I ran with both PI cams and Compcams 102200 grinds N/A in NPI heads. I had the PI cams installed when Renegade built up the ported heads with compcams springs and stainless hardware, etc. When the compcams went in, they bolted right in with no issues. I went from 225rwhp to 245rwhp with just the PI to compcams swap and a very conservative SCT tune. Yeah the compcams gave me at least 20rwhp. But there was something a bit special about my cams.
Off the shelf 102200 grind Compcams have a 114 degree LSA, so there is a bit of overlap, but not so much to make them unusable in a low compression or blower application, but better suited for N/A than for SC.
The specific Compcams I had were 102200's but I had them custom ground with less than 114 degree LSA, specifically for N/A application. There was a very large overlap. The purpose of that overlap is to scavenge vacuum from the exhaust to help draw the air into the cylinders on the intake cycle. While I had no vacuum issues and no idle issues, the guys at SSHS 3 witnessed some driveability issues. The idle was very lumpy, and when I tried to move short distances at low speeds, like in the staging line, or getting in and out of parking places, the engine wanted to stall. Jerry was able to tune those problems out, but initially they were issues.
PI cams have an LSA of about 116 degrees and no ovelap. Which means the exhaust valve is closed when the intake valve opens. That is why they make a good cam for supercharged appication. None of your boost is blown out the exaust. Another reason they make a good blower cam is that there are no driveability issues, such as low vacuum at idle, or at low rpm's under load, which affect the way the car runs and of course our brakes. When you add a blower to the mix, you have to be concerned with things like surge, and PI cams offer good performance and they are tame. Also, normally, engines built for blower application are low compression, and at idle and low rpm before the boost really kicks in, with significant overlap, it is difficult to idle, and you may have vacuum issues.
That being said, Chadg is running with cams that have 111 degree LSA and they are working fine, but tricky to tune.
Initially I got the radical N/A cams cause I was headed for 12's N/A. When I found out that I could not go there safely without a forged bottom end, I changed my plan and decided to go low compression and SC. The compcams I had would not work for a blower application. I had basically two choices, or three, actually. Go with aftermarket blower cams, have a set of cams custom ground, or use the PI cams I had sitting in my garage. Since the aftermarket cams would cost $800+ and custom grounds would have been $1200, and the PI's were free, it was a no brainer. Actually I would have gone for new cams but because of the extent of what I am doing, we wanted to keep driveability issues out of the picture, and if I want more power, I can just spin a smaller pulley.
Now about the rumors of piston to valve contact with compcams. There were some issues early on with the specs on the compscams, but although there was some variance from cam to cam, most were within .003" which is fine. Compcams changed some things and began inspecting their finished product better and I believe those issues have resolved. My cams were fine. My understanding is that the piston to valve contact problems were valve stem length issues, not cam issues.
And for those of you that might wonder what happened to my N/A compcams, they have found a home in a high compression, forged, explorer block, Bullitt intake red '97 (edit) T-Bird in Texas. And when they were installed, the new owner had no idle or driveability issues because of the higher compression.
I loved my compcams for the month or so I used them, but the truth is they were under-utilized in my application. The cams are designed to come on in the 5000-6500 or so rpm range and with the stock NPI intake the most I could get before wheeze time was 5400 rpm. My plan was to put an SVO intake on, but with a stock bottom end, I could only turn 6200 rpm, I'da been around 340 or so at the crank and my bottom would probably have not held up.
If you want to put cams in, and you only want to do it once, you gotta decide what your goals are and whether you're gonna run N/A or SC. Just like when you decide on a short block... either high compression or low compression. If your goals are mid to high13's, you can get there with a stock bottom and PI cams, if you want to go faster than that, you'll need to do more.
When you are ready for either N/A or SC aftermarket cams, talk to John at Modular Performance, he'll hook you up. By the way, the compcams only cost me $525 shipped.
'96 T-Bird LX 4.6L Alive & well & living in S. Florida
N/A: Renegade NPI heads/Comp Cams; OEM intake manifold; Bolt-ons
245 rwhp; 13.713 @ 99.35 (Commerce, GA - November 2003)
BLOWN: Renegade NPI heads; Renegade shortblock; Intercooled T-Trim; some other stuff
Pump Gas Numbers - 547 rwhp / 525 ft.lbs; Best Time - 11.388 @ 118.68 (Commerce, GA - November 2007)
Last edited by 96 GoldBird; 06-20-2004 at 09:46 PM.