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View Full Version : SB Stroker vs. supercharger



Donziweasel
09-27-2013, 09:24 AM
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.

MOP
09-27-2013, 09:45 AM
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

Donziweasel
09-27-2013, 11:37 AM
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.

joseph m. hahnl
09-27-2013, 07:33 PM
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.:wink: 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. :tooth:

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?:rolleyes: $ Priceless :biggrin:

Carl C
09-27-2013, 07:55 PM
You need to supercharge to compensate for the thin air there. IMO.

Donziweasel
09-27-2013, 09:17 PM
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.

Donziweasel
09-28-2013, 10:06 AM
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.

Planetwarmer
09-28-2013, 11:52 AM
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:tooth:. 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!!:D:drive:

Moody Blu'
09-28-2013, 11:28 PM
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..

osur866
09-30-2013, 09:18 AM
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.

Donziweasel
09-30-2013, 05:37 PM
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.

joseph m. hahnl
09-30-2013, 06:21 PM
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 .:rolleyes: 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:biggrin.:

osur866
09-30-2013, 08:28 PM
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.

GG Donzi
09-30-2013, 10:55 PM
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?

Donziweasel
10-01-2013, 08:45 AM
I looked at the GM LSA engine, this one-

http://www.gmpowertrain.com/2013_pdf/FHR_REV_6.2LSA_Marine_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.

dsparis
10-01-2013, 09:22 AM
http://www.keitheickert.com/p-13471-typhoon-ls-small-block-chevy-headers-polished.aspx ?

Greg Guimond
10-01-2013, 10:10 PM
The 383 spec sheet ............

joseph m. hahnl
10-02-2013, 06:15 PM
The 383 spec sheet ............

That is an inboard motor. 1:1 on the prop turn 5600 to 6000 WOT. Made to run a low pitch really fast:biggrin:

Pat McPherson
10-02-2013, 07:03 PM
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Greg Guimond
10-05-2013, 08:27 AM
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.

Steve (osur866) gave me a ton of really helpful guidance on the phone about the Whipple option for an MX6.2 I was considering. Steve has "been there done that" for sure. My problem is that the only gas I can get on the water is 89 and I tend to take pretty long runs. The MX6.2 motor stock burns 87.

Moody Blu'
10-05-2013, 06:18 PM
low comp motor, efi square bore self tuning with turboooossssssssss 87 octane! :)

Scott Pearson
10-05-2013, 06:38 PM
Dont waste your time on the Scorpion. I can promise you...you will have issues all the time! And Merc and CMI will not help you. There are huge issues with these. I know first hand from the 2 that we put into "The Sting"...NOTHING BUY ISSUES!!!!!! Stay away from this set-up!!!!:frown::frown::frown::frown::frown:

Greg Guimond
10-05-2013, 10:03 PM
Be more specific. Are you including the MX6.2 ?