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Comp Cams or PI Cams

  • Comp Cams

    Votes: 3 60.0%
  • PI Cams

    Votes: 2 40.0%

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Discussion Starter #1
I am trying to figure out the best route to go with, concerning camshafts.


Here's the setup I am going with.

NPI Stage 2 PnP heads
Zex Nitrous
PI intake
3.73's
Custom TC 3K stall

SC (eventually)

Will I make more power with Comp Cams:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=1469&item=5501046094&rd=1&ssPageName=WD1V

or PI cams?

I'd figure Comp Cams, but I have heard about possible Valve Piston contact with these cams. Is there a way to guarentee no valve piston contact? What is the best way to go?

Thanks for any insight you may be able to give me (kinda time sensitive, 1 day or so)

Dave
 

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just remember, if you go compcams, you need upgraded hardware in the heads, i think i heard the valve springs may bind or something...

ask Mike (96goldbird) or JL about that if you need more info...i do know that certain people sold compcams and put PI cams back in when they installed a blower...
 

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Discussion Starter #3
Really.....I am not patient enough to change out the cams once they finally get in there so this is a one shot deal. As the heads and cams will be swapped by a shop or anyone on here who wants to do it, and has done it before and get paid.

PI cams = 100 or so

Comp Cams = 600 or so.....

I'll buy the Comp Cams if they will be better, but there has to be no chance of a problem with the above setup I listed.

So I may just have to buy the PI cams.

We'll see!

Dave
 

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you also have the option of VT cams, i know the GT guys on moddepot use them, and they have VT blower cams available too.. but i think using those require a tune because of drivability issues..

so PI cams may be your better bet for now, especially if you are going for FI later on.
 

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Well, as I was told by JL(the great one, hisself), comp cams have more duration, overlap, and less lift tham PI cams, which may have issues with the NPI heads,,, duration is where you get power, and the PI cams are going to put more stress on the valve springs(.050 more lift)... Valve springs are a weak point in those heads, and the $200 or so to buy them is good insurance against lunching your valve train... He Is going to be useing 268 degree grind NPI cams in his next engine, and I am pretty sure the comp beehive valve springs too. At his advice thats what I put in my engine, and couldnt be more pleased... PI cams on NPI heads is do-able, but I understand there are some mods that you have to do, thatIi choose not to even contemplate to do that one right...good lucl
 

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you sure? everyone has just been droppin the PI cams right in.. myself included

just not on 94-95 heads
 

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"Well, as I was told by JL(the great one, hisself), comp cams have more duration, overlap, and less lift tham PI cams, which may have issues with the NPI heads,,, "

Isn't overlap something you don't want with a blower? I had always thought that PI cams were good (for blowers) because they don't have much overlap.
 

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Well, my heads are 97+, and when I talked to the comp guy,(tech support) , he said the NPI , .500 lift would drop in either NPI , or PI heads, but the .550 lift In a NPI head was a potential prob, and to be absolutely sure the head/valve hadda be modified slightly to be safe...This discussion due the fact that my heads are Factory Experimental as were the cams in the engine, so I wanted to be on the safe side... also they said the .550 lift would require the beehives on the NPI head for sure regardless of duration.... In any case if the .500 lift 268 degreeis what JL recommends, and NPI heads , thats good enuff for me...
 

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yeah brian.. that is why mike sold his compacams and put his PI's back in.

overlap is how long both intake and exhaust valves are open no? i think with the blower, the fuel and boost goes right out hehehe

kind of defeating the purpose with THAT one.. :D
 

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Palm Guy: Gee, I dunno, there isnt all that much oveerlap in the 268 grind, and the no overlap camz certainly didnt do crap for my engine....go figure
 

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Well while we are talking about cams. Crower offers what seems to be some serious cams. Here are the specs....


check out the stage 4 N/A cams in the high lift chart.....they sell springs to lift that high.

Cam Specs

what do you guys think?

-Derrick-

(FIXED THE LINK)
 

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You could also PM Chadg and ask what he is running, as he has pulled some phenominal power out of his engine, useing some pretty rad ModMax cams, I think,
 

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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.

-mike
 

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AHEM


he meant a red 1997 bird in texas..not 96..

ahem.... :D
 
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