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Thread: Heads = Zero HP Gain

  1. #1
    Lifetime Member minytrker's Avatar
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    Default Heads = Zero HP Gain

    I sent my stock 243 heads off to a well known shop and had them do there magic, port, polish, valve job, and so on. I also went with thinner head gaskets per there instruction. I also added bigger injectors. I had 430/390 before and did 431/391 after the heads. Per the machine shop I needed 7.350 instead of the 7.4 push rods, so I swapped them out. The preload was now in limits so I retuned the car but it doesnt seem any faster. I can see from the data that the heads are flowing more air, they just aint making anymore hp. The dyno sheets look exactly them same like I didnt change anything. How can heads make zero hp. The well known shop claims the lowest thay have ever heard of or even seen is 20rwhp gain from there work. The said I should see 20-50rwhp gain. I have the car a little rich at 12.2 with 26deg of timing at wot.

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    Lifetime Member Doc's Avatar
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    What kind of intake and exhaust (manifolds) setup are you running?

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    Lifetime Member minytrker's Avatar
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    02 Electon Blue Z06 430hp/390tq (before CNC heads) (431/391) after
    237/242 .603/.609|CNC ported heads|Halltech CAI|FAST 36 injectors|NX TB150 wet shot|Powerbond UD Pulley|LG Pro headers|Borla Stingers|DTE Transmission Brace|Harden Output Shaft|Ram HD Clutch| B&M Ripper Shifter|Slotted & drilled rotors|Tuned by LS1 Power Tuning

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    Lifetime Member SSpdDmon's Avatar
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    Did you try leaning it out to 12.6~12.8 with 28-29 degrees of timing? Will it take that much?

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    Lifetime Member minytrker's Avatar
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    No I had it at 12.2 for nitrous along with the timing. I dont see going to 12.8 and 28-29deg of timing picking up 20-50 rwhp like they claim I should have. I am going back to the dyno next week again and Im am going to try leaning it out and more timing just to see, because Im sure they are going to use it as an excuse.

  6. #6
    EFILive Distributor Trippin's Avatar
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    Typically on an engine dyno we look at BSAC. Or Brake Specific Air Consumption. This is basically a rating of how efficiently an engine converts air to HP.

    If your moving more air and making the same power, assuming the tune is correct, then my suggestion would be that the camshaft and cylinder heads are not getting along. A large cmashaft can make up for the fact that the cylinder heads don't flow to a certain extent. But then improving the cylinder heads now makes the cam seem that much bigger.

    What cam does the head shop recommend for their cylinder heads? 237/242 @ .050 seems fairly large for a 346.

    I've had the best luck with a 224/228 Comp XER lobe.

    What manifold and throttle body are you using?
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    Lifetime Member minytrker's Avatar
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    They recommend my whole setup, I ordered everything from them. I have the stock ls6 intake and stock z06 tb which is a 80 I think.

  8. #8
    EFILive Distributor Trippin's Avatar
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    If your going back to the dyno next week then I agree with Speed Demon. Run a timing loop to see what it wants and then lean it down. I've seen the LG headers and Random cats make some pretty good power at much leaner AF ratios than what you might think.
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  9. #9
    Lifetime Member minytrker's Avatar
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    I wil try it but I only had 26-28 deg wot and a/f of 12.8 with cam only when i did the 430/390 and it made the exact same numbers and it has the exact same hp and tq curves now after the heads. Thats the werid part, you would think the heads would make the hp and tq curved atleast a little differnt somewhere.

  10. #10
    Guess who's back!!!! Black02SS's Avatar
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    Quote Originally Posted by Trippin
    If your going back to the dyno next week then I agree with Speed Demon. Run a timing loop to see what it wants and then lean it down. I've seen the LG headers and Random cats make some pretty good power at much leaner AF ratios than what you might think.
    Listen to him on this subject. He has very good info and knows what he is talking about. And I will agree 110% with the above statement.

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