white1

iTrader: (5)

I was planning to drop either a TR220 or tsp 220 in my 4.8 just cause. Mostly for the sound but want to gain some much needed horses.
I've talked to a few people that recommend split durations. So now I'm thinking 218/222. But can someone please explain the reason for the split duration on a full exhaust truck. LT, ORY, cut out or straight through muffler.
Need some help. I got a 6.0 I plan to drop in, or build to a 408 but for now my main goal is sound. I actually considered a thumper or mother thumper but don't think that much of a split would perform worth a crap

ByuTrukr

Might check these out.

Preston129

iTrader: (3)

Part of the idea is that most stock heads have (relatively) poor exhaust flow. Stock, you'll be hard pressed to find a head that has an exhaust flow that's better than ~70-75% of intake, where typically if you're discussing optimal flow figures, closer to 85-90% is really sought after.

So you've already got a relative flow deficiency, and the gasses exit into a header design that also may not be optimized, so if the header has a poor collector design, or the primaries don't scavenge well enough, you're just compounding the problem of exhaust gas evacuation. Add poor Y pipe designs, cats, and mufflers and you're left with a system that doesn't flow all that well compared to the intake.

A way to mitigate these deficiencies is to lengthen the period of time the exhaust valve remains open, giving the spent gasses enough time to exit through an inefficient system.

Now this isn't all there is to it, but it's a pretty fair representation of one of the big factors for split patterns.

ByuTrukr

I always wondered why the intake was larger than the exhaust but I just realized the piston sucks air into the cylinder and the piston actually forces the exhaust out. That's why the intake valve needs to be bigger, that's why there are different profiles for Forced Induction vehicles. You could probably put a smaller intake valve on a forced induction engine and get more volume because forcing something in or out is better than creating a vacuum. Just my rambling on that subject

white1

iTrader: (5)

I saw those!! Interesting to say the least. Only issue with those for me is the lift. This is a temporary engine of sorts, and I was planning to re-use a set of 918s so the lift on these cams is a little high.
Also I wonder if that split is more for stock manifolds, or more for headers.

I kinda want to use an off the shelf cam but may wind up getting a custom grind by the time it's said and done

TXsilverado

iTrader: (19)

just hit up patric g and let him spec you out a custom cam for ~30 bux. then when you order the cam from him you save roughly ~30 bux over comps prices so everything is about the same but you have a custom cam cut from a comp cams grinder. going from the 226/226 .584/.584 112+2 to patrics grind in my truck was a 20 HP gain on the dyno.

budhayes3

iTrader: (19)

Those new Comp cams seem to be geared toward the newer L92 heads, which don't flow as well on the exhaust side. I think that for a GENIII, you would want one of the more traditional grinds that we've been used to seeing on our engines.

I just asked this same question a week or so ago, in relation to my future build, and it was determined, that even with a cutout, I should be looking at more exhaust duration. (my SW LT's only have 2.5" collectors) As mentioned, traditionally, heads flow better on the intake side, and exhaust systems also provide for restriction that would warrant more exhaust duration to allow the exhaust gasses to escape from the cylinders. A lot of guys run single pattern cams in applications that would warrant more exhaust duration and they do just fine, but it's not the optimal combination.

There's a percentage that your exhaust should flow in relation to the intake, I believe that it's 70% but I'm not sure, before a single pattern cam is warranted...I know that number is floating around this section if you do a search though, this is where I've seen it. With all this being said, I can't understand how a reverse split cam would ever be a good idea, but once again, guys have used them with good results. Seems these LS motors are very forgiving in the camshaft department lol.

skipperdaddy

iTrader: (7)

Yea if ur gonna buy an off the shelf cam, let pat g spec it as stated... in the build sheet he sends u can ask for a hard lope... then u get the sound and the best cam for the motor... if ur gonn buy new for the 4.8 that is..i love my pat g cam... but if u doin it just cause and buying a used cam the two u have selected are pretty good choices from what ive seen..

fastrt

iTrader: (48)

split for the win!! stay low duration with that 4.8. I wouldnt go over 220 intake. most small bore motors run good on a 4* split. get Pat G to spec you a cam its $25. and get Geoff at EPS to grind it on his lobes. I really like my cam, and cant woait to see the track results.

budhayes3

iTrader: (19)

Here's some info that I found when I googled "split vs. single pattern cams"

http://www.camaros.net/forums/showthread.php?p=900454