To much head for my 327 - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #16 (permalink)  
Old 01-14-2009, 01:54 PM
How fast is fast enough?
 
Last photo:
Join Date: Jun 2005
Location: St. Louis, MO
Age: 28
Posts: 8,244
Wiki Edits: 0

Thanks: 12
Thanked 221 Times in 206 Posts
Quote:
Originally Posted by Jsup
Straight from the AFR marketing handbook. AFR has a marketing department I am jealous of, I've been dispelling their myths for a year or more now. It is refreshing to see that there are still people who think clearly and don't drink the Kool Aid. FWIW, whatever you read in a magazine is bought and paid for advertising. There are very few articles that give information. They exists, but they are few and far between.

Small runners big flow making more power is a MYTH. Here's why, something I wrote a while back:


Looking above we see that there is a great deal of effort put into not only how much air could be pulled through the port, but mostly, how it will get through the port (thatís what we are really working on, getting air into the engine during actual operation). You must always remember that a flow bench is only measuring how easily air can be pulled into the cylinder, not how much WILL be pulled into the cylinder during operation. This means that when comparing cylinder head sizes the most important aspect as the SHAPE of the port and how that shape relates when viewing flow all the way to the combustion chamber. Airflow must be controlled, and hence the shape and measurements of the port are far more important that just looking at restriction versus runner size. Again; a flow bench does not measure how much air will be pulled through the port during operation, it measures how easily it can be pulled though in isolation. When looking at a port design one must look to see what the airflow demands will be; they also must look to what type and how much fuel will be induced into the mix, what RPM the engine will be operating at and lastly, must look past the port into the combustion chamber and into the intake manifold. Significant hp can be gained or lost with or without the proper entrance and filling of the cylinder. A cutting edge cylinder head not only has low restriction, a proper shape for tuning purposes (has to control the velocity along with cutting back irregular flow), a combustion chamber to promote flow (how a cylinder is filled is as important as how much is filled); it has all of the above working together and then promote proper flame travel once the cylinder is ignited (another very complicated aspect of how the engine makes its power, valve and spark plug placement and combustion chamber shape have to consider this as well as how much air can pass through it)!

If you can match the flow with more volume what do you gain? The aspects you discussed are why runner size is njot the only concern, but it does not explain why it would be of little concern (which I assume is what you're trying to suggest). All of the things you mentioned are key in improving flwo but none of them adress runner size, really its a good argument for smaller runner size as they would have to take advantage of all of the elements you detailed.

the flow ratings are a volume over time, the runner size is a volume, dividing the 2 give you a velocity, in street applications a higher velocity has been shown to make more power- there is a limit to this but from all I have seen it is only approached in racing conditions.

I'm not trying to be a ******** or anything I just want to learn what it is you're talking about as I have never seen a street engine gain from a lower velocity with an equal flow.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #17 (permalink)  
Old 01-14-2009, 02:03 PM
Registered User
 
Join Date: Dec 2008
Location: New Jersey
Posts: 612
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by ap72
If you can match the flow with more volume what do you gain? The aspects you discussed are why runner size is njot the only concern, but it does not explain why it would be of little concern (which I assume is what you're trying to suggest). All of the things you mentioned are key in improving flwo but none of them adress runner size, really its a good argument for smaller runner size as they would have to take advantage of all of the elements you detailed.

the flow ratings are a volume over time, the runner size is a volume, dividing the 2 give you a velocity, in street applications a higher velocity has been shown to make more power- there is a limit to this but from all I have seen it is only approached in racing conditions.

I'm not trying to be a ******** or anything I just want to learn what it is you're talking about as I have never seen a street engine gain from a lower velocity with an equal flow.
I've been battling AFR idiots for a long time. This small port big flow thing is nothing more than marketing crap...

Port Velocity is another aspect of delivery, yes, but air can not compress until .6 Mach. If you can't compress air, you can not make more power. The reason is you can't get past 100% VE without compressing the air.

Air in an engine RARELY moves past .6 Mach unless we're talking about the highest end engines like those in the Engine Master's challenge that make 120% VE. Not the everyday motors we talk to here.

Also, for a variety of reasons, port velocity will start working against you if the design is off.

Bottom line, it's about QUALITY of the delivery and being able to suspend fuel effectively not the QUANTITY. Dart will tell you that even though they have bigger ports and smaller flow numbers they can suspend more fuel more effectiely into the cyl than AFR. Do they? IDK but it is based on solid science.

Magazine articles are written to the lowest common denominator and simple concepts are easy to grasp. Marketing brochures are made to sell a product, not educate anyone. Do not take either as gospel, and please, don't spread it as such.

To say you 've never seen a street engine gain from less velocity with equl flow simply means you've been looking at the wrong engines, and have never possibly seen these engines, I suspect it's just internet ball swingers telling stories. Let me rescue you from the ball swingers. Again, it appears you're drinking AFR Koolaid Hook, line, and sinker. Think about it, where did you get this information and how valid is it?

Last edited by Jsup; 01-14-2009 at 02:09 PM.
Reply With Quote Quick reply to this message
  #18 (permalink)  
Old 01-14-2009, 02:10 PM
How fast is fast enough?
 
Last photo:
Join Date: Jun 2005
Location: St. Louis, MO
Age: 28
Posts: 8,244
Wiki Edits: 0

Thanks: 12
Thanked 221 Times in 206 Posts
How does all of that apply to a street engine though? I understand what you're talking about but with all of the wrongs of a typical street duty dual plane intake being on the other side of the head those things are of little consequence IMO. In race engines all of that has merit, but with the compomises of a street engine I can't see it.

The heart of this thread is about runner size. If runner size was so inconsequential then "hogging out the runners with a carbide bit" would be the ideal method of porting and their would be a lot of expierenced ehad porters wasting their time over worrying about where to leave material or even add it. The fact that it is possible to reshape a runner with epoxy to flow more but have less volume, and make more power I think proves that runner volume does matter.

I understand that you can gain some flow by enlarging the runner size in the right areas but if your talking about equal flows how will a bigger runner make more power? I understand that flow isn't everything (albeit a VERY good indicator on a street engine) but I'm still at a loss as to why a bigger runner with equal flow would make more power.
Reply With Quote Quick reply to this message
  #19 (permalink)  
Old 01-14-2009, 02:13 PM
How fast is fast enough?
 
Last photo:
Join Date: Jun 2005
Location: St. Louis, MO
Age: 28
Posts: 8,244
Wiki Edits: 0

Thanks: 12
Thanked 221 Times in 206 Posts
Oh, and I really don't pay much attention to AFR, my info is primarily from fluid dynamics text books, which is barely anything compared to what these people are working on but its what I got.
Reply With Quote Quick reply to this message
  #20 (permalink)  
Old 01-14-2009, 02:41 PM
cool rockin daddy's Avatar
1.21 giga-watts???!!!!
 
Join Date: Aug 2003
Location: wherever cool cars are
Posts: 1,535
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
That's our gool ol' ap72. Text book knowledge, no real experience. You have just proved my point about all your posts. Thank you. I do like how you actually admitted you didn't understand something and wanted learn more. Admirable. Will probably get you back in good graces with a lot of people on the forum if you continue down this much better path of posting.
Reply With Quote Quick reply to this message
  #21 (permalink)  
Old 01-14-2009, 02:49 PM
Member
 
Join Date: Dec 2004
Location: Madison, WI
Posts: 1,885
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Reshaping the port with expoxy can increase flow NOT due to the port being smaller, has nothing really to do with it, but by the new shape.
Reply With Quote Quick reply to this message
  #22 (permalink)  
Old 01-14-2009, 03:02 PM
BOOMER SOONER
 
Last photo:
Join Date: Jun 2008
Location: Oklahoma
Age: 39
Posts: 227
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Well, I did not know that I would get all this response on this. To answer some questions about use, and vehicle it is going in.

64 Chevy Nova II
2800 lbs
Muncie close ratio 4 speed, lakewood bellhousing
Ford 9" rear end with 31 spline Moser axles, Moser full spool, 4.56 gears

NOT, a daily driver. Just a weekend curiser, possibly a few passes a year at the Tulsa Dragway. The heads are stock from Brodix, no port work, only factory machine work. My plans were to mill them .018 to get the comb chambers to 64cc, run a thinner head gasket, hopefully get to arround 9.5.1 comp. Run arround a .550 lift cam, tight lash, no more than .250# @ .050 lift, and 108* lobe sep. Any ideas, comments????? Thanks

Shawn
Reply With Quote Quick reply to this message
  #23 (permalink)  
Old 01-14-2009, 04:26 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 12,263
Wiki Edits: 326

Thanks: 610
Thanked 770 Times in 660 Posts
Well, I like to fiddle around with this stuff on the DynoSim, so thought I would take a swing at this combo.
350 block bored 0.060", 3.25" crank, 336.6 cubic inches.
Flat-top pistons, 4vr. Could only find 2vr on Flatlander site. Their graph shows 9.27:1 with 64cc heads, bored 0.060" over, so that's what I used for this simulation.
Brodix Track1 heads, 221/67, milled for 64, flow as follows:
.200 124 103
.300 179 138
.400 228 164
.500 264 178
.600 276 186
.650 278 188
.700 279 190
Hi-rise, dual plane intake manifold such as RPM, 650 carb.
1 5/8" headers, dyno'd through the mufflers.
CompCams 12-501-5 Tight Lash mechanical flat tappet camshaft, grind #272TL-6, 272/276, 242/246, 0.510"/0.520", 106/106/106, timing events @ 0.050" with camshaft advanced 4 degrees, 19/43/53/13, 62 degrees overlap. Dyno'd 13 different cams to get to these results.....
RPM HP TQ
2000 133 349
2500 179 376
3000 218 382
3500 268 402
4000 317 416
4500 354 413
5000 386 405
5500 408 390
6000 416 364
6500 411 332
7000 386 290
7500 354 248

It is amazing what a couple of small changes will do for power output. Dyno'd straight out of the collectors with 1 3/4" stepped-tube competition headers and a 750 carb, here are the results.....
RPM HP TQ
2000 133 350
2500 197 415
3000 242 423
3500 285 428
4000 332 436
4500 374 436
5000 406 427
5500 436 416
6000 452 396
6500 454 367
7000 443 332
7500 419 293
This combo makes in excess of 400 ft/lbs of torque from 2300 to 5800. That ought to be a lot of fun in a stick car.

Last edited by techinspector1; 01-14-2009 at 05:58 PM.
Reply With Quote Quick reply to this message
  #24 (permalink)  
Old 01-14-2009, 04:33 PM
Member
 
Join Date: Dec 2004
Location: Madison, WI
Posts: 1,885
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
250 duration @ .050 with a 327 is going to be one high revving deal. Compression is light for that type of spec though. You'd be better off cutting it back closer to what Tech posted.

Bolt the Brodix heads on and have fun.
Reply With Quote Quick reply to this message
  #25 (permalink)  
Old 01-14-2009, 05:24 PM
BOOMER SOONER
 
Last photo:
Join Date: Jun 2008
Location: Oklahoma
Age: 39
Posts: 227
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Man, you guys are great! You do not know how much I thank you for your input. What about the valve size? Will it matter much below 7000 rpm with the 2.08's? Or does this help on the upper end of the rpm scale? Also, with the desktop dyno figures in the earlier post, does it matter if you change the bore size to 4.060 with 3.25 stroke? That is what I accually have. As for my pistons, I wanted to re-use them because they only have about 2000 miles on them from the previous build. Thanks again fellow hot rodders!

Shawn
Reply With Quote Quick reply to this message
  #26 (permalink)  
Old 01-14-2009, 05:34 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 12,263
Wiki Edits: 326

Thanks: 610
Thanked 770 Times in 660 Posts
That raises the static compression ratio. I'll re-figure and change the figures on the sims....
OK, numbers on both sims changed to reflect 9.27:1 SCR.

Last edited by techinspector1; 01-14-2009 at 06:01 PM.
Reply With Quote Quick reply to this message
  #27 (permalink)  
Old 01-14-2009, 07:13 PM
Registered User
 
Join Date: Dec 2008
Location: New Jersey
Posts: 612
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by ap72
How does all of that apply to a street engine though?
The laws of physics don't know a street engine from a race engine.
Quote:
I understand what you're talking about but with all of the wrongs of a typical street duty dual plane intake being on the other side of the head those things are of little consequence IMO. In race engines all of that has merit, but with the compomises of a street engine I can't see it.
See above

Quote:
The heart of this thread is about runner size. If runner size was so inconsequential then "hogging out the runners with a carbide bit" would be the ideal method of porting and their would be a lot of expierenced ehad porters wasting their time over worrying about where to leave material or even add it. The fact that it is possible to reshape a runner with epoxy to flow more but have less volume, and make more power I think proves that runner volume does matter.
I didn't say that. I am saying again, it's as much about design as it is dimensions.

Quote:
I understand that you can gain some flow by enlarging the runner size in the right areas but if your talking about equal flows how will a bigger runner make more power? I understand that flow isn't everything (albeit a VERY good indicator on a street engine) but I'm still at a loss as to why a bigger runner with equal flow would make more power.
It is not a good indicator for a street engine or anything else. It is CHEAP and people can grasp onto it easily. A cheap easy to understand measurement is something simpletons can soak up and fits well in a magazine.

No, flow can be manipulated. You do realize how inaccurate a dry flow bench is. I can show you two benches on two sides of town that are 15CFM apart. A dry bench is effected by altitude, barometric pressure, and setup to mention a few.

Dry flow benches are good to get a starting point and to measure how much your flow has improved from change to change. But it does not tell you if it is a good change. Also, it has to be the same head on the same bench to telly you anything. It is actually quite archaic..
Reply With Quote Quick reply to this message
  #28 (permalink)  
Old 01-14-2009, 07:30 PM
How fast is fast enough?
 
Last photo:
Join Date: Jun 2005
Location: St. Louis, MO
Age: 28
Posts: 8,244
Wiki Edits: 0

Thanks: 12
Thanked 221 Times in 206 Posts
Quote:
Originally Posted by Jsup
The laws of physics don't know a street engine from a race engine.


See above



I didn't say that. I am saying again, it's as much about design as it is dimensions.



It is not a good indicator for a street engine or anything else. It is CHEAP and people can grasp onto it easily. A cheap easy to understand measurement is something simpletons can soak up and fits well in a magazine.

No, flow can be manipulated. You do realize how inaccurate a dry flow bench is. I can show you two benches on two sides of town that are 15CFM apart. A dry bench is effected by altitude, barometric pressure, and setup to mention a few.

Dry flow benches are good to get a starting point and to measure how much your flow has improved from change to change. But it does not tell you if it is a good change. Also, it has to be the same head on the same bench to telly you anything. It is actually quite archaic..
The fact taht it is cheap is one of the things that to me make it a good indicator, and sure the tools used to measue it can be off, but that isn;t the fault of the testing method its the fault of the tools used. I'm not saying that a certian flow can eqwuate a certain power level, but it gives you a good cheap and fast way of comparison that can be equalized if starndards are used in testing. Its not perfect but in a lot of ways its still a great test. IMO


As to "Reshaping the port with expoxy can increase flow NOT due to the port being smaller, has nothing really to do with it, but by the new shape." the new shape is smaller and works better because it eliminates dead spots- which is part of what I'm trying to say. Presumabley if a runner has a smaller size and has more flow (at all lift points) then it has a better shaped runner with less dead spots. I realize its a gross presuption but one that GENERALLY holds true.

Again this is just the way I see it.
Reply With Quote Quick reply to this message
  #29 (permalink)  
Old 01-14-2009, 08:10 PM
Registered User
 
Join Date: Dec 2008
Location: New Jersey
Posts: 612
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by ap72
The fact taht it is cheap is one of the things that to me make it a good indicator, and sure the tools used to measue it can be off, but that isn;t the fault of the testing method its the fault of the tools used. I'm not saying that a certian flow can eqwuate a certain power level, but it gives you a good cheap and fast way of comparison that can be equalized if starndards are used in testing. Its not perfect but in a lot of ways its still a great test. IMO
Don't get me wrong, it's not a bad thing, just people put WAAAYYYY too much emphasis on it. I'd rather have a well designed head with lower flow numbers than an average head with big ones. It's about the finer points

Quote:
As to "Reshaping the port with expoxy can increase flow NOT due to the port being smaller, has nothing really to do with it, but by the new shape." the new shape is smaller and works better because it eliminates dead spots- which is part of what I'm trying to say. Presumabley if a runner has a smaller size and has more flow (at all lift points) then it has a better shaped runner with less dead spots. I realize its a gross presuption but one that GENERALLY holds true.

Again this is just the way I see it.
Look there is an entire industry that spends BILLIONS AND BILLIONS on research and development. Incluing drag racing, track racking, marine racing, dirt track, oval track, etc.

If small port big flow were SOOOO important, why isn't everyone pushing it? Are the guys at Edlebrock that stupid? Brodix? Dart? All Pro? Canfield? etc... Serious, do you think with all the money they have and spend they can't come up with it? Only one manufacturer makes that claim, AFR. Is AFR so much smarter than the rest of the world? I don't think so.
Reply With Quote Quick reply to this message
  #30 (permalink)  
Old 01-14-2009, 08:35 PM
How fast is fast enough?
 
Last photo:
Join Date: Jun 2005
Location: St. Louis, MO
Age: 28
Posts: 8,244
Wiki Edits: 0

Thanks: 12
Thanked 221 Times in 206 Posts
Actaully most of them advocate smaller runners on smaller displacement engines. And most of them offer a particular head with different runner sizes for that reason. I'm not saying a 220cc runner wouldn't do better than a 170 on a 400sbc that was gone thru, but on a 327 where the total flow quickly becomes limited by the short block a smaller runner would be of bennefit. that's part of the "same total flow with a smaller runner size" that i was talking about.

And the reason AFr talks about it is because runner size is a way of comparing cylinder heads, if one of them poses less of a restriction (with all other things being equal- which the never are) then it would preform better.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Retorque Head Bolts--New Thread Sealer? Turbo-CBX Engine 5 01-12-2009 10:28 AM
What about this head on my 327 Hacksaw Engine 3 10-06-2008 05:41 PM
Building A 302 Chevy Scorpio Shaping Flow Hotrodding Basics 6 01-16-2007 05:55 AM
Valve Stem Angles, Do they Matter? Truth or Fiction? QuenchPiston Engine 35 12-28-2006 10:11 AM
cylinder head cracked?!?!?!?! Blob Engine 4 01-24-2005 06:12 PM


All times are GMT -6. The time now is 06:36 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.