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4.00"+ Bore question

This is a discussion on 4.00"+ Bore question within the LS2/LS3/LS4/LSx forums, part of the Vehicle Specific category; Hello all, I have been looking into possibilities on upgrading the power in my '02 WS6 and its been mentioned ...

  1. #1
    Senior Member Whamhammer's Avatar
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    '02 Trans Am WS-6, 6M

    4.00"+ Bore question

    Hello all,

    I have been looking into possibilities on upgrading the power in my '02 WS6 and its been mentioned to me several times that power won't seriously increase until a 4 inch or more bore is used. I keep hearing about Ford's Coyote 5.0 and people getting big power number from them. My question is, how? The Coyote has a 3.63 bore and 3.65 stroke as opposed to LS1's 3.89 bore and 3.62 stroke or even the LS3's 4.03 bore and 3.62 stroke. While it is a 32v DOHC engine, the thing doesn't use DFI or anything crazy. Are the heads that much better than what Gen III and Gen IV's are using?

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    Moderator Firebirdjones's Avatar
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    Alot of the HP being made with the smaller bores now has to do with excellent cylinder head designs and valve angles that are 11-15 degrees, something we didn't have 10-12 years ago and was only heard of in Nascar and other forms of high end racing, certainly not on a production engine.
    Those Coyote heads in stock form flow about 300 cfm which is moving some air. That's enough to support 600 HP in naturally aspirated form. You have to port a typical cathedral LS1 head to reach those numbers.

    Bore diameter still plays a roll in HP, as it unshrouds the valves. Flow numbers on cylinder heads are directly related to the bore diameter they are tested on. So it's still something to pay close attention to when shopping for heads. Some manufactures test and publish everything on a 4.5" bore diameter, which isn't realistic for most engine builds. Some don't even list what bore diameter they were tested on, but you can bet it was probably large to make the heads look good.

    So a 4" bore quickly became the smallest diameter to have as a base to start with for making HP, but it's not necessarily critical, especially when building a street car.

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    Senior Member Whamhammer's Avatar
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    So are the aftermarket heads offered by say, Texas Speed or Trick Flow going to move air thats comparable (or superior) to the more modern heads on new cars? Or is the writing on the wall for Gen III's?

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by Whamhammer View Post
    So are the aftermarket heads offered by say, Texas Speed or Trick Flow going to move air thats comparable (or superior) to the more modern heads on new cars? Or is the writing on the wall for Gen III's?
    Cylinder heads are always improving, but I don't think that means the writing is on the wall for gen III's. Just look at how insanely popular the Gen 1 still is. It's still cheap to play with and still makes respectable power. I believe that as Gen III's continue to come down in price they will only gain in popularity.

    My way of thinking is that the generation doesn't matter so much, because there are excellent cylinder heads made for every engine out there, old and new, thanks to the aftermarket. It's nothing to buy heads that flow 300-400 cfm (or more) that can support 800+ HP naturally aspirated. Then top that with forced induction and cylinder head flow suddenly isn't that critical anymore.

    I guess you have to ask yourself, how much is enough? If someone absolutely has to have the latest and greatest, then I'm sorry to say that quest will never end.

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    Senior Member Whamhammer's Avatar
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    Quote Originally Posted by Firebirdjones View Post
    Cylinder heads are always improving, but I don't think that means the writing is on the wall for gen III's. Just look at how insanely popular the Gen 1 still is. It's still cheap to play with and still makes respectable power. I believe that as Gen III's continue to come down in price they will only gain in popularity.

    My way of thinking is that the generation doesn't matter so much, because there are excellent cylinder heads made for every engine out there, old and new, thanks to the aftermarket. It's nothing to buy heads that flow 300-400 cfm (or more) that can support 800+ HP naturally aspirated. Then top that with forced induction and cylinder head flow suddenly isn't that critical anymore.

    I guess you have to ask yourself, how much is enough? If someone absolutely has to have the latest and greatest, then I'm sorry to say that quest will never end.
    Not necessarily latest and greatest, but able to keep competitive with slightly modded' newer setup engines. If our pony-cars aren't able to keep up with them in power, afforability, drivability and economy, It will become pretty hard to justify modifying our GenIII's, or even 4th gen's themselves, don't youthink?

    But for a street application 300-400 cfm head, if priced reasonably, should do okay.

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by Whamhammer View Post
    Not necessarily latest and greatest, but able to keep competitive with slightly modded' newer setup engines. If our pony-cars aren't able to keep up with them in power, afforability, drivability and economy, It will become pretty hard to justify modifying our GenIII's, or even 4th gen's themselves, don't youthink?

    But for a street application 300-400 cfm head, if priced reasonably, should do okay.
    Interesting question. It's hard to gauge cost vs performance ratio, it's different for everybody. Right now the 4th gens are cheap to get into, and it's an LS platform to start. Those are 2 big hurdles. From there it's an individuals taste, and what they consider "enough" power. Those that love the 4th gen LS platform will likely stick with it. The aftermarket is strong for it and it's not hard to make power with an LS engine.

    Some of the new stuff coming out sure looks good though and with blowers and turbos becoming a part of it, it's easy to make silly power with them. Sure is tempting.

    For those that refuse to change, we just keep building bigger and better engines in a quest for more power and try to keep up. It's a sickness
    Last edited by Firebirdjones; 01-07-2014 at 03:23 PM.

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    Senior Member Whamhammer's Avatar
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    Quote Originally Posted by Firebirdjones View Post
    Interesting question. It's hard to gauge cost vs performance ratio, it's different for everybody. Right now the 4th gens are cheap to get into, and it's an LS platform to start. Those are 2 big hurdles. From there it's an individuals taste, and what they consider "enough" power. Those that love the 4th gen LS platform will likely stick with it. The aftermarket is strong for it and it's not hard to make power with an LS engine.

    Some of the new stuff coming out sure looks good though and with blowers and turbos becoming a part of it, it's easy to make silly power with them. Sure is tempting.

    For those that refuse to change, we just keep building bigger and better engines in a quest for more power and try to keep up. It's a sickness
    Well, I'm not sure I want to fork out $40K on a new Camaro (2016) or Mustang (2015), especially with stuff like OnStar and MyTouch, and not getting much more in interior space, when I have a more or less great performing car to begin with, being able to stay ahead of the new pony-car pack is desirable.

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by Whamhammer View Post
    Well, I'm not sure I want to fork out $40K on a new Camaro (2016) or Mustang (2015), especially with stuff like OnStar and MyTouch, and not getting much more in interior space, when I have a more or less great performing car to begin with, being able to stay ahead of the new pony-car pack is desirable.
    I agree, if you are happy with your 4th gen then I see no reason to fork over 40 large for a new car. It's cheaper to mod what you have, even if that means a new 408 and upgrades to go with it, or what ever you desire.

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