Why size is not a bigger is better thing with engines....
05-03-2002, 02:39 AM
#1
Why size is not a bigger is better thing with engines.... O.k. We are guys and we all know (or do we all know?) that size counts. Right? It does for some things, but in engines it's not that way.
I understand completely that ther is no replacement for displacement, that's why we are here, because there are so many Ricers out there with 1.8L enignes and such and good ole American 5.7L pushrod engines still rule the roost. I like to say that the only replacement for displacement is cubic dollars. That's why a 300hp 1.8L Integra costs $10K to make work for street use. Now we all know that a 400rwhp Engine in a LS1 car is easy and will not cost us more than $5000.
I'm not taking about that, i'm talking about our mindset and where we need to take the LS1 too. Recently I read an article in High Performance Chevy. Kevin McClelland (who used to work for GM as an Engineer) started off his april Q&A with this.
"It's a Size Thing
Everyhting bigger must be better! It must be because we live in a "super-sized" world....
As you have seen over the years, Chevy High Performance has preaced that bigger isn't always bettter. This couldn't be more true in the selction of cylinder heads. Warren Johnson once said that he wants the "most airflow possible through the smalles inlet ports." These types of cylinder heads will always acclerate the car the fastest. Remebre taht it;s torque that moves the car. Throttle repsonse and driveablity are also right up there in our top ten requests. The smaller theport volume, the more responsive the engine......
I've always used the recipe that blends the most airflow with the smallest cylinder heads for the application. When you match this with the smallest camshaft for the application, you'lll always have a winner. Horsepower might sell cars, but it's torque tha moves'em!"
This article says alot. For one thing it says that what we need is not 350cfm ports but ports that are 220cc's and flow 300cfm! @ .500 lift. Right now we ask for flow numbers, hell I don't give a **** how well a head flows unless I know how big it is. What we need tho find out for the LS1 aftermarket heads is cfm per cc. Right now we don;t have any aftermarket heads out there that are as good as the 23 degree Brodix WP T1 STD or the AFR 215cc
I really think until we get LS1 heads that are this good we aren't as far as the old Small Block Chevy's are.
I have seen proof of this once on a LS1 car. WizKid (LS1.com Name) did a install of TEA Stage I heads on his car on Install University and it showed how these Stage I Heads with a Hammer/Andy Cam made more over all TQ than the MMS setup did. (and the same HP BTW) This is where we need the head porters to get too, and I think this will keep the LS1 alive as the perfect Hot Rod Engine that it is.
Bret
I understand completely that ther is no replacement for displacement, that's why we are here, because there are so many Ricers out there with 1.8L enignes and such and good ole American 5.7L pushrod engines still rule the roost. I like to say that the only replacement for displacement is cubic dollars. That's why a 300hp 1.8L Integra costs $10K to make work for street use. Now we all know that a 400rwhp Engine in a LS1 car is easy and will not cost us more than $5000.
I'm not taking about that, i'm talking about our mindset and where we need to take the LS1 too. Recently I read an article in High Performance Chevy. Kevin McClelland (who used to work for GM as an Engineer) started off his april Q&A with this.
"It's a Size Thing
Everyhting bigger must be better! It must be because we live in a "super-sized" world....
As you have seen over the years, Chevy High Performance has preaced that bigger isn't always bettter. This couldn't be more true in the selction of cylinder heads. Warren Johnson once said that he wants the "most airflow possible through the smalles inlet ports." These types of cylinder heads will always acclerate the car the fastest. Remebre taht it;s torque that moves the car. Throttle repsonse and driveablity are also right up there in our top ten requests. The smaller theport volume, the more responsive the engine......
I've always used the recipe that blends the most airflow with the smallest cylinder heads for the application. When you match this with the smallest camshaft for the application, you'lll always have a winner. Horsepower might sell cars, but it's torque tha moves'em!"
This article says alot. For one thing it says that what we need is not 350cfm ports but ports that are 220cc's and flow 300cfm! @ .500 lift. Right now we ask for flow numbers, hell I don't give a **** how well a head flows unless I know how big it is. What we need tho find out for the LS1 aftermarket heads is cfm per cc. Right now we don;t have any aftermarket heads out there that are as good as the 23 degree Brodix WP T1 STD or the AFR 215cc
I really think until we get LS1 heads that are this good we aren't as far as the old Small Block Chevy's are.
I have seen proof of this once on a LS1 car. WizKid (LS1.com Name) did a install of TEA Stage I heads on his car on Install University and it showed how these Stage I Heads with a Hammer/Andy Cam made more over all TQ than the MMS setup did. (and the same HP BTW) This is where we need the head porters to get too, and I think this will keep the LS1 alive as the perfect Hot Rod Engine that it is.
Bret
05-03-2002, 09:51 AM
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Re: Why size is not a bigger is better thing with engines.... Actually, this is something that I have been preaching for years... it's not just about the volume of air the port can flow, it's also about the velocity through the port. There has to be a balance.
Think of it this way... let's look at a motor at, say, 2000 RPM (that low simply because we all know that no port will be anywhere near maxed out at that level). You've got a choice of a big port, or a small port. Which do you choose?? With the big port, you've certainly got the air volume available but because of the size of the port your A/F charge velocity will be for ****. With the small port, you've still got the volume available but due to the smaller port size your A/F velocity is higher (than with the big port), which results in a better cylinder fill.
Now, we all realize that if we want to make some power that we're going to have to rev the motor higher than 2kRPM. Fine. That means bigger ports than would be ideal at that 2000 RPM level, right?? Right. That being said, we need to realistically ask ourselves how tight we want to twist the motor (as well as what size the motor is), then find a port that is ideal somewhere in the mid point in our rev range. Why?? Because no matter what the port, there WILL be a point at which it reaches the best possible balance of volume and velocity. Unless you're building a truck motor (where you would want your port to reach its ideal conditions lower in the rev range) or a track-only car (which, I admit, some of the folks on here are doing; you would want your port to reach its ideal conditions higher in the rev range), you want as much access to that "sweet spot" as possible without absolutely choking your motor when you get the revs up.
At least that's my $.02, for what it is worth. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
Think of it this way... let's look at a motor at, say, 2000 RPM (that low simply because we all know that no port will be anywhere near maxed out at that level). You've got a choice of a big port, or a small port. Which do you choose?? With the big port, you've certainly got the air volume available but because of the size of the port your A/F charge velocity will be for ****. With the small port, you've still got the volume available but due to the smaller port size your A/F velocity is higher (than with the big port), which results in a better cylinder fill.
Now, we all realize that if we want to make some power that we're going to have to rev the motor higher than 2kRPM. Fine. That means bigger ports than would be ideal at that 2000 RPM level, right?? Right. That being said, we need to realistically ask ourselves how tight we want to twist the motor (as well as what size the motor is), then find a port that is ideal somewhere in the mid point in our rev range. Why?? Because no matter what the port, there WILL be a point at which it reaches the best possible balance of volume and velocity. Unless you're building a truck motor (where you would want your port to reach its ideal conditions lower in the rev range) or a track-only car (which, I admit, some of the folks on here are doing; you would want your port to reach its ideal conditions higher in the rev range), you want as much access to that "sweet spot" as possible without absolutely choking your motor when you get the revs up.
At least that's my $.02, for what it is worth. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
05-03-2002, 10:07 AM
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Re: Why size is not a bigger is better thing with engines.... There's no such thing as a port that flowed too much..... it's just not over a big enough hole.
05-03-2002, 11:03 AM
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Re: Why size is not a bigger is better thing with engines.... Bigger cubic inches are always better as long as you still have the strength for the task at hand.
Like Joe said, bigger flow is always good - as long as velocity isn't killed to get it.
It's not that bigger isn't better, it's that you want to maximize everything <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
We don't want just the biggest flow, we want the biggest flow with the biggest velocity with the biggest number of cubic inches to make the biggest horsepower.
Chris
Like Joe said, bigger flow is always good - as long as velocity isn't killed to get it.
It's not that bigger isn't better, it's that you want to maximize everything <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
We don't want just the biggest flow, we want the biggest flow with the biggest velocity with the biggest number of cubic inches to make the biggest horsepower.
Chris
05-03-2002, 11:15 AM
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Re: Why size is not a bigger is better thing with engines.... What popular head porter in the LS1 world posts port size and velocity numbers? <img border="0" alt="[jester]" title="" src="graemlins/gr_jest.gif" />
haha.. yep, exactly... <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
Where's Terry when you need him. <img border="0" alt="[devil]" title="" src="graemlins/gr_devil.gif" />
haha.. yep, exactly... <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
Where's Terry when you need him. <img border="0" alt="[devil]" title="" src="graemlins/gr_devil.gif" />
05-03-2002, 02:36 PM
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Re: Why size is not a bigger is better thing with engines.... Well how is it that we can measure/quantify velocity?? Pretty impractical, really...
Anyhoo, you can get the general idea of the port velocity by looking at the port flow, then looking at the size of the port. For X cfm, the velocity through a 220 cc port will be higher than through a 230 cc port. In other words, looking at raw numbers on a case-by-case basis won't tell you much, but when you compare the parameters from multiple head porters, you can see which ones fit your needs the best.
Anyhoo, you can get the general idea of the port velocity by looking at the port flow, then looking at the size of the port. For X cfm, the velocity through a 220 cc port will be higher than through a 230 cc port. In other words, looking at raw numbers on a case-by-case basis won't tell you much, but when you compare the parameters from multiple head porters, you can see which ones fit your needs the best.
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05-03-2002, 04:50 PM
#8
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Re: Why size is not a bigger is better thing with engines.... My first attempt at Ls1 castings is 284 cfm at .550" lift with a 210cc intake port.That is about 10 cc bigger than stock and almost 50 cfm better than stock flow at that lift. I disagree LS1 is behind Brodix and AFR heads in flow per cc.Ls1 casting has small port size for flow numbers, they are apples to oranges when comparing volume sizes, because heads are different lengths, etc. Velocity gradients are much less with LS1 design ports. Great topic BTW.
P.S. remember valve sizes also, that makes a big difference, 2.08" is going to flow alot more than 2.00" that covers up inefficiency of old style 23* heads.
<small>[ May 03, 2002, 04:56 PM: Message edited by: LS1derfull ]</small>
P.S. remember valve sizes also, that makes a big difference, 2.08" is going to flow alot more than 2.00" that covers up inefficiency of old style 23* heads.
<small>[ May 03, 2002, 04:56 PM: Message edited by: LS1derfull ]</small>
05-03-2002, 05:03 PM
#9
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Re: Why size is not a bigger is better thing with engines.... I want to add, LS1 heads have very strong swirl characteristics, 23* heads do not, when swirl is combined with those heads it always costs flow.LS1 has great compromise of both, this is why LS1 doesnt require as much total ignition timing as SBC.I cant think of any aspect that LS1 isnt better than SBC, can you?
05-03-2002, 05:25 PM
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Re: Why size is not a bigger is better thing with engines.... LS1derful... myself, the only thing I prefer about the legacy SBC is the 4" bore. I'm all about the larger bore, but that's just me. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
05-03-2002, 06:28 PM
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Re: Why size is not a bigger is better thing with engines.... I am a advocate of bore over stroke, but when heads are superior bore size becomes less important, thats why 3.900" still makes great power.LS1 doesnt need traditional "crutches" to make above average power. As far as price is concerned have you guys priced SBC aluminum block, and 15* aftermarket SBC heads lately? LS1 is a bargain from any stand point IMO.
05-04-2002, 02:10 AM
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Re: Why size is not a bigger is better thing with engines.... AFR heads rock. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> Can't wait till they start doing LS1 heads. (Or do they already?) I remember reading an article a while back comparing SBC heads and the AFRs basically trounced every other make out there.
'Los
'Los
05-04-2002, 02:14 AM
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Re: Why size is not a bigger is better thing with engines.... I doubt there will be many if any aftermarket castings for quite awhile for the LS1. With ported z06/6.0l heads flowing in the 350cfm+ range when fully worked the heads already flow phenomenally.
Though the comparison really isn't valid because of the valve angle differences, etc. ls6 heads are flowing, when worked, as well as a worked set of AFR's premiere 23 degree SBC head - the 215rr.
Chris
Though the comparison really isn't valid because of the valve angle differences, etc. ls6 heads are flowing, when worked, as well as a worked set of AFR's premiere 23 degree SBC head - the 215rr.
Chris
05-04-2002, 02:35 AM
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Re: Why size is not a bigger is better thing with engines.... I agree with ChrisB & LS1derfull. Cubic inches, if allowed, will beat smaller cubes, all else being equal.....AFR heads? They are good, but your comparing 23 degree heads to 15 degree heads. Look at what the Pro Stock Truck guys the last three years used, Splayed Valve heads, that flowed wayyy better than 23 degree AFR. When compared to that head (Ultimate SB Chev old school), we still have a way to go. Aftermarket heads would be good right now. If Dart, Brodix or similar came out with a superior head, I'd buy two sets right now!!! <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Anyone else would buy some too??? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
Cheers
<small>[ May 04, 2002, 02:37 AM: Message edited by: Will Race 4 Food ]</small>
Anyone else would buy some too??? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
Cheers
<small>[ May 04, 2002, 02:37 AM: Message edited by: Will Race 4 Food ]</small>
05-04-2002, 07:14 AM
#16
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Re: Why size is not a bigger is better thing with engines.... I have AFR 215cc raised runner heads on my 68 NOVA, they are awesome, but they dont flow 350cfm like some LS6 heads, and they have antiquated comb. chambers and spark plug locations.The LS1 is a superior design, AFR head has 2.100" valve flows 325cfm at max lift and is about 230cc finished. My Nova has to leave at 6000 rpm to pull clean off the starting line, that means it doesnt want to accellerate from lower engine speeds, i know some of this is cam choice but believe me the LS1 is doing more with less, IMO.
05-04-2002, 10:42 PM
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Re: Why size is not a bigger is better thing with engines.... So, would it be fair to summarize:
"People are hogging out Stage X Heads too damn much for low to mid-rpm power and it'd be nice to see some true aftermarket heads" ?
I like Stock Heads for the money, unless you have cheap porting DIY options.
"People are hogging out Stage X Heads too damn much for low to mid-rpm power and it'd be nice to see some true aftermarket heads" ?
I like Stock Heads for the money, unless you have cheap porting DIY options.
05-04-2002, 11:39 PM
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Re: Why size is not a bigger is better thing with engines.... There is no magic when it comes to flow versus rpm and port size. Aftermarket heads choose a volume to flow ratio when they design and machine a head, it either fits your engine size/rpm range or you choose a different casting. A LS1 or 6 head that has more flow to volume(cc's) ratio than a stock head will maintain lower and mid range power capabilities while making more peak power than unported and smaller head. I hope this came out clear, im tired. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
05-04-2002, 11:46 PM
#20
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Re: Why size is not a bigger is better thing with engines.... A bigger ported LS1 port can make more power everywhere than a smaller one if velocity is maintained by moving more air to offset the extra volume that is added porting.