Who runs LQ4s?

Discussion in 'High Tech Retrofits' started by badazz81z28, Jan 1, 2010.

  1. LSXZ28

    LSXZ28 Veteran Member

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    It'll probably be a little more with the LS6 heads he has, depending on how well they are ported. The L92 heads have great flow numbers on paper, and don't get me wrong, they are good heads for the price. But there are cathedral port heads that will make just as much power or more...

    Keep in mind those magazine articles only touched the tip of what has been done with LS engines. They tend to show builds with parts that they have been given by someone wanting the press.

    There is one particular late model GM magazine that seemed to be completely owned by one particular company. They always raived about this companies parts and their builds. Here in the real world, their parts were junk and they couldn't tune an LS1 to save thier life. Too many people ripped off because the magazines pockets were lined with that money.
     
  2. Aceshigh

    Aceshigh Veteran Member Lifetime Gold Member

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    LS6 heads would make the compression high
    LS6 = 64cc while L92 = 72cc chambers

    LQ4 = 9:41.1 Compression
    LQ9 = 10.1 Compression
    http://www.carcraft.com/techarticles/general_motors_gen_iii_engine_cylinder_heads/index.html
     
    Last edited: Jan 3, 2010
  3. LSXZ28

    LSXZ28 Veteran Member

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    That's right - I'll take the 10.1 over 9.4:1 any day for a naturally aspirated LS1! These engines like way more compression than you guys are used to with a conventional small-block...

    And they are only correct to a point. What comes into play is dynamic compression. My 408 had 11.6:1 static compression, however, with the cam I ran, my dynamic compression allowed it to run easily on pump gas. That's why it's important to pick a complete combo that works together.

    Also, 70CamaroRS - make sure you use MLS 6.0L head gaskets with that setup!
     
    Last edited: Jan 3, 2010
  4. JAMMINJ007

    JAMMINJ007 Veteran Member

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    Heads

    You are talking about a ported ls6 head vs. a stock l92 head. The l92 flows just as much as a standard big block head if not more. So why not just buy the l92 head and mill it .020. You will still come out alot cheaper and up your compression ratio to boot. As long as the cam isnt too radical you shouldn't have to worry about flycutting pistons. There is a reason why the aftermarket companies too so long to develope an intake. The factory intake couldn't be beat as far a flow. Even the fast intake doesn't make dramatic #'s vs. the stock unless it comes to large cubic inch strokers or heavily boosted motors. I will just port my ls3 and save the coin. :rolleyes: Show me where a cathedral port head will outflow a rectangular l92 head. Apples to apples. I just don't see it.
     
  5. 70 gsconvt

    70 gsconvt Veteran Member

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    What magazine and company was that? I want to make sure that I don't follow that info!!
     
  6. LSXZ28

    LSXZ28 Veteran Member

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    Yes, I was talking about the ported LS6 heads that 70CamaroRS is using vs. the stock L92 heads that 70gsconvt was talking about in the magazine article.

    What you aren't looking at is the fact that the LQ4 iron block has a 4.00 bore. Yes, the L92 head will fit on it, and yes, they do make pretty good power. But, if you do your research, you will find that those heads just barely fit a 4.00 bore and were designed for the bigger bore they came off of originally. Flow numbers aren't the whole picture - there is more to it than that! That huge intake valve is overkill and is very shrouded on a 4.00 bore. So, for a 4" bore, I would still run a good cathedral ported head over an L92 head. If you are talking a bigger bore 6.2L block, then different story...

    As I said above - I had an LQ4 block with a 228/232 cam and bone stock LS6 heads and went 11.41 in a 3675# car. It was a workin combination...

    And yes, I agree with you on the intake - I advise people all of the time that the LS6 intake is better than the FAST for a street driven car that doesn't have a huge cam or stroker motor. They will actually lose midrange power and then be all PO'd when they spent $1500 and the car seems slower on the street.
     
  7. Aceshigh

    Aceshigh Veteran Member Lifetime Gold Member

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    I'd like to know that too.

    Just curious, what was your compression and what octane did you need to run it ??
    All good info BTW , thanks. It's awesome to have more knowledgeable modern drivetrain guys in here
     
  8. 70 gsconvt

    70 gsconvt Veteran Member

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    I'd love to hear more about your combo also.
     
  9. LSXZ28

    LSXZ28 Veteran Member

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    The static compression was calculated to be 11:1 with the stock LS6 heads - you can get away with that because of the amount of overlap that the cam had - that makes the dynamic compression low enough to run 93 octane.

    Now, I would never do that with a stock cam! If you look at the amount of overlap on stock cams, they don't have much. If you look at most any performance cam (with the exception of Forced Induction cams), they have a good bit more overlap than a stock cam. That causes the dynamic compression to be lower, therefore allowing it to run on 93 octane.

    If you look at the specs on a blower cam, they have alot less overlap - cause you don't wanna blow the boost clean through the engine. That is why the stock LS6 cam makes an awesome blower cam for a mild build!

    When I built my 408, I had help from some experts cause I wanted to push the limits on pump gas. We ended up with 62cc chambers on a pair of heavily ported 243 casting heads. That gave it 11.5:1 static compression. But the "Giant" cam I was running made the dynamic compression around 8.0:1. I ran the car on nothing but pump gas and sprayed a 250 shot of nitrous on top of that. A best of 9.41@143mph in a 3675# car was the result.

    So, does all of that help? If you want to learn more about dynamic compression and valve overlap, do some searches on the general internet and you will find some good writeups and even calculators to show you how it is figured.
     
  10. JAMMINJ007

    JAMMINJ007 Veteran Member

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    What you aren't looking at is the fact that the LQ4 iron block has a 4.00 bore. Yes, the L92 head will fit on it, and yes, they do make pretty good power. But, if you do your research, you will find that those heads just barely fit a 4.00 bore and were designed for the bigger bore they came off of originally. Flow numbers aren't the whole picture - there is more to it than that! That huge intake valve is overkill and is very shrouded on a 4.00 bore. So, for a 4" bore, I would still run a good cathedral ported head over an L92 head. If you are talking a bigger bore 6.2L block, then different.

    I did consider it. Essentially I am running the same combo just using the ly6 instead of the lq4. . Correct me if I'm wrong the ly6 has more compression than the lq4. The ly6 makes over 60 more hp than the lq4 the differnce being the heads. And the lq9 runs ls6 heads if Im not mistaken and makes 10 hp less than the ly6. If these heads just "barely" fit then why does gm and mast put them on their 6.0s? Mast claims almost 500 hp by just a cam swap and their phaser kit? Are these #'s inflated also? So the magazine that did just a cam swap and got over 500 is inflated too? I believe that some are biased but not all. I think you have alot of valid points, but for the money you would spend on ported ls6 heads you would save by just milling l92's and using the rest on cam and exhaust or other power adders. I don't know maybe I need to do further "research".

    I understand "flow" numbers are not the total equation and too big of a head can make a car a pig if the combo isnt correct, but he is not using a stock cam either. Maybe your right but I will stick with my l92's I will let you know how it runs when it is done later this month. If its a pig I will procharge it
     
    Last edited: Jan 3, 2010

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