Runner Volume VS. Flow Numbers ???

This will probably get me in trouble, but I keep coming back to Runner Volume VS. actual flow numbers. The shop I work at has a Superflow SF600 flow bench, Bryzinski (SP?) plates,etc. and though I am not a head porter myself, I have flowed numerous heads over the last 15 years, many being Big Block Fords. I am preparing to pull my 514 (basic Eagle kit with out of the box TFS heads and Intake) out of the car and send the heads out for CNC porting, and then a trip back to our dyno to see what gains are there. The reason I posed the question about runner volume has to do with another BBF we built at about the same time that has CNC ported TFS heads by Troy Bowen at Ford Performance Solutions. Our Customer's Combo is 4.500 x 4.150, has a .600 lift hydraulic roller camshaft, compression under 10.1, and has a Victor EFI Spyder intake by Pro Mustang. The flow numbers on these heads rival a set of P51 castings Charlie Evans supplied for my brother's 557, yet have a larger intake runner volume. I guess it comes back to efficiency. This pump gas/efi engine made nealy the same HP and Torque with 2 points less compression, considerably smaller camshaft and an 1 3/4'' header (this engine is slated for a '70's station wagon to tow a boat!). Our Dyno is a little "tighter" than most, and I have had engines from other Pro Shops that have been as much as 100 HP higher that what shows on our Superflo 902. Around 650 Hp and over 600 Ft/lbs of torque is where we are at. I know Dynos and flowbenches aren't all the same, and I'm sure many will start with these numbers being way to low, etc. I will also tell you my car is 3050 lbs., stock suspension, and ran a 9.82 at a little over 135mh on 275 M.T. drag radials with a tight converter and 3.73 gears. Nothing outstanding, just listing the facts I have. The class I ran in was a 10.00 Index class, so the project fit perfectly, for a very modest budget. Back on topic. I have seen with some stroker smallblocks I ran in the past, as well as 460's in my brother's car, that flow numbers don't always equate to the power you would think, but intake runner volume always seems to be the culprit. I have changed heads on a smallblock that have 40-50 more cfm on the intake side, close to that on the exhaust side, yet runner volume stayed about the same, and only saw a tenth and 2 mph gain. If you have thoughts on this, formulas that you know work, etc. please reply.

This subject could take a whole book to address it however, to make the explanation VERY simplified.
A "certain" runner volume and crossectional area is NECESSARY for a given engine to put out a given horsepower at a given RPM reguardless of the air flow but, the more airflow at that necessary volume will be an improvement.
A flow bench measures velocity and CFM at a certain pressure drop and it is NOT realistic in a runnung engine. Once the airflow in a port of a running engine reaches sonic it will not flow any more air, even if a flowbench says it will at it's non-realistic pressure drop. More crossectional area will lessen the air speed and vice versa if the air flows measured are the same.
A flow bench is a tool to get where you need to be, NOT the "end all, be all" of what air flow a specific engine wants.

Advertising policies of some people in the cylinder head buisness rely upon the "ignorance" of the consumer to NOT understand this, basing their entire decisions upon maximum air flows reguargless of velocity, air acceleration and quality of the flow past the open valve.

Matt,

Glad to see you on here, however I just want to clear something up. The P-51 heads I did for your brother Darryl are POCKET PORTED, and that's all I charged him for. It says so on the flow sheet dated 2-20-07. So in your comparisons, please dont think that the P-51's are fully ported, and can be compared to CNC ported TFS Street heads. IMO that's not a fair comparison, because there is more left to be had in the P-51 heads.

Thanks,
Charlie

Thanks for the replies. Charlie, my brother is very happy with his P51 heads (even if his engine only has been on a dyno). What I was getting at was heads with similar flow numbers vs. their port volumes. The P51 heads I believe are between 312-315 CC runners. These CNC TFS heads are larger ( I have seen advertisements in the 2007-2008 Avenger catalog with a listing of 335-355 CC intake runner). Most would say that the low Compress stroker engine with the Mild Hydr. roller cam would be better suited with a smaller runner head that still had good flow numbers. Since I can't take a customer's engine apart and swap parts to prove or disprove this point, I am looking for thoughts from those that are familiar with BB Ford heads. Since I have dyno numbers and flow results on my own project, I will pull mine apart, have the head work done, and then re dyno. I plan on playing with a Victor Intake, a QFT 1050 Carb, and your header adapters with larger primary Chevy Headers, not all at once. Thanks for the input. Heading out on vacation tomorrow, but hope to pull he engine out in the next week or two.

If possible by the time you are ready to try different parts, the TFS Mafia intake may be available, I'd give that a try vs. the Victor.

How can you compare the actual c.c. volume between a P51 and a TFS head when the length of the port is so much difference? The P51 and SCJ has a shorter port due to valve placement change.

Bret

So; you finally came over here, and I see that you have already started some controversy. Things never change hunh little brother.

And so no one gets confused, Matt was comparing the CNC ported TFS heads on the pump gas motor at his work to the unported TFS heads on his motor when talking about the power numbers (not my P-51 headed 557).

As far as my engine goes I'm more than happy with the results I had with the power output. It peaked at a little over 800 HP from 5800 to 6600 rpms, with over 740 ft/lb of torque throughout the intended power range. Nothing wrong with that. Like anything, it's all about the right combination (and price) for what YOU want to do, which may or may not be what someone else feels it should be.

After 21 years of running Big Block fords in various racecars througout the Mid-Atlantic region, I think we both can say we know a little about how to make one of these motors run well. Hell, the first 460 we built is still alive and kicking and is in it's 4th car (knock on my wooden head). That engine was good for mid 10's almost 20 years ago with home ported iron DOVE heads in a AMX (we like to be different).

In looking at the different style of heads, I still like the fact that the P51 flow numbers were high starting out from .400 lift and up; right where my relatively small cammed 557 (traction limited) street legal drag radial car will be operating the most (thanks Charlie). Again, each person wants to build something that works for them, not necessarily what appeals to the masses. Hell, if trying to conform was the only point in doing this, we would be no different than the millions of Chevy "Braggarts" that I have had to deal with my entire life.

Now, as far as putting my car together little brother, when are you heading down here to sunny Florida to give a hand? There are 4 project "vehicles" sitting in the garage / trailer / driveway just begging to be finished; take your pick.

And by the way, the trip to Alaska was great. You should have seen the Bald Eagles!

DJ

Back in town. Some of the most interesting info I have was swapping heads around on my brother's basic 460 in his fastback. 10.40's with a steel Cobra Jet head that had some porting done. This combo ran no faster with the Alan Root Cobra jet heads which had minor bowl blend, unshrouding of the chamber and valve job (even with better exhaust flow numbers), but a smaller intake runner. I won't even mention the time it ran with one of each. Trying to slow up the car for a 11.00 Index class, he swapped out the Victor intake for a Ported Port A Sonic, added a K&N air cleaner, and 130 lbs of weight and then I think it only slowed up a tenth. Once a set of smaller passenger car heads were installed then the E.T. fell off, but mostly on the 2nd half of the quarter mile and in the MPH department. Sometimes it's harder to slow down than go faster.Companies like Dart offer many different CC runer heads for SBC and BBC, yet when discussing runner volume they will always steer someone to a smaller runner head vs. the larger runner, even if the flow numbers are similar. We have ran an engine with a set of their 355 CNC head, then swithed to their 380 runner head (N/A), and didn't see any difference, Pro or Con. I remember that it was in the 540-555 CI range and made a little over 800 HP (bracket car). Since you can't call many places and discuss BBF theory, that is why I posted here. Thanks again for those that did offer thoughts. Brother, I plan to be at the Yellow Bullet Nationals Labor Day Weekend at Cecil County beating on that poor old Windsor, feel free to come up.

Welcome, Matt and Darrell. Been a while since I talked to you guy's. Keep on keepin on.

Travis