Big block vs small block
 

I have a 91 wellcraft nova w/ 2 stock 330's that goes 65 mph. I do alot of rafting and the fiberglass swim platform is under water most of the time. I in the process of puchasing some 400 small blocks. Does anyone know the weight difference between the big blocks and small blocks. I am hoping to get a better ride out of the boat. These motors will come with headers and the other engines had stock exhaust with silent choice.

Thanks for the info, somemore quick questions for anyone. What kind of speed do you think these engines would make. The engines suposably push a little over 400 hp a piece. I currently have 26 pitch 4 blades on there that spin 5000 rpm. With these engines I may spin upto 6200 rpm. Does anyone think that i may need to reprop this boat also.

Thanks,
Fourmulafastech

You really need to look at how much torgue the small blocks are making. Torgue is the key. If they are low on torgue they will never turn enough RPM to make the HP you are expecting. I do think the 400 small block is a good combination. Without knowing more on your small blocks I would not speculate on speed. There are some on the board running small blocks maybe they can help more.

By the way a set of aluminum heads and good exhaust would save you weight on those BBC. Would be bolt on power also. I would think putting in small blocks would be a fair amount of work. Not only mounts but exhaust changes. Just a thought. :)

Paradigm shift, are you saying the width of the small block and big block are signifigantly different?

Yes, the width is smaller with small blocks. You can get a good idea how much by going to a store with aftermarket intake manifolds and look at a small block and big block manifold

Exactly. I am not sure of the amount of differance. Even changing from a std 9.8 to a 10.2 tall deck BBC is a noticable differance in width.

Patriot is a good freind he is looking to go faster and take some weight off the back of the boat(looks like its sinking all the time) he is getting a good deal on some small blocks with a lot more horsepower, from my uderstanding torque is more important? when I think torque I think big block. Is he doing the right thing I can forsee a lot of hidden costs like exaust holes.

You will save about 300 lbs total off the back of the boat. There is a signifigant difference in width, I have a 29 Fountain with twin small blocks, I have plenty of room between the engines to change plugs, mess with the starter etc, the big block 29s.....you can barely get a finger between them, the cutouts in the transom for the drives are the same. You can mouse around on Yachtworld.com or Boattrader and find some engine bay shots for both and see, there will be a lot more room between them with the smallblocks.....Doug

You will have more room with small blocks for sure. In any project you have to watch for those hidden costs!! :D Unfortunally I uselly fiqure a dollar amount and double that cause that's what I end up spending anyway. Live and learn. :rolleyes: Depending on what exhaust he runs someare more adjustable then others.

Small blocks can make HP but are not really known for torgue. Like I said there are some others running small blocks on the board that should have better info on small block VS big block so maybe they will jump in here soon. They like me will need more info on build specs to know. 383 and 400 small blocks can have pretty good torgue #'s but I don't think they can match a big block. Those stock 330's are not much as for perfomance from a BBC though.

Just make sure he does the research first before he jumps. Could save a lot of headachs and $$$ down the road. Were the motors in another boat or ???

You will only have 3 extra inches of clearance on the inside banks of the engines.

32 -29 = 3 / 2 = 1.5" on each side x 2 = total of 3".

What would man do for 3 more inches!!!

shoot
 

I've been so excited thinking about the wieght loss I didn't even think of exhaust holes. Are you still interested in the silent choice let me know?

You may need them with those engines they will be louder than your old ones but If you do get rid of them let me know.

silent choice
 

I don't think that i can use the with the headers i may need to buy some mufflers also.

Hidden costs like Paradigm shift said take the price and double it. Don't worry though I think you are still getting a square deal. Just promise you are not going to go faster than me I can't afford it this year.

I just want to get over the 75 mph mark, when you do that you are usually faster that most. I would like to take it for one last ride with the big blocks. That is after I have the props refinished. I know they weren't to bad but knicks are knicks and every little bit helps. Unfortunatly if rerun keeps growing at his rate the the small blocks won't even make a difference.

I heard that.

OUCH!

Ouch is right, Rerun getting slammed. How's it going boys? :D

My (pretty mild) 383 made 466 ft-lbs of torque @ 4,300 RPMs...with over 400 ft-lbs from 2,500 RPMs up.

It idles nice, and has been turn-key everytime. I went with aluminum heads, intake, and exhaust manifolds (EMI) which probably knocked off a couple hundred pounds...

Hey friend of mine has a 31 Scarab with twin 355"'s and it runs 70-71 on GPS.

Max you might be surprised at how the boat runs:D

small blocks
 

Patriot,

The night we were running next to you, we were doin about 66 or so. Currently, the Thunder Runs almost 71. Basically it runs as fast as the other ones out there with 502's (and exhaust).

I only have 355's. Like I said before, I still have some tweakin to do, but as for not having enough torque, there isn't an issue. Right now, I have 23 MP's on there, and with the drives in, if I get on it hard, it just blows the props right out. It gets up on plane fine, and accellerates well. It still has a hell of a lot more of a punch with the 21's though. If they've got good parts in them, you should be able to spin them at 6000 or so, and have then live reliably (I had almost 400 hours on mine with the .600 solid roller cam before the "freshen ups"), and the only thing I did was replace a circ pump & starter in 4 seasons.

In anycase, the swap is not too bad..........I bolted the offshore mount to the blocks and popped the engines in. The only thing I had to do was modify my risers...........The boat originally had 525's in it with Gills, so the holes were a bit higher. If yous does not have the 3" spacer, there shouldn't be much of a problem.

As for weight........if you have aluminum heads, an intake, and especially exhaust, it'll be quite a bit less.

Talk to Lenny at Millenyum (586-468-7361). Lenny is a good guy & has put small blocks in place of big blocks, on a checkmate, and some others. He can tell you the in's & outs. Also, his customers seem to be pleased wth the work he does, and he also is one of the most reasonable guys when it comes to price.

Later,
RJ

RJ
Good to hear from you, I'm glad to hear your running faster. It sound like everything is in tune now. I have Sparky form Vicious working in the job already. I've just purchased IMCO hydraulic steering also. Now I just have to remove that crapy bottom paint. I'll put everybody on my buddy list.
See Ya!

I considered the opposite, switching from small blocks to big blo-cks, but, they would not fit in my scarab P29. I ended up building 383s, procharging and making a few mods to the efi system that came on the 350's. Best money i ever spent. boat went from 68-70 mph, to 92.8 and dyno shows 610 hp each. Good luck with the retro, but i dont see much performance gains naturally aspirated. Let us know how it goes.
Steve

Kevin Don't tell me this is your other handle?

Thanks..............I still have a few things to try - I expect to be at 72-73 next year.

See you around..............Let me know how the change goes, and if you need anyone to go fort a "snot dripper" (ride with ya) when it's done - lol

Later,
Mike (AKA - RJ)

Patriot I could only wish I was goin 92. Steve how does that boat handle at those speeds?

I considered the opposite, switching from small blocks to big blo-cks, but, they would not fit in my scarab P29. I ended up building 383s, procharging and making a few mods to the efi system that came on the 350's. Best money i ever spent. boat went from 68-70 mph, to 92.8 and dyno shows 610 hp each. Good luck with the retro, but i dont see much performance gains naturally aspirated. Let us know how it goes.
Steve

I have no idea why that post last night showed first one ever! Maybe i was logged in wrong. The boat handles just as it did with stock power. Only other changes were a switch to IMCO shorty's and 32 in. bravo props.

Steve is that the boat they didnt put oil back in the drives? I read some of your old posts when I started on my boat. Weight was a big factor for me, we do a lot of rafting and people sit on the back and I was wouried about water coming in. Plus at the time I did that Procharger diddn't have a v belt setup for mpi. But what I did was put aluminum heads exuast and different cams that was good for 10 mph. That put me at 80 last year, the boat handled better seems it likes to be on top of the water. This year I blew a drive and they ordered the wrong gear, but changed the timing and everything else to correct the probem now I am going 78. I need to take the boat back to the guy who did the engines and have him reset all that.

Yea, that is same boat. You could have used sbc carbed 3 groove pulley set up for crank. You still running same efi set up?
Steve

Da, You will have plenty of room. I have an 86 26' Nova II. It still sits ass low but not too bad. I have Twin 409's in mine. The old 406's came apart. Right now the boat runs 60 but I have alot of tuning to do. I'm thinking I will be in the low 70's. I've got a picture of the boat at home, I'll post it so you can see how it sits.

Jeff

JR - Depending on how radical your 409's are, you should be able to get into the 70's. My 355's used to run 73-74 in my 85 Nova II. I'll have to admit, it was a handful after about 65 w/ no steering.

Do you have counter rotators ? I didn't, and when it used to come out of the water, the rear of the boat would always skip to one side slightly when you were in the 70 plus range.

Rachet, Hydraulic steering is in the plans, eventually. My 409's aren't to radical. I should be getting around 425 HP. I wish I had counter rotation. I'm spinning Alpha SS's. So I have even less in the water but they are alittle stronger than alphas. They will also give alittle more stability side to side because they have a wider profile than an alpha. Once I get them tuned they should scream. They run good, but there is more potential.

70's
 

I have Bravo's that are counter rotating. And I just purchesed hydrualic stearing. I don't know if the older syle of Nova's are heavier but I am praying that I will push at least 75 mph by GPS. I hope these engines have enough tourqe to turn 26 4 blades. I would hate to throw new engines in for a 3 mph difference.

Here is the boat. And me with a stupid hat.

The boat dry is 5200 lbs, and with 108 gallons, me, and gear, around 6200-6400 lbs.

JR- were you running stock alphas before the SSs??? If so how much of a speed gain did you see with the swap. Im running the stock alphas and my X is VERY conservative, my 3 bladers never ventilate...........Doug

Twinn29, the SS's were on the boat when I bought it so I cant say if I got any gains. But with the SS's which are about 2 inches shorter, I theoretically have a blade tip out of the water from the 10 o'clock to the 2 o'clock position.

Right now I'm spinning 22" Hydromotives. They don't really hook up all that well with my X. I'm running about 15% slip. I can also cavitate all day if I hit the throttles alittle too hard coming out of the hole. Or if I'm trimmed out just alittle. But they do handle well in turns. Next year I'm going to give a couple Mirage Plus 25's a try. I'm hoping the extra cup will help them hook up.

Jeff

Cool JR, I was aware that the SSs were two inches shorter which is alot when talking X dim. Maybe I could find a shop that would let me try a set. hmmmmm. I wouldnt want to go out and buy a set and have them not work at all.
P29 Scarab-If your listening How much shorter are your Imco's and did you get any gains with the swap alone??

Switching from big blocks to small blocks will require some re-rigging of the boat and you may have more time in it than what you think. I think you'll be alright with the small blocks, but personally, I would have modified those big blocks. It will be interesting to see your results though. Have fun.

Cubic inches is horsepower, stick with the big blocks. Put the money into the big blocks that the small blocks and conversion will cost........ultimately will be cheaper and faster

Better Ride
 

The engine change isn't just for the speed. The boat sits in the water very low in the back. I don't think that twin bb's in a 26' boat make it sit to well in the water that's alot of weight in the back.