[rumair]

lee- sorry to hear about your trouble and that you seem to be giving up on the V's. i hope the new setup works well and you see the results you've been chasing for so long. keep the faith, your hard work will eventually pay off.

[Tom Vaught]

I told Lee that Marty made 1600 hp and 1400+ lb/ft of torque with "D-port" heads. He went 7.40s skipping 2nd gear at Norwalk.

Lee wants to run Mid 8s.

What am I missing here? That is ONE SECOND difference in the performance requirement. With a decent head it should be a minimal effort and cost deal.

Tom Vaught

ps ALL of the stuff lee had for the Ram Air V engine was "first cabin"
stuff. The Ford Tunnel Ports heads had the same issues with some of them cracking and leaking water years ago.

[johnta1]

anyone is interested in a complete ram air 5 topend for an alchohol steup with blower cam, headers for a stock frame rail 70 bird, complete heads ready to bolt on and a sheet metal custom injected intake with rails

gregsgto probably would have been interested in this, especially the headers.
He had a custom set made.

[455-4+1]

Brian

I dont want to list peak numbers as I am involved in heads up class racing
Appart from over 280 at 0.500" already mentioned to get you in the ball park

They were flowing more at .600 than .500
They were flowing more at .700 than at .600
After 0.700 they did level off but were still flowing more at .775"

Thats along way from the .550 you mentioned for "any D-port, ported or otherwise"
Sorry I cant offer more, just wanted to point out that not all ported D-ports stop at .550"

Think about lift vs duration and the time a valve spends at a certain flow rate over the whole intake cycle.

Also remember (obviuosly) that the induction cycle isnt a steady state flow on a valve held open at a pre determined lift in a static manor (ie flow bench)

On an intake cycle we cannot "crank up" the cubes to create a certain depression accross the port at any lift as you can with a bench

[Brian Baker]

Originally Posted by 455-4+1

Brian

I dont want to list peak numbers as I am involved in heads up class racing
Appart from over 280 at 0.500" already mentioned to get you in the ball park

They were flowing more at .600 than .500
They were flowing more at .700 than at .600
After 0.700 they did level off but were still flowing more at .775"

Thats along way from the .550 you mentioned for "any D-port, ported or otherwise"
Sorry I cant offer more, just wanted to point out that not all ported D-ports stop at .550"

Think about lift vs duration and the time a valve spends at a certain flow rate over the whole intake cycle.

Also remember (obviuosly) that the induction cycle isnt a steady state flow on a valve held open at a pre determined lift in a static manor (ie flow bench)

On an intake cycle we cannot "crank up" the cubes to create a certain depression accross the port at any lift as you can with a bench

I never mentioned .550"...I mentioned .650". Regardless of whatever the benchmark is however, the same question can be applied to any head. Even with a roller cam, the valve opening event is spending more time getting to and from peak lift than it is at peak lift. So what benefit is there in running more lift into an area where port flow increases are negligable (if they exist at all)? I know the flow has to stop, and start again for every valve opening event, which is not seen on a flowbench, which emphasizes my questions even more.

[455-4+1]

Originally Posted by Brian Baker

Is there really any point in running more than .650" lift in any d-port head, ported or otherwise, considering the flow numbers level off around .550"?

I was referring to the flow leveling off

Looks like .550" to me ??????????????

[Brian Baker]

Originally Posted by 455-4+1

I was referring to the flow leveling off

Looks like .550" to me ??????????????

Very well, but can you address my questions?

[gearbanger]

If your heads flow the best at .650 and you put a 650 lift cam in it, then you are really kind of screwing yourself because the valve only spent a millisecond at the lift point that it flows the best. If your heads flow best at .550 then you need a lift makes the valve spend the most time at or above that point.

The way I see it, you need to run the duration and overlap to operate the engine in the desired rpm range and type of use that you need, then you need to run as much lift as possible, taking into consideration valvetrain reliability. If you are drag racing and you dont mind to replace parts regularly, then you should run the lobes with the most lift you can find. If it is a street car and you dont want to fool with the valvetrain then I would stay less around .600-.650 for reliability.

[Skip Fix]

Brian from my discussions with head guys and cam guys even on heads that don't flow more with the higher lift a "square" cam lobe like the stockers use because they are lift limited is much harder on valvetrain than a "normal" lobe that goes higher in the lift. You then get more total duration at those higher lifts with better valvetrain dynamics than a square lobe, asl long as the port does not go into turbulence at those lifts, and loose flow.

Before porting was allowed in SS they used rollers with high lift and bigger durations on ports that did not flow more and made more HP.

[johnta1]

Before porting was allowed in SS they used rollers with high lift and bigger durations on ports that did not flow more and made more HP.

Like .720" lift?
I have a SS roller cam for the 400 with that lift.

You have to think about 'Area Under the Curve'.
The amount of time the head sees .550" lift (or whatever), you need to have more lift for the valve to see this.
The flow doesn't 'stop' at .550".
It will keep flowing above that lift, just not at the max flow.

[Brian Baker]

John, I realize that. Simplified, my question is, at what point do you take diminishing returns into consideration regarding lift?

[Half-Inch Stud]

Engage intellect: Perhaps the Ideal INTAKE Valve event would open "Instantly to about 0.3" at XXBTDC then "instantly jump to .8" after piston move away, then about 90Degree down dropped back to .5", at BDC slammed to .05", then slammed shut at xxdeg ABDC vs RPM.

Such the profile would match the Vacuum-pull from the Exhaust overlap, the Piston Velocity, and the Containment needs. Make it so. HIS

[Half-Inch Stud]

Point is: Our Peak lift occurs too late compared to Maximal Exhaust Pull event thru to Maximal Piston Velocity.

Opportunity Wreaks for the Biz team: We would need a Rhoads Intake Rocker arm: 2.5:1 Ratio at start followed by a 1.1:ratio or less after bleed time. Make it so. HIS

[Brian Baker]

Originally Posted by Half-Inch Stud

Engage intellect: Perhaps the Ideal INTAKE Valve event would open "Instantly to about 0.3" at XXBTDC then "instantly jump to .8" after piston move away, then about 90Degree down dropped back to .5", at BDC slammed to .05", then slammed shut at xxdeg ABDC vs RPM.

Such the profile would match the Vacuum-pull from the Exhaust overlap, the Piston Velocity, and the Containment needs. Make it so. HIS

Could this type of engineering be employed in a rotary valve design?

[Half-Inch Stud]

Not sure: I'm not sure about the Rotor rate on the induction-side. The effective rotary chamber growth vs rotor angle is unknown to me. If the equivalent "piston velocity vs crank angle on the induction cycle was found/known, then the optimum Intake valve requirement defines itself.

[Brian Baker]

Originally Posted by Half-Inch Stud

Not sure: I'm not sure about the Rotor rate on the induction-side. The effective rotary chamber growth vs rotor angle is unknown to me. If the equivalent "piston velocity vs crank angle on the induction cycle was found/known, then the optimum Intake valve requirement defines itself.

OK, we've gone beyond the parameters of my original questions, but this is good stuff to ponder.

[Wareagle]

Originally Posted by Brian Baker

Is there really any point in running more than .650" lift in any d-port head, ported or otherwise, considering the flow numbers level off around .550"?

Yes - Winning SS Championships with D-ports .

[Brian Baker]

Originally Posted by Wareagle

Yes - Winning SS Championships with D-ports .

That's nice.

I can't beleive there is nobody that can address my questions that knows what the hell they are talking about.

[fasteddy]

Brian, here's my take on it. Iron Pontiac heads, unported or poorly ported, will go turbulant around .500. The stocker guys know this of course but they do not care. Why, because they have to use .440 max lift. They use the so-called cheater cams with an almost square lobe to create long duration and fool the poor flowing head. I have asked the question of stocker guys and they said: "if I went with more lift and same duration charateristics I would kill performance". I would say from this, that if your heads go in reverse (ie turbulance) at .500 or so, do not exceed .500 lift. If your heads level out at .500 to .600, it would be wise to lift 'em to .600. My .02

[gearbanger]

Brian, why don't you just tell us what the answer needs to be.