|
So I had last week off, and had plenty of time to sit around and ponder stuff that's pretty much useless to most people, namely Volvo camshafts. It seems there's been a lot of debate about which cam is best, how much HP a particular model will give you, and the benefits of a "modern" grind versus the Volvo originals and cams like the Isky (ipd) VV71. What got me on the subject is that there didn't seem to be a big difference in numbers between my D grind and the VV71: D-280 deg...425"...VV71-268 deg...428". Now keep in mind these are all numbers I've pulled off of various websites, but they all seem to be in agreement when it comes to the stock cam numbers. Is my D actually a "bigger" (slightly) cam than the VV71?? I realize that a lot more comes into play when it comes to a cam actually producing power, such as the overlap and the shape of the lobes. I found a site, rbracing-rsr.com, that has a calculator for determining overlap with the valve opening and closing numbers in degrees; VV71 from Isky's site:intake:26-62, exhaust:62-26. With these numbers the calculator gives overlap, duration, and the installed centerlines. The overlap for the VV71 came to be 52 deg, and the D 71 deg(33-71, 77-38). (I got the factory numbers mainly from ozhotvolvo.com & kgtrimning.com) So with more duration and more overlap, does not the D have more potential to make power, and at higher rpm due to the overlap, than the VV71?? Another example is the KG-17 from KG Trimning..285 deg...437", I didn't have the numbers to get overlap, but the lobe seperation angle on the KG is 107, vs. 111 for the D, which potentially gives it more overlap. How much of a difference would be noticeable over the D?? Are these cams worth the money? The factory R specs: 287 deg...457"..102 deg lsa & 80 deg overlap(42-61, 65-38) The lsa & overlap are obviously why it makes it's power at high rpm, but it's not signifigantly larger than the D, so does it really make that much more actual power?? Is there a part of the equation I am missing, or does the rest simply come down to the lobe shape & how quickly/slowly the valves are being opened, which is darn near impossible to find out? Please let me know your opinions!! I'll take any opportunity to learn a little more!
--
Damn, down to only one exhaust pipe now!! less rice by the minute
|
