DaddySS

Objective:

Maximize torque and power on the low end without giving up too much up top - while going easier on the valve train than an XER lobe (220 224 581 581 114 +4 is recommended by AFR). Engine has AFR 205s, headers with cats, LS6 intake. M6 with 373s

Proposed:

218/224 xe high lift 560 568 112 +4 with comp 1.75 rollers (576 584).

Any thoughts apprciated.

OldSStroker

Everything is a compromise in engine design. Sit down with your engine designer and discuss all of your objectives. Decide how long you need the valvetrain to live without having to change parts. Discuss what you want the car to be.

Perhaps your chassis/tires/gears really can't put down "maximum" low end torque. If you like 1200 rpm 6th gear rolling start races, let your designer know. The LSX engines can be tailored for towing (GM trucks) or racing (Z06) or almost anything in between.

You need a plan, not a cam.

DaddySS

Thanks, but here's the plan; right now the engine comes alive at 3500 and pulls hard up to 6500 but I spend very little time up there. Sure I could put a Z06 in there and maximize spring life, but that leaves too much on the table. When I step on the gas at 1500 rpm I want it to pull hard. I only put 5000 to 7000 miles per year on the car, so I don't mind changing springs every couple of years. I'm not too worried about holding maximum torque, I just want it to pull harder than it does now in the 1500 to 3500 range. The head manufacturer recommends the 220/224 cam for what I want, Im wondering if the cam described above will give similar results with a little less noise and stress than the XER lobe.

Greed4Speed

The only time you'll feel that range is right when you hit the gas. After your run through the gear and shift into the next you'll never drop below 3k RPM. Especially w/ 3.73's. In a race, very little time is spent below 3k rpm.

A smaller cam will only move to power range down. You'll have less torque and HP than a larger cam but you'll get in it earlier and drop out of it earlier. Its a trade off.

The difference between XER and XE lobes is negligable. You're talking ~.02" difference. They'll both wear springs out. How fast depends on your driving. The good thing is that AFR heads comes with patriot golds.

DaddySS

Thanks, I appreciate the feedback. I only take the car to the track once a year maybe, so racing is very low on the priority list. I drive it mostly very gently so I'm shifting between 2200 and 3000 RPM. When I jump on it on occasion, it's usually a rolling 2000 RPM and then shift 4000. Don't get me wrong, I enjoy winding it up to 6000 every once in while but not all that often.

The car is a fair weather cruiser, to enjoy the power, the sound, the feel of a six speed V8.

1racerdude

Pull your cam down to a LSA of 108 and an ICL of 104. It will give you a little on the bottom over a 114. It is hard to work more than 3000 RPM range for torque. You may be able to stretch it to 3500RPM's but that's about all. To get the "feel" you will have to go with more gear in the rear or grab another gear in the tranny.
Either cam mentioned is not a BIG cam and shouldn't be any strain on the train with the right springs.

4U 2 NV

sounds like a pretty reasonable set up.

Refresh my memory real quick...A cam with 112+4 LSA has 112 degrees of lobe seperation angle with +4 degrees built in..meaning depending on the install will depend on the LSA?

1racerdude

The LSA is ground into the cam and can not be changed.The ICL is judged by the drive pin and can be changed only by a timing sprocket set up that has different keyways, an adjustable cam sprocket or offset bushings but not on an LT1. If ya do then it moves the injector timing and ignition timing because you move the Opti and the maps in the computer has to be changed.

DaddySS

112 LSA and 4* advance ground in. LSA doesn't change with the install.

OldSStroker

No offense, but if you are WOT pulling from 2000-4000 and don't want to downshift, what was wrong with the stock cam? It was designed for almost the exact conditions you describe. If you want to accelerate faster, downshift, as was mentioned.

It almost seems like a waste to spend big bucks on aftermarket heads and only run the engine to 4K in anger. Personally, there's no way I could force myself to shift at 4K if I was running someone, and I was born early in WWII.

DaddySS

So given the choice between having 400 rwhp and 300rwhp, I should stick with 300 because I wouldn't use the 400 enough? It's kind of like saying when the 327 300HP Impala ss came out in our day, we should have said no thanks, I'll take the 283 2bbl with 200 horses, I really don't need the other horses?

I get the enjoyment from this car through building it up, bragging rights for my 450+ fwhp, and the power I feel when I step on the gas. I just want more of it available without winding it out.

I don't shift it 4000 when I run someone at the track - I shift it at 6000. And I shift it at 6000 when I take off on a deserted road and let her rip up to about 70mph before I back off. I also like to step into it at about 2000 in second and let it scream up to the speed limit.

Right now with the 226 228 on a big block journal which acts more like a 230ish cam the idle is very choppy, the gas smell is bad and it surges in traffic. For what I want, it's over-cammed. A nice compromise then is the 220 224 which will still give good power, but bring it in sooner, and have better driveability. With that in mind, my thinking was to go a little milder on the ramp rate, a little shorter on intake duration which will help to build cylinder pressure, and a little tighter on the LSA which will bring the torque in sooner. So my question was - will it work, am I overlooking something, should I keep the LSA at 114, has anyone else tried this, etc.?

Kraest

This thread makes my head hurt.

teke184

a cam that size shouldn't surge much. maybe a better tune is in order.

Greed4Speed

I totally agree. Something isn't right because that is far from a large cam.

DaddySS,
Do a search on LS1tech.com for some 108-110* LSA. I think the cams in that range would fit you bill.

rskrause

I agree that something close to the stock cam is what you need, at least as far as duration; if you really want acceleration in the 2-4K range. If you want even more power in that range and are willing to use good supporting components, stick with stockish duration but go for more lift/more aggressive lobes (i.e. something like the XE or XE-R lobes).

Rich