larby

Hi all,

I'm rebuilding a revenger 25 in the UK, and was going to be using a blown big block for power, around 600hp.
Trouble is, at this power my bravo drive will struggle with racing use in very heavy offshore waters.

I was wondering about using a lighter smallblock of slightly less power, with the idea that it will require less hp due to less weight. I also noticed some companies make aluminum big blocks for quite some cost.

Is it all worth while? Or will I not see the difference I'm hoping for?
Any suggestions for what to use?

Cheers, James

Philm

Wouldnt think you would need to supercharge for 600hp.

There are aluminum BBC's, but they really arent that much lighter.

larby

No, I wouldn't, but I've got the blower and a guy who's very experienced in setting it up, so for me it's the easiest and cheapest route. And it looks cool!!

Interesting that the ally ones aren't much lighter, i thought there was about 640lbs in it?

Chees, James

HTRDLNCN

LSx series smallblocks make 500-600hp naturally aspirated pretty easily and are about 200lbs lighter than a big block.

Griff

IMO, not enough of a weight difference to justify the loss in torque.

Jon H

Hi James, hows it going?

wjb21ndtown

If you're going to run it in salt water I wouldn't build an aluminum block motor. A fully assembled small block with iron heads and an iron intake is only about 575lbs. If you run aluminum heads you can knock 40-50lbs off of that number, and if you run an aluminum intake you can take an additional 25lbs off.

You should be looking at around 500lbs. for a high performance upgraded GM small block.

n20michael

The advantage to the aluminum block isn't always about weight, most aluminum blocks run iron [Nitrile] "liners" in the cylinders, if you hurt a piston or scuff the wall of the liner you can change it pretty easily, instead of having to remachine the block. If you suffer some form of catastrophic engine failure and put a hole in the block you can weld it back up, I have seen blocks from Top Fuel cars that have had the entire corner of the block busted off and welded back together. If is had been an iron block it would be junk.

So, Having said that, UNLESS you plan on making enough HP to hurt blocks or burn pistons on a regular basis, I would follow the suggestions above and go with a healthy small block or a mild big block, the blower set up should be pretty similiar for a big block or small block, different intake and carbs and that should be about it I "think" the drives and blower itself are the same, if its a standard roots blower.

Michael

fireboatpilot

Maybe it's just me, but I'm confused. First, he's building a BBC blower motor because he has the blower and has the erge to use it. The question was how his Bravo drive was going to survive at 600hp? Then he went into the SBC questions? What happened to needing to be a BB blown motor? To answer, no your Bravo wouldn't hold up for long under racing conditions. Look for a stronger drive that will handle the HP. B-Max, Imco SCX, Konrad, ect. Ths BBC is the most commonly used for the the old reasoning of "There's no replacement for displacement" and of course there's the subject of torque. Sorry, I lost track, what was the question again?

larby

Hi Jon!!

Fireboat - The idea was to go to a lighter motor, and therefore not need so much power, so the drive would live longer. I figured with a lighter engine, I could drop to 450-500hp, much closer to the suggested hp of the bravo.

By the sounds of things, the weight difference isn't enough to warrant it though.

James