98Z28CobraKiller

iTrader: (17)

Well, I am serioulsy considering swapping out my cam and would like some opinions. I am currently running a Comp XER 244/248 .613/.617 that was originally ground at 111(-2). I have advanced the cam 5* and it is ok. Why do I want to switch cams? I feel that I am leaving some power on the table with the XER lobes. I believe that I could get more power and less overlap with an LSK lobe. With my rather limited understanding of cams, my understanding is that less overlap = more vaccuum = better streetability. Here are some of the combo's that I have been looking at. Please critique. Also, keep in mind that I am currently spraying a 200 shot thru a plate system and intend on going up to a 250 shot once I get a dedicated fuel cell for the spray. Track numbers in sig are NA.

Thinking of going from the XER (currently) to an LSK lobe. Maybe slightly less duration and a little more LSA. Thinking of 240/244 .649/653 on a 113 LSA w/ +2* ground in. Or maybe a 244/248 .653/.656 on a 113(+4). This gives me way more lift and about 4* less overlap. Might even try a little more split like a 240/248 .649.656 on a 113(+3)as I have heard that the nitrous responds well to more split.

98Z28CobraKiller

iTrader: (17)

No one has any input? Maybe I should change the title to please help me put together an imaginary combo that I may or may not build. Those seem to get a lot of replies

Patrick G

iTrader: (14)

To pick up more peak hp, you're going to want a later intake valve closing point. This is why Your cam originally came -2. But as you found out, there's no free lunch...the dynamic compression was lacking. Advancing the cam to 108 ICL was a smart move.

If you're happy with the power rpm peak, then keep the IVC the same as it is now (50 degrees ABDC at .050"), Your DCR will be the same too. To have less overlap and the same IVC, you'll want something like this:
244/248 113LSA +5
Personally, I don't like this much advance, but this is what you'd have to do to maintain 50 degree IVC. If you run less advance, then you DCR will drop a little, but your power peak will be a little higher.

Your 240/248 113LSA +3 is a very balanced camshaft from an overlap standpoint. It will have nice manners compared to your current cam, but don't get your hopes up on big power gains. Most likely you will make comparable power to your current cam, but with better street manners (68 degrees of overlap vs. 73 degrees). Keep in mind, LSK lobes have around 50-51 degrees of ramp from .006-.050" whereas the XE-R lobes have only 49 degrees. XE-R lobes will tend to give you the cleanest idle (due to the faster ramps right off the seat). :shrug:

DrkPhx

iTrader: (15)

I'm in the same boat. I run a custom 244/250 .612 113 LSA (no advance) that is very streetable and pulls like mother up to 7200 rpms (if I rev it that high) I also feel my 11.3 SCR and 7.97 DCR is leaving power on the table as well. I have the 72cc AFR 225's and was thinking of raising the the SCR to 12.1 and/or changing the cam. I got the tune almost nailed down, so I don't want to change it unless it I have to. Before I built the 402 I called Futral who spec'd a 250/267 .650 lift cam; now I'm wondering if I should have went with that cam.

98Z28CobraKiller

iTrader: (17)

Thanks Patrick! I spoke to Tony today and he said pretty much the same thing. He also mentioned that the heads are optimized for the .600 lift area and that going crazy with the lift will not net much better results. Basically, going to the LSK lobe will cause added strain on the springs and for my application (almost daily driver) it is probably not the best way to go. Not to mention that I would have to change my springs (additional $$$) just to get into one of those cams. We are looking at sticking with the same duration (maybe less but I dont like the sound of that) and opening up the LSA to say the 114 area with 2 or 3 degrees of advance. I might pull the heads and go to a cometics .040 head gasket to get the SCR and DCR up a bit also. I gave Tony my race weight (about 3750) and my MPH (125.2), he plugged it into some sort of calculator and basically told me that I am at a pretty healthy power level and that I should put me and the car on a diet and work on my suspension instead . So I am going to think about it some more. I am basically looking at spending $450 (plus a solid day of labor) for a little better driveablity and maybe 1-2 mph on the long end (maybe not).

98Z28CobraKiller

iTrader: (17)

Hmmmm, what kinda power are you making with that cam?

Do your pistons not have reliefs in them? Trying to figure out how you are at 11.3 SCR with a 72cc head.

DrkPhx

iTrader: (15)

I was wrong, it's 11.19. .007 out of the hole and .040 head gasket with 2cc valve reliefs.

98Z28CobraKiller

iTrader: (17)

Gotcha. Do you have any numbers with that cam (HP, TQ, 1/4, 1/8)? I am curious as to the performance on your cam.

DrkPhx

iTrader: (15)

No dyno numbers. Only 6 tracks runs so far. It went 11.1 @ 121.49 mph on a base tune in hot weather. Raceweight is 3,560-lbs with a 1.5x 60-ft. Not bad, but not great. I'm sure I can squeak out a high 10 in better weather with a better tune. But to be honest I expected a easy 10.7 out of the car.

98Z28CobraKiller

iTrader: (17)

Damn you and your automatic trans . I cant 60' to save my life with this damn M6. Does it feel stronger now or have you not had it tuned yet? Do you have software to tune it yourself?

My first time out I had similar MPH but much worse ET. Thru tweaking, I have been able to get my MPH up 4 mph. I picked up 2 mph by switching mufflers from my 2 single chamber to the 2 XR-1's.

DrkPhx

iTrader: (15)

I tune it myself. But when I hit the track the PE and higher VE table was still from a mail order tune I purchased 2 years ago. Since then, I have tweak those tables, but have not hit the dyno or track. Yes I noticed it pulls better, but only the track can tell.

I'm amazed you picked up that much mph just from tweaking. If I see 2 mph from tweaking I will be happy.

98Z28CobraKiller

iTrader: (17)

Tweaking includes degreeing the cam, changing to less restrictive mufflers, adding a balancer pipe to my exhaust, taking 100 lbs out, torque arm, and slicks. I'm not implying that I picked that up from tuning as the tune was in pretty good shape (at WOT) on my first trip out.