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Thread: SB Stroker vs. supercharger

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    SB Stroker vs. supercharger

    Looking for some input for my 18. Obviously, I like hp and the stock 300 MAG MPI ain't gonna cut it, especially at my altitude. Thinking about a serious 383 or 406 in the 450 hp range. If I went this route, the question becomes whether to buy a short block, long block, kit or crate. I can build it myself or get one off the shelf. Second idea is a SC, preferably a whipple, but Procharger is also a consideration. I will 20% of my power due to altitude.

    I am also looking at the FAST self adjusting fuel injection. Currently, it is for automotive use, but Jim is working with the factory to see if it can be adapted to marine use.
    1979 Donzi Criterion
    1997 Classic 16
    2007 G3 w/ Yamaha 90 hp jet outboard
    Jackson Hole, WY
    www.jacksonholealltrans.com


    Just my .02, which in this economy, is only worth .01, and actually is less than that since my original .02 isn't really worth .02.

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    Have you considered a N/A Dart 427 setup, if my memory serves me right Don Tamm had around 500hp in his 18. Might be worth a call for his input. Though a nicely built 383 with a Whipple would do a nice job. The 406 you mention is that using a 400 block? I have never liked the small journals, especially when adding a huffer.

    Phil
    No matter what your beliefs are "GOD BLESS AMERICA"

    Fully retired marine tech near 60 years in the biz.

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    Phil, good points. I will call Don, he has been out here hunting with me before and is a good friend. The 406 is a stroker kit off the 350. About as much as you can go relaibly.
    1979 Donzi Criterion
    1997 Classic 16
    2007 G3 w/ Yamaha 90 hp jet outboard
    Jackson Hole, WY
    www.jacksonholealltrans.com


    Just my .02, which in this economy, is only worth .01, and actually is less than that since my original .02 isn't really worth .02.

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    Quote Originally Posted by MOP View Post
    Have you considered a N/A Dart 427 setup, if my memory serves me right Don Tamm had around 500hp in his 18. Might be worth a call for his input. Though a nicely built 383 with a Whipple would do a nice job. The 406 you mention is that using a 400 block? I have never liked the small journals, especially when adding a huffer.

    Phil
    All the misconceptions. My Dart 4.125 Bore uses a 350 Crank journal .Throw any notions you have out. After market blocks are a different animal altogether. They have fixed every defect known to a GM 400.

    You have to notch the hell out of the oil pan rail to stoke a 4.0 bore to a 406. or a 4.125 bore to a 427.

    It all comes down to how much do you want to spend? a 383 with a Whipple $15,000 easy

    A Dart SHP 400 with all forged 4340 inners? $ Priceless
    machinist ,bore it deeper,ream it bigger, and lap it to a fine finish



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    You need to supercharge to compensate for the thin air there. IMO.
    Lake St. Clair, Lake Huron, Lake Erie, Lake Oakland

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    Carl is right. One thing to consider is that NA stuff falls off more at altitude than forced induction. Turbos and Superchargers hold there hp better. For NA, the rule of thumb is 3-4% hp loss for every 1000 ft over sea level. SC is 2.5-3.0%. Either way, a 500 hp engine out here at 7000 ft is going to be worse case scenario, 380, best maybe 410 horsepower.
    1979 Donzi Criterion
    1997 Classic 16
    2007 G3 w/ Yamaha 90 hp jet outboard
    Jackson Hole, WY
    www.jacksonholealltrans.com


    Just my .02, which in this economy, is only worth .01, and actually is less than that since my original .02 isn't really worth .02.

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    Been talking with Steve about his whipple 18. That is a serious build. 600hp, 92 mph. As Steve pointed out, whipple makes a direct bolt on kit for my engine that includes the Merc Mefi 555 reflash. My engine has less than 50 hours on it and should be a good candidate for the blower. If I ran 5 pounds of boost, that would be 500 hp at sea level. At my altitude, 400. The Alpha should hold up for a while at 400. I think my engine has a cast crank, which should also hold up reasonably well at 400 hp. I guess I could always change the crank to forged, but that is kinda a pain in the ass. If the hypereutectic pistons are heat treated, technically, they are good for 600 hp. Still have some research to do, but 90% sold.
    1979 Donzi Criterion
    1997 Classic 16
    2007 G3 w/ Yamaha 90 hp jet outboard
    Jackson Hole, WY
    www.jacksonholealltrans.com


    Just my .02, which in this economy, is only worth .01, and actually is less than that since my original .02 isn't really worth .02.

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    Super chargers were originally developed for airplanes to overcome the drop in HP at altitude. With a supercharger, you can adjust the pulley size to compensate for the drop in O2 to maintain the same HP that it would naturally have at sea level.

    Another option is a head, intake, cam, and exhaust swap to help it breath better......All this does is make the motor a better air pump, naturally. This may be a better option if you are looking to get 100 more HP and save some fuel. Superchargers take HP away from a motor to turn the blower itself, which means you have to burn more fuel to get the same HP.

    I wouldnt think it would be very difficult to get 400 hp out of a NA motor at 7000 feet, but it may be easier to bolt on a blower. Either way, its gonna sound better!!
    Never Kick a opossum at 40 mph!

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    id figure id throw this in here, think about a turbo setup like this. when you go from lake to lake, You decide what boost to run to get you to a particular MPH. just turn the boost up or down. with the self adjusting efi carbs your set.. with a SC you have to physically change the pulley.. also, the S/c puts mroe stress on a engine by stressing the internals all through out the rpm range..
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    There's a lot to the merc 555 computer, like knock sensors smartcraft capability etc. all of which I didn't want to give up. I'd call Dustin and chat with him about what you have and what your wanting to accomplish. You won't be able to run more than about 3 psi of boost on 91 oct fuel, with the stock compression ratio unless you change to dished pistons and drop it down.
    2006 CLASSIC 18 WHIPPLED MX 6.2, BRAVO 1, STAINLESS MARINE EXHAUST, LATHAM STEERING, IMCO 2" SHORTY, LABBED MIRAGE PLUS

    TALK IS CHEAP, I'M FROM THE "SHOW ME STATE" SHOW ME

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    Steve,
    Good points and thanks for the info. A couple of questions. What compression is the current Merc 350 MAG MPI running? I take it has flat top pistons? Can you get the compression low enough by simply going with a slightly thicker head gasket? I am a little put off by Whipple. I emailed them about the kit, and they replied it was basically 7,100.00. Their website clearly states 6700.00. I emailed back asking what was up, and he said the website was old and not up to date. Still, it is a published price and how much time does it take to update the pricing on the site? I personally think he should honor the published price, which is still on the website.
    1979 Donzi Criterion
    1997 Classic 16
    2007 G3 w/ Yamaha 90 hp jet outboard
    Jackson Hole, WY
    www.jacksonholealltrans.com


    Just my .02, which in this economy, is only worth .01, and actually is less than that since my original .02 isn't really worth .02.

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    Quote Originally Posted by Donziweasel View Post
    Steve,
    Good points and thanks for the info. A couple of questions. What compression is the current Merc 350 MAG MPI running? I take it has flat top pistons? Can you get the compression low enough by simply going with a slightly thicker head gasket? I am a little put off by Whipple. I emailed them about the kit, and they replied it was basically 7,100.00. Their website clearly states 6700.00. I emailed back asking what was up, and he said the website was old and not up to date. Still, it is a published price and how much time does it take to update the pricing on the site? I personally think he should honor the published price, which is still on the website.
    350 Mag MPI is 9.4 ,and it most likely uses a stock GM 350 dish piston . They are prime candidates for detonation . I'm thinking altitude would allow higher CR or Psi, It may become a problem at sea level. Then you may need to stop at the airport to fuel up
    machinist ,bore it deeper,ream it bigger, and lap it to a fine finish



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    Whipple has a proven package for the 350 mag/6.2 that makes in the 450-460 hp at 3 psi with all stock internals with an ECM reflash and 91 octane fuel. Many of these have been sold and are in use with the stock compression.
    2006 CLASSIC 18 WHIPPLED MX 6.2, BRAVO 1, STAINLESS MARINE EXHAUST, LATHAM STEERING, IMCO 2" SHORTY, LABBED MIRAGE PLUS

    TALK IS CHEAP, I'M FROM THE "SHOW ME STATE" SHOW ME

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    Quote Originally Posted by Donziweasel View Post
    Looking for some input for my 18. Obviously, I like hp and the stock 300 MAG MPI ain't gonna cut it, especially at my altitude. Thinking about a serious 383 or 406 in the 450 hp range. If I went this route, the question becomes whether to buy a short block, long block, kit or crate. I can build it myself or get one off the shelf. Second idea is a SC, preferably a whipple, but Procharger is also a consideration. I will 20% of my power due to altitude.

    I am also looking at the FAST self adjusting fuel injection. Currently, it is for automotive use, but Jim is working with the factory to see if it can be adapted to marine use.
    What about a crate LS motor 525 HP pump gas?

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    I looked at the GM LSA engine, this one-

    http://www.gmpowertrain.com/2013_pdf...ine_010713.pdf

    Problem is cost. I can not find a current marine exhaust that will fit. I can have CMI make a set, but then just the exhaust costs as much as the whipple, and that is not counting the cost of the engine. I bet the GM Marine with exhaust would be 25,000.00.
    1979 Donzi Criterion
    1997 Classic 16
    2007 G3 w/ Yamaha 90 hp jet outboard
    Jackson Hole, WY
    www.jacksonholealltrans.com


    Just my .02, which in this economy, is only worth .01, and actually is less than that since my original .02 isn't really worth .02.

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