My thinking on LSA is the wider you put the lobes the less bottom end that motor will have, the closer thier ground on the more bottom end and less upper RPM power it have That is based on stock type Mopar production heads, bigger heads more LSA, smaller heads usually works better with closer LSA on my stuff most of the time

Just seems to work the best that way. Some of the EMC guys went with 100 or even lower while some of the really high power engines like Pro Stock have gone later than 112, but typical street/strip V8 stuff is usually between 104 and 110.

Depends on the air you are moving, ie the cylinder head. The reason most "old school" Mopars grinds are short, is because the heads SUCK, especially on the exhaust side. Later model and more modern high flowing heads with really good exhaust flow will want a wider LSA. Thinking wider LSAs are for power adder motors and kill bottom end is frankly 70s thinking.

I wouldn't put a whole lot of stock in what EMC guys do either. That competition and they way they test those motors has little to do with "real world" performance. What works great on the dyno for that contest, MANY times is not what would make a car go down the track the quickest

Because that's the area that works the best. 112 ICL is stretching it IMO. Even comp cams recommends around 4* advanced from their normal 110 LSA cams. Meaning 106* ICL

The tech reason why, is the piston reaches max speed between 72* to 78* ATDC where peak air demand occurs, depending on rod ratio.

Be nice to have the Full lift ICL there. But cant do that, because we need duration too. Cant lift the intake valves that soon and get them up to max lift. Hence it occurs Later then the desired Max piston speed event.

We also have to deal with overlap and we also want that event occurring around TDC to take advantage of the exhaust pulse pull cycle event thats very important.

So Everythings a compromise of things tested over many years. We get to enjoy the fruits of labor and testing of times past.

IMO, some of the newer cams don't have anything to offer except slightly faster ramps. The Centerlines and LSA have been figured out long ago.

Gotta disagree with you regards wide cams not killing bottom end in N/A deals.
I had a well scienced out combo that ran mid 10's at the time with a 107 LSA cam that was Specced by who I consider to be a sharp guy on cams.
Another such " guru" who was familiar with my combo suggested running a cam of his choosing. It was on a 112. Try as I might, the car was numb out of the gate with the 112, It was off so much that it couldn't get closer that a full tenth away from the 107 deal.
Same everything except cams. Nothing different. 3400 pound smallblck without a ton of compression( under 12 to 1).
I knew( and I am not very smart) that in a typical bracket deal like I had without a lot of compression, wide kills.The wide deal just bled off squeeze.
In fairness to the 112, it ran almost the same mph, that was real close. Big difference in 60 foot though, car just couldn't overcome that and the first 1/3 of the track to catch up to the narrower cam.

Funny we are NA with a 118, car 60's in the low 1.teens on a TRUE 10.5 tire and is only 400" SB at 2800lbs. So apparently it makes enough steam to get out of its own way. My old PS piece had a 118lsa and my current 604 has a 118 and makes plenty of power down low. I think many here try stuff and expect one change to show a gain. It is an overall combo of parts that make or break combos, not a magic camshaft. I agree with Monte that wide LSA in an NA deal is current thinking.....

Al, what RPM does that motor start at against the converter and what RPM does it get shifted at
My thinking on what is high RPM starts at 7500 RPM or above and gets shifted at or above 8500 RPM

The NA 10.5 deal is indeed a high RPM deal. We shift it at 8800,9200,9300 respectively. The converter is getting closer but currently stalls about 8300.

The Predator makes peak power at 7200 with a 118lsa camshaft. The ole PS motor made peak at 8800 with a 120. I have been using wide LSA stuff for years.

The Pontiac guys have been doing it for a very very long time. Pretty much where I first saw it making power, and those old Pontiacs couldn't or at least should not be above 6500. Back in my speed shop days I was amazed how many of their cams had 114-116 LSA. I think you would be hard pressed to find a shelf piece UNDER 110 and there are plenty over 114. Where I first started to wonder what all that stuff meant, I mean every Mopar cam I looked at was on a 108 or less back then. I was young and dumb back then. Now old and dumb. But it got me started on the path I am on now and have been for a long time. I don't buy that a wide LSA will hurt and engine down low. To many other factors in play there for sure. IMO as pointed out I think narrow LSA is old school thinking..

I am giving my cam a chance at n/a with a 112 lsa in at 109 ISL 260/269 @ .050 9.5cr on a 446

I'm guessing you were using heads that were less than great? Maybe you missed the variable Monte mentioned about the better the exhaust port the more wider LSA will help

After reading all the posts, the one thing I see missing is guys don't look at the true effect of the longer exhaust duration combined with wide lsa's.
If I did the math right, a 284 int 284 ex at 108 lsa installed at 108 has the following events
int open 34* BTDC
Int close 70* ABDC
Ex open 70* BBDC
Ex close 34*ATDC
Total overlap is 68*
A 284 int 300 ex on a 112 lsa in at 108 has the following events

int open 34*BTDC
Int close 70* ABDC
Ex open 86* BBDC
Ex close 34*ATDC
Total overlap is the same 68*.
The only event at .050 that moved is the exhaust opening. It is now 16 degrees earlier

very interesting topic and answers. but the thing that confuses me the most, and has since i believe comp started it, is the
'x* advance built in". for the life of me, i can't seem to get it through my thick head what that is supposed to accomplish, given a person degrees in [or really should no matter the circumstances] the cam of choice. is this only a marketing gimmick for those that only line up the dots ? smack my old idiot head around 'till i get it through my noggin before i croak.

Maybe that is where the events work best on average? For that reason, it would make sense. If the cam runs better advanced, then ground that way it has a lot better chance of being in right on the first try, saving Joe average some work.

What compression? I was under 12 to 1. Bet you were not

Good W5's on a mild mid 10 flat tappet combo as I stated. These heads were good enough to go 140 mph in a 3220 pound car a while back. Much different combo obviously.
Dwayne Porter did the 107 cam. Scott Brown the 112 cam( knowing exactly the 107 specs and all the combo specifics. The 112 was flat a dog on a " low" compression motor. It was a full tenth off in ET. That's a bunch. I told Scott I bet it would slow the car down.

Let me rephrase my question. Does rod ratio affect the cams intake centerline?
Looking at how the rod ratio changes piston acceleration and dwell times around BDC more than dwell times at TDC, would the rod ratio influence where the intake centerline should be?

I'm not talking about LSA, or overlap, just intake centerline.

I have heard a lot of misinformation on rod length, the piston still travels the same distance up and down no matter what the rod length is, correct
I don't believe the rod length affects cam timing, maybe the rod bearing clearances do
I have notice on some RB/B motors with stock rods and loose(.003+) rod bearing clearances that the piston does seem to take longer to get from 2 degrees BTDC to 2 degrees ATDC when degreeing cams
On the last stroker motor I assembled last year, 4.25 stroke with a 7.100 long rod and .0027 oil clearances, it seemed to me that the time at TDC on the piston was shorter than what I normally see, hence the rod bearing clerance affect comment

I can go on and on. I have been using wide LSA stuff since the late 90's with plenty of success. In street and race stuff. Our BB Camaro has a 114 and is a street car that runs 9's on pump gas at 3600+lbs with a tad over 9-1 compression. My Belvedere was 11.2-1 and had a 116 went mid 10's on pump gas at 3700lbs. My Valiant was on a 117, the Duster was a 114, with iron heads. As I say I can go on. All of the race motors had 13-1 or more compression of course. Its all about the combination not one magic part. For me wider has been better.

As for rod length. It don't matter, within reason. Get the stroke you want, the piston design you are happy with and order the rod accordingly.

When I talked to Rod at Isky about grinding my roller, he said the exhaust system or lack there of also influences the centerline needs based on backpressure............

Would that be the exhaust centerline then?

Here is a hypothetical, a 4" stroke engine, one with 5.5" rods and one with 7.5" rods, and duration measured from when the piston is 1" from the bottom or or less through BDC, the engine with the shorter rods takes nearly 5-6 degrees more rotation (time).

I know the rod lengths are silly, when you plug real rod length differences of maybe 0.5" the changes are much smaller, like 2 degrees comparing a 6.5" rod to a 7" rod. FWIW, this 1" from BDC (distance just used for comparison of dwell times) or 3/4 stroke point starts around 111 to 112 degrees through BDC and 248 to 249 crank degrees, so the shorter rod "dwells" through the lower 1/4 stroke length 38 degrees vs the longer rods 36 degrees.

Just curious if using the same cam in basically the same engine, except with different rod ratios, if the installed centerline should stay the same or move slightly because of the different amounts of time the piston dwells around BDC?