383 vs 396 rotating assembly
Le Mans Master
Joined: Sep 2001
Posts: 7,739
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From: Unreconstructed, South Carolina
Just about any head you might choose will breathe better on a 400 block's larger bore (4.125" v. 4.000")
bigger bore's wall is farther away from intake valve.
Dunno 'bout BC ... but around here I can find 'em with decent cylinders for $200 - $500 ...
... don't waste time&$ unless CERTAIN it'll clean up at +0.040" or Less.
If you're already stuck with a nice 350 crank ... it'll fit a 400 block w/ spacer bearings.
I've collected a few 400s but ain't sellin'
bigger bore's wall is farther away from intake valve.
Dunno 'bout BC ... but around here I can find 'em with decent cylinders for $200 - $500 ...
... don't waste time&$ unless CERTAIN it'll clean up at +0.040" or Less.
If you're already stuck with a nice 350 crank ... it'll fit a 400 block w/ spacer bearings.
I've collected a few 400s but ain't sellin'
Le Mans Master
Joined: Sep 2001
Posts: 7,739
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From: Unreconstructed, South Carolina
https://blueprintengines.com/product...lock-bp3503ct1
But, if you know what you're doing, you can buy a brand new Vortec crate and swap roller cam-springs for same money.
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
Arent most 396 crank kits all forged?
OP if you arent spinning it up high nothing wrong with a scat 5140 crank.
Id use a forged piston, internal balance
Check the fine print on assys, heads some are ready...others start with subpar stuff and nickel/dimes by the time its to your door.
So it costs more upfront than a cheaper crate but worth it in the long run. I cant wrap my head around something for under 3k being good maybe they are? A good stroker can easily run 8+...there are 540 crates on ebay for that much seems like its too good to be true.
OP if you arent spinning it up high nothing wrong with a scat 5140 crank.
Id use a forged piston, internal balance
Check the fine print on assys, heads some are ready...others start with subpar stuff and nickel/dimes by the time its to your door.
So it costs more upfront than a cheaper crate but worth it in the long run. I cant wrap my head around something for under 3k being good maybe they are? A good stroker can easily run 8+...there are 540 crates on ebay for that much seems like its too good to be true.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
That is a good idea but I have too sunk into this engine. Unless I can list the entire motor and recoup my money, I don't think another engine is in the cards at this point in time. Considering everything on the motor aside from the block is brand new and probably has less than 150 miles on it.
406’s run a LOT harder than 383’s because the bore is .125 bigger....your Brodie heads will love it.
Easy 525 plus horsepower.....
Jebby
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 963
Likes: 57
From: Vancouver, BC
But you are buying a rotating assembly anyway....so just search for a clean 400 block and everything else will fit....you will have to drill steam holes in the heads...(I only did the bottom ones)....but that is it....should not need any clearancing on the block....just bore it to 4.155....
406’s run a LOT harder than 383’s because the bore is .125 bigger....your Brodie heads will love it.
Easy 525 plus horsepower.....
Jebby
406’s run a LOT harder than 383’s because the bore is .125 bigger....your Brodie heads will love it.
Easy 525 plus horsepower.....
Jebby
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
never notice the difference????? I gained .2 in the 1/4 and I gained a lot of bottem end power using the the exact same cam, intake, and heads. My idle vacuum went up about a point.
The amount of grinding on the front cylinders of a stock block is more determined by the rods and bolt sizes. I used the same .980 base circle cam size.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Ohhh I see what you mean. So I would get a 400 block and then get a rotating assembly for the 400 block such as a 406 stroker kit? Then it would need to be bored out to accommodate the 406 kit? And all the top end such as the heads, intake, carb, valvetrain etc can be transferred over to the 400 block? Pardon my ignorance, im a novice.
Jebby
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
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From: New Braunfels Texas
Jebby, You should know that little 16 ci equates out to lots of additional across the board TQ. I also build 3.875 stroker 400 Dart SHP block motors. 415 ci kick butt over a 400 ci or at the .030 overbore size the 421 ci motors would kick butt compared to a 406.
never notice the difference????? I gained .2 in the 1/4 and I gained a lot of bottem end power using the the exact same cam, intake, and heads. My idle vacuum went up about a point.
The amount of grinding on the front cylinders of a stock block is more determined by the rods and bolt sizes. I used the same .980 base circle cam size.
never notice the difference????? I gained .2 in the 1/4 and I gained a lot of bottem end power using the the exact same cam, intake, and heads. My idle vacuum went up about a point.
The amount of grinding on the front cylinders of a stock block is more determined by the rods and bolt sizes. I used the same .980 base circle cam size.
a I would not build a 415 out of a GM stock block....and for sake of conversation....we all understand we can just keep bumping cubes.....my 421’s run hard....but are talking down and dirty street power with real cams not the .630 solid rollers.....
I will probably never build another 383 unless somebody had to have it.....the extra bore just make the head so happy
Jebby
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Thread Starter
Burning Brakes
Joined: Jul 2013
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From: Vancouver, BC
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Jebby
Thread Starter
Burning Brakes
Joined: Jul 2013
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Likes: 57
From: Vancouver, BC
Also I see online that there are a lot of 415/421 rotating assemblies on CNC but for 406 and 412 they only have a couple to choose from. Is this because the 415/421 is the most popular kit for the 400 block?
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 963
Likes: 57
From: Vancouver, BC
Also I see online that there are a lot of 415/421 rotating assemblies on CNC but for 406 and 412 they only have a couple to choose from. Is this because the 415/421 is the most popular kit for the 400 block?
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
wow that's good to know. im more inclined to go this route since now I know that the top end of my current motor can all be put on this block. are there any items that cannot be transferred over?
Also I see online that there are a lot of 415/421 rotating assemblies on CNC but for 406 and 412 they only have a couple to choose from. Is this because the 415/421 is the most popular kit for the 400 block?
Also I see online that there are a lot of 415/421 rotating assemblies on CNC but for 406 and 412 they only have a couple to choose from. Is this because the 415/421 is the most popular kit for the 400 block?
Jebby
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
Ohio crank is popular with some. 421s are popular as they make killer torque and piston speed isnt too terrible.
Best part is nobody would be the wiser as to its true size.
Best part is nobody would be the wiser as to its true size.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
if it's truly std bore & will clean up at +40 or less & No cracks in block ... Go get it
If you're buying rods ... go with 6" not 5.7"
AND ... regardless if building 383 or 406 ... if decks are good and do Not NEED cutting ... you can often buy a 3.8" stroke for less $ than a 3.75" ...
... that 3.8" makes zero deck and adds a few more cubes ... and any typical 0.039"-0.041" gasket makes perfect Quench.
Race Director
Joined: Jul 2015
Posts: 13,082
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From: SW Florida.
So .050 more stroke with same pistons? Aren't they coming 20 or 30 out of the block? I know a 41 gasket will cover that, but aren't the rings kind of close to getting airborne? OH! .050 stroke is .025 each way. Not .050 each way...
Last edited by derekderek; Oct 2, 2019 at 08:32 PM.
Team Owner
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From: altered state
St. Jude Donor '05
.the price of this **** has been going down dramatically since everyone went LS
Cant seem to sell parts at all unless its literally free and still ask for extras. If theres interest at all.
Last edited by cv67; Oct 2, 2019 at 09:52 PM.
Thread Starter
Burning Brakes
Joined: Jul 2013
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From: Vancouver, BC
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
tpi421vette@comcast.net
He has done a ton of 421s, strokers for guys here, Knows his stuff, reasonable honest best of all they dont come apart.
He has done a ton of 421s, strokers for guys here, Knows his stuff, reasonable honest best of all they dont come apart.
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Longevity of any motor actually comes down to hp per ci. In years past 358 ci NASCAR motors were iffy to even last through a 500 mile race producing @ 900 hp and turning over 9000 rpm every lap. Now they dropped 100 +hp and they last for a series of races
If you keep below 7000 rpm and less than. 600 valve lift you could have a very high mileage motor. My bottom ends seem to last for years and have exceptional leak down results, but the motors start smoking because of worn valve guides. So I have dropped my lift on the last refresh to mid 600s
If you keep below 7000 rpm and less than. 600 valve lift you could have a very high mileage motor. My bottom ends seem to last for years and have exceptional leak down results, but the motors start smoking because of worn valve guides. So I have dropped my lift on the last refresh to mid 600s