 AM
cams will let air in and out at differnent times and with differing efficiency as RPM increases. The biggest single mistake in cam selection is getting too much cam. The mustang intake is pretty heavily biased toward TQ production, and it falls on it's face at really high RPM, so getting a cam that makes good numbers all around with best performance between 1800 and 6000 RPM is better in many senses than getting a cam that makes 20 more HP but you have to wind up to 7000RPM to do it. PI cams aren't as high winding as I'd like but they're pretty close to ideal street cams. more wild grinds are better for drag and road course racing and not much else. More HP farther up the RPM band means in general a loss of tq at lower RPMS.
#12
01-25-2006, 04:06 PM
If you ever look at a before/after dyno of a cam swap, the more aggressive cam starts out being weaker but crosses over somewhere and has more power up top. If you go too aggressive, the bottom end can become so weak that you actually have to spin at higher RPMs to keep from stalling. The idle becomes noticably lopey (car people recognize this as a good thing, other people think your car doesn't run well). Furthermore, all that increase air flow may decrease gas milage since your injectors will compensate.
With better valve springs, most people find they can rev their car 500 or so RPMs higher with cams and get an even better peak hp but still be reasonably reliable. If you over rev your car much more without a stronger bottom end and even perhaps a shorter stroke, your car could experience all sorts of problems ranging from busted rings to broken rods.
The problem of a weaker low-end for a better high-end is the reason v-tec was invented. variable timing cams mean that it's a bit more streetable down low but once you get to a certain RPM, the cam-shaft moves to a position where different lobes operate to open/close the valve. This high-rev position is closer to the aggressive cams while the low-rev position is more like a normal stock cam. I believe that ford has this technology integrated into the 3valve 05+ GTs.
With better valve springs, most people find they can rev their car 500 or so RPMs higher with cams and get an even better peak hp but still be reasonably reliable. If you over rev your car much more without a stronger bottom end and even perhaps a shorter stroke, your car could experience all sorts of problems ranging from busted rings to broken rods.
The problem of a weaker low-end for a better high-end is the reason v-tec was invented. variable timing cams mean that it's a bit more streetable down low but once you get to a certain RPM, the cam-shaft moves to a position where different lobes operate to open/close the valve. This high-rev position is closer to the aggressive cams while the low-rev position is more like a normal stock cam. I believe that ford has this technology integrated into the 3valve 05+ GTs.
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