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 ?
David Vizard - Which to prioritize - PORT FLOW or PORT VELOCITY?
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RAMM
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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
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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.
Yeah but you don't want too much is what I was gettin at.
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Newbomb Turk
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So true. You have to learn to live with overlap. Otherwise power levels will drop.
9secRR
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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 #.
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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.
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
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I hope you enjoyed you vacation away from the forum, I know we all have.
I hope you enjoyed you vacation away from the forum, I know we all have.
Was he a bad bad boy.
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
Well-Known Member
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
Well-Known Member
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
Well-Known Member
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.
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.
Dale Davies
Well-Known Member
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.
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.
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)
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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
Well-Known Member
No one arguing there accuracy, but there more useful than your nonsense.
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