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Twin aluminum Small Blocks good idea, or a bad idea?

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Old 08-13-2015, 03:10 PM
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My 2015 Yukon Denali 6.2 LT1 has 420HP and 470FTLBS of torque stock. I haven't even given it a tune yet, better intake and long tube headers and you are talking about some decent power and you haven't even opened up the motor yet.
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Old 08-13-2015, 06:23 PM
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Why not stick with what's been tried and tested? BBC parts are readily available for marine use and how much weight are you really going to save? Also you can probably find some BBC parts you need used or nearly new and save some money. SBC parts will all need to be bought new as they are hard to find. Another thing to consider is the web strength of the aluminum SBC. I had used one in my race car, 65 Chevelle, SBC, 1100hp on 3 stage bottle. After several hard wheelie landings it bust the side of the block out at the mount. Went back to using Dart blocks again, same internals, no more problems. Now consider the pounding a boat takes, I wouldn't risk it. Besides you can build a BBC with a few more hp to compensate for that little extra weight.
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Old 08-14-2015, 09:16 AM
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I lost one of my 6.2s and rebuilt both to 400 HP 383s. I have a lot of fun with them and I'm glad I built them like this instead of stock rebuilds. That said, I've driven my buddy's Sunny with 496 HOs and it's just a different ball game. I think the biggest thing is when you're throttling in heavy seas at middle RPMs, the torque difference is huge. Much more responsive. I have to wind out mine harder for similar torque. If I were starting from a blank sheet with an empty hull, I'd probably go with big blocks. Admittedly my engine isn't LS based but I can't imagine the difference is that huge for low RPM torque.

Coming from the LS world and I absolutely LOVE the idea of people building these, one thing I think everyone in the LS world gets too caught up in is peak numbers. I remember seeing so many heads cam combos with crazy peak numbers but make practically no torque down low. For boating...most of your fun will be had in the mid-RPM range. I'm sure there's some grinds that make some awesome power in the mid range but you need to make sure you're considering that and not just peak power.

Just something to consider!
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Old 08-20-2015, 11:49 AM
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Look at some of the offerings from Ilmor marine.. They are using Aluminum small block and aluminum heads on the recreational series engines
with close loop cooling..
430 hp.. 813 lbs..

I think this engine with a set of CMI tube headers would be a nice little set up!

Link below..
http://www.ilmor.com/en/marine/recre...8-62L-OPS.aspx

anyone know what this engine is priced at?

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Old 08-20-2015, 12:19 PM
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Quite a bit. Send me a PM.
Quote:
Originally Posted by unreal offshore View Post
Look at some of the offerings from Ilmor marine.. They are using Aluminum small block and aluminum heads on the recreational series engines
with close loop cooling..
430 hp.. 813 lbs..

I think this engine with a set of CMI tube headers would be a nice little set up!

Link below..
http://www.ilmor.com/en/marine/recre...8-62L-OPS.aspx

anyone know what this engine is priced at?

-unreal-
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Old 08-20-2015, 01:31 PM
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Send me a PM as well.

I would like to know if it's a viable option to rebuilding the BBC's.
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Old 08-20-2015, 02:02 PM
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Quote:
Originally Posted by MILD THUNDER View Post
In my merc literature, a fully rigged bobtail 350 MAG MPI is 946lbs. New big block closed cooling 8.2L bobtail, is 990lbs, and 6.2L is 862lbs. Thats fully rigged with all accessories, coolers, etc, ready to bolt in and go. Not including the transom assembly, or outdrive.
seems hardly worth the change?
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Old 08-20-2015, 03:13 PM
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the boat already has small block mpi 350 mags.. 300 hp.

BB at a serious consideration. for sure.
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Old 08-07-2017, 10:17 PM
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My Donzi 28ZX runs 80 mph with naturally aspirated blue scorpions headers and 3 blade worked mirage props if I did just a head mod and increased the compression I could gain a probably another 3 to 5 mph. If I put a couple sbc 427 in there she would do 90"s all day long . Mighty mouse motors not given enough credit . I use to love spanking those big blocks back in the day with my 350 roller motor in my 65 GTO hemi 4 speed and 538 gears 15x32's 10's in the quarter 3000 pound car . I ll stick with my small blocks . Thats the fun part of it . anyone can put huge cubes in and go fast . the challenge is doing it with half the cubic inches and no superchargers pump gas . It can be done. . I know a guy same boat just put whipples on it and went triple digits , CHEVY TURN KEY SBC 427 STAGE 5.2 DART BLOCK, AFR HEADS, CRATE MOTOR 628 hp | eBay
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Old 08-08-2017, 06:28 AM
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Another thing to keep in mind when taking a pair of small blocks out of any boat is the distance between the engines. A lot of twin small block setups Big Blocks will not fit.
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