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Thread: alum. heads or steel heads?

  1. #1
    racingrascal
    I am thinking of putting together a 540 merlin for a new shadow and want to know if anybody has any input on this matter, for me its like $2,000-$3,000 more for alum. heads.

  2. #2
    Senior Member
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    hey rr,whats the point,alumminum heads are nice but you can get a set of merlin 345's that will flow all you will ever need,and at a lot cheaper price.its a boat so the cooling quicker deal really dosen't come into play it;s just a weight and money issue,save a lot of money and use it score a couple of chicks that are a 100#'s lighter and your way ahead.

  3. #3
    racingrascal
    Thanks, I was wondering how much of a weight diff. is there? It is going a 19' tunnel.

  4. #4
    racingrascal
    boatnam2, I just started using the message board. I thought all of you guys went to the river everyweekend.

  5. #5
    froggystyle
    I just actually went through this debate. It is not actually so much of the cooling per se that you save, but the ability of the head to transfer heat from the combustion chamber to the water that matters. Aluminum heads mean you can run a higher compression ratio with the same fuel as cast iron heads. This equates to more power on pump gas. Now, what you should really do is buy a blower for a 509 Merlin, make 850 horses on pump gas, and save the aluminum heads for Racing Ray's doorslammer.
    Or buy my Eliminator http://free.***boat.net/ubb/tongue.gif

  6. #6
    Senior Member
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    hey rr,i wish i work every other weekend it sucks but i only work 14 days a month so thats cool.froggstyle is right about the heat transfer.but i know using a chiller on a blown deal you can run about 1 1/2 more pounds of boost on pump gas.right now im running 8 1/2.i was running 14 pounds on av gas but im thinking about buying a new boat(no time to blow it up now) the rule of thumb is about 7 max with steel heads.racing ray could probaly tell how much more boost to safely run with alumminum heads.but i really dont think its much more then with steel.

  7. #7
    froggystyle
    Ya know, not to throw too big of a whammy on the line of logic here, but I am running 10# at 6600 with pump gas. No dramas. 781 rect. port heads with a hydraulic cam. The chiller cools the charge, making it denser and more powerful, but I didn't know of the correlation with psi and the chiller vs. pump gas.
    Or buy my Eliminator http://free.***boat.net/ubb/tongue.gif

  8. #8
    Senior Member
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    froggstyle,if the charge is denser i may be wrong but dosen't that have a big affect on detionation.if 7 pounds is close to detionation with out a chiller,by droping the intake temp and making the charge denser wouldn't that allow you to run alittle more boost.i dont really know im no mechanic but when i visited the shop pfm where they make the super chiller the info i got was what i was trying to tell rr.i might of thought the guy i was talking to was trying to blow smoke up my ass since i was not sold on the super chiller but gregg at gs marine and paul pauff told me the same information.froggstyle dont get rid of that eliminator yet maybe i will get a chance to pull up along side of it.maybe just maybe we can see how my little 471 will hold up against all them big chevy cubes.offcourse it would have to be from a rolling start.just kidding i really know for sure how it all works just as long as it works.

  9. #9
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    my last sentence should of said i really DONT know for sure how it all works but as long as it works.

  10. #10
    racingrascal
    froggy, i wanted to put together a blower motor but john said it would be like another 9 grand just for the blower. I wanted the blower for looks and power. but at the sametime the shadow runs about 45mph at 4000 rpm i think, so that means that as long as i was cruising the lake i would be on boost.Right? I was told 540" single carb all the good shit 650hp. on pump gas.

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