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Tell me about the 396 BBC

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Found a mid 70's 20' V Drive boat that caught my interest. It has a 396 BBC 4 bolt main and a velvet drive. I know nothing about them as I asked if 396 was a typo for 496. How is the 396 overall and how does it perform in a marine V drive application? Speed and big power isn't too important to me. Just looking for something that is reliable, enough power to plane easy, and top speed around the 55 mph range. Parts easy to find and repair? What are the thoughts on velvet drives?
 

mash on it

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What's to know?
Same stroke as a 427, at 3.76".
Smaller bore tho.
Same physical size as a 427, 454, 496, 502, etc.
Early 70's Chevy 396's had a 325, 350 and 375 hp versions.
Guessing on how much hp a 396 is in a 40+ year old boat is nearly impossible.

A stockish 325 hp should be 50-ish mph. A lot depends on rigging, gearing and prop size, bottom condition, plus weight of the boat.

396's have typical big block problems/issues. Nothing that enough money can't solve.

Dan'l
 

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What's to know?
Same stroke as a 427, at 3.76".
Smaller bore tho.
Same physical size as a 427, 454, 496, 502, etc.
Early 70's Chevy 396's had a 325, 350 and 375 hp versions.
Guessing on how much hp a 396 is in a 40+ year old boat is nearly impossible.

A stockish 325 hp should be 50-ish mph. A lot depends on rigging, gearing and prop size, bottom condition, plus weight of the boat.

396's have typical big block problems/issues. Nothing that enough money can't solve.

Dan'l
Thanks for the info. I've seen many for sale ads but don't recall ever seeing a boat with a 396 for power. It seems rare. I just don't know anything about them. If they are a good engine for marine use or should just stay on the road? Temperamental on the water like Fords or pretty good like 454s and 502s? I would have no interest in building power out of it. I get it's a mechanical device... but want something that is add gas and go. Are there USCG approved parts for a 396?
 

rivermobster

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Thanks for the info. I've seen many for sale ads but don't recall ever seeing a boat with a 396 for power. It seems rare. I just don't know anything about them. If they are a good engine for marine use or should just stay on the road? Temperamental on the water like Fords or pretty good like 454s and 502s? I would have no interest in building power out of it. I get it's a mechanical device... but want something that is add gas and go. Are there USCG approved parts for a 396?

It's a BBC. Same as all rest of em, just a different displacement. https://en.wikipedia.org/wiki/Chevrolet_big-block_engine

Any engine, ford, dodge or chebby, is only as good as the guy that built it, and more importantly, tuned it. You'd have to talk to the guy that built it to see if it was built to marine specs, or not. It's unlikely to be stock after all these years, since it's probably around 50 years old.

If it runs good, run it! 👍
 

mash on it

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Thanks for the info. I've seen many for sale ads but don't recall ever seeing a boat with a 396 for power. It seems rare. I just don't know anything about them. If they are a good engine for marine use or should just stay on the road? Temperamental on the water like Fords or pretty good like 454s and 502s? I would have no interest in building power out of it. I get it's a mechanical device... but want something that is add gas and go. Are there USCG approved parts for a 396?

USCG approved parts?
Alternator, yes
Distributor, yes
Starter, yes
Carburetor, yes
Fuel pump, yes
Flame arrestors, yes.
I think that's about it. All of these would fit a 396 or a Mk IV 454.

Likely half of this wasn't USGC approved when it was new.

I'd check block casting numbers to determine what it started out as.
Same with head #'s.

Fwiw- a neighbor down the road bought a '74 ish Nova. It was advertised as a 383. Ended up a 283 by the casting numbers. It ran ok, but not like a big cammed 383 should run.

Dan'l
 

gottaminute?

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USCG approved parts?
Alternator, yes
Distributor, yes
Starter, yes
Carburetor, yes
Fuel pump, yes
Flame arrestors, yes.
I think that's about it. All of these would fit a 396 or a Mk IV 454.

Likely half of this wasn't USGC approved when it was new.

I'd check block casting numbers to determine what it started out as.
Same with head #'s.

Fwiw- a neighbor down the road bought a '74 ish Nova. It was advertised as a 383. Ended up a 283 by the casting numbers. It ran ok, but not like a big cammed 383 should run.

Dan'l
the 396 will run an early vdrive all day long for summer after summer. late 60s early 70s their were a lot of them racing up and down the river/lake. They came in 2 and 4 bolt main versions, cast and forged cranks. the original rectangular port heads were developed for the 396. it was factory bored to 402ci for the 70 chevelles and pickups. then the bore increased to 4.25 and the 427 was born. Later the stroke was changed from 3.76 to 4.0 an we had 454s. A bigger bore made the 502.

if the boat is the one you want, buy it. you can always build more horsepower. with the exception of just a few parts, everything on the 396 will transfer to a bigger big block.
as far as carbs, fuel pumps, starters, flame arrestor etc, such approved parts are not required on an open hatch boat. state laws may be different . Early v-drives used 390/406/427 fords, 394 oldsmobiles, 389 and 400 pontiacs, 401 nail head buicks.... embrace the nostalgia and RUN IT.
 

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I should have mentioned the boat is a Howard day cruiser. Dog house engine hatch.
 

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the 396 will run an early vdrive all day long for summer after summer. late 60s early 70s their were a lot of them racing up and down the river/lake. They came in 2 and 4 bolt main versions, cast and forged cranks. the original rectangular port heads were developed for the 396. it was factory bored to 402ci for the 70 chevelles and pickups. then the bore increased to 4.25 and the 427 was born. Later the stroke was changed from 3.76 to 4.0 an we had 454s. A bigger bore made the 502.

if the boat is the one you want, buy it. you can always build more horsepower. with the exception of just a few parts, everything on the 396 will transfer to a bigger big block.
as far as carbs, fuel pumps, starters, flame arrestor etc, such approved parts are not required on an open hatch boat. state laws may be different . Early v-drives used 390/406/427 fords, 394 oldsmobiles, 389 and 400 pontiacs, 401 nail head buicks.... embrace the nostalgia and RUN IT.
Thanks for the information. Sounds like the 396 is the predecessor to the 454. It's just a smaller big block making less power due to size but has that GM reputation.
 

gottaminute?

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Thanks for the information. Sounds like the 396 is the predecessor to the 454. It's just a smaller big block making less power due to size but has that GM reputation.
correct, BUT, The doghouse engine cover does change the rules a bit. As kids, we had a family we camped with that had a 24ft Taylor with a 354 hemi that came out of their retired 17 footer. no speed demon . pulled the kids and the "full size" dad on a water ski for quite a few years before it was upgraded to a 454 chevrolet.
 

74 spectra20 v-drive

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dimensionally the 396 is the exact engine as a 454, the "meat on the bones" so to say is different. In a typical 396 block, boring the cylinders to a larger diameter could cause some issues with heat down the road. I am actually doing some homework on one right now for a friend. My current game plan is to use the 396 crank in a 454 block and make a 427. It's a good motor not going to push that howard much past 50 to 55 in my opinion, but can be a solid cruiser.
 
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obnoxious001

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dimensionally the 396 is the exact engine as a 454, the "meat on the bones" so to say is different. In a typical 396 block, boring the the cylinders to a larger diameter could cause some issues with heat down the road. I am actually doing some homework right now on one right now for a friend. My current game plan is to use the 396 crank in a 454 block and make a 427. It's a good motor not going to push that howard much past 50 to 55 in my opinion, but can be a solid cruiser.
If you are going to the trouble of getting a 454 block, get the crank as well. More cubic inches just means a bit more power and torque given the same basic parameters. Or for that matter, buy a new cast 4.25" stroke crank for more cubic inches. The cast ones are super reasonable and good if you aren't doing something with big power. 1 horsepower per cubic inch is very easy now days with a good match of cam and heads.
 
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74 spectra20 v-drive

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Hey Barry, we are just screwing around with a worn out 396 in a friends Sanger. She is in her early 60's and just cruises the boat on Kings river during the summer, I re rigged the boat for her and she loves it but its generating so much crank case pressure that it pushing oil out everylace, has terrible compression as well. Was supposed to have been a fresh rebuild but i don't think so. She says the boat is plenty fast for her and I have always just loved saying 427... :) Thanks for the input and i may just heed your advice as well.
 

fast99

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This is an older thread but if the engine is an original GM 396 with 4 bolt mains it is rare. The engine might be worth quite a bit to someone for a car restoration. I know other very rare engines have been located in boats and put back in cars.
 

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What's called the big block Chevy has three distinct iterations, and they have key differences that a builder must be aware of. Broadly generalized, the Mark IV (1965-1990) is the oldest, has a two piece rear main seal, two bolt main caps, and the cylinder heads are interchangeable with the Gen V and Gen VI blocks in most cases.

The Gen V and VI blocks are the essentially the same, and the four bolt main cap, oil pump, oil pan, crankshaft and flywheel are unique to those engines. They also have an improved oiling architecture, and they do not have a cast and machined mechanical fuel pump boss on the block. The Mk IV heads have different coolant passage alignments compared to the Gen V and VI, and for the most part, gaskets can resolve those issues.

Again, broadly speaking, the Mk IV has the most performance parts available, and the World Products and Dart blocks incorporate improvements which make them the killer app, including the availability of splayed bolt main caps and 55 mm cam bearing journals.

Big Block Chevy Marine Performance, by Dennis Moore, is an excellent book that explains the evolution of the Chevrolet big block engine. It provides insight into the differences between the engines, and gives guidance on the selection of many Chevy parts that will produce a high performance durable engine. It also has valuable information on machining clearances and techniques specific to the marine environment. It's a great starting point for educating yourself about the BBC.

IMG_20201226_035019779.jpg


A Mk IV engine with the correct machining procedures and carefully chosen parts can easily produce 650-700 HP on pump gas with a single 4 barrel carb, and it'll last for years with basic maintenance.

As for the 396, don't get stuck on that displacement. There are several bore and stroke combinations that can be optimized for a marine application. Again, the book is a great starting place for general knowledge, but also it'll also show you the possibilities of the engine.

BTW if you have a four bolt main 396 block, it's probably been converted from a two bolt. The only stock four bolt 396 blocks were the 375 HP engine, and all of those disappeared long ago.
 
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74 spectra20 v-drive

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HOLY CRAP, just tried to buy this off amazon...$495.00, quick they have 4! Thinking an issue with procing right now ill check back in a few. :)
 

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I looked at the boat and passed on it but got the story on the engine. The seller built a 468 for it. The 468 blew up, for a better lack of terms. After sitting awhile he just wanted to use the boat. His buddy had this 396 sitting in his auto shop. He installed it and enjoyed his time on the water. Said it is a 50mph setup.
 

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rrrr

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Pretty amazing to think there would be something in that book that people would pay that type of money for! Maybe I should write a book?

It's a good book with informative basics, and there's no doubt it took some effort to assemble. But jeez, five hundred bucks?

There must be some odd computer algorithm that priced it.
 

fast99

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Can you get the casting number off the block? I have an old machinists manual with most of the casting numbers from the early 60's into the mid 70's. Can decode exactly what the motor started out as. Wonder if it could be a 366 tall block? They were 4 bolt.

The bottom 2 pictures are a big block HP manual. It's good if one can be located. 2 pictures of drag boats on the back cover.

100_0194.JPG
 

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Nikwho

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What's called the big block Chevy has three distinct iterations, and they have key differences that a builder must be aware of. Broadly generalized, the Mark IV (1965-1990) is the oldest, has a two piece rear main seal, two bolt main caps, and the cylinder heads are interchangeable with the Gen V and Gen VI blocks in most cases.

The Gen V and VI blocks are the essentially the same, and the four bolt main cap, oil pump, oil pan, crankshaft and flywheel are unique to those engines. They also have an improved oiling architecture, and they do not have a cast and machined mechanical fuel pump boss on the block. The Mk IV heads have different coolant passage alignments compared to the Gen V and VI, and for the most part, gaskets can resolve those issues.

Again, broadly speaking, the Mk IV has the most performance parts available, and the World Products and Dart blocks incorporate improvements which make them the killer app, including the availability of splayed bolt main caps and 55 mm cam bearing journals.

Big Block Chevy Marine Performance, by Dennis Moore, is an excellent book that explains the evolution of the Chevrolet big block engine. It provides insight into the differences between the engines, and gives guidance on the selection of many Chevy parts that will produce a high performance durable engine. It also has valuable information on machining clearances and techniques specific to the marine environment. It's a great starting point for educating yourself about the BBC.

View attachment 955438

A Mk IV engine with the correct machining procedures and carefully chosen parts can easily produce 650-700 HP on pump gas with a single 4 barrel carb, and it'll last for years with basic maintenance.

As for the 396, don't get stuck on that displacement. There are several bore and stroke combinations that can be optimized for a marine application. Again, the book is a great starting place for general knowledge, but also it'll also show you the possibilities of the engine.

BTW if you have a four bolt main 396 block, it's probably been converted from a two bolt. The only stock four bolt 396 blocks were the 375 HP engine, and all of those disappeared long ago.

Just for the sake of making sure that quality information is put out there, there are many Mk. IV blocks dating to at least 1968 that have 4 bolt mains. Four bolt mains are not exclusive to Gen 5 and 6 blocks. I own a few 4 bolt main Mk. IV BBC blocks. I cannot speak to availability of 4 bolt main 396's, but I own a 4 bolt main 1969 427 and two four bolt main Mk. IV 454's that are 4 bolt main blocks. And they are four bolt main offerings from the factory, not modified 2 bolt blocks.

Here are just a few (photo taken from David Vizard's book, I highly reccomend it)
20210110_224323.jpg
20210110_224331.jpg
 

Nikwho

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HOLY CRAP, just tried to buy this off amazon...$495.00, quick they have 4! Thinking an issue with procing right now ill check back in a few. :)
I've seen this with quite a few books on Amazon. They jack the prices way high, when only a few (or one) copy is available. Just their way of price gouging people. I was recently shopping for an older fire service leadership book and the only copy I found was $600 on Amazon. After a few weeks of randomly searching, I found it elsewhere for $30. If someone NEEDED it, though, it may be worth it for them. Was also similar recently when I was looking for the Oldsmobile engine building bible.

Nik
 

fast99

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Just for the sake of making sure that quality information is put out there, there are many Mk. IV blocks dating to at least 1968 that have 4 bolt mains. Four bolt mains are not exclusive to Gen 5 and 6 blocks. I own a few 4 bolt main Mk. IV BBC blocks. I cannot speak to availability of 4 bolt main 396's, but I own a 4 bolt main 1969 427 and two four bolt main Mk. IV 454's that are 4 bolt main blocks. And they are four bolt main offerings from the factory, not modified 2 bolt blocks.
Hope I didn't mislead anyone. Yes on the larger 454 and 427 4 bolt mains were available. I have been around big blocks all my life and have never seen a 4 bolt 396. They were probably only used on high HP 396 Corvettes for one or 2 years. The engine could be a conversion to 4 bolt but if a original 396 4 bolt someone might pay quite a bit for it.
 

Nikwho

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Hope I didn't mislead anyone. Yes on the larger 454 and 427 4 bolt mains were available. I have been around big blocks all my life and have never seen a 4 bolt 396. They were probably only used on high HP 396 Corvettes for one or 2 years. The engine could be a conversion to 4 bolt but if a original 396 4 bolt someone might pay quite a bit for it.
My response was to rrrr, specifically responding to post #17. He even said that his statement was broad. I was just clarifying that there are many 4 bolt main Mark IV blocks out there. Not just the Gen 5 and Gen 6 stuff. 👍🏿

Nik
 

fast99

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My response was to rrrr, specifically responding to post #17. He even said that his statement was broad. I was just clarifying that there are many 4 bolt main Mark IV blocks out there. Not just the Gen 5 and Gen 6 stuff. 👍🏿

Nik
Ok, Just FYI found a short article on the 396 4 bolt. It was a 425 hp 396 option code L78. Looks like it was produced 68-70?
 

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My response was to rrrr, specifically responding to post #17. He even said that his statement was broad. I was just clarifying that there are many 4 bolt main Mark IV blocks out there. Not just the Gen 5 and Gen 6 stuff. 👍🏿

Nik
Not that it really matters, but my first boat was a 69 Hallett jet boat with 69 427 4 bolt, 390 hp version. They had a forged steel crank, square port heads and Weiand intake.
 

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3855961....396.......65-66...2 or 4 bolt
3855962....396.......65-66...4-bolt
3902406....396.......67......2 or 4 bolt
3916323....396.......68......2 or 4 bolt
3935440....396.......68-69...2 or 4 bolt
3955272....396.......69......2 or 4 bolt
3969854....396.......69......2 or 4 bolt
3969854....402.......70-72...2 or 4 bolt
3999290....396.......68-69...2 or 4 bolt, Truck
3999290....402.......70-72...2 or 4 bolt, Truck
 
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