Why is ther no formula to figure out port volume?

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Interesting about the small LCA's bringing smaller port heads to life. Could the increased overlap be facilitating the ram tuning effect of the smaller ports or do the smaller ports just need the additional overlap that a larger port doesn't need? If this is the case, that smaller ports just need the additional overlap that a larger port doesn't need, would you consider the larger ports more effieceint at higher rpm regardless of rated flow?

Small ports with high velocity work the best with large overlap cams, as if used with a large port head would have a flat spot or sag on the bottom end because of low or slow air speed in the port. As for the larger ports being more efficient at higher rpms, well all heads will become efficient at some point in the rpm range, but where is determined by the amount of engine under them and how well the engine was built.

Lets say I start with two identical heads. Just for fun, lets say they are W2's. One heads intake ports are hogged out to 210cc and the other is 195cc. Both flow 290 cfm @ .600" lift. I am using a cam with .610 lift at the valve, 260 degrees of duration @ .050" and a 110 lobe center on a stroker SB 408. Carb is a 850 cfm Holley double pumper derivative on a Mopar W2 single plane intake. Compression ratio is 11.5:1.

Will the 210cc head have more top end than the 195cc head? Would the dyno show identical numbers? Would the peaks (TQ and HP) be the same? Would the hogged out head have less TQ under the curve? Would the higher velocity of the small port head beat the large port head on all points?

The 210 and the 195 cc head should have about the same top end on a 408 as a engine that size won't need much more than 195 cc's so the larger head should ET and MPH similarly. As for the dyno showing the same numbers NO it won't happen, the smaller would show better TQ and maybe 10 HP less verses the large port head.
 
With what you have in mind in terms of use and driveline , I don't think there's any reason not to run the RPM 60779s. The power brakes are the kicker. If you run the vacuum booster (factory) setup, you must maintain solid vacuum. That means a cam of less than 245°@.050 and milder performance. If you use the hydro-boost now available, you don't have to worry about vacuum levels and I'd run a cam in the 250°@.050 range that will be more snotty. The tranny.. I know you're reading that 904s can take some abuse... Only if built well, and stock isnt enough IMO. You will want to upgrade at least the convertor to something in an efficient 2200 range. That's 2200 with a 4" stroke. Not a catalog "2200 stall for small blocks". IMO, I'd build a 727 for it and never worry again.

Now, for the sake of discussion...
I ran the 5800 hp peak for this package, with a 250°@.050, .550 lift intake and 255°@.050, .570 theoretical cam, and it spit out a range of 215-230cfm max with closed exhaust. If you're running good mufflers and large pipes, and the larger primary headers, that should go up about 20-30cfm. 60779s are around 170ccs out of the box, about 174ccs as I run them, and typically flow about 245cfm @ .550 lift. that's more than enough for what you propose. Enough plus room to grow should you want to go faster. Ryan has progams to get these to 280cfm with a 2.05 intake and I believe that is at 185ccs. Not sure on the volume. I've never measured his ports. Interestingly, max effort RPMs will make over 550hp with a flat tappet solid, and a bit more with a solid roller cam. If this were a max strip effort, then I'd more than likely be looking for a much different package. But for street duty, I'll stay smaller to keep the driveability good. I also feel that the port volume is not as critical to me in choosing as is the flow rate and valve size. There is such a thing as too fast, and it's easy to reach the choke point of small block port volumes when running around at street level rpms (under 5000) with a stroke of 4" and stock small block based port volumes.
 
With what you have in mind in terms of use and driveline , I don't think there's any reason not to run the RPM 60779s. The power brakes are the kicker. If you run the vacuum booster (factory) setup, you must maintain solid vacuum. That means a cam of less than 245°@.050 and milder performance. If you use the hydro-boost now available, you don't have to worry about vacuum levels and I'd run a cam in the 250°@.050 range that will be more snotty. The tranny.. I know you're reading that 904s can take some abuse... Only if built well, and stock isnt enough IMO. You will want to upgrade at least the convertor to something in an efficient 2200 range. That's 2200 with a 4" stroke. Not a catalog "2200 stall for small blocks". IMO, I'd build a 727 for it and never worry again.

Now, for the sake of discussion...
I ran the 5800 hp peak for this package, with a 250°@.050, .550 lift intake and 255°@.050, .570 theoretical cam, and it spit out a range of 215-230cfm max with closed exhaust. If you're running good mufflers and large pipes, and the larger primary headers, that should go up about 20-30cfm. 60779s are around 170ccs out of the box, about 174ccs as I run them, and typically flow about 245cfm @ .550 lift. that's more than enough for what you propose. Enough plus room to grow should you want to go faster. Ryan has progams to get these to 280cfm with a 2.05 intake and I believe that is at 185ccs. Not sure on the volume. I've never measured his ports. Interestingly, max effort RPMs will make over 550hp with a flat tappet solid, and a bit more with a solid roller cam. If this were a max strip effort, then I'd more than likely be looking for a much different package. But for street duty, I'll stay smaller to keep the driveability good. I also feel that the port volume is not as critical to me in choosing as is the flow rate and valve size. There is such a thing as too fast, and it's easy to reach the choke point of small block port volumes when running around at street level rpms (under 5000) with a stroke of 4" and stock small block based port volumes.

So the 904 is a no go unless its beafed up? Is that something that you can do with a kit or is it just not worth it? Will any old 727 do? What about a 4 speed auto, what are my options there?
 
Small ports with high velocity work the best with large overlap cams, as if used with a large port head would have a flat spot or sag on the bottom end because of low or slow air speed in the port. As for the larger ports being more efficient at higher rpms, well all heads will become efficient at some point in the rpm range, but where is determined by the amount of engine under them and how well the engine was built.

The 210 and the 195 cc head should have about the same top end on a 408 as a engine that size won't need much more than 195 cc's so the larger head should ET and MPH similarly. As for the dyno showing the same numbers NO it won't happen, the smaller would show better TQ and maybe 10 HP less verses the large port head.

I gather but what you're saying is that the port volume essentialy acts as an extension of the intake manifold runners regardless of the port flow and acts on manipulating the pressure wave just as the intake manifold runners do? Am I correct in this assumption? :read2: And furthermore (you knew this coming right? lol!) a mis-match between intake manifold runner volume/port volume/engine displacement/cam can be quite detrimental to power production but having all of these things matched properly can and will be symbiotic to power production in the chosen rpm band?

Mac, I apologize for hijacking your thread but I think it's pertinent to your original question if it is going a bit beyond.
 
I gather but what you're saying is that the port volume essentialy acts as an extension of the intake manifold runners regardless of the port flow and acts on manipulating the pressure wave just as the intake manifold runners do? Am I correct in this assumption? :read2: And furthermore (you knew this coming right? lol!) a mis-match between intake manifold runner volume/port volume/engine displacement/cam can be quite detrimental to power production but having all of these things matched properly can and will be symbiotic to power production in the chosen rpm band?

Mac, I apologize for hijacking your thread but I think it's pertinent to your original question if it is going a bit beyond.

Yes your correct. But it will depend on how bad the mismatch is and what the CI of the engine is. And what it will be used for.

But if the engine is going to be used for street and Tq. is what your after then I would use a 360 and a set of 318/302 heads and a small cam and the Tq. will be superior and more than likely make more Tq. than HP.
 
I gather but what you're saying is that the port volume essentialy acts as an extension of the intake manifold runners regardless of the port flow and acts on manipulating the pressure wave just as the intake manifold runners do? Am I correct in this assumption? :read2: And furthermore (you knew this coming right? lol!) a mis-match between intake manifold runner volume/port volume/engine displacement/cam can be quite detrimental to power production but having all of these things matched properly can and will be symbiotic to power production in the chosen rpm band? .


ram, if I might take this a little further... The pressure waves are similar (albeit a much more complicated dynamic) to the pressures an exhaust pipe. So lets look at that... You know when the pipes are small, they are restrictive because of volume and temperature and surface friction, and that is with the predominant push provided by the piston. This is especially true with street exhaust limited by room for headers or manifolding. You know a drop in diameter, or sudden drop in size creates a bad flow situation because of the turbulence and interuption in the flow of these waves. And that's true with a piston pushing it thru. So back to the intake port... A few extra things are working with the piston to get the mixture in efficiently. The harmonic waves (pressure waves) of varying frequencies, the inertia of the mixture itself caused by the port speed, the smooth transitions between components, the friction reduction of the surface finish... The port from a physics standpoint, extends from the base of the carb or throttle body to the intake valve seat. It's one system including a plenum area, a total length, and a volume. If you seperate out one cylinder, you can easier see the effect a change in matching parts can make. Run a small intake with longer runners, and a small port, and you have a system designed for torque. It makes use of the earlier harmonic waves to push the mixture down to the port, and the inertia is greater and the friction is lowest in a small fast port. Stick a large port large plenum intake on it, and the change between the sizes effectively ruin those waves' effects. It becomes a choke and you will lose tq and hp as those waves are disturbed so far that they cannot help anymore and the piston is the only part supplying energy to move the mix in. Similarly, a small, long port, small plenum intake, combined with a large volume port, and the waves get a good start, and then loss energy when the larger volume is encountered. In addition, there is a pressure wave that helps force the mix down the port when the valve is closed. In a small port, that wave stays fairly strong, and the length of the port gives room for the mix to fill before the valve opens. It's part of the "sonic tuning" in long rams mopar used. If that particular wave started up a large port, then hit the size change, it will also be reduced. So the mix goes into the intake, hits the port, the change in size slows it, the waves fall apart, and the power level drops as a result because cylinder filling is reduced. Unfortunately, with regard to physics, there is only one perfect port for every engine at a certain rpm and camshaft design. So the problem becomes what rpm range does the port need to work over and you go from there.
 
No doubt Bro! Highjack away... I'm learnin'!

Cool!

Yes your correct. But it will depend on how bad the mismatch is and what the CI of the engine is. And what it will be used for.

But if the engine is going to be used for street and Tq. is what your after then I would use a 360 and a set of 318/302 heads and a small cam and the Tq. will be superior and more than likely make more Tq. than HP.

Agreed! Smaller ports, valves, intake manifold runners, carb, header primaries all work together to create more torque in the lower rpm ranges. Great for mileage and instant throttle response on the street.

Everyones idea of streetable is different though, lol! In a car that's not daily driven I can handle manual brakes with a big cam and 8" of manifold vacuum as long as the gearing and stall is right for the cam. Some people would consider that intolerable.

ram, if I might take this a little further...

Please do! :)

The pressure waves are similar (albeit a much more complicated dynamic) to the pressures an exhaust pipe. So lets look at that... You know when the pipes are small, they are restrictive because of volume and temperature and surface friction, and that is with the predominant push provided by the piston. This is especially true with street exhaust limited by room for headers or manifolding. You know a drop in diameter, or sudden drop in size creates a bad flow situation because of the turbulence and interuption in the flow of these waves. And that's true with a piston pushing it thru. So back to the intake port... A few extra things are working with the piston to get the mixture in efficiently. The harmonic waves (pressure waves) of varying frequencies, the inertia of the mixture itself caused by the port speed, the smooth transitions between components, the friction reduction of the surface finish... The port from a physics standpoint, extends from the base of the carb or throttle body to the intake valve seat. It's one system including a plenum area, a total length, and a volume.

Ok cool, so I am getting this right.

If you seperate out one cylinder, you can easier see the effect a change in matching parts can make.

Interesting that you mention the single cylinder example as that was what got me interested in Hot Rodding when I was 13. I had a mini bike with a 5hp Briggs & Stratton engine and different lengths and diameter of exhaust pipe made drastic changes to where power output peaked.

Me being me, I had to find out why so I went got "The Design and Tuning of Competition Engines" by Phillip H. Smith. There are some excellent explanations of wave tuning for both intake and exhaust and everything started to make sense.


Run a small intake with longer runners, and a small port, and you have a system designed for torque. It makes use of the earlier harmonic waves to push the mixture down to the port, and the inertia is greater and the friction is lowest in a small fast port. Stick a large port large plenum intake on it, and the change between the sizes effectively ruin those waves' effects. It becomes a choke and you will lose tq and hp as those waves are disturbed so far that they cannot help anymore and the piston is the only part supplying energy to move the mix in. Similarly, a small, long port, small plenum intake, combined with a large volume port, and the waves get a good start, and then loss energy when the larger volume is encountered.

This is the mismatch I was speaking of and you hit it right on the head. Just like how a dented/ballooned out pipe will put a brass instrument like a tuba or a trumpet out of tune.

In addition, there is a pressure wave that helps force the mix down the port when the valve is closed. In a small port, that wave stays fairly strong, and the length of the port gives room for the mix to fill before the valve opens. It's part of the "sonic tuning" in long rams mopar used. If that particular wave started up a large port, then hit the size change, it will also be reduced. So the mix goes into the intake, hits the port, the change in size slows it, the waves fall apart, and the power level drops as a result because cylinder filling is reduced. Unfortunately, with regard to physics, there is only one perfect port for every engine at a certain rpm and camshaft design. So the problem becomes what rpm range does the port need to work over and you go from there.

Excellent explanation Moper!
 
sorry, I tend to get wordy... And it sounded like you and I were thinking alike. That last part is why we have 20 opinions about each question too. We all take different approaches to the same issues beased on our experiences and perceptions of what we've read.
 
But if the engine is going to be used for street and Tq. is what your after then I would use a 360 and a set of 318/302 heads and a small cam and the Tq. will be superior and more than likely make more Tq. than HP.

For a combo like this, would you use a small runner intake for a 318 as well, or woud you go with a more modern design like an Air Gap and gasket match the heads to the 360 port size?
 
Moper and Ramcharger,
This is why I like the small runner heads that have been opened up to the larger runners of a fairly large intake like the M-1 or the super victor, then taper them down to the smaller valves and this keeps the velocity up and the air/fuel charge moving. Creating a ram effect and it produces very good Tq. and very good HP through the range. This way you can get away with the smaller valves and smaller ports, and they will make power like the larger ports of say a 360 head.

From my experiences the heads being done this way pull vary hard up to about 6,200 rpm's with 318/302 castings and up to 7,000 with the 360 castings with the 1.88 intake valves. After 7,000 rpm range I then use the 2.02 valves. But correct me if I'm wrong but the larger 2.02 valve heads tend to lose low rpm Tq and HP, thus the need for loose converters and steep gears.

Also too when flowing a cylinder head you really should have the intake manifold that is going to be used also attached to the head so the flow and or modifications can be made in real world circumstances. The only other effect that will be but cannot be accounted for is varying air pressures and changing corrected altitude's (Baro readings), and density. Which this has a direct effect on how the heads and air moves through the engine and it's ability to perform properly. This will also change the wave or pulse of the port/intake, thus the need for leaning or richening the carb, or fuel system.
 
Moper and Ramcharger,
This is why I like the small runner heads that have been opened up to the larger runners of a fairly large intake like the M-1 or the super victor, then taper them down to the smaller valves and this keeps the velocity up and the air/fuel charge moving. Creating a ram effect and it produces very good Tq. and very good HP through the range. This way you can get away with the smaller valves and smaller ports, and they will make power like the larger ports of say a 360 head.

Interesting that you mention this as every text I've read states that the ideal shape is a gradual "funnel" if you will towards the valve rather than a straight cylinder. I assume from what I've read that this will increase the speed of the air/fuel charge as it nears the turn and the restriction of the valve itself. Would this be to "even out" the velocity of the mixture at the short turn from the naturally higher velocity of the charge running along the port roof thereby somewhat negating what would be an uneven charge flowing across the underside of the valve?

From my experiences the heads being done this way pull vary hard up to about 6,200 rpm's with 318/302 castings and up to 7,000 with the 360 castings with the 1.88 intake valves. After 7,000 rpm range I then use the 2.02 valves. But correct me if I'm wrong but the larger 2.02 valve heads tend to lose low rpm Tq and HP, thus the need for loose converters and steep gears.

I'm in no position to correct you or anyone else since I don't have a flow bench, lol! If this is what you've seen and done, that's great stuff. I will say that I when I had my heads milled and the valve job done and hardened seats installed, I just had them stick some 2.02 Ferrera's in there since I got them way cheap and the valves had to be replaced anyway. They did zero throat, bowl or port work and when they installed the guides, they left all kinds of metal splinters sticking out from the guide boss. I thought that they would at least clean that up. They did a lousy job all in all including leaving lapping compound on the back side of the valves and and not seating the springs correctly on the retainers.

Anyway, after dissasembling the heads I did smooth out the throats, re-profiled the short turns and smoothed out the guide bosses as well as gasket matched about 1.5 inches into the port. I have no way of knowing what improvements I made if any but this engine runs very strong with a mild cam and 1.6 ratio Crane rockers (Lunati Voodoo 60401, Duration @ .050 (Int/Exh): 213/220 Gross Valve Lift (Int/Exh): .454/.475 & a 112 LCA) Far stronger than it should in such a heavy vehicle at this altitude.

Another thing that I noticed is that I have to run it quite a bit richer (74s in the primaries, plugs still look a little lean) than i expected at this altitude and also had to go up 2 sizes on the squirter (.024 to .032). I suspect that this may be due to the valve size being larger thus requiring more fuel to do the same amount of work due too to low of intake/port velocity. Or, the larger valve may be compensating for the lack of air here and that's why i have to jet like I would if i was back in Chicago.


Also too when flowing a cylinder head you really should have the intake manifold that is going to be used also attached to the head so the flow and or modifications can be made in real world circumstances.

This makes perfect sense.

The only other effect that will be but cannot be accounted for is varying air pressures and changing corrected altitude's (Baro readings), and density. Which this has a direct effect on how the heads and air moves through the engine and it's ability to perform properly. This will also change the wave or pulse of the port/intake, thus the need for leaning or richening the carb, or fuel system.

Aha! Odd how true density altitude has affected this engines tune. I'm running 10.2:1 with no ping with open chamber 360 LA heads milled to 65cc and .040 piston to head clearance (very little quench area), it loves lots of advance and likes it early and likes fuel.
 
On the "funnel effect"-
While I agree this is the result, I don't believe the funnel should go to the valve. As I understand it should be the entry of the short side radius. Then problem I see with this approach is the pushrod area is the smallest cross sectional area in a factory head port. With every mopar wedge head this is the case. So the funnel simply cant be maintained without some serious working unless you go from pushrod pinch to short side entry... Which makes the funnel only a segment of the head's section of the port, rather than the entire port. This get's back into the larger/smaller/larger issues with speed thru the entire length. Honestly, I do not typically cc a port, my heads get flowed after the work's done, and not every set gets tested. So in truth, it's hard for me to say the funnel approach isnt all that critical with no backup numbers. However this is one area I take a different approach than BJR, and it's worked for me. I tend to keep my inlet size at gasket size, and I don't enlarge the pinch more than I have to to keep it from being the restriction. I concentrate on the port sides, short turn, and the venturi to the seat, and do very little to minimize the guide boss. Overall, the port remains a very small, and the volume around the bowl is the largest. This is so the air can make the turn to the seat with little tubulence, and the venturi above the seat speeds it up into the chamber. I also tend towards larger intake valves, but not for flow reasons. I normally run 1.88s in the 318 port heads, and 2.05s on everything else and I don't see losses in low end. I run larger valves because on 40 year old seats, I will lose more power by sinking seats and enlarging chambers than by any loss of low lift flow. I'm buying valves anyway, so I place the seat angle right on the edge of the chamber, and the top cut is an unshrouding cut of the chamber itself. (5 angle valve job...)


On the rpm limits of them - Again, simply pointing out a difference of opinon based on my limited experience... No 318 port head I've ever seen or run, when on a running engine of larger than 318cu inch and paired with a street type cam, pulls past 5500. The cars heal over when they pass it. I've also never flow tested a set I ported...lol. And by running a larger cam (larger than the typical 268 style cams) perhaps that might be different. So it may be a simple deal of not enough air available. It might just be me. But I don't reccommend them for a build beyond 318 inches unless the rpm limit was 4K rpm. I'd rather run the Magnum designs with the better chamber and better all around flow in stock form then spend dollars modifying the small ports.

BJR said "Also too when flowing a cylinder head you really should have the intake manifold that is going to be used also attached to the head so the flow and or modifications can be made in real world circumstances. The only other effect that will be but cannot be accounted for is varying air pressures and changing corrected altitude's (Baro readings), and density. Which this has a direct effect on how the heads and air moves through the engine and it's ability to perform properly. This will also change the wave or pulse of the port/intake, thus the need for leaning or richening the carb, or fuel system."

I agree 100% on the above. However, on teh intake deal, in order to compare numbers with everyone else you need to be all using the same methods., nobody else does it....lol. Or at least publishes results. Hughes started flowing manifolds alone, and claiming huge increases in flow with porting. I think this is akin to gaging water flow thru a dam by watching the level drop on the shore when a gate's openned. You know there's more going out, but you can't accurately tell how much. There's so much more at work in a running engine, that simplifying the intake flow to X cfm is rediculous. Ona race engine, you can science it out. For the vast majority of users, the simple plenum size and runner volume/length is all you need. A related note, it is seldom mentioned, but flowbench packages (which includes the operator) are never going to be 100% exactly the same in results. There are calculations and formulas to even the filed. But even things like the test bore size can make a huge difference. Flow a set of Edelbrock RPMs on a 4.35 test bore, then flow one on a 4.5". Then take it to a shop close by, abnd have the same thing done. You'll end up with 4 seperate numbers. One number will be largest, one below average, and the head never changed...lol.

PS - I still cant get the color thingy going... sorry for the black and white.
 
I was always taught that velocity is everything. Doesn't really matter how much volume you have, if you can't get it in the cylinder quickly it doesn't matter. Maybe there's a member on here that has a flowbench.
 
The bench need a pitot tube to get airspeeds in the localized areas of the port. Volume of the entire port tells little when you get really into things. It's volume of small sections of the port that combine to create fast and smooth. That's where the tueb and local speeds come into play. I think something like a Super Flow 600 is the lowest level bench that can use the pitot tube, at least with factory software. Speed is a big part, but not the fastest outright speed. The fastest non-turbulent flow is what you want. Too fast is when turbulence occurs due to speed, and the result is what's called port choke.
 
hi, I've been reading this thread. port velocity and port shape are everything.
the stock and super stock guys cannot have big ports. how ever their heads
flow very well. they use port velocity and port shape to get lots of cylinder fill. as I was told by super flow at one of their semminars, port shape and velocity are most important. high velocity will put more air in. the super stock guys are flying with stock size ports and valve sizes. they use lots of valve lift also. we're talking 1.88/1.60 mopar and 1.94/1.50 gm motors. I figure if a small block stocker can run low 11 sec and same S/S runs in the low 10 sec must be putting a lot of air in the motor. I have also found test pressure makes a big difference! most people test at 28" gives the big numbers!
25 " is more realistic. newer flow benches are set at 25" test pressure.
also, super flow, stated don't get hung up on the big numbers of size and port volume.
 
I was not a party to his flow info... however, my old neighbor (who does have his own personal SF600 bench runs a SS 351 Cleveland. It's making over 500hp. The biggest fix... weld in port reducers to lower the volume and help in the shape. These were taking out large amounts. Like 30ccs worth. Shape controls velocity, and as fast as the port can move cleanly is the goal.
 
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