|
This is more of backyard tuning I did. I installed 272/272 cams with adjustable cam gears in my car. I noticed a decent gain with them when i put them on, but nothing like I expected.
I went out one night with my tools, two friends and a stop watch. I found a long deserted stretch of road and did a couple pulls in 2nd to 3rd gear from 40mph up to 100mph and I timed it. I had some lumpiness in my idle when i started. My first pull was 9.2sec. I averaged the out time and back time to compensate for uphill/downhill, headwind/tailwind. My cams were at this point set at I/E 0/0. I figured the valve overlap was hindering my performance since my exhaust valve was opening slightly sooner than before and my intake valves taking longer to close because of the bigger cam this would allow some air to escape. I adjusted to a 0/-2 setting and did another pull. Average time was 8.7seconds, and I could feel the difference. I wanted more sense I had just made one correction. I then went to a -2/-2 setting. My resulting pass was an 9.1. Thinking the intake cam had "caught up" with the exhaust cam I adjust to a -2/-5 setting.
Why did I adjust just the exhaust cam? To keep one variable. If I adjusted both and got a different time, I wouldn't know which actually helped me. So I adjusted just the exhaust cam. I did another pull and cam back with an 8.5. Another very nice gain and she was pulling a lot easier now.
I wanted to try some more things out, so I adjusted to a -1/-5 setting, to see if I couldn't get the air in sooner (was my thinking). I did another pull and had an 8.6. I adjust back to the -2/-5 setting and did another pass (I know I just made a -2/-5 pass earlier), again an 8.5.
Thinking I had the car where I wanted I did one other adjustment to see if I could find anything else. I adjusted to -2/-4 and did another pull. 7.8seconds. I did one more pass to see if it was accurate and had a 7.8second pass. I then let the car idle for a while and cool down and noticed my lumpiness had gone away.
Overall I was quite impressed with how the car improved, I was not expecting that big of a gain out of it. If anyone where to buy a straight set of cams whether its 264/264 or 272/272 or 280/280, I would definetly recommend adjustable cam gears just so you can adjust for the valve overlap you are creating. An offset set of cams probably won't see as big of gains as I did just because of the timing of the valves opening and closing.
A few weeks later I went and got tuned with Al. I had some major boost problems, got those fixed and with my cams set the way they are I put down my 351whp and 375wtq numbers.
__________________
Liam
|
