jason.sabovich

iTrader: (1)

Hey guys
I'm somwhat new to cams and I need some help deciding how much valve lift I should get on a new cam.
- The car is a 99 SS Convertible, M6 with 50k on the odo.
- My goal is a stock idle and like stock drivability and 380 RWHP or so. I really like MTI's stealth II cam(220/224 .576 .581 116 LSA) but question the need for .581 valve lift being I am keeping my stock heads?
-My setup will be Pacesetter LTs, ORY, magnaflow catback, TSP lid, Bauer TB and LS6 intake manifold. Right now the car is stock.

-MTI offers custom grinds for their cams. Is there any need to go with anything more than .500 on the lift while keeping the Stealth IIs 220/224 duration? I would think that going with .580 lift would compromise valve spring life compared to a lower lift like .500. I don't want to be replacing the valve springs every 30k.

Recap: How much valve lift should I use given my goals? Any other cam change suggestions are more than welcome.

Thanks

Cal

iTrader: (1)

Since you don't want to change springs, I'd get something with about a 0.525 lift. Since you want a stock idle and drivability, get a cam with 218 degrees or less duration. But I doubt you will get 380 RWHP with a cam like this unless you put some good heads or a blower on there as well. I would sugest changing your requirements a little and getting a TR220 114 cam.

Tin Indian

Ditto what Cal said ...

J-Rod

As you get into the more radical Xe-R lobes and uber lift, valve spring life will go down. There are a lot of factors to consider, but I think going with MTI's cam and spring pacakge would be ok, and not require a lot of spring changes. To retain a stock idle you'll need to be around 218 or less on duration. You can do 220, but with other than stock exhaust, you get lope. The tradeoff for power on duration is more lift. Its not a perfect inverse relationship, but there are some cams that are not spring friendly which will idle like stock and make big power.

FILE

iTrader: (5)

Before doing the my cam swap, I wanted my truck to sound stock. It turns out it does not. You can now hear a mild lope that I learned to love.

93PONY

Stock LS1 heads stall out around .550 lift. Behond that lift point the heads get turbulant. To push over .550 lift on a stock headed setup is not a bad thing....in fact it actually helps atomization of the A/F mixture!

380RW with an M6, stock heads, LS6 intake, longtubes & off-road exhaust is pretty easy & if done right will give near stock idle & drivability.

J-Rod

One of the other things to keep in mind. Many of the spring issues folks are running into (IMHO) are because they don't set the springs up properly. Things like spring height, open and closed pressure, height to coil bind, are all ignored. Insufficiant spring pressure, and uncontrolled spring harmonics are what most of the spring failures and loss of spring pressure can probably be attributed to...

niphilli

I agree that a lift over .550 on stock heads is a waste.

For idle I would stick to 224 duration or less on a 114 LSA or higher.

You should note that you will have to spin the motor a little higher to get peak HP and you will probably need to change valvesprings every 20K or so.

If I were you based on what you posted I would go with an '02+ LS6 cam you should make between 370-380 with that cam and all of your bolt ons. It will be cheap, reliable, and pretty stealth through full exhaust.

jason.sabovich

iTrader: (1)

Thanks for the responses guys.
I don't think that the LS6 cam will do the trick, besides for just a couple hundred more I can get a cam with more duration.
It seems that the general consensus is that .525 lift and above will involve valve spring changes. Basically I don't want to ever have to touch the valve springs again after I do the cam swap.
So now I'm looking at .525-.550 lift with 218-220 duration on a 116 LSA.
That would look alot like the TR220 cam, but just with two extra degrees duration
Are you guys sure that the 224/220 MTI cam will lope? The "Colonel" who has one claims it sounds totally stock. Also, with stock heads will I see any performance decrease with .550 valve lift Vs. .580? From what I've read, the extra lift is just for aftermarket heads.

Thanks for your help, also I'd like to thank all you guys for supporting us over here in Iraq. I've had a few buddies of mine go home on two week leave and tell me it's unreal how well us soldiers get treated when we return home. By the way, I'm a maintenance officer (1LT) with the 3rd Brigade, 1st Armored Division.
.

Colonel

Jason, for reasons that no one can completly explain, the same cam in one car may lope and may not in another cam.

About the Stealth II...

It DOES idle 100% (and I DO mean 100%) like stock in MY car even idled at only 600-675 RPM. My engine has LS6 heads at 11.1:1 CR. I run QTP headers, no cats, an electric cuttout, and the stock muffler. BUT, other people have noted mild to moderate lope with this cam. Again, for me, it sounds exactly like stock at idle.

Due to it's reverse split, it likes a free flowing exhaust system.

It obviously will respond best to heads that flow great at higher lifts.

It has very aggressive ramp rates and requires top of the line springs. I expect about 25,000 miles out of my springs. Might be more or less...I just don't know at this point. So far I have about 8000 on them.

I ran 11.20 and 121.47 MPH with a 3525 raceweight and stock 3.23 gears with this cam. This is way more than I ever expected from this combo.

jason.sabovich

iTrader: (1)

What do you think about the comp 216/220 cam? I should offer similar power to a TR220 (maybe 5 hp less) but be much easier on the valve springs. Anyone with experience on this cam?

GTBMad

I have used this cam in a car for 60000 miles, if you are looking only at peak numbers dont bother. if you are looking for a good all round performance cam with good manners it is a great cam.