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Big block vs small block

Old 11-09-2002, 08:51 PM
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Default 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.
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Old 11-10-2002, 08:42 AM
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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.

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Fourmulafastech
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Old 11-10-2002, 09:55 AM
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Originally posted by Da Patriot
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.
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Old 11-10-2002, 10:46 AM
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Paradigm shift, are you saying the width of the small block and big block are signifigantly different?
 
Old 11-10-2002, 10:51 AM
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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
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Old 11-10-2002, 11:04 AM
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Originally posted by Scarab P-29
Paradigm shift, are you saying the width of the small block and big block are signifigantly different?
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.
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Old 11-10-2002, 11:33 AM
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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.
 
Old 11-10-2002, 12:04 PM
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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
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Old 11-10-2002, 12:29 PM
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You will have more room with small blocks for sure. In any project you have to watch for those hidden costs!! Unfortunally I uselly fiqure a dollar amount and double that cause that's what I end up spending anyway. Live and learn. 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 ???
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Old 11-10-2002, 02:56 PM
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Originally posted by formulafastech
The small Block is 29" wide, the Big block is 32. So in a twin engine deal, you are gonna save 6", which when you go to change your plugs etc is a MAJOR difference.
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!!!
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