Call this one "Project -- How much cam can I get away with in my wife's vette before she notices?". LOL. The big question is - how much overlap before the idle gets noticeable?

Here are the goals:

1. address the insanely early IVC of the stock LS2 cam. I want a IVC of 45 degrees at 050 lift to aim for peak HP at 6500 RPM.
2. Maximize duration before the idle gets noticeable.
3. EVO around 55-58 also to help it breathe
4. Future plan for 62cc combustion chamber, yielding a final DCR of ~8.5

Here are the constraints and options already available to me:

1. it's a 07 LS2, so I think there is room to push it vs a 5.7.
2. Can't do long tube headers or she'll notice the sound. I don't think this will hurt too bad since overlap will be negative anyway due to stealth. intake reversion won't be an issue
3. I have the fast102 I pulled off ghost hawk for the MSD still sitting in my garage. it will go on also, and should be ideal for a 6500 peak HP target.
4. I have roller rockers, so I can push the lift into 625 territory without scrubbing fears.
5. Current LS2 cam has -26 degrees overlap (which is really 26 degrees of separation between 050 intake and 050 exhaust lift).
6. I have other mods planned like a lighter clutch and EWP that i think I can pull off without her noticing other than "it's faster".

So, again, the big question - how far can I push the overlap?

Now, before you answer me with "you should try the ultra-mega-uber cam from Acme Industries" or some such similar comment, I'm not looking for a recommendation on a shelf cam, unless it has a 45 degree IVC, 55-58 degree EVO, and a stock sounding idle.

Here are some examples of what I'm looking at in my calculator, and all of them meet the 45 IVC and 55-58 EVO requirement:

227/237-116+4 has exactly zero overlap at 050.
228/232-116+5 has -2 degrees overlap
224/232-117+4 has -6 degrees overlap
220/230-118+3 has -11 degrees overlap

Now, obviously, I know which cam will be the stealthiest. but I also want to push lift, and there comes a point where the duration is too small to adequately push lift, which is why I want to maximize duration.

So anyway, there's my new project until I break the motor on ghost hawk.

Fire Away!!

 

I have always heard that -10* overlap was sort of the "line" between smooth and starting to lope. Obviously more goes into the argument, but I use it as a guideline.

 

Add in lift with a 1.8 rocker (if you want over .61x lift) and you wont have to worry about low duration high ramp rates. Those cams will still have a noticeable idle. Not just overlap determines idle, but so does tuning and afr at idle as well as overall duration.
Id go a tad smaller on the duration with a max exhaust of 225/226 and run a 1.8 rocker and let that take up the slack so to speak. A 218/219 intake woul prob be all id go max honestly. Otherwise you are chasing your tail on overlap and hurting the lower end and tq output for more top end/broader power range. The stock exhaust will help keep the power band lower but running a 115+lsa just to keep the overlap happy on a higher duration cam wont help.
My .02

 

You'll have to tell her that long tube headers are good for fuel economy/mileage



as is everything else you're putting on.

 

I like Cam 3, 224/232, good exhaust split with factory exhaust manifolds
(Extrude Hone of any benefit?) 117+4 will Idle well and work with RPS BC2
Clutch. 1st Cam listed would be my 2nd choice.

 

@Navy -- I'm with you on the splits. Since its stock untouched 243 heads, I feel 8-10 degrees of split is about right. And you called it on the clutch. Not looking forward to dropping that torque tube. I figure a 62cc MMS 235 would top it off nicely down the road.

@tech - that's a good point about gaining lift with rockers. As to torque and overlap, that's where I struggle going back and forth. I was thinking with DCR at 8.5+, I wouldn't lose any torque. That was my thinking anyway. If it was MY vette, I'd aim for 8 degrees overlap, but keep the same IVC and EVO, which would naturally pull LSA down to about 112-114 just by making duration bigger. The only reason the wider LSA isn't scaring me TOO much is the factory LSA are all 116-122.

@Joe - lol. I've tried that argument.

@ G -- I was thinking I read something like that. But I also thought it was displacement dependent too. Larger engine would take more to make it really stand out.

 

Yeah, I just kinda use the -10* thing as a rule of thumb when comparing cams. Now I know displacement "eats" duration(I think you said that...) but does it also "eat" overlap?

 

The wider lsa is on a MUCH smaller duration cam. The duration also determines the power band but max rpm of the cam. Changing the lsa wont really change it much from 116 to 121 really because the weak duration would only carry it so far. Adding much more duration changes that and the difference becomes much more apparent the larger the duration is. Basically your costing low end tq instead of chasing it with a very advanced icl you can just narro the lsa a bit put in a 108 or 109 icl and be ok. There is a point of diminishing returns where you cant make any more power but just increase cyl pressure and cause odd vacuum signals at low load circumstances.
Adding in lift helps but still.
Just toss in an ls9 cam with 1.8 rockers if that's your goal. Super wide lsa and lots of exhaust duration. advance the icl and be done. Even though the lobes and intake dur lack alot its what you are saying really. Dont chase overlap with lsa on a med sized cam if you are wanting to stay at reg shift rpm etc. The extra adv and @.050 will taddle on you

 

I did cut a 225/229 on lsl lobes 116 lsa for an 05 ls2 auto vette. He was upset because it had little lope. After tuning it was more noticeable due to timing and fueling. It was a fun cam but you could tell it lost a little down low with a stock stall. A 6spd auto would absorb it and youd have no issue.
Im prob just conservative, but in cases like yours its usually best to err on the side of caution.

 

Tech, I agree with you, especially since nowadays it is becoming more about what's "under the curve" (almost getting to be a cliche'). Too many are concerned with the peak, while what gets you going, at least on the street, happens down below that. Plus, a cam that is stealthy doesn't let on to the other guy that what you have ain't stock.
That, a good set of heads, and a righteous tune will catch 'em by surprise every time.

 

TSP 228r with a 112 LSA.

 

NOT stealth.... lol

 

Grand am cup cam

 

Yeah, I can see that. This is a really unusual case. If it was mine, I'd be looking at the tick street heat or something similar. And I have considered a ls9 cam plus rockers, but I don't like that 19 degree split. And that's not totally off the table either.

I also should have specified, my wife is one unusual chick. She wanted a M6. It's not an auto. She'll drive it in four inch heels. Which is kinda hot actually.

I think if it had a little extra pop to the exhaust it'd be ok, but def can't buck. Hard to explain what I mean. But she won't want it louder or hard to drive. So a 225ish cam won't be bad.

And if you drive a bone stock LS2, they're kinda weird. They don't want to take any timing because that IVC is so early AND SCR is pretty high. I believe that a later IVC combined with being able to get some timing in it will minimize the torque loss off idle. I also think the higher lift will help bouy the torque in the off idle range. But by 2500 RPM, I'd bet the bigger cam already pulls harder.

 

See there was that statement in the first post NOT to recommend a shelf cam unless it has 45 degree IVC, 55-58 EVO and stock sounding idle.
Lol. And the title of the thread.
Lol! Go great with ls3 heads too

 

She might be unusual, but I'd bet you're glad you have her! I bet she knows how to burn 'em when "necessary"..... lol

 

I look at power under the curve differently. Most people say that in terms of maximizing the tq curve. I actually look at maxing the HP curve. If I can peak at 6500, carry the peak to 6800, and shift at 7200, the car will run REALLY strong from 4800-7200, which will flat SHOCK lots of guys on the street. In that sense, I'm not worried about hitting a high peak hp number, but I am wanting hp to peak at a target RPM.

Does that make sense the way I said it?

If you look at my ghost hawk stuff, it peaks 6800-7000, carries out to 7200, and i shift at 7400-7500, dropping to 5200 on the upshift. The car is still making more power at 7200 than it is at 4800. That's how I look at power under the curve.

And yes, pairing with a great cylinder head will make a mild cam scream. I think for the street, awesome heads and moderate cams make the funnest rides.

 

All that you said above makes sense. Your last statements above is what I was driving at. To me, at least, a rowdy-sounding cam on the street just screams "I'M GONNA KICK YOUR BUTT!" Where a stock-sounding, or nearly so, engine will just putter up to the stop, then pull a hole shot on the poor unsuspecting slob who didn't know what hit him! lol

 

Low 220s int mid to high 220s exhaust on a 114 would be my max. Esp for cruising around the mall parking lot looking for a parking spot by Victoria's Secret. Add in lift then put a 1.8 rocker and itll be pretty quiet. Id be more for maximizing .200 honestly and adding in a bit more adv dur. keep it quiet under the hood but make the curve swell. youve got @.050 lsa and icl covered, look at the rest.

 

I think its going to be more about exhaust setup than the cam itself, relatively speaking. We did an El Toro cam with a stock catback that kept it quiet, still noticeable, but the car had longtubes and ORY on it. I'd bet my F13 with a stock exhaust would be quiet and thats like +2 of overlap. The muffler and maybe an extra resonator would muffle quite a bit of cam. Put a pair of E-cutouts on it and don't tell her so you can have it loud when you drive the car.