David Vizard - Which to prioritize - PORT FLOW or PORT VELOCITY?

[273]

Here's a thought. After you work out what the ideal port velocity is then you can work out what the perfect fuel droplet size is to go with it.

Then after that you can tell me how you plan to control the size of that droplet?

How far off is the average guy with a decently built and well tuned engine from being an ideal atomization, vaporization etc.. Machine ? And how much HP could one expect to gain refining their combination and how much time money and energy would it require to do so ?

 

[RAMM]

If you have reversion then you have the wrong camshaft.

If you have reversion you have overlap. If you don't have overlap you dont make much power. Overlap equals RPM. IE. You always have reversion. J.Rob

 

[RAMM]

But I think for most of us, that aren't bound by strict rules and highly competitive racing, the average performance guy. To build an engine with Slightly less inefficient HP is generally gonna be easier and less expensive to build.

A highly efficient 1.35-1.65 lbs-ft per cid is generally gonna be out of the range for most of us.

If you want 500-550 hp and torque with peak hp around 6000 rpms most don't think to build a highly efficient 360 to do it with only 220-240 cfms but a less efficient 408 with 275-300 cfms.

Even most mild engines would require less port volume than a 273/318 head has with more cfm then it generally does.

At Peak hp @ 5000 rpms these engine would need these port volumes and cfm to have optimal velocity, 273 = 99cc/167cfms, 318 = 115cc/195cfms, 360 = 130cc/220cfm, 408 = 147cc/250cfms so generally we would need to shrink the port while gaining cfm beyond most capabilities to have ideal velocities with a mild street engine.

In 2011 for EMC I built a 371 (.060" 360) that made 513 ft/lbs 1.38 tq/ci 532hp on pump gas with teeny tiny EQ iron Magnums that at the time only flowed 267-272 cfm . IMO I made them a bit too big in the bowls. Weiand X-celerator manifold/750 XP. That engine was surprising for what it was. When I was done with that engine I made the heads bigger for 292-300cfm and used them on a 416--made 564 ft/lbs 1.355 tq/ci----Port speed was always just way too fast but I only needed 6500 rpm. Those heads just work. J.Rob

p.s. Every EQ headed build I've done , I've been told the engine is pure majic.

 

[273]

In 2011 for EMC I built a 371 (.060" 360) that made 513 ft/lbs 1.38 tq/ci 532hp on pump gas with teeny tiny EQ iron Magnums that at the time only flowed 267-272 cfm . IMO I made them a bit too big in the bowls. Weiand X-celerator manifold/750 XP. That engine was surprising for what it was. When I was done with that engine I made the heads bigger for 292-300cfm and used them on a 416--made 564 ft/lbs 1.355 tq/ci----Port speed was always just way too fast but I only needed 6500 rpm. Those heads just work. J.Rob

p.s. Every EQ headed build I've done , I've been told the engine is pure majic.

I remember that one, was a nice build.

 

[RustyRatRod]

If you have reversion you have overlap. If you don't have overlap you dont make much power. Overlap equals RPM. IE. You always have reversion. J.Rob

Yeah but you don't want too much is what I was gettin at.

 

[Newbomb Turk]

I attended a seminar put on by superflow,in 1999, harold betts was the speaker. bottom line he stated was, port shape and port velocity is everything, don't get hung up on flow numbers. port velocity fills cylinders' fast and creates more cylinder pressure, which makes more torque , also power , just food for thought.

If you have reversion you have overlap. If you don't have overlap you dont make much power. Overlap equals RPM. IE. You always have reversion. J.Rob

So true. You have to learn to live with overlap. Otherwise power levels will drop.

 

[9secRR]

my head porter (he is well known on this site) told me don't worry bout the big CFM #'s as long as the port has velocity. i wanted to see a certain flow #. i was a bit disappointed that the flow #'s didn't hit the magical # until i got the timeslips. i guess i didn't need the big advertised flow #.

 

[273]

my head porter (he is well known on this site) told me don't worry bout the big CFM #'s as long as the port has velocity. i wanted to see a certain flow #. i was a bit disappointed that the flow #'s didn't hit the magical # until i got the timeslips. i guess i didn't need the big advertised flow #.

Are those your 355 W2 ? From you signature, sounds like a pretty sweet setup, like you didn't go 4".


Velocity, cfm, port volume are all interrelated if you know any two you can basically calculate the third like everything it's about balance.

 

[fishmens67]

big CFM #'s as long as the port has velocity.

Only going to pull the air the intake will allow.

 

[273]

Only going to pull the air the intake will allow.

Most engines fall way short of Max hp per cfm (from what I understand is around 2.5 hp:cfm) most don't even make 2 hp:cfm.

 

[9secRR]

Are those your 355 W2 ? From you signature, sounds like a pretty sweet setup, like you didn't go 4".


Velocity, cfm, port volume are all interrelated if you know any two you can basically calculate the third like everything it's about balance.

3.46” stroke. It has surpassed my goals so I’m very pleased with the outcome.

 

[Hysteric]

How far off is the average guy

A lot more than you can imagine.

 

[dowboy1970]

A lot more than you can imagine.

I hope you enjoyed you vacation away from the forum, I know we all have.

 

[pittsburghracer]

I hope you enjoyed you vacation away from the forum, I know we all have.

Was he a bad bad boy.

 

[Mattax]

If you have reversion then you have the wrong camshaft.

I can hope he is meaning the sound/flow wave naturally created when the valve closes and the intake charge reverses??? Time that reversion with the next intake and you can overfill the cylinder. So choosing intake runner length, port velocity/size and cam shaft profile.

Yes. And Calvin Elston points out his (frustration) that the exhaust ports are often ignored, but the same could and should be done there. While he can't control that, he chooses the exhaust tubing diameters and lengths to keep the flow moving away from the port even as the ex. valve is shutting. Larry Meaux's Pipemax gets us pretty close especially with 4 into 1 headers.

 

[Dale Davies]

What's the velocity in the port when the exhaust is pushing back into the plenum?

No simple answer to that. Intake port volume referenced to cylinder volume and exhaust pulse tuning all affect the reversion. Have any AR tactics been used?
Theoretically you should not have exhaust pushing out the intake valve. Cast log manifolds can promote that reversion.

 

[Dale Davies]

I'm not saying velocity not important, just for most part we have vary little control about it.

Plus look at the Cleveland and it 4 V head and 302/351 Boss these engines have to be one of the biggest examples of too much cross section for a given cfm for engines of small medium sizes generally not spinning the craziest of rpms.

Some will probably argue these engines especially the 302 are soft, but even if they are, these are some of the most extreme examples, the average small block Mopar can't even come close to over csa like the Cleveland. And there's got to be a ton of examples of strong running Cleveland based Fords out there. Not to say they wouldn't do better with an appropriate sized port. Point is a too big of port is probably better than to small for a given power. (within reason)

Most of us don't have the luxury to tailor match port cc, cas, cfm to each engine.

A stock X head can support 200-400+ hp engines, for a 200-300 hp engine a 273/318 head could easily do it too but gonna need way more cam over the X head which way is better ? On paper a stock 175 cfm 318 head should be able to make 400 + hp but is it the wises choice to do so?

On a single purpose race engine obviously the better you can match all this up the better the combo will be, a street engine that has multi-tasks to accomplish I feel velocity important but not at the compromise of everything else.

Australian company CHI builds Clevelland style heads they call 3V. They started with basically the 2V ports with the 4V quench combustion chambers. Now they have a range of port volumes to match the engine displacements.
Ford Australia built many 302C engines over the years and used them for a number of years after Ford North America dropped them.
Port volume has to match the displacement and intended RPM, but velocity is of prime importance to efficient cylinder filling.

 

[Dale Davies]

Often, We have gotten Greedy on the ports in both the heads and
intake and the turbulence has not only wiped out any gains but
really cost me power on the Dyno and on the Track!

I have turned some extremely good parts into only so/so stuff.

On a running engine, the intake flow is pretty much guarranteed turbulent. That is unless the ports are 4" DWV pipe. When you start talking laminar and turbulent flow, you get into some complex math I do not understand and I doubt 99.9% of the people on here do not understand that math either.

 

[273]

Australian company CHI builds Clevelland style heads they call 3V. They started with basically the 2V ports with the 4V quench combustion chambers. Now they have a range of port volumes to match the engine displacements.

Yes I know.

Ford Australia built many 302C engines over the years and used them for a number of years after Ford North America dropped them.

Port volume has to match the displacement and intended RPM, but velocity is of prime importance to efficient cylinder filling.

Ideally but obviously it ain't as sensitive as some make it out.


People bring velocity a lot especially warn about too little velocity never really hear warnings about too much though (which is a thing), but those that warn seem to have no idea what the right velocity or csa or port volume is but their sure you probably need smaller than your thinking of.

 

[Dale Davies]

Yes I know.



Ideally but obviously it ain't as sensitive as some make it out.


People bring velocity a lot especially warn about too little velocity never really hear warnings about too much though (which is a thing), but those that warn seem to have no idea what the right velocity or csa or port volume is but their sure you probably need smaller than your thinking of.

As DV related in the video, Darren Morgan says velocity, velocity, and velocity. That said, a smaller volume head on a larger displacement head will have the flow stall at some point. Essentially what we see on a flow bench when the flow gets to a plateau or drops as the valve is lifted more.
Again it all comes down to the rest of the engine combination for port volume, flow and velocity.
As stated previously, the Ford Boss 302 engines had ports designed for TransAm racing. Those race engines ran up to 9000 and sometimes 9500 RPM. The 1969 street engines had the largest valves, and proved to be a bit soft at the bottom end. For 1970, Ford reduced the intake valves a bit, which helped street performance a little. Ford installed a rev limiter in the distributor to limit the RPM to 6500. The intake ports and solid lifter cam would let the engine rev freely to where the con rods would fail. The Boss rods were upgraded HiPo 289 rods, with stronger bolts and half moon machining for the bolt heads. Same length as the 289 at 5.155", but much heavier. Then there was the race rods that are visibly heavier to stand up to the 9000 RPM race conditions with occasional runs to 9500 RPM.
The Dodge/Plymouth 304 engines were destroked 340 engines and ran at 9500 RPM with occasional runs to 10,000 RPM.

 

[273]

As DV related in the video, Darren Morgan says velocity, velocity, and velocity. That said, a smaller volume head on a larger displacement head will have the flow stall at some point. Essentially what we see on a flow bench when the flow gets to a plateau or drops as the valve is lifted more.

Most of us aren't building Darin Morgan type engines.

Again it all comes down to the rest of the engine combination for port volume, flow and velocity.

Generally it comes down to the head that's is the best compromise and is readily available to us.

As stated previously, the Ford Boss 302 engines had ports designed for TransAm racing. Those race engines ran up to 9000 and sometimes 9500 RPM. The 1969 street engines had the largest valves, and proved to be a bit soft at the bottom end.

But still functional and for most they would have a hard time getting close to that level of port volume mismatch.

Not saying velocity ain't important, but generally it's not a thing most of us have the ability to do much about it, like many important functions of an engine. The problem I generally have with people uses of the theory of velocity is they generally push people towards going too small in fear of too large. And especially without any idea what's ideal in the 1st place. And don't even factor in other issues cause they got their velocity blinders on, like cam size for a given head to reach power goal, or possible extra hp and usable rpms over the original plan, cost effectiveness, convenience etc..

Most of us aren't building a single purpose no compromise race car that max efficiency it the utmost importance and gonna have custom ports that are epoxied to squeeze every last drop of performance.

 

[273]

If you look at most of the descriptions of each of these velocity FPS #'s most the list is fairly useable except vary top and bottom which is a huge difference in in port volume, and if your turning and decent size engine to even relativity moderate rpms your more than likely be higher up in the list. (higher velocity)

 

[Hysteric]

No simple answer to that. Intake port volume referenced to cylinder volume and exhaust pulse tuning all affect the reversion. Have any AR tactics been used?
Theoretically you should not have exhaust pushing out the intake valve. Cast log manifolds can promote that reversion.

There is. Some one has a chart. That chart must be true.........My flow bench tells me everything I need to know about airflow dynamics in a running engine.

 

[Dale Davies]

Most of us aren't building Darin Morgan type engines.

Generally it comes down to the head that's is the best compromise and is readily available to us.

But still functional and for most they would have a hard time getting close to that level of port volume mismatch.

Not saying velocity ain't important, but generally it's not a thing most of us have the ability to do much about it, like many important functions of an engine. The problem I generally have with people uses of the theory of velocity is they generally push people towards going too small in fear of too large. And especially without any idea what's ideal in the 1st place. And don't even factor in other issues cause they got their velocity blinders on, like cam size for a given head to reach power goal, or possible extra hp and usable rpms over the original plan, cost effectiveness, convenience etc..

Most of us aren't building a single purpose no compromise race car that max efficiency it the utmost importance and gonna have custom ports that are epoxied to squeeze every last drop of performance.

U R just not comprehending what I am relating.

 

[273]

There is. Some one has a chart. That chart must be true.........My flow bench tells me everything I need to know about airflow dynamics in a running engine.

No one arguing there accuracy, but there more useful than your nonsense.