0.200 lobe lift duration questions

[JodyB]

I have an honest question guys.
Given a 383 sbc with a valve lift limit of .650, i'd be looking to improve intake port flow in the 300-650 lift range. Making sure the port didnt back up at higher vacuum depression. I might even try to kill some flow below 200 valve lift to fight reversion.
I start looking into camshaft valve events. I have 1.5 rockers, and it occurs to me that the .300 up valve lift intake port numbers I'm chasing start at 0.200 lobe lift. Again, 0.200 cam lobe lift with my 1.5 rockers equals 0.300 valve lift.
Could you then look at the 0.200 duration and lift area vs intake port flow as an idicator of potential hp?
In this example, is 0.200 lobe lift duration/area directly linked to 0.300 up intake valve lift flow?
Do advertised duration and 0.050 duration become secondary events or products of available valvespring, valvetrain weight, and rpm required?

[JodyB]

A long, long time ago, uninformed/ignorant folks would tell you a .450 lift cam in a sbc was a hot street cam. A .500 lift cam was full race. Magazines (rhs and comp) then introduced seat duration as the way to generalise cams. Shortly afterwards, 0.050 duration became the method preached by magazines for the uninformed to compare cams. Next, the "fastest" cam in degrees between advertised duration and 0.050 became the best thing ever in magazines.
Now, other than a yardstick to compare other manufacturers advertised 0.050 duration numbers, Where does that 0.050 number get you?
Your 0.050 camshaft lobe lift numbers are 0.075 valve lift.Nothing is happening there.

[pastry_chef]

I recommend you read some of Mike Jones / CamKing previous posts.

Look at requirements at the valve and then work backwards, true valve seat timing is very important.
Also please list details of your engine combination and goals here.

bore, stroke, rod, valve sizes, port flow / port CSA, desired RPM, compression ratio. What style of cam, solid roller?

[JodyB]

Some of Mr David Vizard's research.

[JodyB]

Given Mr David Vizard's research, tell me why advertised duration and 0.050 seem to be nothing more than details? Actual cylinder filling seems to happen in a totally different valve lift/ duration area .
I am asking these questions because i am ignorant. I do not know the answer.
I am asking because I am looking at data produced by some of our best, and i am searching.

[JodyB]

Given a comp 3024 thumpr intake lobe
291 adv, 235 @0.050 , 150@0.200 .521 lift with 1.5 rocker. Then..

A Comp 3316 extreme energy lobe
288 adv, 236@50, 157@0.200, 521 lift with 1.5 rocker.

The potential hp difference will mostly be the extra 7 degrees durationat .200.

[JodyB]

Should we be focusing on 0.200 duration and area?

[digger]

Clearly it's the net effect of the entire valve lift curve that matters, so no a single duration value wont ever tell you everything or correlate 100% of the time.

[CamKing]

Actual seat duration controls where the engine makes peak HP.
Area under the curve, controls how much HP it makes.
.020", .050", .200", they're just points on a curve.
They're like pieces of a jigsaw puzzle. You can't get the full picture, with just a few pieces.

[hoffman900]

Actual seat duration controls where the engine makes peak HP.
Area under the curve, controls how much HP it makes.
.020", .050", .200", they're just points on a curve.
They're like pieces of a jigsaw puzzle. You can't get the full picture, with just a few pieces.

I never understood why people don't look at duration at zero lash to determine these things. Anything beyond that is an open valve.

[digger]

Actual seat duration controls where the engine makes peak HP.
Area under the curve, controls how much HP it makes.
.020", .050", .200", they're just points on a curve.
They're like pieces of a jigsaw puzzle. You can't get the full picture, with just a few pieces.

I never understood why people don't look at duration at zero lash to determine these things. Anything beyond that is an open valve.

Why would you look at duration at zero lash ? You’d look at duration at valve with actual lash

[CamKing]

I never understood why people don't look at duration at zero lash to determine these things. Anything beyond that is an open valve.

Why would you look at duration at zero lash ? You’d look at duration at valve with actual lash

I think he meant zero lift(at the lash point)

[hoffman900]

I never understood why people don't look at duration at zero lash to determine these things. Anything beyond that is an open valve.

Why would you look at duration at zero lash ? You’d look at duration at valve with actual lash

I think he meant zero lift(at the lash point)

I did. Thanks, Mike.

[JodyB]

Actual seat duration controls where the engine makes peak HP.
Area under the curve, controls how much HP it makes.
.020", .050", .200", they're just points on a curve.
They're like pieces of a jigsaw puzzle. You can't get the full picture, with just a few pieces.

Sir, i am here to learn. Thankyou for contributing. I will ask a question though. If i compare a hyd flat tappet 350hp327 cam with 291 advertised duration and 222@50 to a comp 292 adv, 244@50 hyd flat tappet, can conclusions could be drawn to peak hp rpm from seat duration?

[CamKing]

Actual seat duration controls where the engine makes peak HP.
Area under the curve, controls how much HP it makes.
.020", .050", .200", they're just points on a curve.
They're like pieces of a jigsaw puzzle. You can't get the full picture, with just a few pieces.

Sir, i am here to learn. Thankyou for contributing. I will ask a question though. If i compare a hyd flat tappet 350hp327 cam with 291 advertised duration and 222@50 to a comp 292 adv, 244@50 hyd flat tappet, can conclusions could be drawn to peak hp rpm from seat duration?

"Advertised" duration, and "Seat" Duration are not the same thing.
Seat duration, is the actual opening and closing points of the valve.
Advertised duration can be wherever the cam company wants to measure it.