hogie roll

4.53” bore space and 9.65” deck height. Should be good for 10% more cubes than an LS, all else being equal. If it will take an equivalent overbore and stroke to a 427 LS, you would end up with a 472”.

Note sure if any of that would be worthwhile compared to a big block. But maybe a stock one with exhaust manifolds would be a decent, cheap option for 450-500hp.

hogie roll

we already covered that pages ago. Yes, you can make your big block into a pseudo giant LS. The heads and required shaft rocker system are pricy though. Hence you see most boats stick with 24* normalish big block heads, and then get superchargers after that.

hogie roll

Well you wouldn’t want LS equivalent part sizes. A big block is almost exactly 10% larger in bore space and deck height. So 1.1^3 gives you a 33% larger engine. You’d end up with something like a 70mm cam core (possible but not common), and a 1.1” lifter dia (.904 and .936 are common).

Then you’d want an enormous spread port 12-15* head. These are also available, just expensive, and they need special shaft rocker systems.

GMs 632/1000 motor is very close to being a scaled up LS. They’ll make 1100hp on a dyno. They may be a bit aggressive on the cam lift and compression for a boat, but I’d bet there’s also a little left on the table with a nicer 2x4 intake manifold.

If you were starting from scratch you could do a 600-632 (some people think 632 is too much rod angle and not enough piston skirt for a boat) and use the brodix or dart SR20 20* heads. A 55mm cam and .904” lifters, this is a fairly common drag racing bracket combo now.

LakeBoat4

Guys it is more like vanilla or chocolate, here both engine are from Chevy. Both are good but different guys like different tastes. I think the big thing is the firing order both are different. That said the 565's I have do have an LS firing order. As for heads there has been many types on a BBC. More than any other block over the years. If there was a clear advantage for a head it would outshine the rest by now. If I could build a big Hemi for a boat I would. Been running them for years in old Dodges and Plymouths. From 426-605cu/in. Cast iron to all Aluminum. Fact is my Plymouth is named "Rat Killer"

My point is that I can get "more out of less" with a LS. It is still a 427cu/in that the BBC was made by the 10,000's. Car, Truck, Industrial, Marine, etc. It does come at a cost but it can be done to make big HP and Torque. Reliably< I guess I will see real soon. I don't think it will be any worse than a 1000hp BBC have rebuilds at 100 hours. Not trying to engineer a new engine out of 20 year old LS Tech, 60 years for a BBC, but to stimulate Great conversation here.
To build anything these days is not just the money it is parts availability, I waited on a Callies crank for a Year for the LS. Been waiting on BBC pistons for 3 months now, they came in wrong once already. To say that a junkyard engine is what most start with is just wrong and a waste of time to think it could work.

On the OB engines, how long do you think they will go being all aluminum and salt water cooled before corrosion takes it toll? At $50-70K for a Mercury R, are they really worth the $$$ Are they throw away power units?

Tartilla

The new breed of men are far less knowledgeable on wrenching their own boats. Even foroil changes and the like. So outboards start winning the day now that they've got big hp. They totally ruin a rear deck on a 50+ft open deck party boat. Where twin diesels with Arneson drives would be optimal.

Big HP outboards are out of reach for many, and they have their issues as well.

Maybe one of the key questions, why did Merc Racing use the BBC for the 520?

Precision

Another issue is the 20 somethings of today are not getting into performance boating like we were. Partially because of the exponential cost of entry compared to the recent past I imagine. I remember 15 years ago buying my first "performance boat". It was a 1990 Checkmate Maxum 281 and we paid $16K for it on a Eagle trailer. I saw the same boat for sale last year for $30K, but I have no idea what it sold for. It seems that the younger crowd that are getting into boating come from a background of means and are able to jump over the 20-30 year old boats and go right for the OB cats and CC's. That's obviously a generalized statement, but it does seem to be a theme in recent years.

As for why they used a BBC for the 520. I'm 95% sure that is still made on the same line at GM as the 502 Mags were.

SB

Of course.
For every red blooded male (and engines) …nothing beats good head.

Brad Christy

Yup. Saw this very thing in the model boating world. I came into the hobby just as guys were just starting to tinker with gas engines (as opposed to nitro). At first, they were little more than a running joke, as they were mostly just worn out weedeater engines that guys were cannibalizing to put into older boats. The nitro boats would lap them time and again. Then we started to see bespoke gas engines that could somewhat keep up. The hobby has since transitioned from a community of tinkerers, guys who got into the hobby because they like to work on things and make them work better, to a community of credit card captains with little drive to work on anything they can fix with money. The driving skill has suffered as well, as there was an inherent learning curve that coincided with getting a boat up and running competitively; by the time your boats were running halfway decent, you'd learned the ropes of driving and CoC of the racecourse. With the more "plunk-n-play" options available, a first month model boater has a veritable rocket with little to no understanding of what a "lane" is, let alone any respect for it. Race participation has also suffered. When I first started going to races, host clubs were forced to cap entries to whatever their club could handle, with some of the bigger races seeing 300+ boats and at least a hundred racers. Today, you're lucky to see a hundred boats and fifty racers. Some of this might me economic, but we didn't really see hardly any dip in participation between 2008 and 2012, where you'd think we'd have seen one. It's really more about the will of the individual that has changed. I think you're spot on with the rise in interest in outboards. It's the same effect. An equivalently powered outboard boat doesn't run as fast as an inboard of the same or same type hull (this is changing with development of hulls designed specifically for outboards, TBF), and they aren't significantly cheaper to buy or operate, but they're easier to work on because doing so implies backing it into a shop and handing them a credit card, no contortions or greasy hands required. The will to do the work and the interest in the rewards for doing so just isn't there, and MFRs are simply following the will of the consumers.

Personally, I applaud anybody willing to try something new. I just think displacement is still going to rule the end result, be it LS or BBC or whatever.

Thanks. Brad.

Wally

Brad, the "LS" is just the next generation of smallblock so you have to compare the new to the old versions....
I think the main differences are the skirted block and 6-bolt mains that makes it stronger to handle more HP stock. ( the LS platform with stock cranks can easily handle 1000hp and has been shown all over the net)
the cranks are also better compared to the old SBC (again can handle 1000HP stock compared to around 500hp for the old sbc)
Larger Cam bearing diameters on the LS compared to the old sbc ( i think the LS has a 2.3" OD and the old sbc had around a 1.8" OD) so it makes it like a little over 20% bigger than the orriginal
Better head flow design on the LS
and revised firing order for reduced crankshaft vibrations and eased the load on the bearings

So could you make a quasi-LS BBC motor? sure you could...i dont know if anyone makes a skirted BBC block but i have seen some custom ones done out of some billet.
The rest is just parts that you put together.

Brad Christy

Wally,

Would the skirt be of any real benefit for the typical BB powerboater? Splayed caps, I would think, resolve most of that, and certainly for those seeking HP levels in the range where a SB LS might be applicable.

Otherwise, what I'm hearing is that the semi-raging debate between the LS guys and the BBC guys is kind of moot. There really is no inherent reason to choose. We CAN do both. Pretty much anybody building engines, with adequate budget, can satisfy both camps. Right?

If the interest is in SB displacement, I'd think you'd be in the same boat at 1000HP that those with 1550's are in: Rebuilding every season, or every other.

Thanks. Brad.