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Woodski

Aluminum SBC Block? BuCrew Member help.

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Woodski

A request to the great Crew members to keep a lookout for something I am looking for.

Some of you know that I have modified my engine / boat over the years and the next step is staring me in the face due to a recalcitrant rear main seal.  Since the engine is out to change it, I am now scrounging to see if I can find an aluminum L31 engine block (standard small block Chevy or old style cast iron engine) to swap out for the cast iron one currently in use.  I appreciate any feedback or leads on tracking a 'budget friendly' one down.  They are hard to find particularly used ones.  Why am I on this hunt, it represents another 80 # weight reduction over the cast iron one.

Thanks for any leads and everybody have a great holiday season, Merry Christmas and a Happy New Year.

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Pra4sno

Meanwhile, I'll be doing the really technical stuff like moving my battery further forward in the bow.  

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oldjeep

Isnt a l31 a truck engine?  They made an aluminum block truck engine? 

Edited by oldjeep

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MalibuNation

Are you going to make it closed cooling like I have with my 2003 LS1 to keep lake water out of the aluminum block?

MN

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Woodski

@oldjeep:  Yes, L31 is the truck block and latest gen 4" bore, no but the aluminum blocks do have the same bolt patterns.  Sources are going to be more the late model / sprint car suppliers.  I am fine with an aftermarket version.

@MalibuNation:  No on closed cooling, I have been running aluminum heads / intake and exhaust on open cooling for 10 years with no issues.  I also only use the raw water pump so no circulation pump in my system, I just have a stainless T tube with a bypass to push water in to the block via the raw water pump.  Don't want to add the weight of closed cooling.

My boat turned in to a weight reduction project and basically I got a bit carried away once the results became so damn promising:-)   Although the boat really sucks for wake sports it is awesome on the slalom side, LOL!

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justgary
1 hour ago, Woodski said:

... My boat turned in to a weight reduction project and basically I got a bit carried away once the results became so damn promising:-)   Although the boat really sucks for wake sports it is awesome on the slalom side, LOL!

Wouldn't it be easier to just throw out the engine hood and drill a whole bunch of lightening holes in the deck and floor?  You could probably save 150 pounds that way, and get it all done in an hour with the same 3" hole saw. :crazy:

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Woodski

@justgary:  good one except that I have already done a lot of lightening via carbon fiber engine box, along with various other panels plus excess part removal.

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justgary
1 hour ago, Woodski said:

@justgary:  good one except that I have already done a lot of lightening via carbon fiber engine box, along with various other panels plus excess part removal.

I see, you have already harvested the low-hanging fruit.  I guess you are trying to replace function without losing it. 

The windshield is heavy.  You could replace it with a wraparound frameless plexiglass one.  Or just change the glass out for polycarbonate. 

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justgary

For that matter, carpet is heavy also. 

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Woodski

@justgary:  Yes, low hanging and quite a bit more, fuel tank moved to center of boat as one example.  The stuff forward of the pylon is a poor ROI as it tends to pitch the boat nose up when removing weight forward of original CG, transom is the best bang for buck, then there is a lot of cast iron parts on the older SBC's that can go on an aluminum diet.  Windshield is an interesting idea, the optics of plexiglass may be a bit challenging for a course use boat, worth looking at regardless.  I found the carpeting to be lighter than I expected, not insignificant but lighter than other flooring options other than nothing over the glass.

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justgary

This is interesting (and getting to be a hijack, but it's your thread). 

I'm wondering if maybe the forward stuff could go away also if you put a smaller amount of weight in the most forward bow section to balance CG.  Even better, just remove the bow weight and use a Scarpa Plate to trim the bow back down.  I assume you don't care at all about speed, just wake size.

I had a friend who was into drag racing outboards, so he went to the Hydrostream factory and asked them to make his boat with the least amount of resin possible.  They did it for him, and the boat didn't fall apart at 100 MPH like we all thought it would.  Perhaps you should call Malibu and start from scratch....

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Woodski

@justgary:  Not a real hijack as the purpose of tracking down an aluminum block is weight reduction.  Correct, stripping a bunch of stuff off and adding say, a tungsten block at the tip of the bow would result in added weight reduction with the CG held constant or even moved farther forward.  Since you opened that box, I did strip out some stuff in the bow and it hurt the wake, so back it went but it was a simple A-B-A experiment without taking more weight out of the transom to rebalance the CG.  The aluminum block would actually allow that experiment to be rerun since the CG is forward of the engine.  One bummer I do have is heavier drivers lately and that requires a bit of lateral ballast to level the boat, it was perfect with my 'lighter' driver, so there are compromises that have to be considered, I have moved the battery over against the gunnel for that.  I have not heard good reviews on the Scarpa plate relative to slalom wake, perhaps more tuning would make it work.  I do barefoot, so speed is a consideration but my boat has no issues with speed, it is 400 hp as it sits.

It is amazing how thin you can actually make parts and still have the rigidity needed.  My buddy says I should simply make a carbon fiber hull:-)

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justgary

I'm glad you mentioned the drivers.  I wasn't going to ask if you weigh them in. 

Tournament drivers keep a ballast bag or plate handy that they can move laterally to account for the observer's weight.  Perhaps that would work, but then you need for the driver to understand why you want the bag moved two inches more.

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MadMan
23 minutes ago, Woodski said:

@justgary:  Not a real hijack as the purpose of tracking down an aluminum block is weight reduction.  Correct, stripping a bunch of stuff off and adding say, a tungsten block at the tip of the bow would result in added weight reduction with the CG held constant or even moved farther forward.  Since you opened that box, I did strip out some stuff in the bow and it hurt the wake, so back it went but it was a simple A-B-A experiment without taking more weight out of the transom to rebalance the CG.  The aluminum block would actually allow that experiment to be rerun since the CG is forward of the engine.  One bummer I do have is heavier drivers lately and that requires a bit of lateral ballast to level the boat, it was perfect with my 'lighter' driver, so there are compromises that have to be considered, I have moved the battery over against the gunnel for that.  I have not heard good reviews on the Scarpa plate relative to slalom wake, perhaps more tuning would make it work.  I do barefoot, so speed is a consideration but my boat has no issues with speed, it is 400 hp as it sits.

It is amazing how thin you can actually make parts and still have the rigidity needed.  My buddy says I should simply make a carbon fiber hull:-)

Tungsten - now you're talking about some real money.

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Nitrousbird
22 hours ago, Woodski said:

@oldjeep:  Yes, L31 is the truck block and latest gen 4" bore, no but the aluminum blocks do have the same bolt patterns.  Sources are going to be more the late model / sprint car suppliers.  I am fine with an aftermarket version.

Why not go a GEN-III+ motor?  Much easier to find all aluminum (with composite intake) setups and many making 400+ HP stock.  A lot can be hand relatively cheap as well.

L92 would be a great boat engine; basically an LS3 with more low-end torque.  Same as an LS3 but different cam, intake manifold and intake valves.

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justgary
9 hours ago, MadMan said:

Tungsten - now you're talking about some real money.

Yeah.  And here I was picturing lead. 

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Woodski

@Nitrousbird:  It would be easier to find an LS3 but my current configuration is actually very close in weight to an LS setup so that would be significant work to swap compared to simply switching the block on what I have.  The ancillaries of the LS add weight that I don't have.  Heck, if I were going LS may as well go LS7!

@justgary:  I am going with the bag of weight, slide it along the gunnel.  Good thing a guy is the heavy one, probably would end a set real quick if needed to add a bag of weight for ...

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Steve B.

Interesting. So the L31 is an aluminum direct "copy" of a standard 350 iron ? Intake ports, exhaust ports, bolt patterns. You'll plop in new bearings, rings, etc.

Steve B.

 

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oldjeep
3 minutes ago, Steve B. said:

Interesting. So the L31 is an aluminum direct "copy" of a standard 350 iron ? Intake ports, exhaust ports, bolt patterns. You'll plop in new bearings, rings, etc.

Steve B.

 

No, an l31 is a vortec 5700 cast iron truck engine.  He wants a compatible aluminum block, which pretty much means aftermarket. 

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Woodski

As @oldjeep noted the L31 is a cast iron small block, it is the basis for the 5.7 L iron small blocks used for marine applications in our boats.  The L31 is the last generation 350 CID iron small block before the LS series was launched.  The marine version has a specific camshaft v the truck cam. 

Also correct, I am simply searching for an aluminum block, whether just a block or even a short block if the price is right.  Aftermarket SBC short blocks (new) list for $5k or better, so not very economical for a hobby project, thus the hunt for a used one.

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solorex

Man... I should start doing weight reduction on my Tantrum... I wonder how light I could get it :)

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ahopkinsVTX

Well I’m not much help for this, but I’d really love to ski it when you get it done! :)

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justgary

So this might seem silly, but have you thought about a foil to lift the boat at speed?  I can't think of a better way to instantly lift the rear of the boat, which would then make all of your bow mods viable again.  Pretty easy to get several hundred pounds of lift if you want it, I imagine.

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MadMan

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