Chicago Crew UnderBoss

iTrader: (1)

PREDATOR Z and Other big cubed N/A gurus, I am looking at getting a LS7 427 shortblock built for my 02 C5 Z06 and need the perfect street/strip cam that will make the most power N/A (no juice)throughout the entire rpm band and get my z06 down the 1/4 mile with stock 3.42s the fastest.

Will be going with either TRICK FLOW HEADS or L92 ported Heads (put leaninng towards TFS 225s) and will be running a ported fast 90 and making between 11:5 to 11:8 compression with a dynamic compression of 8:6 to 8:7 to 1. Car will be driven on the street a lot so it needs to be totally streetable but i certainly don't mind an aggressive 112 lsa/chop and need this baby to shine and run 10.5s all day down the 1320 (although it will live on the street the most and see some road racing tracks). Would like to hit 550rwhp and make crazy power and torque everywhere.

My own guesstimate based on my own reading here would be a 244/250, .629 lift on a 112 lsa (for the Trick Flows), and that is just a shot in the dark and want to get your objective opinions.

Thank you and have a GREAT EASTER!

BLKWS6

Whoever you get to build the motor would be the best person to discuss cam selection with. You want something matched to your combo to make the most out of it.

1936FordPU

iTrader: (3)

Let your engine builder spec the cam.

Patrick G

iTrader: (14)

Look at the cams that are putting big area under the curve for 346s, then compare it to the 408 and 427 cams and you'll begin to see some trends. Using your target compression ratio as an example:

346 cams tend to average 236/240 on a 110-111LSA

A 408 will want 10 more degrees of duration than a 346 and take 1 degree wider LSA (because of the longer stroke). Call it 246/250 111-112LSA

A 427 will want 13 more degrees of duration than a 346 but if it runs the same valve sizes as a 408, it will typically want a little lower LSA than a 408 because it's considered more under-valved. If the valve sizes go up with bore size the LSA will remain around the same as a 408.
Example 249/253 110-111LSA with smaller 408 valves or 111-112LSA with the valve appropriate for the large 4.125" bore.

Again, these are general approximations, but they get you into the ballpark. Specifics on head flow with the intake attached and exhaust configuration will sway these numbers around, but at least you should have a starting point.

Patrick G

iTrader: (14)

By the way, your title says max effort, yet you're asking for a street-driven cam with compromises.

A true max effort hydraulic roller cam for a 427 would be closer to 255/260 in duration.

No Juice

iTrader: (11)

Ask TPIS a sponsor, they have numerous 427's that all are in the +530rwhp range and are drive daily. Well when its not below freezing like today anyways.

Chicago Crew UnderBoss

iTrader: (1)

Your right, I am more interested in a cam that is going to make great power throughout the entire rpm band with a huge flat torque band and that can be street driven without rattling my teeth out, and not be a dog in the lower rpms, and still make great peak hp, as well as mid range and low end stop light to stop light torque (and have the power to run 10.5s at the track all day) assuming driving skills and proper traction.

Off the top of my head i am thinking something like a 244/250, .629lift on a 112 lsa (but that is just an educated guess).

wavrdr

iTrader: (1)

You could probably look into the TSP Giant....IIRC it's 248/254 on a 112 or there abouts....

I've been trying to well execute a good all around cam for my 402 for quite some time now.

I went with a 240/244 .609/.612 111+3

Good luck!

JL ws-6

iTrader: (50)

Alot will depend on what head you go with, there's a big difference in an l92 cam and a cam for the cathedral heads.

Off hand, something like a 244/250 in the 610ish lift, with an lsa in the 112 range would probably be a good starting point for a cathedral head, whereas the l92 would need something like a 244/256 with similar lift/lsa, due to the intake bias of the head.

Once you pick the heads, talk to your builder..... by far the best way to go about it.

Chicago Crew UnderBoss

iTrader: (1)

CAM EXPERTS, need to get one picked out quickly so please keep your choices flowing. RIght now, per my builder (LME), the leading canidate is 244/250, .649 lift on a 112 lsa. Not second guessing them they are the PROS (oh yeah going with Trick Flow 225s) just gathering more info based upon your guy's real life experiences also!

Stang's Bane

iTrader: (22)

I would trust LME. You are paying them a **** ton to build it, why not trust them.

Chicago Crew UnderBoss

iTrader: (1)

I do trust them 100% but its just my pain in the *** personality to always gather more information and look at all options before my final decision is made (when it comes to such big decisions such as the perfect cam for my dream motor).

GrannySShifting

iTrader: (10)

That first sentence is backwards is it not? If you lengthen the stroke on something, Ive always narrowed my LSA. Longer stroke, same head, makes it more cylinder head limited. More cubes, less head, needs more overlap to fill a cylinder

Next paragraphed you argued yourself back backwards... making it the right direction i think

Careful who and why you trust people. Just because they crank out a LOT of engines doesnt mean they are even half good at what they do. Im more worried about the guy that does ALOT of engines than the guy that only does a few.

Stang's Bane

iTrader: (22)

By increasing the duration and keeping the LSA, you have effectively increased the overlap, correct?? That is how I understand it, if not I have made a fool out of myself 1,236,756 times.....

GrannySShifting

iTrader: (10)

Yes you are but I always err away from increasing overlap by addnig valve timing and then widening LSA like he was mentioning. Im not saying he was right or wrong just he used the same logic to argue it one way for a 408 and another for a 427 kinda confusing to me

moderate rpm range (7000 or so) I always tend to pick up overlap from tightening LSA in a case like that first then add duration everywhere. If the cam is long by wide and advanced in the motor, I normally find it makes more middle tightening it up and sometimes shortening up the duration if the heads dont suck

slow95z

iTrader: (33)

if you want a good bottom end cam thats good on the street go for something mild like i did. sure i could make more power up top with a bigger cam but i love the fact that you cant tell my car from a stock LS1.

JakeFusion

iTrader: (7)

Cam Motion 257/266 .646"/.622" 113+0 LSA Camshaft for real max effort.

Patrick G

iTrader: (14)

First sentence was not backwards...let me explain:

A 346 running pump gas friendly compression running a plastic intake manifold has shown best performance in the 236/240 on a 110-111LSA range. If we can agree on that in principle, then let's move on to the part where I lost you.

A 408 (with larger valves to accomodate the larger bore) will typically want 1 degree wider LSA to account for its longer 4" stroke. Here's why. The longer stroke increases piston dwell time at TDC, making the engine act like it's got more overlap, thus call for a little bit wider LSA than a 346 with the 3.622" stroke. So if you're wondering where I came up with that figure, that's where.

But if you move up to a 427 and don't further increase valve and port size to accomodate the larger bore and increased displacement, the engine is now considered more "undervalved" compared to a 408 and will need a narrower LSA. See, you haven't change the stroke, just the displacement with a bore increase.

GrannySShifting, you've been a well respected member of this board for years and I've always valued your tech. Why you've decided to take shots at my ability to spec custom cams puzzles me. Just because I turn wrenches as a hobby and not a profession does not diminish my knowledge or real world experience when it comes to these LS1s. I've been messing with them constantly from a racing and R&D standpoint since '98. Just because I don't go to the race track every week like I did a few years ago doesn't mean I've lost my edge. On the contrary. Since I've gotten EFI Live and 24/7 access to a Mustang chassis dyno, my combinations have gotten more and more refined over the past 2 years. I'm sure you can say the same thing about your efforts. Experience counts for a lot.

1997bird

iTrader: (2)

Just a cam that I have been playing with on my Dynomation program.

294/302 Adv dur.
256/262 @0.050" dur
113+2
.629"/.629" lift with 1.7 ratio rockers

71CamaroLS1

If I might throw something out here that might dampen the fire - or might blow it up - engines really don't give a damn about LSA, *per se*. LSA is a convenience for the cam grinder, but from an engine performance standpoint all LSA does is change the relationships between the IVO/IVC and EVO/EVC events. (Guide to acronyms: I = intake, E = exhaust, V = valve, O = open, C = close, e.g. IVC = intake valve close). LSA is the angular separation between the intake lobe and the exhaust lobe. So if you narrow LSA, what will happen is that IVO and IVC will happen earlier relative to EVO and EVC. If you reduce the intake centerline (ICL) at the same time, the IVO/IVC and EVO/EVC events will happen earlier relative to *crankshaft position*. It is the relationship between IVO/IVC events and EVO/EVC events, and the timing of those events relative to crankshaft position, that really matter to the engine. I know Patrick G and GrannySS know these things, but it's worth reviewing it for all those who might be following this thread and just wanting to know "what LSA should I use!" without knowing what LSA really means.

Now, relative to the discussion about stroke and displacement versus LSA - this gets very complicated indeed. First off, recognize that the velocity of the piston down the bore reaches its maximum before 90 degrees past TDC (top dead center). Just draw some pictures of the crank/rod/piston configuration at various angles if you don't believe this. Or look at this link: http://www.epi-eng.com/ET-PistnVelAccel.htm for an example. Now, notice that real world cams don't reach maximum intake lift until *after* 90 degrees past TDC - for instance, if your ICL is 110, your intake valve reaches maximum lift at 110 degrees after TDC. So, at the point where the piston is "sucking" the hardest on the intake stroke, the intake valve is not yet all the way open. This creates performance problems, particularly on a 2-valve engine, because 2 valve engines are short on what is called "curtain area", which means, among other things, that they need the valves open a long way to flow well. This is what Patrick means when he talks about "under-valved".

Now, when you increase displacement, for a given head, the engine does indeed become even more "under valved". This would suggest that you open the intake valve earlier, which means in cam grinder terms some combination of more intake duration and/or earlier ICL. There is another factor associated with greater stroke - if you keep rod length the same, but increase stroke, max piston velocity occurs earlier - even more reason to open the intake valve earlier. But to counter those two factors: the increased displacement will create increased air velocity for a given head/intake. This increased air velocity means increased air momentum in the intake tract, which means that the cylinder will continue to fill for longer after the piston begins to move up the bore in the compression stroke. To take advantage of this effect, we want to close the intake valve later.

Completely ignoring the exhaust side of things for a moment, increasing stroke and displacement means that we want earlier IVO and later IVC (meaning, for sure, more duration). *How much earlier and how much later* will determine how the LSA changes when we call the cam grinder - if the "opening earlier" effect is greater than the "closing later" effect, we will want less LSA, and if the reverse is true, we will want more LSA. There are some "general rules" derived from real world experience - meaning, often, "experience with 1st gen small block Chevys" - that suggest increasing displacement will call for IVO/IVC tradeoffs that lead to smaller LSA specs. But there are a ton of variables ignored in such a "general rule", and ultimately there is no substitute for real world experience, ideally informed by analysis from advanced engine simulation programs like Dynomation.

The exhaust side of things changes with more displacement too, and further affects EVO and EVC, and thus LSA. No time to comment on that now, will post more later.

Edit:

OK, now for the exhaust side. Exhaust gasses have very large volume, and are under very high pressure. When considering exhaust valve open (EVO), we are balancing two things. First, we want to open the exhaust value early, so as to let the high pressure exhaust gasses escape before the piston starts back up the bore (bottom dead center, or BDC). High pressure after BDC works against us, and robs power. So we want most of the exhaust pressure dissipated before BDC. This exhaust pressure dissipation is known as exhaust "blowdown". On the other hand, we don't want to dissipate exhaust pressure too soon before BDC, because that pressure is exactly what the engine uses to create power (that pressure, in engineering terms, is known as Brake Mean Effective Pressure, or BMEP). The optimum point for opening the exhaust value depends on the "blowdown" event time, and therefore is dependent on desired RPM range.

Incidentally, exhaust "blowdown" is mostly complete before the exhaust valve opens very far at all. Thus, very low level exhaust flow - below .100 inch - is very important in cylinder head design.

Now, the piston starts up the bore for the "exhaust stroke". There is still quite a bit of exhaust gas volume in the cylinder at this point, and the goal is to minimize the pressure on top of the piston as the piston exhausts the rest of this gas, since any pressure on the piston at this point just steals power from us. So we want max exhaust flow when the piston is moving most quickly - when the piston is past 90 degrees after bottom dead center (ABDC). Once again, if the rod length length is short compared to the stroke length, the point where the piston moves most quickly will be closer to top dead center (TDC) - which says that we want max exhaust lift closer to TDC, which says that we want less LSA (ignoring intake considerations, for the moment).

Finally, we reach the point where the piston nears TDC on the exhaust stroke, and the intake valve opens, beginning the overlap zone. Overlap is very important to a high performance engine, because overlap uses energy from the exhaust system to help move fuel/air through the intake system - but only if your exhaust (headers) and intake (manifold) are tuned to help each other in your desired RPM range. Increasing displacement means that you might want to increase overlap more than it is already increased by earlier IVO (see above), and therefore close the exhaust later (later EVC). The balance of earlier EVO versus later EVC will determine whether LSA is smaller or larger, assuming constant IVC/IVO. The details of how overlap works to create what David Vizard calls a "5 cycle engine" are beyond a simple forum post - for those with appetite for a moderately technical description, download the users manual for Dynomation, and read the section called "Wave-Dynamics Analysis" beginning page 231: http://www.proracingsim.com/download...sersManual.pdf . Unfortunately, a 44MB download, but well worth it for those seeking a shortcut to graduate-degree level knowledge of high-performance engine behavior.

If all of the above sounds complicated, it is. And it's further complicated by the behavior of your intake and exhaust systems - in fact, ideally, your intake, headers, cylinder head, compression ratio, rod/stroke ratio, and cam should all be designed together for your ideal balance of displacement, desired power, RPM range, idle and part throttle drivability, etc. But headers, intake, heads, CR, rod/stroke are all much harder to change than cam, which is why we have so many "perfect cam" threads!

None of the above is intended to suggest that I know more than the experienced gurus about cam selection for LS series motors that the other gentlemen on this thread - indeed, I know far less. But hopefully this is a guide to asking intelligent questions from your cam designer - "why close the intake later, or open it sooner/later" or "why open exhaust sooner" or "what is the optimum compression for your IVC" or "does the RPM range of your cam match my intake" or "do I need an earlier EVO considering I'm using stock exhaust" or other such pertinent questions. And then let the cam specs - duration, LSA, ICL - be determined by the answers to those questions, rather than allowing those specs to be goals in themselves.