I never said a big split doesnt work. People keep confusing this with "Big splits arent needed for big power". There is a difference.

The 'myth' I keep talking about is that you need a big split to make awesome power all the way to redline.

To prove this untrue, you only need to find a single example that makes good power without a big split. I supplied that. so a 230 114 with a 4 degree split is still maing 490rwhp at 6700:


A big split cam in the mid 480's with one example hitting 493rwhp is a 229/242 114.5LSA. Its 6.5 degrees overlap. A 229 cam on a 114 LSA will make power all the way to redline (my cam pulls to 6700rpm with a 230 114) so the use of the big split isnt needed for top end. A 229/229 114 LSA has the same intake closing point but it has 5.5 degrees less overlap. This increases low end vacume and the throttle response and tq is better than the same 229/242. The top ends will look exactly the same up to 6400 or so. If you have dynosym software you can model this. After 6500 the bigger split holds on but at what cost? 5.5 degrees overlap is a lot worse driveability.

Now enter dynamic compression:

Stock compression is what most cam designers conceptualize and thus they want the intake valve closed sooner raising dynamic compression to make a flatter TQ curve. It will never match the top end of a bigger cam with the same overlap. With a 219/231 115 LSA, the split is needed and I would use it because the split is needed to take the power band to redline and the cam is still only -5 overlap and drives great. A 219 on a 115 would peak at 6000rpm without it. In this case my big cam doesnt need a big split statement doesnt apply; its not a big cam and has small overlap. While the split would take it to redline, it also doesnt make 500rwhp. Its early intake valve closing point also limits static compression to about 11.2:1. A 236 on 114 with 11.8:1 compression whcih it can use, will obviously pull to redline so it needs no split to make up more top end but will make better low end because the dynamic compression is still the same as a 219 115 with 11.2:1. If the two were both installed with compression untouched, then the 219 will have better low end TQ.

Intake duration is the primary power maker because it is what determines you basic shot of gas and air. Scavenging can add to the HP past the HP peak by using the faster evacuation of the spent gases to pull in more gas on the next phase. The LSA is picked for you once you have the durations because it determines the width of the power band. If you pick a tight LSA with a small intake duration, then you are then forced to use a wider split/bigger exhaust duration to make up the power. The reason to do the later is for stock compression with an early intake valve closing point.

If you can raise compression the reason for using short durations and tight LSA's is gone. The LS3 heads have one constraint and short intake durations arent it; they dont like overlap over 4 degrees or so. If you exceed this, reversion occcurs. So its not that the LS3 likes small intake durations, its that smaller intake durations make less overlap. My approach was that exhaust durations conribute the same amount of overlap as the intake degree for degree. So I picked the specs for a cam that hits 500rwhp and limited overlap with shorter exhaust duration to limit overlap. The result was a cam that hangs with any cam of any size on the LS3 stock heads/compression. Raising compression later raises the bottom end to optimum low end TQ, but the compressioon cant make up a small cam's lack of top end. If you remove the LS3's reversion issue you can run more amount of overlap.

What I say doesnt get contradicted by GM's 211/230 because its a -15.5 degree overlap cam and its also in a bigger displacement that needs power extended to redline and a 211 on a 118LSA cant do that alone. So anyone following along can see that the GM 211/230 cam in the LS7 was properly designed (but it makes no power). Its big split is needed and thats how I would make the stock LS7 cam. It has low emissions and drives great. **These rules dont apply once you get to big intake durations because that makes the power carry to redline on its own. Big splits then are useless. If a 236/236 makes it to redine, then you dont need more split to make up the top end power. The narrow split then gets you less overlap and better driveability with more low end TQ.

So there it is, splits are determined by all the specs taken into consideration. There is no such thing as "the LS3 likes small intake durations". Charlie at RPM hit 508rwhp with a 238 cam and EG hit 509 with a 239 cam. There is no such thing as "it has a weak exhaust runner". The 193cfm is coupled with a high velocity on an 85cc runner. Hogging it out to 99cc's kills velocity. Low velocity on an exhaust runner is death to scavenging.

Im not a split hater, I just know a 230 on a 114 pulls to 6700rpm and doesnt need much split. So that is why I say: Big splits arent needed to make big power. Some seem to think that means I said,"Small splits are better than big splits for any size cam". Thats not what I said or mean. I think intelligence can see the difference.

"Big splits arent needed to make big power"

 

Great info, as always...thanks for posting buddy!

 

Excellent!

 

And don't worry about the ones who don't understand/complain...they're really not worth renting space in your mind.

 

I love these kind of discussions. Good information!

I have an LS2 but I can vouch for Spin's comments on the short intake duration / Big exhaust split.

My cam specs are at the extreme end of his analysis. They are 215° / 231° duration with 118° LSA and lift of .631" / .644". That makes the overlap -13° which is close to stock. Low speed driveability is virtually the same as stock. Power peaks at 457 rwhp at ~6200 rpm with all my mods. Will this cam ever make 500 rhwp in an LS3? I doubt it. The power flattens out as it nears 6000 rpm and peaks at about 6100-6200 rpm then drops pretty quickly over 6200. To make 500 rwhp, it needs another 500 rpm at least. This cam simply does not have the intake duration to do it. Spins comments on the long exhaust duration make sense to help evacuation and short intake duration.

As a side note, on the abnormally high lift, this cam was created by LPE for LS1. I believe it was originally designed to work well on the smaller bore LS1 because of the big lift is there to help reduce the affect of valve shrouding.

However, for the bigger bore LS3 and to a certain degree the LS2, I believe the shrouding is less so this kind of lift won't have the same impact as id does on the smaller bore LS1.

Lingenfelter's cam/head philosophy is to make the greatest average power in the acceleration RPM range. This will not make necessarily the highest peak power.

 

Great discussion. Wish I'd read this when I was researching cams 4 years ago. I will say I'm very happy with mine, with a lot of overlap, but not until I learned to self tune it. It takes a lot of time to tame a big cam for around town driving and it would be very expensive to have a tuner do it.

Mez, my friend RWSjr here on the board went from my cam to yours. Exactly as you noted he says he appreciates the better around town matters, but he notices it falls off a lot sooner than mine. Since he doesn't drag race all the time like I do, it was a better choice for him.

 

Sounds logical to me.

Have you designed any LS7 cams with the same basic parameters?

It seems most of the posts I read on cam's for LS7's make a point of bragging on how bad they idle. I got tired of that along time ago.

 

I spec'd Phil Jimenez' cam for his forged 427 with trick flow 235 heads and it made 570+rwtq on his automatic car with gears. I dont recall the HP. It was a 236/242 114. I used a 6 degree split to take the power out to 7200rpm. A 236 on a 114 wont do that on its own.

I dont work on LS7s because I never backstep if I break something. Risking 10k to make 1k on a cam swap isnt a good bet. If I blew up an LS2, I could repair it for 2k. Fortunately, I have never had a failure but sooner or later mechanical parts have a failure rate out the gate and all it takes is a chain break and if I sourced the parts for install, I own it.

No matter what the cost, I stand behind my work. The best of the best tuners can have a failure. Its not by failures that you should judge them by but rather how they handle fixing it. I've heard of a ported head leaking that destroyed an engine and that tuner completely rebuilt the engine for the customer.

 

Thanks. I was wondering if you cam philosophy carried over to the LS7 with it's factory heads. Along with what it would like like. Sounds like it would.

Yep, I don't blame you.

 

Plenty of people made awesome power in the LS1 without big splits too. One of the most popular cams was the 228R from texas speed which was a 228/228 cam usually on a 112 lsa.

It's nothing new with the LS3 that you can make good power on small split cams.

 

I recall their L92/LS2 package making 460rwhp and it was a geared car if I recall. I think a 112 would peak too early on a 228 intake duration. Its more likely wider. A 114 would be ideal. I used the 228/232 with a 114LSA and Leon made 500rwhp with a trick flow head. The same combo only makes 470-480 on the LS2 with LS3 heads. The trick flows are awesoem heads making the same CFM flow as the LS3 with a much smaller 225cc intake runner. Same flow from a smaller runner= much higher velocity and higher velocity with the same flow=more power.

260cc's and 330cfm is pretty poor. The LS3 head was the prototype LS7 head but the final version shrunk the intake runner down to 240cc's and it is a 380cfm head....thats sick. The LS7 head's top end is unparalleled. Great product numbers even bettering aftermarket castings. 355+cfm when they port the LS3 head to 275ccs is really bad. On stock displacements they dont perform well but stroker applications see 20rwhp from them and the TQ isnt an issue.

 

I'm talking about what people were running in ther LS1 Fbodies. Almost everyone was running a 112 or 113lsa on the 228R and it was a solid performer.

My point was single duration cams have been making good power for ~10 years now.

 

suscribed

 

Spin,
Thanks again for all the help.We had a great time!
Joe & Nancy

 

More like 50+ years

 

 

Spin
I had not seen this thread
this is the cam 610 rwhp 575rwtq
Sound Clip!!

 

so hard to choose which cam to go with my ls3 m6, still cant decide between big max effort and mild. BIG LG g6x3, TSP 231/236 or MILD Spins 230/234, Vengeance Racing Stage II, Cartek custom grind 3X camshaft. So many to choose from...

 

A 230 duration cam isn't neccessarily mild, its just going to drive well with decent manners and good average power without many compromises. Going max effort in a street car you start to compromise fun normal driving characteristics for maybe 10-15hp at 6500rpm; just doesn't make sense for a street car IMO.

 

Even though this is a very old thread, I meant 10+ years in reference to the LSx world.