gregrob

iTrader: (8)

So I'm finding that the only "commonly" available cam lobes for the LTx platform is

Magnum Series - Comp
XE series - Comp
XFI series - Comp
Mystery lobes - AI
Mystery lobes - LE

My questions is

#1 has anyone experimented with having comp custom grind an LTx cam with the XER or LSK lobes like the LSx guys use.

#2 when I look at cam specs on AI's or LE's site they have a big split duration cam with the same lift on both the intake and exhaust side. The only way that can be is that they are using a different lobe profile on the exhaust and intake, right?

I'm thinking about trying a different style lobe on a custom grind so I can get all the potential of the AFR heads I plan to run (because they keep screaming up .600 lift) but want to keep the duration low.

The Cam I'm thinking about would look something like this 22x/22x .599ish lift 111+?

Thanks for any meaningful input

DAVE00

iTrader: (10)

What AFR's are you running as most AFR heads come with an installed height at 1.800 which will cause some problems if you want to go .600 lift as you will bind those springs pretty quick. Unless you had them installed higher double check and have them corrected before you start shooting for higher lift.

gregrob

iTrader: (8)

The springs on the street heads are good to .600 lift, comp heads are good to .650...

96capricemgr

iTrader: (1)

But these days lift capacity is NOT the only concern.

You seem to believe you can come up with a better plan, stop asking questions you wont listen to the answer too and prove us all wrong already.

JAKEJR

CompCams can custom grind whatever your want. I just received a custom grind for my son's 96 LT1 and I specified their CRC lobes.

Cam cost $303.00 and I kept the duration short too.

I also spec'd what LSA to use and how much advance to grind in. I'm going with .604 valve lift to take full advantage of my son's new heads.

Yes, there can be, and often are, different lobes used for the intake and the exhaust. Some of Comp's lobes are specifically designed to be used on the intake and some are specifically designed to be used on the exhaust.

My goal is max torque for a 100% stock CID street engine
and I opted for a single-pattern grind. After running well over a hundred simulations and reading up on duration splits, I found single pattern best met my goal.

In fact, Ron Isky said "A single pattern cam will always make more torque, let me repeat that, a single pattern cam will always make more torque". That pretty much sealed the deal.

Jake

West Point ROCKS!

gregrob

iTrader: (8)

Duane,


I'm not out to prove anyone wrong. How about you offer some data instead of rhetoric.


I fully intend to take installed height into account
and I appreciate the other poster for bringing it up.


If I have springs good to .650 I don't thing .600 is going to be a problem.


Regardless of the heads I go with I will run the better springs.

gregrob

iTrader: (8)

Jake,


Thanks for the post. I'm curious to see how yours works out if you get done before me :-)

96capricemgr

iTrader: (1)

Different lobes have different rates of lift. Think of it like hitting a 4" speed bump at 5mph vs. 10mph. Same "lift" but nowhere near the same forces.

Ask the idiots who tried the XFI lobes with basic cheap double springs even ones with more seat pressure than the spec'd beehives. For that matter Comp fails to consider the additional RP{MS the LT1 intake causes for the same duration throwing their rpm ranges way low and therefore their spring recommendations are often too light.

You seem more interested in what the guy with desktop dyno and ZERO MEASURED experiance has to say.

I am sure all the LT1 shops that use split pattern cams do so because they just aren't as smart as JAKEJR.

The gen 1 and gen 2 smallblocks almost always use split pattern cams because the heads are weak on the exhaust side compared to the intake or on the street to overcome restrictive exhaust.

I bet if you asked Isky to more fully explain his statement you would find he does not believe single pattern to be always best. probably just best if the heads and exhaust are perfect.

You get these bench racers who take half a comment and think it is gospel without the slightest unerstanding of what was actually meant. Then the ignorant kids follow them and they endup dragging the whole communities results down and dismiss the FEW cars donw well as freaks.

Puck

iTrader: (17)

Although I wouldn't say it that bluntly, that is a good way of putting it.

It is hard enough to spec the proper duration, lift, LSA, valve events, etc for a cam without even getting into lobe profiles. Then it starts to get wicked complicated. I would honestly tell a pro exactly what you want out of the car and let them spec the proper cam. It will depend on a LOT of factors.

BTW: I will be running a single pattern cam myself, but was assured by more then one pro that it will work great with not only the heads but the stall, gears, and other specs of the car. Its all in the package as a whole.

engineermike

I ran across a cam lobe designer (who does some development for GM, among others) a couple of months ago and my eyes were opened. I used to think that more aggressive lobes were better, but you just had to put enough valvespring in it to control it. I thought that surely, the Comps and Cranes of the world wouldn't sell us some junk that couldn't be controlled. However, he pointed out that certain widely available lobe series' were nearly impossible to control. Most racers tear up the valvetrain and assume is was from abuse or improper assembly, when it was really a lobe design with too high acceleration or infinite jerk.

I'm just saying that 99.9% of enthusiasts really don't have any business getting creative with lobe profiles because we don't have the tools to know if we are causing real long-term problems.

speed_demon24

iTrader: (6)

I'm going to have to agree with this, and the sad thing is a lot of "experts" don't know any better than this.

And to the OP there's also cam motion, lazer cams, bullet cams, isky, crane, ect. There's a hell of a lot more lobes out there than just the comp stuff. With that in mind I figured that I would let the experts with a good track record and happy customers spec my cam instead of trying to do it myself.

Puck

iTrader: (17)

Probably the most meaningful post of the last few days.

Speculating and playing with sims is fun and everything, but the real world effects of changing cam specs are much more complicated then just changing a field in desktop dyno and seeing how the graph looks.

gregrob

iTrader: (8)

Translation: if you dont use AI and blindly take what ever they give you, you are an idiot bench racer.

Actually I think the definition of a bench racer is someone who does a lot of talking and doesn't actually try anything new. Yet when someone wants to to try something in the real world to see how it works, you condemn them.

I do have a lot more respect for Jakejr because he is researching things for himself and making his own decisions, instead of using off the shelf parts with off the shelf results.

Anyone can buy your setup, what have you really added to the ltx community by running it, or pimping ai for that matter, or condemning anyone who tries anything else?

gregrob

iTrader: (8)

To everyone else, the only problem with your theory is that the lobes I plan to use have many people out there already using them, in a more aggressive lift configuration than I plan to, and have great results.

You make it sound like I'm trying to design a lobe from the ground up. The lobes I plan to use lift the valve off their seat gently, and set it down gently, not slam it.

As long as they are shimmed to within .050 of coil bind, there should be no issues I can see. Actually less aggressive than running some of the more commonly avaliable lobes for ltx with a 1.7 rocker.

I do appreciate and respect all the input here, just trying to allow you to see both sides of it. I don't need to be "talked out of it".

engineermike

Unfortunately, there is A LOT more to it than that. Just an example...the particular expert I spoke with was very happy when Solidworks came out because he can now draw the rocker arm in 3D and have the program solve for the moment of inertia, rather than measuring it on a test rig. And then, learning how to incorporate this information into the lobe design is an order of magnitude more complex.

speed_demon24

iTrader: (6)

How do you know the lobes are less agressive than LSx lobes? LSx's also have much lighter rockers and valves than us.

96capricemgr

iTrader: (1)

That is just a copout to try and discredit me.
There are plenty of good parts that have nothing to do with AI. The 503 is a good cam, the Lingenfelter stuff works awesome for it's size. Crane had some nice cams as well. VERY recent link of me recommending parts. https://ls1tech.com/forums/lt1-lt4-m...ottom-end.html

JAKEJR punches numbers into a CHEAP inaccurate program and then comes here and acts like it is meaningful data. There are good programs for this stuff but they cost a LOT.

Ask for MEASURED results on everything he suggests, you wont get any. If there is no measurement it is wildly irresponsible to go recommending things.

I on the otherhand can DRIVE 500 miles each way to the national Impala gathering, couple hundred cars from all over the country and be the second fastest naturally aspirated qualifier running faster than almost all the strokers. That shattered my confidence in the community, I knew folks were making mistakes but till I got to run same track same day and go faster than trailered stroker cars I had no idea just how badly they did things.

I try plenty of new things too, I was the first one on the Impala board to give AI a shot.
I own one pair of headers that was among the first 10 built, same with my x-pipe, driveshaft loop, I was one of the first on the Impala boards to try Edge. The set of headers on the car is as far as I know still the only set make like them, I do know there were the prototype and don't know of anyone else using them.
I try all kinds of stuff some good, some bad, been at this so long some of the things I was one of the first to try are now common and popular.

NightTrain66

iTrader: (7)

I think what he meant by "a single pattern cam always makes more TQ" would be in comparison to a cam with everything else equal other than the exhaust lobe (220/220 112 LSA VS a 220/226 112 LSA cam).

The later you open the exhaust valve and blow down the cylinder, the more low end TQ you will make and the more mid range TQ you will make BUT the sooner the #'s fall after peak HP and TQ is made. A reverse split is gonna show this even more (fatten up low end TQ, kill top end power).

This is another general statement though. The engine has pulses and waves (harmonics) going through intake and exhaust tract and you are trying to catch these and timne things just right to use them to your advantage.

I use Dynoamtion 5 and it is a REAL nice program where you type in mca, venturi diameter, intake runner length, intake manifold runner length, cross section at plenum area (port taper), plenum volume, header primary diameter/length, collector diameter/length, etc, etc, etc, you are still just dealing with a program and rthere are gonna be variables that it will not account for that exist in the real world.

You are better off getting lobes that remain stable and create power from the valve timing events. The difference in a moderate lobe and a VERY aggressive lobe is not that much in terms of HP/TQ but there is a difference in how long the parts last (or don't last) with an agggressive lobe.

Lloyd

Puck

iTrader: (17)

Well said.

The single pattern cam I mentioned in my earlier post was actually spec'd by you and I am anxious to get it down the track with the new engine.