Why so many bb's vs. sb with procharger??
 

I was wondering why performance boaters choose big block power over using a 383 stroer sb with a procharger? Another quetion, I notice every few weeks in the classifieds, theres a new post for someone selling a bb procharger. Why is that? I'm looking to build something for a 24ft Mirage offshore cuddy, to run on the ohio river in cincinnati. I wanna be able to hit 70+ if I feel the need, but would like to cruise majority of the time. what would be the most suitable setup?

Torque.

No replacement for displacement . The guy to talk to in your area would be Bill Burk in Fairfield Ohio if he is still in business , been working with prochargers for ever.

I have an M-2 procharger head and bracket going cheap - just upgraded to M-3.

I heard so many procharger horror stories from a friend who tried to make one work.....

I say what I am about to say from experience.

A small block can be made superbly, but its actually harder to do and requires extremely expensive parts you are not likely to find used.

Its easier and cheaper to get moderate to high power out of a BBC than a SBC.

the reason for this is severalfold but boils down to these 3 things.

1. Availability of quality marine parts like exhaust.

2. The BBC can be made very powerfull without sacrificing "driveability". Things like idle quality and low end torque while making a good spread and high power are simply harder to do with less CI's.

Not that #3 has aything to do with power, but its noteworthy that.....

3. boats originally outfitted for small blocks usually have low end alpha drives and no hydraulic/external steering


All that air pushing stuff is a nightmare unless you have extreme talent and budget- or leave it alone completely.

Build a powerfull well built engine NA or Injected and save the huffing componentry for racers and guys that like wrenching on stuff all the time. Youll be chasing that stuff for an eternity.

small blocks can be really cool, and A wicked small block is a thing of beauty this is my latest build, and this little 406 makes a few ponies shy of 500hp, and puts out 510 lb ft with a wide flat curve- its nasty. basically a 500/500 setup.

http://www.offshoreonly.com/forums/d...ent-years.html

I could have built a 600HP big block for the same dough.

The only reason to do a SBC is if you already have one, or simply like trying to get the most from the least, but its not how you lay down a reasonable number for the least amount of dough.

That said in an 1800 lb boat I can put big blocks on the trailer all weekend long.

Uncle Dave

I went around and around on this very topic a year ago. I then decided to build a BBC. I decided on a bored out 427. I get the small block stroke/reving ability with the big block bore and superior heads of a bbc. It's not been a cheap project. I'm having some of the best guys in the offshore engine world spec and build this project and when all is said and done I'm hoping for at least 550 hp in a bbc that should weight close to a stock small block.

Your Mirage is quite similar to my Formula 242 and you're going to need a very stout engine to hit 70 mph. For the Formula a Merc HP 500 is good for 69 mph. I really don't think your going to hit that speed with a small block, super charged or not.

torque and reliability....getting big block power is no problem, but you just removed the pin....

Depends on how you do it.

Only if you use cast internals,

Even then I got 10 years out of a 500HP small block with forged pistons, but cast crank and stock rods.


UD

Thanks guys, Endeavor I talked to Bob @ rmbuilder and am going with the same setup as you...427 .60 over with afr heads etc.

thanks

I'm planning on having my engine in the boat and on the water late next week if all goes well. I'll let you know how it goes, but I honestly don't see why this engine won't rip!

Just a quick question. Is a 427 not as heavy as a 454? I'm not real familiar with the 427 vs a std 396/402/454 block. Is the block that much different that it weighs close to what a small block does?

Same block, same weight. But by the time you replace everything but the block with Aluminum its very close to the same weight as an iron 350. There would have been no difference with a 468 or 496 other than I wanted a shorter stroke. I really don't care about the "no replacement for displacement" deal, I prefer to make more with less when possible.

My opinion is that you run boats much harder than a car. An engine with a shorter stroke has less stress on its internals. I did loose about 50 hp and 50 lbs torque by going this route vs a 496 but I can live with that. Next to the 427, I really like the 502 with its big 4.5" bore and somewhat short 4" stroke. Why GM ever killed that engine for the current gen 8.1 liter is beyond me!

I say for power to weight ratio, a 540" standard deck BBC is the best bet... unless you go with an internally balanced crank. Then it weighs a million pounds but is smooth as glass..

As far as short stroke "theory" goes, the 502 is a good motor. Bore is big enough to unshroud the valves, and the stroke is short enough to allow it to rev well.

Bottom line is that no BigBlock is going to rev like a smallblock. Bearing journal diameters are too large. You can have a custom forged crank done with SBC bearing diameters, and run spacers in the main caps and get a revvy bigblock, but that's only for kicks and giggles. Boat motors like to be beefy, and we don't really rev them high anyhow. 5,000-5,400 bigblock rpm is your effective ceiling on a normal boater's budget.

The 8.2/502 has a better bore/stroke ratio and rod length to stroke ratio than the 496/8.1, but the 502 was being phased out by GM as far as longblock availability. The 8.1 was much more readily available in mass produced "dress" so there's your answer as to why the 502 black motor was killed.

But the 8.1 is a good motor. Better designed cooling system, and better oil control past the pistons (due to smaller stroke and hypereutectic pressure cast pistons) than a metric ringed forged piston 502.

Nothing wrong with a 427, but if I am starting from zero, I'm going siamese bore and as long of an arm as I can afford. A 540" shorty.

MC

Help me understand why anyone would build a 427 BBC in this day and age with so much more displacement available for little to no increase in cost if starting from scratch.

Making "more with less" usually means more money spent on better parts- which is ok.

does RM builder have a dyno sheet we can look at ?

Making an engine scream is no problem.
Making one that screams, idles, and makes a gob of power at 3K is a much harder proposition.

UD

If you plan on putting aluminum rod's in a boat motor I would just use zippers on the oil pan , it will save you a lot of time when you have to change them ever week .

By Aluminum I mean, AFR heads, Aluminum Intake, Stainless Marine Exhaust, crossover instead of cast iron water pump. It all adds up to a lot of weight loss. No aluminum rods, that would be a dumb move, I'm running h beam rods.

UD-
I'm building a 439 because I already had the 427 rotating assembly. I'm at best giving up 20 hp over a 4" crank. So I might be loosing 1 maybe 1 1/2 mph on the top end. I could be all wrong on this I will soon see. There are a lot of forum doubters on this project, but my goal is 70 mph, not 80 or 90 and I think I can hit that goal with this combo.

As for dyno sheet look at the GM ZZ 427 480. That little engine kicks out 480 hp & 490 ft lbs torque out of a factory GM crate engine, with a very flat torque curve from 3300 to 6000. Now take that engine add a marine kenitics cam, afr ovals and a pro systems carb and I think I'll have a very solid engine.

If you already have the rotating assembly then it makes complete sense as long as the crank isn't swiss cheesed from being rebalanced over and over. High bob weight hurts acceleration as well.

If starting from scratch I'd do something different, but if you have these parts Id definitely use them.

That zz427 makes almost EXACTLY what my 406 makes for a little less money. (see dyno chart)

You'll kill some HP when you put a wet exhaust on it, but it should flat out rock.

http://www.shopfbparts.com/servlet/Detail?no=434

If you end up with something really close that zz427 youll get to 70.

Uncle Dave

That 406 is an impressive little engine.

As for my crank it was new old stock that was balanced to a set of speed pro pistons and thumb rods which I dumped for h beams and srp pistons. So the crank has only been balanced twice. I'm running the exhaust dry to the tip so I shouldn't loose too much there. Hopefully in a week this thing is on the water. I'm getting sick of talking about it and not using it.

Get-r-done and get it wet! Then give me a ride!

Good luck

Uncle Dave

Got it ready to roll now.

Hows your project coming?

significant mods make this a potent small block.

I like the new speedway valve covers.
I need to detail out the engine bay this winter, and Id like to go with a single belt kit - but once again hard to find for a small block.




UD

Thats a nice looking engine...... My project is getting closer. Bob has the cam on its way to Dave and Patrick at Pro Systems is working on the carb. I'm hoping I can pick the engine up monday or tuesday. My fingers are crossed. Bob called me friday and said one of his customers with a 502 with the same afr heads I'm using, a milder cam and 1 point lower compression and a std 4 barrel carb made 650 hp. So even if my engine only builds the same hp per c.i. that puts me right around 570 hp. These new afr oval port heads are something else.....

Thanks, its got some neat parts, but looks rather bland- specially in comparison to my Ilmor 710. It shard to find a single belt kit for small blocks that has the ability to run a sea pump.

Your engine sounds awesome. Who is going to dyno it?

Whose exhaust are you running you said "dry to the tip" earlier?

Bob hooked me up with a couple sets of the AFR ovals and custom cams to upgrade some 502 MPI's - converted to carbed. They made 630hp and 600tq on 89 octane with a huge flat curve. They are truly an impressive head for their size and Bob knows how to design a cam to make them work. :flag:

I believe they may have been your engines he was talking about. Those are some great numbers you got! Do you have a print out of your dyno session?

UD- I'm running stainless marine w/long risers. If I can ever find a good deal on a set, I'd like to get Eickerts.

I'll scan and print a couple when I get back to the shop tomorrow. It's a great little package that anyone could bolt together. It idles nice and the throttle response is awesome. They're going in a 29 Baja, should be a fun ride! :D I think by now everyone knows that Bob is the Man when it comes to camshaft design. He is also a great source for engine parts and is willing to share a wealth of knowledge with his customers. The next one going on the Dyno is a 502Mpi with Bob's cam and a custom tune from Mark Boos. I can't wait to see how it tuns out.. :drink:

Sorry for the hijack

I second Bob being the man and sharing his knowledge. Choosing him to build my cam was the best thing I did. After that he helped me design the entire engine.