[formulabird428]

trying to determine the best velocity of KRE-D heads vs. CFM.

what are the port volumes for KRE-d heads ported to both 310cfm & 325cfm?

just out of curiousity, does anyone know the port volumes for 310 and 325 cfm E-heads?

[Steve C.]

Hard to answer with exact runner volume numbers as they will vary depending on who did the port work and whats involved. Example, my 87cc Edelbrock castings that flow 313 cfm at .600" lift on our SF600 bench have about a 227 cc intake runner volume. My friends 72 cc Edelbrock castings from KRE that flow 310 cfm are about 236 cc's.

Obtaining intake runner volume numbers would seem to be easy.... just ask. Not always so. Next time you hear a fellow tout his flow numbers ask him what the intake runner volume is on the heads. In most cases you will get a blank stare!

The only thing I have seen mentioned about a ported version of the KRE D-port head was about 215-220 cc's on a set reportably worked to 323 cfm.
These had 85 cc chambers.

Again look at the area under the curve for the flow from .100 thru .600 lift and look at the runner volume difference and the KRE D-port will be tagged a "better" head. I will agree as I always have. But between the two different heads with both having the same flow numbers and regarding STREET performance.... I'll stick to my un educated hunch that MOST would probably not see a rats ass of difference in streetability because of the intake runner volumes ... except one apparantly has more smokeability.

Oh and regarding track performance ... was it 0.1 or so difference in ET ?

[Jim Hand]

Steve,
Good information about actual port volumes!

However, I am intrigued by your comment about "only .1 difference in ET. Are you saying .1 is not important? If it is not, what is important? Maybe 1 second? I have found that .1 is extremely important when trying to find best possible performance!

I understand you had planned to try a slightly smaller solid roller cam in your car. How did that work out? A change of .1, .3 or was that one second? Whatever, were you pleased with the amount of performance you lost? Or did you simply say to yourself - it just isn't important - no one will ever notice it!

Jim Hand

[Chris Petersen]

I cant answer for the 310 or 325 cfm ones, but food for thought...

My 85cc (really 83cc) KRE-D's cnc'ed by KRE for 290cfm
intake port volume is 190cc's I checked 3 ports on
one head, all right at 190.

[Steve C.]

Thanks Chris. I'll add those figures to my library of notes on this stuff.

Two similar heads, the 85cc chamber KRE D-port head with 290 cfm flow and a 290 cc intake runner volume & the 87cc chamber Edelbrock head with 275 cfm flow and a 215 cc intake runner volume. With the improved chamber design, and assumed better area under the curve regarding air flow, and the smaller intake runner volume the KRE design mentioned above is a "better" cylinder head in theory, on some dyno testing, and with some known and very realiable track testing.

That said, it is again my opinion that any difference with idle and low speed driveability, and the lower RPM throttle feel between the two heads mentioned above would be MOOT if any on most street performance applications in conjunction with the use of such heads. Again keeping in mind the heads used on a optimized combination, both engine & drivetrain, capable of supporting the cylinder-head airflow mentioned.

And presumbing such a combo, if nothing or little was changed, other than the two cylinder heads and header types, what would the difference be in ET performance .... 0.1, as in 11.40 or 11.50... or .2 or .3, I do not know. Again I suspect many would not care about a 0.1 to 0.3 difference in ET. One obvious exception would the serious bracket racer looking for consistancy, he would care. But I will suggest the difference would not be seconds.

And on a personal note, for me I don't care much about ET's except for general bragging rights.... like in having a true 10-second street car. I have two time slips to back that up, enough for me. And at the '04 PSN races when my car ran 11.099, 11.098, 11.081, 11.084, 11.085... and opps a 11.16 in the final round. I wasn't bothered. But then in '05 when I'll we could muster was 11.30's. Damn ! But we did find some specific contributing factors... but neverless on that day I decided to start on a 505cid combo. For bragging rights and to waste more of my money on all those razzle dazzle high tech modern parts.

( my recent cam change to something smaller and in conjunction with testing a Q-jet by Cliff Ruggles was in fact very interesting. Its a 11.50 dog now even with the Holley. But I do suspect spring pressure issues are contributing. Besides a possible mis-match with the converter & gears with the smaller cam (?) Don't care now though, the 505 is in the works )

[Jim Hand]

Steve,
So if I read you correctly, you are now saying that every .1 second in ET is important, whether it is due to a change in heads, bad valve springs or even a change to a 505 cube engine!

Just curious - why did you find it necessary to make such slanted and silly comments about the real effects of port volume on performance in your first post, when you obviously feel it is important to have your car run as well as possible?

Jim Hand

[Steve C.]

Jim, I personaly don't care or feel that 0.1 differeance in my personal ET is a big deal, and I suspect many others don't either. And I'm certainaly not suggesting that track testing for evaluation of products to within 0.1 to 0.3 is not important. Not sure about my silly thoughts regarding intake runner volume, after reading hundreds of pages of related tech article, and a big fan of David Vizzard & Jim McFarland theory stuff, I do know and respect the fact for a given horsepower level, you want to see max airflow out of the smallest port possible. It's the streetability issue, or proposed lack of, between the two head types that I find amusing.

Yes sir, more smokeability

And on a light side.... as some know I design and build a new, and much different, engine combo for my car every few years or so. Its my hobby.
The 505 is to try to gain back that lost 0.5 in tenths.

[P@blo]

Here is a piece or a HP article regarding port volumes

"Velocity of the charge, as the pumping effect of the piston creates a low pressure region in the bore, will affect VE. The larger the port area, the slower the velocity and the higher the rpm the engine will require in order to use this port effectively."

Now this suggests that a larger port will still function but will need to do so at a higher RPM to compensate for slower charge velocity. Which is I assume why the added stall and gears are required to "make up" the difference of a more efficient smaller port.

I guess the rest comes down to where you draw your line in the sand and how you choose to draw it.

Now I'm not picking sides here but Jim has run a 11.32 with a 4100 lb car using 260 cfm "small port" iron heads a 355 gear, 3200 stall, hydraulic flat tappet cam, mechanical water pump and a Q-jet. Steve has run a 10.88 with a 3750 lb car with a 373 gear, 315 cfm E-heads, solid roller cam, 4200 stall, electric water pump and a Holley HP950.

To me there would be very little difference if any between the two once the weight difference is calculated so it would appear to be a matter of choice and preference. However if the plan is to live in the lower RPM band then one must consider which parts will work "best" in these areas.

A big stick or a sharp sword, choose your weapon


Cheers
Brent

[JSchmitz]

In my mind, port volume (or cross sectional area) is the same as cam size, intake volume, gear ratio, stall, etc. etc. They are all chosen with a certain operating range in mind. The proper application of these parts gets skewed from one case to the next depending on C.I.D., vehicle weight, etc. Some of it comes down to personal preference. Steve says he doesn't care about a tenth or two. But, he's building another engine to go faster. Jim says he cares about every fraction of a second. But, he chooses to race a two ton car. Lots of irony in the hobby.

[Jim Hand]

JSchmitz,
Good observations. But do want to clarify several points.

When we have good running cars, be it Steve's 3700# Bird, or my 4000# wagon, finding or losing .1 seconds is a significant change. The claimed gains of a half second for solid rollers, or one second for new heads, or .4 for a different cam seldom happens. And if it does, something was drastically wrong before the change! So when Steve inferred the .1 second change due to too much port volume was unimportant, I chose to speak up.

Concerning the car I use as a rolling labratory, it provides outstanding traction and repeatability and has provided a lot of surprising test results over the past 20 years. In fact, it was probably one of the key factors why I was selected to write the Pontiac book for CarTech Publishing. Be assured that if I really wanted to run as fast/quick as possible, it would not be with a 4000# car. But since that is what I have, I do want it to run as well as is practical.

If I wanted to make serious additions to power, I would do just what Steve is doing - add displacement and lots of it. And then as you indcated, select all other components and adjustments to complement the power in the RPM range I wanted to use. Displacement adds real power at all RPM and not just at higher RPM.

Jim Hand

[Steve C.]

Actually its not about my car or Jims car, or how he and I approach our builds. This has been affirmed before. Nor in fact about any potential small track performance differance between two types of cylinder heads. Or which one is better, today I'd give serious consideration to the use of KRE D-port heads if given a choice. So its not any special allegiance to Edelbrock heads on my part.

Its the streetability issue between that two different heads thats on my mind.
And I will still stand firm in my opinion, as I have for quite some time and in other discussions, that for most of us there won't be a rats ass differeance on idle and low speed driveability, and the lower rpm throttle feel between the two different heads. Given similar combos and both heads with similar flow capabilites.

And Jim, I had no specific intention to point out to you personsly that any testing you do or did to a point of .1 differenace ET is not important.

[JSchmitz]

Jim, I love your wagon, or almost any vehicle that's off the beaten path. I bet you've freaked some people out on the street! The long wheelbase is great for drag racing, and a good ride. I agree about .1 e.t. I would love to pick that up. But, I can see where Steve wouldn't care. To each his own. Your two ton wagon is a lot more sensitive to minor changes, especially low end torque, than Steve's car.

Steve, That's why I said "Some of comes down to personal preference". A small difference to some is huge to others. The distinction here is whether we are trying to establish fact or opinion. Not always an easy thing. Especially on a message board, where peoples intent often gets misinterpreted.

[Steve C.]

"The distinction here is whether we are trying to establish fact or opinion."

I have no facts as in track testing to within .1 ET, not my thing. And again not suggestioning that's not a good thing here. My comments are obviously driven by opinion.... and to add to opinion, here is a comment made by a good friend. Someone most on this board would recognize, and one who has a street driven 455 combo using the dredded Edelbrock heads:

"Drive my car and I'll guarantee there is no loss of bottom End! The Nittos go up in haze anytime."

And a local friend with his Edelbrock heads, un-ported with just a clean up, and on a simple 455 based low 5200 rpm street combo ... I know his opinion on his streetability with 570 ft.pounds of torque. He's not harping about low speed drivability issues.

[JSchmitz]

Agreed, a gain in torque that only produces a loss in traction, however fun it may be, is not a net gain. It's all about balance. If your car is "in balance" that's all that matters. I don't think they are the "the dreaded Edelbrock heads". I would love a set. All I have is some lightly cleaned up #96's. But, then again, I run the dreaded Flowmasters (Throw rocks here).

[slowbird]

Steve or Jim
Is it possible to have a port to small?

[Jim Hand]

slowbird,
Like all other aspects of engine building, port size is relative to the required airflow of the engine. The smallest port that will deliver the airflow needed by the engine is desirable. That means we will have excellent velocity for port filling, but without any choke that may limit required peak airfow. The needed airflow depends on engine displacement, RPM, and VE at that RPM. And a port big enough to deliver 400 cfm may well be too large for any engine that can only use 300 cfm.

Jim Hand

[slowbird]

So what is more important, cfm, size or velocity? You could fill the floors on you ports (maybe 1/8") and increase cfm (or atleast keep it the same) and increase velocity and decrease size (all good things right?). What do you think would happen to you wagon if you tried something like?

[Jim Hand]

Slowbird,
What you asked is basically what I have done with the 6X-4 heads now on the car. After seeing the low RPM loss due to 186 cc ports, while seeing a MPH gain due to the same heads with about 20 cfm added peak airflow, I reworked the 6X heads.

While minimizing any metal removal, I increased flow from about 252 to 267 @ .55 lift. That required enlarging the ports to about 170cc. As a result of the work, gained 15 cfm air flow and 5 cc port volume. And understand these are averges of all eight ports, not just one sample!

One of the rules I and others use in porting to determine porting effectiveness is:
An effective porting job will always have a greater ratio of airflow increase then the ratio of port volume increase! Using that formula, I gained 5.95% increase of airflow with only 3% gain in port volume. So in theory, the re-porting was a success. The real test came at the track.

The result was/is the car runs just as fast as the higher flowing heads, which represents peak HP, but several tenths quicker, which represents average power over the loaded RPM range. And it is considerably quicker to 60' by almost a tenth, which represents low and mid range power.

Note that my car passes the 60' marker in first gear at about 4700 RPM!

For much more detail on my head work, check out the topic at:
http://216.178.81.108/forums/showthread.php?t=469645

This was discussed just last week. And keep in mind that I shift both gears at 5500, so low end power is important both at the drag strip and at normal light throttle driving on the street. I don't always launch on the street at full throttle trying to spin the tires! And the improved low end power means less throttle opening and quicker throttle response for any normal driving!

Jim Hand

[slowbird]

Jim
Could you give the height and width of your intake port at the pushrod bulge, if you know it. Im trying to get a feel for how small your port is dimensionally.

[Jim Hand]

Slowbird,
I can get pretty close even though the heads and intake are installed. I use standard Fel Pro blue intake gaskets that are packed in the standard full gasket set, and enlarge the holes to match the head port openings using a file. And I make a spare set before installing the heads, so measured off them.

The gasket opening is 2.17" tall by 1.15" wide.

I did not break through any of the push rod bulges, so that may provide you a clue on actual width at that point. I have finally realized that that the push rod bulge is not the restriction on 270 cfm ports! However, I do widen and smooth them slightly. And the slight height increase helps that some.

The 2.17 height is a bit more then pure stock but a bit less then the standard HO height.

The max diameter of the bowls is about 1.72" just below the second cut under the seat on these heads.

Jim Hand