When you look at the performance of stock eliminator cams, stock lift with lots of duration,and before roller cams, is there a point where higher lift makes up for longer duration with respect to a relatively stock motor?

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How about this...for simplification... take a stock 1971 340 cam spec 462/473 with a twist of 320-330* of duration. How do I calculate how much more lift can I substitute and lower the duration and achieve the same results. Back in the late 60's and 70's they were referred as cheater cams. I recall that Cam Dynamics was doing cams like this. They were/went towards the new stock eliminator cam rules, stock lift and any duration, back then.

At least in the mid 70's when I ran my stocker - going through tech in 1975 at Englishtown - they checked lift, duration and overlap.

NHRA Tech used a degree wheel on the damper and tape around the damper to mark the opening and closing events.

Yes they were called cheater cams back then - why I don't know because they checked all the specs. Today they only care about lift.

I'm guessing the lobe had a fast acceleration ramp so at any point between the base circle and toe you had more valve opening but never exceeding max lift - so you were cheating compared to the standard cam rate.

Maybe you can clarify what you are actually trying to achieve - are you limited to some specification and if so why? There are a bunch of cams to choose from - why are you trying determine the trade offs - not being critical - just wondering why.

In my experience in the real world
as you said stockish engines on the street
lift unimportant--duration is the way to get it done on hyd cam street engines--as a first step--it simply works-- and is the governor when aiming to make more HP on a street stock type engine ( in addition to more compression up to pump gas limit) Lift on stock heads is chasing the last area to look IMO Lift tends to benefit more at higher RPMs that a street engine usually never sees
The ones section of Hi lift cams in the Comp book are aimed at engines with everything else dead on and to take last bit of advantage with really nice heads -- or at least let you THINK that is what is happening--it is all marketing--a street pump gas engine does not need all the latest theory and tricks -- Decent heads with sharp valve job--all the compression you can run with cam and fuel choice--correct intake a sharp carb and most importantly a correctly curved distributor is all you can do on a street engine --then you get the 511 CI big blocks that have it all done right and you can't stick it to the slick public pavement and a 340 Duster with a 4.10 gear smokes you so.........
Keep it simple folks--keep that loot in your jeans not under the hood

Cheater cams with that flat nose for lift rule--is the only way they can do it in that crazy class of a few folks--Those cams beat the S%#* out of the valve train and are just stupid to use unless you run in one of those classes In the end...drag racing has some very evolved stupid rules that street guys should never even look at

The world famous .509 cam was made so it was the max lift you could squeeze in on a STOCK 440--just add valve springs and go--NO topping of stock guides --changing seals etc so...they did consider it important to get all they could but really less lift and that same duration would get you 97% of what they were after I bet

I think the cheater cams went the other way. I had an old Cam Dynamics hydraulic cheater cam that was .470 lift but was advertised at 352/360 duration. I think they might have only checked duration above a certain lift, so low lift letting extra air/fuel in was flying under the radar.

When my friend first started running his gto in Stock, and it was kind of a dog, we were trying some cams.
After about the 5th cam, and not really seeing any noticeable improvements we decided to put the old street/strip solid lifter cam in the motor to see how it responded.
We wanted to know if there was something significant to be gained with the right cam, or if we were just chasing our tails.
The car picked up like .35 ET and 3-4mph with the "real" cam in it.
So, after seeing that, we continued on with our search for the right legal stocker cam.

I guess what I'm saying is, 99% of the time it's going to be pretty easy to beat some lift rule type cam by using a cam that does a better job of providing more area under the curve.
And it will probably be more reliable at the same time.

The duration numbers quoted came from lifter rise much less than .050".

I think NHRA started their duration checks back then at .001" lifter rise.

If I recall correctly the SAE specs for these motors that I saw used the same methodology.

I think you would agree no production engine actually had this kind of effective duration.

I had an older Cam Dynamics 'Stocker" cam for my 350 Buick. It would check legal for lift and duration in the '80s. Instead of looking egg shaped the lobes were almost rectangular. The idea was it opened the valve to full lift very quickly, held it at max lift longer, then slammed it shut. They were murder on valvesprings.

I still have an old smallblock TRW hydraulic cam that had a lot of duration and almost the stock lift which really worked nice in a 340,I didnt have any official time slips but it ran very close to a .562" solid CompCam that I replaced it with

I think that crabman173 focused on what I am trying to achieve ...."lift unimportant--duration is the way to get it done...", so a Mopar/Purple Stripe SB mechanical cam with .509 lift and a duration in the 280-300* range gives me a similar result. I had that Cam Dynamics stocker 340 cam in a Duster that eventually became more of a street car than a stocker in the 70's. 4.88 and a hemi style converter made for spirited driving and a great street racer. I have a legal 318-4 stocker motor that makes in the 345 + HP range. I'm aware of the requirements of good machining and assembly practices. I am always amazed how much power many small cubic engines can make. I'm also aware of the beating that these motors take. So I looking for that cam that can help make similar power while maintaining a single valve spring and the factory components with a 273-4 motor without beating it to death. Probably 4.88 gear and a 9" converter with a stock motor.

You should know that longer durations within a given lift contributes to steeper ramps. That requires more spring pressures. That's why some "Stockers" run 200+ seat and 400+ open!

I'm under the impression that there can also be big differences between cams with with the same "advertised" durations even though they have the same lift.

You can't.

Google "David Vizard cam duration vs lift" and see what you can find. Although not a direct comparison like you're looking for, he does have at least one example showing how a lower-lift/longer duration cam performs vs a high-lift/shorter duration cam with both making about the same peak HP.

There is no direct (linear) cross-over, and it's highly cylinder head-specific. The cylinder pressure curves of "high lift short duration" vs. "low lift long duration" will look completely different even with the same torque and power peak numbers.
A hemi or steep inclined stem axis (SBC 23°) unmasks the intake valve toward the cylinder centerline immediately.
A shallow wedge (B/RB & Buick 15°, Olds 6°, Cadillac 11°) doesn't and needs lift to clear the wall.

Depending on whom you read, one of 2 events is primary:
1. most authors: intake closing point ABDC, which has no relation to lift
2. Vizard (and Harold Brookshire?): intake opening point BTDC, which has no relation to lift

longer durations within a given lift contributes to steeper ramps
That's a design feature, not an engineering requirement. The ramp must be faster when the valve has less time to open.

are any of those profiles designed to toss the valve open, and close it smoothly?

I have heard that a valvetrain (pushrods?) can be "tuned" to loft the valve over the nose of the cam lobe far enough to be very much worth the trouble. I would asume that would be brutally hard on valvetrain parts!

Not sure if we're saying the same thing. I'm open to gaining a better perspective. But basically, unless I'm misunderstanding something, the longer the duration at a set lift, the less room there is left for the ramp, so it has to be more aggressive/steeper. That's where the exaggerated term "square lobes" come from. It doesn't look like one has a choice.

Anybody that was around class racing back in the 60-70's can recall the sound of the 'STOCK' cam, the only thing stock about them was the specs. Square lobes as Locomotion stated. Similar to running a flat tappet lifter on a roller cam, roller lifters weren't around at that time. Maybe that's where the roller idea came from.

I use to race a 1968 street hemi in NHRA stock back in the early 1970s, the first "cheater cam was a Clay Smith conventional lobe type solid lifter cam. The last legal 340 motor I built had a Isky round nose, AKA as a "square" nose cam that would check legal in the motor with the proper rocker arms on it I tested three different cams in that customers motors, the best performing cams was a Lunati with standard designed lobes, pyramid or pointy nose lobe cam. Both Iskys where square nose cams, one ground on a 107 LSA and the other one was on a 105 LSA where real peaky on the engine dyno, they made 10 HP more than the Lunati did but the Isky cams wouldn't make 400 HP until above 5500 RPM and would nose over real bad after 5900 RPM and be below 400 HP at 6100 RPM. The Lunati would make 400 HP at 5000 RPM peaking at 6000 RPM with 420 HP and make 400 HP at 7000 RPM That was back in the early 1990s
I think I ran 160 lbs on the seats and around 350 + lbs. opened. The Isky cams in that motor liked to be shifted at or lower than 6400 RPM, the Lunati liked to be shifted at or above 7000 RPM, it picked that car up around 2 MPH in the 1/4 mile also

The technology to vet cams to stock specs is 100 years old (how about duration @ .100", .200" and .300" - I have some of that data from 1940). Why do they allow it? Because the cam manufacturers: $$$.