Vizard's method of selecting LSA

His most recent work on the BBC basically attacks everything we know about cam selection.
It appears to be relevant to the aftermarket 24° inclined intake valve heads which have huge flow, including .200" flow.
The idea is very simple: if the head has good flow at very high lift, use a really big rocker ratio (like 1.8:1 or more) but a very short cam and (critical) really narrow LSA - like 104.
Result: big power without high RPM.

Anyone read it?

Link?

It's a book.

Short duration but open the valves as fast and as high as you can? Sounds like a roller cam...

Won't 104 LSA make it idle like crap? (although some people actually select cams based on the worst possible idle)

the over lap on narrow LSA cams helps pull in the next charge..
the wide LSA cams have very little over lap... thats why N/A
engines tend to like the narrow LSA... any pressurized engine
likes the wide LSA so it doesnt blow it out the pipe

The narrow LSA cam probably has close to the same "window" at overlap for proper scavenging. Faster valve opening and closing rates would allow a few degrees less total overlap time. Later opening of the exhaust would keep pressure on the piston longer but that benefit decreases as compression ratio increases. The early intake closing must help build torque and the real high rocker ratios must increase the mid lift duration numbers enough to make it all work.

He also loves a low installed ICL. Read a lot of his stuff. Hes done a lot of actual testing on the dyno vs just theorizing about things.

One of the reasons the Old MP .590 cam hangs with most of the New modern cams is because of its tight 106 LSA.

Vizard Proved many years ago that the overlap exhaust pulse pull was stronger then the intake strokes atmospherics pulse pull/push.

Your post shows hes still focusing in that direction, for NA.

Jim @ Racer Brown told me once about the intake valve "you'll never get it open fast enough"

i'v read his writings also. seems every cam grinder i'v talked to is never on the same page as vizard with the narrow LSA suggestions. I followed his scale on picking the correct LSA for my 408 and it recommended something like 104* LSA and in at 100*. never tried, maybe it does work.

I just ordered a new cam for my 514 dyno mule with 112 LSA. That is what the last cam had and the power curve seemed about right so I stayed with it. New cam is 282/288 at 0.050 with .890 lift. Should have it on the dyno in a month or two.

I do have some old Super Stock roller cams with narrow lobe angles. One old Crower cam is 106. I've never run that cam but I'm sure it worked well in the right combo. The Ultradyne roller in my 406 motor is ground on 108. That cam makes great power.

I've had some dyno and cam guys say that my 112 LSA is
loosing a lot of power vs the tighter LSA, like a 106..
I have a 105 in my 416 and I installed it at 105.. because
I didnt want to increase the torque and higher which would
have increased the stall point on my already 5000 stall conv
for the street.. oh and the trans has OD so the slippage would
even be higher than the 9% in OD

If the head flows that much air and has a good exhaust port, why would you possibly want that much overlap. That makes zero sense and is exactly the opposite of the most powerful N/A motors currently out there. Theory is great.......build it, put it in a race car and PROVE it

Monte

Monte, I am betting the cams that work don't increase the overlap event. If my theorizing is right, then the tight LSA with less duration on both lobes makes the overlap event shorter or close to the same but with higher lift to compensate, providing the same "window" for scavenging. Of the three cams I have for my motor, the overlap period is very close to the same, with the main change being the exhaust opening point.
A motor like mine may respond to this because I have 80 percent exhaust to intake flow, and might be able to cut the exhaust duration I run way back for that reason. An all out motor sacrifices exhaust flow percent to allow for a bigger intake valve, and makes it up with exhaust early opening and duration. And like you said, put a cam in and find out. I plan on that with the next tear down. My current cam,
282 296 112lsa duration .775 lift int, .685 ex. .200 numbers 203 ,206
time card at 108
intake opens 33 close 69
ex opens 84 close 32 overlap 65 degrees

New cam?
278 278 106 in at 106- switch from 1.5 to 1.7 rockers
intake opens 33 closes 65
exhaust opens 65 closes 33. overlap 66 degrees.
The big difference is the exhaust opening, with 18 degrees later event on the exhaust of the narrow cam. The intake close on the narrow cam is 4 degrees earlier. The high ratio rockers will increase the .050 and mid lift duration and compensate some for the overall shorter duration.
My biggest concern is not having a big enough cam core for the lift rates I would like to run. Also I still have stainless intake valves, which don't help. The one thing in my favor is I want to keep the shift points the same, 7100.

I have not read the article, or book. But I do get the opportunity to be around some pretty state of the art NA stuff and can tell you this is as Monte said pretty contrary to what those engines are using. In fact almost diametrically opposed to what I've seen. This is Comp, SS and NA 10.5 stuff I have seen or been around. Maybe the tides are changing but the stuff I have been around is pretty cutting edge front running stuff.

I would like to see some testing on a more typical Mopar bracket race motor, like Andy's 514 mule. He does have a super valve train system but still would be more applicable to most of us on this board.

FWIW, my 540 has a 112 LSA cam from BEST Machine, 279/290 at 0.050", 0.777/0.744" (1.65 T&D) with Indy 440-1 CNC-345

Havent read the book, but agree with Gregs description as to what vizard "might" be doing.

In the above example overlap only increased by 1°

In Polys sentence it stated "Critical' on shortening duration while using the tighter lobe sep. Also in relation to this one type head only.


We really don't have enough info to draw real conclusions.

It started out w/ the Vizard (pronounced "V-eye-zerd") article published in PHR back in 2006 or 2007: http://www.hotrod.com/how-to/engine/0607phr-camshaft-basics/

His approach is to drive the LSA selection based on a variety of factors, but the primary two are (a) how much intake valve area there is to support the cubic inches being fed and (b) the acceptable amount of overlap based on the application.

Then he factors in LSA adjustments from his baseline results according to other characteristics, such as compression ratio and cylinder head design (valve angle / canting). More CR = wider LSA; better heads = wider LSA, etc.

He's since refined the details some over the years as can be seen in his latest series of books, but the concept hasn't changed. He used to (and may still?) offer a service to spec "optimal" camshaft specs for any given combination through the use of his proprietary camshaft design software. The linked article and what he's published since then in his books are supposedly based on the core logic of his software.

I have no first-hand knowledge of how effective his approach is, but can throw a few comments out as "food for thought".
1. I paid for his camshaft selection service many years ago for an old combination I was running and thought the suggested LSA was extremely narrow (102 or 104 IIRC, installed +4).

2. I plugged his specs into my Engine Analyzer Pro software vs. the cam I ended up using and found the Vizard-spec cam showed very good peak torque, but not much more than the actual cam I used, nor did it predict it would make power out to the necessary peak RPM I expected to run. The "real" cam was comparable duration, but on a 108 LSA installed +4.

3. The chart-based approach in his article did NOT give the same specs as the software, so IMO something got "lost in translation" trying to create his "Everyman's guide to cam selection" article.

Funny thing... go back through the Engine Master Challenge write-ups on some of the big-name engine builder's top-placing entries over the last five to ten years and look at the cam specs they listed. A LOT of them look as if they could have been products of the Vizard approach, w/ LSAs in the 100-104 range and advanced anywhere from 4 to 6 degrees on top of that.

However, since the EMC is RPM-constrained and uses that "best average" approach to scoring, something intended for a higher & narrower working RPM range would (should?) result in a different set of specs.

Peak numbers on a Dyno are well and good. Accelerating a racecar down a track is a different matter all together. Which is why while there may be a peak power advantage?!? to what he is getting at. From what I have seen from some really smart folks doing work on some very fast cars is very different. However I am no expert for sure, just listen when people designing and building these things that are out there performing speak.

I wonder how many of those EMC(something I don't really follow either)engines perform in the real world. Or do or have any of them ever really been put to the test so to speak?

Super Stock cams are completely different than most people want to understand. I've used so many different grinders and lobes and have come to one conclusion, short duration, fast ramp, really high lobe lift cams work. Cylinder head flow and valve placement will determine the lobe separation from 104 to 113. And that's all I have to say about that.

IMO, the EMC engines are all about the wide spectrum performance build. Not about getting the car down the track the fastest.

I would like to see what "Window of HP" Vizard is working with.

I don't think too many of the EMC entries ever make it into a real car. One of the few I did hear about is a member here that participated with a SBM combination. I wish I could remember his name, but he did post after the EMC event how the engine did on the track and it seemed to run pretty strong.

Sort of how I have always picked cams.

For a street car pick the overlap for the desired idle, pick intake closeing point based on compression, exhaust opening as late as possible to get the desired lift (as much as possible).

For a more race oriented engine I pick the overlap to get the most HP in the desired RPM range, intake closing based on compression and RPM range, as much lift as possible...

Other things play into it a little like not lifting it way past where the flow tappers off...

if its purple, I slide it in

ummmm......

I have to wonder about the LSA thing, according to his chart I should be running a 103 LSA, which seems a bit ridiculous. But I will say I'm working on tuning my car, and maybe I still have a long ways to go, but with Stealth heads and 252/260 @ .050 on a 110 LSA I'm not really impressed. I've been in cars with 509 cams and pocket ported 906s that feel like they would blow this thing away. I'm beginning to wonder if I should have gone with a tighter LSA.

The LSA thing is a very cylinder head dependent thing IMO. There is no blanket statement than can be made, no one "magic bumpstick". Even comparing what works on a canted valve head to an inline wedge is apples to oranges..Just saying don't everyone jump off the cliff or sip the koolaid at once

I am running a EMC small block and very happy with the results so far. I think it will be even quicker when I get all the bugs worked out. It is a pump gas 394 ci.

Overlap changes with duration regardless of LCA. The more duration the wider the LCA needs to be to maintain the same overlap. Cutting edge motors run more duration than the street stuff, thus many have wide LCA. LCA is just a function of the correct closing point for the exhaust and opening point of the intake. When duration and overlap are correctly selected LCA is just a number.
Doug

Quote from Herb McCandless around 1983....."Don't get hung up on duration,,,put all the lift in it you can get" I know I have gone with different ideas since,,,but,,,it seemed to work back then.

Nothing really new here from Vizard IMO, Myself and several others right here on Moparts I believe have been building stroker motors for years with tighter spreads and earlier (100-102) ICLs....and if you look back it's pretty standard practice on most of the EMC style builds that try to get the most power out of their cam/head combos with either rules-limited or self-imposed) RPM ceilings. I think back when I was doing it with Strokers it was to offset the comparatively poor rod ratios and high piston speeds by using up as much of good head flow power potential in as few peak RPM as possible. The EMC's came along judging primarily on the highest "streetable" average 2500-6500 torque curves, so the cam phasing philosophy to get there really seemed to go hand-in-hand, IMO Where the EMC's take it to the extreme is with spring killing lifts and higher rocker ratios than most people would be comfortable running in a "real world" street car. But I concentrate mostly on having great to extremely great head flows in the more moderate, real streetable .300-650" lift ranges and not chase the .750-up lifts. It seems Davids writing at the more extreme limits of such a build, but the principals are essentially the same, and the extreme builds (1.8:1 rockers, etc) will generally have the best brag rights HP numbers too, which I suppose sells more books. (which is what he's probably after).

I think he's just writing about (but hopefully not trying to claim as his own) a trend that's been out there for quite a long while for anyone who cared to see it.