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Thread: Now let's Get Serious About Things Eric

  1. #1
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    Now let's Get Serious About Things Eric

    Since you clearly lose sleep over your GM V8 heads,

    here is a quote from GM discussion hereabouts which may help you to design and tune manifolds and head choice.

    Other people here are actually quite dismissive of doing things with art, but few actually love machinery the way they admit at least///

    >>Re: Ls1 vs 6 Ltr heads

    --------------------------------------------------------------------------------

    Quote:
    Originally Posted by SLugg
    L76/L98 Heads have bigger valves and better port design (330CFM on the inlet std) from memory I think the inlet valve is 2.16" (55mm) and the exhaust is 1.7" (44mm)
    read this article (its been posted b4)

    http://www.gmhightechperformance.com...ine_l92_heads/

    also the inlet manifold on the L76/98 is the go.

    Exhaust valve is 1.57"


    Quote:
    Originally Posted by VooDoo
    L76 heads are totally different to the LS2 head.

    L76 heads are based on the LS7 design and use different ports, 12 degree valves, different positions and dont fit a LS1 without a lot of work. The valves are in different locations to the LS1 setup (i believe they require offset rockers). Try to bolt a L76 head to a LS1 and you will have valves hitting the block/pistons and lots of problems.

    The LS2 head is actually a LS6 head with unshrouded valves and a chamber that was modified to suit the 4" bore. The ports are the same as LS1 heads and will bolt onto a LS1. The comp ratio is also different between the 2 types of heads.

    L76 heads have a 15 degree valve angle like an LS1/6 head.
    LS7 heads have a 12 or 11 degree valve angle(I always get C5R and LS7 valve angles mixed up).


    Quote:
    Originally Posted by VX8255
    Exhaust valve is 1.57"



    L76 heads have a 15 degree valve angle like an LS1/6 head.
    LS7 heads have a 12 or 11 degree valve angle(I always get C5R and LS7 valve angles mixed up).

    I looked up the information.

    L76 Exhaust valve = 1.59"
    LS7 Heads have 12 degree valve angle.
    C5R Heads have 11 degree valve angle.


    Quote:
    Originally Posted by VX8255
    Exhaust valve is 1.59"



    L76 heads have a 15 degree valve angle like an LS1/6 head.
    LS7 heads have a 12 or degree valve angle.

    L76 intakes flow 330cfm out of the box on a 4.125 bore.<<

    Now that is cruelly basic stuff. But I'm guessing that you know this stuff already, and the issue for you is likely manufacture-integrity. GM engineers are the best V8 engineers, or as good as, in the world. So the numbers are not relevant
    Most would go alloy when it works better. Factory.
    I don't care for disguising.

    Seems to me the standard heads compromise power. What would the factory do?



  2. #2
    Vulture of The Western World Eric's Avatar
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    Re: Now let's Get Serious About Things Eric

    Chevy/corporate blasphemy!

    Pontiac heads (last cast in 1978, fyi) are very different animals. None of the mass produced versions ever offered in aluminum (though a few very rare race-oriented versions of the so-called "round port" Ram Air IV design were produced for very limited use by race teams, etc.).

    The vast majority (mine included) were cast iron - with "D" ports. These do not flow as well as the round port designs, but are much more readily found (and less expensive). Most of the early hi-perf. heads featured 2.11 intake and 1.77 exhaust valves; later "smog" designs had smaller 1.66 exhaust valvesl typically, these heads also had larger combustion chambers, with resultant compression ratios no higher than about 8.5:1.

    The Edelbrock heads are of the round port style and have combustion chambers designed to yield an appx. CR of 9.5: 1 (or with the optional "race/competition" head design, something like 10:75:1). They are said to flow far better than any stock head - and be worth about 50-hp, all else being equal (as well as shaving some 75 pounds off the front end of the car).

    I am pretty sure that with these heads and a "step up" cam of about 280-290 degrees (I have a 270 degree cam right now), I'd probably be in the honest 400 hp area - which would be fun!

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    Re: Now let's Get Serious About Things Eric

    That's very interesting.

    If I ever got good at anything about engines it was head design and choice, and I got very good at turning race-intended heads into streetable and in fact idle-up tractable carb-fed setups. For fun. Curious circumstance in the wheelchair thing meant I had and have more thinking time than many, less profitable at work itself.

    Goodbye marriage ... nah that's cruel, I'm sure she's happy with bigger money.

    This of course was with mostly BLMC and Jag XKs the latter were near-optimal from factory. I'll bow to nobody on these engines. Certainly is the heart of a conventional I/C engine.
    Just in the last few days I have had time to research the Chevy small block a bit, and concentrated on 1995-on with alloy, but the cast iron ain't too different in some aspects.

    Is you wantin top end? No. I think you want the essential character of the car.

    I think you should mothball it and drive it as is and use the money to buy an LS7 and put that under the coffee table.

    If you want to go fast, use the bike.

    I'm serious.


  4. #4
    Senior Member Kwozzie1's Avatar
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    Re: Now let's Get Serious About Things Eric

    Quote Originally Posted by robmcg
    .

    This of course was with mostly BLMC and Jag XKs the latter were near-optimal from factory.
    Yep you could have those Minis almost valve bouncing ;D
    Rex
    On the Sunshine Coast, in the Sunshine State Queensland (QLD), Australia

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    Re: Now let's Get Serious About Things Eric

    Quote Originally Posted by Kwozzie1
    Yep you could have those Minis almost valve bouncing
    Didn't do 'em any harm. Thrash 'em. That's what they do to kids in TX y'know.


  6. #6
    Vulture of The Western World Eric's Avatar
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    Re: Now let's Get Serious About Things Eric

    Quote Originally Posted by robmcg
    That's very interesting.

    If I ever got good at anything about engines it was head design and choice, and I got very good at turning race-intended heads into streetable and in fact idle-up tractable carb-fed setups. For fun. Curious circumstance in the wheelchair thing meant I had and have more thinking time than many, less profitable at work itself.

    Goodbye marriage ... nah that's cruel, I'm sure she's happy with bigger money.

    This of course was with mostly BLMC and Jag XKs the latter were near-optimal from factory. I'll bow to nobody on these engines. Certainly is the heart of a conventional I/C engine.
    Just in the last few days I have had time to research the Chevy small block a bit, and concentrated on 1995-on with alloy, but the cast iron ain't too different in some aspects.

    Is you wantin top end? No. I think you want the essential character of the car.

    I think you should mothball it and drive it as is and use the money to buy an LS7 and put that under the coffee table.

    If you want to go fast, use the bike.

    I'm serious.

    Pontiac V-8s are interesting animals; I will see if I can dig up some stuff you might find interesting. The SD-455 had excellent airflow; and Pontiac also designed a "tunnel port" 5-liter racing engine for Trans Am (racing, not the car!)

    These engines have quite different powerbands/operating characteristics relative to a Chevy V-8. My 455, for example, doesn't need to rev much beyond 5,000 RPM to produce more than 300 honest horsepower. And the torque (450-plus pounds-feet) is just awesome. Ideal for a heavy car like my Trans-Am, which weighs 4,000-plus pounds.

    In current form -- mild head work, 270 degree "street" hydraulic cam, medium-rise dual plane and single Q-Jet four-barrel, my 455 probably delivers about 320 horsepower to the wheels. That's not half-bad. The big problem is getting it to the ground. Traction is severely limited with the stock rear suspension and 15x7 wheels with 245-60 rubber. I usually "walk it out" for about 10 yards, feathering the throttle. Anything like flooring it from a stop just spins the tires! With sticky compound drag-style tires and some suspension tweaking, I bet I could run low 13s, maybe even tickle the high 12s. That's ok!

    As far as fast, though... I don't like to take her up much over 110 mph ("top speed" ballpark at the end of a quarter-mile run). While it probably has the power to hit 140-plus, its '60-era chassis and suspension make me nervous about exploring that territory.

    For fast, I take the bike. At 150, it feels more stable and in its element than the Pontiac does at 80!

  7. #7
    Senior Member Kwozzie1's Avatar
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    Re: Now let's Get Serious About Things Eric

    Quote Originally Posted by robmcg


    Didn't do 'em any harm. Thrash 'em. That's what they do to kids in TX y'know.

    Wish they would do the sae to a few kids in NZ and OZ..... everyone is so PC
    Whimpish I say!
    Rex
    On the Sunshine Coast, in the Sunshine State Queensland (QLD), Australia

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