I'd consider something like this cam here......
http://www.tickperformance.com/tick-...1-ls6-engines/

 

Tooley's cam in his TFS 245 headed 454 is a great example of this. 15 degree's of intake/exhaust split on a 115+3. Makes 600lb. ft. of torque at 4500rpm on the engine dyno and 600rwhp through a stalled 60e that flashes 5200rpm. Smaller runner, port velocity, high exhaust flow, and reduced overlap at TDC. When you can reduce overlap at TDC aka .006" and keep a nice chunk @.050 and even more @.200" and still control the valve now you're beginning to get somewhere.

The other big thing people don't think about and it plays right back into the hands of overlap and what I just said above is 9/10 times these large cubic inch LSx street engines have Fast intake manifolds on them. They have a 10" long intake runner and create an intertia-ram column of air all on their own. They don't need as much overlap as others have said to create a strong mid-range signal and if you over-scavenge them with a lot of overlap at or around TDC you will kill off that power band. This is even more so an issue as the intake valve gets larger and larger and creates more curtain area.
Look what I've started....
I would personally do this grind....243/250 .624"/.595" 114+3

 

Pure gold right here IMHO. Excellent tech. If people can grasp this, then they have the visualization needed to understand camshaft theory.

 

A lot of the physics and true movement of air mass entering the intake runner and exiting the exhaust runner are totally misunderstood and a lot of times overlooked for "it has to have this duration" or it "needs to have this". It has to have what it wants, and it needs to have what it needs plain and simple.

Now I am not a physics expert, and I will admit I have never even taken a physics class in my life(I am actually enrolling in a few classes this spring at the local community college to further my understanding of valvetrain movements and events...wish me luck), but I have a pretty good grasp of how it works.

Thanks for a great civil discussion Tigger, the site needs more of this instead of the poo slinging that usually occurs. I have noticed though that if a few certain members stay out of a thread, that normally doesn't happen...funny how that works.

 

Ok, it looks like I'm about to get this project started. Though I still haven't decided on my cam yet, I'll be making a call to Martin tomorrow. I do have a couple other questions though. My current setup has an unported FAST 90. Will this be sufficient or will I need to look into having it ported? Would an unported FAST 102 be just as effective? What about exhaust...do I need to now consider 1 7/8 headers now to reach my goals?

 

Ok, it looks like I'm about to get this project started. Though I still haven't decided on my cam yet, I'll be making a call to Martin tomorrow. I do have a couple other questions though. My current setup has an unported FAST 90. Will this be sufficient or will I need to look into having it ported? Would an unported FAST 102 be just as effective? What about exhaust...do I need to now consider 1 7/8 headers now to reach my goals?

 

I would swap headers to 2" headers or a 1x7/8" stepped to 2" before I worried about the intake manifold. Once you get the header situation taken care of, have the intake ported. IMO there is no need to go to a Fast 102 if you already have the 90.

 

I replaced my stock LS6 short block with a TSP 418. Reused my TFS 215 heads (opened the chamber to match the bore), LG G5X3 114 cam (234/242/.600/.610) installed at 114 ICL, Mamofied 90/90 intake, LG long tube pro 1.75 headers with high flow cats & 3" Big 3 exhaust. The CR is 11.48.

With the 5.7 engine there was a light throttle/low RPM surge (4th gear @ 30 mph) that I hoped would be better with the 418 engine. But the surge was only slightly improved. Also I'm tired of the valve clatter at certain rpm's.

So I'm looking at a smaller cam like a comp LSL 231/.615 int & LXL 234/.612 ex. on a 114 LSA. This cam will have 4.5* overlap vs 10* overlap of the G5X3. I don't see how a 243/250 114 cam with 18.25* overlap would have the same driveabililty in a 408 as a the Torquer V2 cam in a 346.

Also waiting on EPS to spec me a cam with his LSG lobes.

Russ Kemp

 

Done it many times with great results.

 

Also if you're just looking at overlap figures@.050" and using that figure to determie whether or not you think the drivability will be impoved upon or decreased, you're only looking at a very small portion of entire picture. Seat to seat overlap figures(.006" a.k.a. advertised duration) plays just as large of a part in drivability if not more than the @.050" numbers. This is where lobe selection plays a critical part in cam selection as you can have the same @.050" numbers as another cam profile, but be totally different @.200" and @.006".

Russ those XE-R lobes your current cam has are notorious for clattering and banging around especially at idle making for the "sewing machine" noise that is frequently discussed and talked about on this site. Ramp rates, assymetrical vs. symmetrical lobes, and lifter preload are big big variables in this equation for having a quiet valve-train

 

Realisticly, in a 408, what could you expect to see by going from the ported 5.3 heads to a set of high-end castings like the PRC 237, AFR, or Trick Flow? I understand that a cam optimized to work with the 5.3s wouldn't be the best for the better heads but what would a set of heads alone gain?

 

pretty awesome thread here! i like that big dave is into pinching pennies like me!!!!

RUSS K----got any dyno results before after the shortblock swap??? interested in seeing...

and on the heads...they would gain for sure.

i once was told, "if you have the worlds best heads and a mediocre cam...youll make great power...but crappy heads with the best cam you can get....you wont make good power..."

---may be opening a can of worms on this one...awesome cam info here...now onto the heads...lol

 

If your going to run them heads and stroke the motor u should go a bigger cam to utilize the power.

 

Unfortunately my motor expired before I was prepared to build another one. If it had been planned, I would've saved for a better set of heads, and have a cam designed for what I'm looking for. For now, cost is be a factor...this is why I'm asking so many questions. Racing isn't cheap, we all know that, but it's a lot easier when you have the funds, and the time to plan for your goals.

I was totally against the 408, mainly because of the weight. When I added up what an aluminum 402 would've costed, the 408 made more sense. I don't plan on autocrossing my car, and the additional weight on the nose won't help in drag racing, but I'm hoping to overcome those factors with some good ole fashion horsepower...and torque.

 

Made 434 RWHP on a DynoJet with the stock short block. Haven't dynoed the 418 yet.

Geoff specced a 234/242 .602/.615 117 +2 camshaft. Should have more top end power with a smoother idle & very little to no low RPM/light throttle surge with 4* overlap. Plus no more valve clatter.

Russ Kemp