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Author
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Topic: Heads and flow rate ?
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Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-12-2004 02:51 PM
   
OK all these flow numbers on make my head spin. How much flow can a SBF handle anyways.
Is there a limit based on exhaust, compression, and or cam choices ect.
And to what point will I notice a difference. Will a head that flows say 40 points more make that much more power ?And doesn't it matter how lift your running too ? Is bigger always better with flow numbers ? ------------------
SCOOP oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
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itlbrnmoff
Gearhead Posts: 1585
From: Indianapolis,IN.USA
Registered: Nov 2002
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posted 02-12-2004 06:14 PM
Sorry Ron, I'd tell you, but I'd be afraid you wouldn't take my advice seriously.   I'm sure one of the masters will chime in shortly. ------------------
'83 Mustang GT T/tops 306, 5-speed, 3.45 trac-loc, 650 dbl. pmpr. RPM intake, headers, 2 1/2" exhaust, 2 chamber Flowmasters = LOUD....
'88 Lincoln Mark VII LSC 5.0 HO, AOD, leather, A/C, 3.27 trac-loc...
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Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-12-2004 06:28 PM
Why not Perry ?There has to be a point that a heads are to big for the motor. ------------------
SCOOP oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
IP: Logged |
itlbrnmoff
Gearhead Posts: 1585
From: Indianapolis,IN.USA
Registered: Nov 2002
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posted 02-12-2004 06:41 PM
I don't have any experience with flow testing, or any aftermarket heads for that matter. All I can do is quote what I read and learn, and I have a good understanding, but, then again, no real experience, so why believe me?
I just spend the better part of a day researching things and typing until my fingers are numb just to get the same responses.
Are you sure my thermostat won't give me 50 more HP?
I'm just pullin' your leg SCOOP.
I write stuff on here sometimes because I like to, it's up to others whether or not they want to make any sense of it. 
I wouldn't intentionally try to steer someone into oblivion.
But it's hard to figure stuff out when you don't have all the relevant specs to try to figure it out.Oh...now Perry's got a downloaded engine analyzer...now he's an instant expert.
All the downloads in the world won't do a damn bit of good if you don't understand the reasoning or theory behind it.
I'm just saying I understand it, that's all. ------------------
'83 Mustang GT T/tops 306, 5-speed, 3.45 trac-loc, 650 dbl. pmpr. RPM intake, headers, 2 1/2" exhaust, 2 chamber Flowmasters = LOUD....
'88 Lincoln Mark VII LSC 5.0 HO, AOD, leather, A/C, 3.27 trac-loc...
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steve'66
Gearhead Posts: 7226
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-12-2004 06:57 PM
Ron,Of course heads can be too big! Why do you think everyone wants "a little head"? SteveW
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Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-12-2004 07:13 PM
Perry don't take this the worng way, but what ? ------------------
SCOOP oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
IP: Logged |
Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-12-2004 07:15 PM
quote:
Originally posted by steve'66:
Ron,Of course heads can be too big! Why do you think everyone wants "a little head"? SteveW
Dang I knew someone would say that, but not you too. No sharing of your knowledge or opinions, just a smart ass remark, your sounding more like me.
------------------
SCOOP oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
IP: Logged |
itlbrnmoff
Gearhead Posts: 1585
From: Indianapolis,IN.USA
Registered: Nov 2002
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posted 02-12-2004 08:03 PM
quote:
Originally posted by Fastymz:
Perry don't take this the worng way, but what ?
 You didn't understand that? What's funny is, that the first engine I ever selected parts for and put together turned out to be a home run hit the first time.
Was it luck? Sure it was. But not a stab in the dark. I read up, and used what made sense to me...the rest was just hoping my novice assembly semi-skill was better than the average yahoo...well, you know what, it was.
The only improvement I can make now to my combo is, maybe upping the compression and a different cam...maybe some real heads. The rest up until now was just finding the right tuning to make it run best. But one thing's for sure, if a gearhead who never really understands what he's doing, or why he's doing, and can't get his combo performing the way it should, even after years of trying to learn, he's just fartin' in the wind. Let a mechanic build the engine, and just drive or race the car, then tell others how they painstakingly learned and prepared the combo just for fun. This is not at you SCOOP, or at anyone in general, I'm just using your post as an ear for others. I'M NOT SUPER-GEARHEADMAN!! But, I know a thing or two!! I learned on my own, and did my thing. I didn't have a computer website to coach me through the tough stuff. If I screwed up, it was my loss, but fortunately, I screwed up enough to know when to get smart. Do I have any followers? Please drink my Kool-Aid... ------------------
'83 Mustang GT T/tops 306, 5-speed, 3.45 trac-loc, 650 dbl. pmpr. RPM intake, headers, 2 1/2" exhaust, 2 chamber Flowmasters = LOUD....
'88 Lincoln Mark VII LSC 5.0 HO, AOD, leather, A/C, 3.27 trac-loc...
IP: Logged |
Mpcoluv
Gearhead Posts: 1144
From: Charlotte NC usa
Registered: Apr 2001
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posted 02-12-2004 08:20 PM
As I am sure as others will say, flow numbers only tell some of the story.
Velocity and swirl is also very important.
Also valve angle and chamber design make a big difference with respect to power.
A very rough rule of thumb is that heads will SUPPORT 2.2hp per CFM. It is up to the rest of the engine to make the power however.
so if you want 400hp you need about 182 cfm (using this guideline). The port volume also tells quite a bit. If you decide that you want 225 cfm and you have a choice of 165cc heads and 185cc heads that both flow the required amount, you would likely be better off with the 165cc heads (because the 165cc heads would have better velocity).
Another thing that most people don't talk about much is swirl. Swirl refers to how the fuel air mixture travels around the combustion chamber. It is normally measured with a propeller type of gizmo on the flow bench. A high swirl head generally produces great low end and midrange.
All of the above is only "Theory" and never means as much as actually running the engine where the rubber meets the road. You will find that some heads make less power than the "bench" says they should, while some will overachieve.
First ignore sales propaganda and decide what is your goal. How much HP and torque? What vacuum at idle is required? How long should it run between teardowns?
Boy this is a long winded rant 
[This message has been edited by Mpcoluv (edited 02-12-2004).]
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itlbrnmoff
Gearhead Posts: 1585
From: Indianapolis,IN.USA
Registered: Nov 2002
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posted 02-12-2004 08:53 PM
Very good! See, I learned some more, and I'll probably remember it too. Because I choose to believe Mpcoluv makes sense, doesn't mean I'm naive and would actually listen to him and him only. I'd weigh the differences of others and then decide who makes the same sense.
If there were more people willing to say what they know so a goal can be achieved, instead of backing away from certain topics just because an unknown is sharing what he knows, this would be a great big happy family. And EVERYONE would benefit from the topic. Even the unknown who might have his wires crossed a bit, but gets the general idea.
Where's the love people? ------------------
'83 Mustang GT T/tops 306, 5-speed, 3.45 trac-loc, 650 dbl. pmpr. RPM intake, headers, 2 1/2" exhaust, 2 chamber Flowmasters = LOUD....
'88 Lincoln Mark VII LSC 5.0 HO, AOD, leather, A/C, 3.27 trac-loc...
IP: Logged |
steve'66
Gearhead Posts: 7226
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-12-2004 10:01 PM
Ron,I couldn't help it, sorry. Mpcoluv beat me to the real answer anyway! Good job! An engine has to be a matched set of components, and even be matched to the correct drivetrain to be effective. Too big of heads, cam, intake, headers, compression ratio, etc. without the other matching "too big" components will kill the combo. Heads that will flow enough to support 700 h.p. will be slugs on a torqey 400 h.p. engine. Find a proven combo of parts that works with your converter and gears and build it. SteveW p.s. I think I've said this before.
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Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-13-2004 12:57 AM
Steve I have my heads picked out already. I was more asking the question just to help me understand the how flow rates apply to a given motor. What Mpcoluv said helped a lot.
So what your saying is you have to have an idea of a HP range and then pick the parts that work together to get that HP rating. But how do you know what parts will do that, you ask those that have been there already. Like all the questions I've asked and all the emails you've all been so kind to reply to.------------------
SCOOP oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics [This message has been edited by Fastymz (edited 02-13-2004).]
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