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How Much HP gains?

This is a discussion on How Much HP gains? within the Internal Engine forums, part of the LSx Technical Help Section category; How much could I expect to gain from a good port and polish job on a set of lt4 aluminum ...

  1. #1
    Junior Member 95TA383's Avatar
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    How Much HP gains?

    How much could I expect to gain from a good port and polish job on a set of lt4 aluminum heads. Is 60hp reasonable? How much does port and polish usually cost ...and for the money should I buy AFR heads?

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    Grand Imperial Wizard Sarge's Avatar
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    Oh hell no...mebbe 15-20....tops...

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    Tech Junkie hammertime's Avatar
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    The only way you could get that kind of increase from the stock LT4 heads, would be if they were the last restriction you removed from an otherwise optimized setup.

    Presumably you are a 383ci LT1 right now, what other mods do you have? What has been done to your current heads? Are you running a cam?

    If you have headers and supporting exhaust, decent size cam and high flowing intake, you might get 30 hp from swapping the heads, maybe more with good porting.

    Keep in mind an engine is a system of devices that comprise an air pump. One single component, short another pump forcing air through it, can increase power output by 20%. You'll need a host of supporting mods for the best results.
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    Junior Member 95TA383's Avatar
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    My current set-up is 383 stroker with lt-4 manifold and heads. It has comp cam 224/230 cam and engine is 10/5/1 compression. other mods consume of full slp LM exhaust, slp shorty headers, ram air intake with k&n filter, 58mm throttle body on ported intake, high flow cat, 160 degree therm, 4.10 gears, PCM tune. With these mods and say the best port and polish job you could get on a set of lt-4 heads what kinda gains can i get? Is it worth paying 2 grand for the port job and install? or should I buy AFR heads?

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    Tech Junkie hammertime's Avatar
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    Quote Originally Posted by 95TA383
    My current set-up is 383 stroker with lt-4 manifold and heads. It has comp cam 224/230 cam and engine is 10/5/1 compression. other mods consume of full slp LM exhaust, slp shorty headers, ram air intake with k&n filter, 58mm throttle body on ported intake, high flow cat, 160 degree therm, 4.10 gears, PCM tune. With these mods and say the best port and polish job you could get on a set of lt-4 heads what kinda gains can i get? Is it worth paying 2 grand for the port job and install? or should I buy AFR heads?
    Based on that, who are you looking at to port & polish? Best advice would be to look at what your porter has flowed his past heads at. Pay attention to low and mid lift flow numbers, not just the peak. The better the numbers you can get from a smaller size intake port, the more part throttle perforance and drivability you can expect. AFR makes heads up to 227cc, but your cam is mild enough that the 195 is more along the lines of what you would need. A good porter can probably get you there cheaper than the AFR heads, but depends on what he can do.

    Good luck!

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