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Old 06-01-2006, 09:46 AM   #1 (permalink)
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sbc 350 to 400 conversion ?'s

I have a sb 350 that i want to make into a 400. i was planning on having this engine produce 400+ hp. i was wondering what i needed to change out to up the c.i. to 400 and what parts i should get so i can reach my hp goals. i am thinking about getting some trick heads, and doing cam, intake, etc. but if anyone has any other ideas that are a little cheaper that would really help a lot. thanks.
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Old 06-01-2006, 09:54 AM   #2 (permalink)
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Easy, just change the block, crank, and pistons. Most of the other parts will interchange.
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Old 06-01-2006, 10:27 AM   #3 (permalink)
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Block, heads, rods, crank and pistons are all different to a great degree. Really IMO you are getting now big gain by going to the 400 over a well built 305 except for the long stroke for a better low end but you are egtting that stroke by sacrificing rod length which kills performance over all. Plus the 400s can have some cooling and block rigidity issues when pushed hard.

I am not a fan of super high horse motors for off roading, they tend to be consitant and reliable but if I where to build for power I would start with a bored 350 and a good set of heads, you shoudl be able to get 400HP out of that with out to much work. Or possibly a 400 with a 5.75 or 6" rod and good heads if I really wanted the displacement.
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Old 06-01-2006, 02:34 PM   #4 (permalink)
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easiest way to go is by just changing the blocks, cranks, and pistons, high horse motor isn't the greatest for off roading becuase of how much it will work for the power. Its not a good off road style
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Old 06-01-2006, 03:04 PM   #5 (permalink)
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Yah i dont want to go too crazy on the hp, but i wanted to make sure i have enough power to move 1 ton axles and 39's and have enough power on the street and merging on the freeway. It would be ideal to have 400+ hp but i realize i need huge amounts of low end torque for climbing too.
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Old 06-01-2006, 03:07 PM   #6 (permalink)
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Dude, I run 40 inch iroks with 4.56 gears and I have a bone stock 350 that is like 250 hp. It gets up and runs great. If reliability is what you are looking for just get a good stock motor.
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Old 06-01-2006, 03:17 PM   #7 (permalink)
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jus ttake out the crank and rods and put them in to the 350 block that makes the 383 and thats all the power you need
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Old 06-01-2006, 03:40 PM   #8 (permalink)
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first of all, do not waste your money on a 305, all of those engines are boat anchors.
second, the easiest way to get 400 cubes, is to find a 400 sbc in a junk yard and do a rebuild on it. any 350 chevy heads will fit on a 400 sbc, if you are going to go this route, have the heads drilled for steam holes. if you do not drill the steam holes you will have over heating problems. this is where the myth of over heating 400's comes in. this is something any machine shop can do. I personally have a 400 that i pulled out of a chevy van with stock rods and crank. i rebuilt it with new rings maching work and hyperutectic pistons. it's currnetly in my corvette and it dyno's at 374 rear wheel horse power, at 5800 rpm. i shift it at 6200 rpm. as long as you stay under 6000 rpm the cast crank will easily provide you with years of service. engine speed with lots of horse power kills stock cranks. your goal of 400 hp can easily be accomplished bby going this route. if you do find a 400 make sure you get the flywheel and harmanic balancer to go with it. the 400's are externally balanced and 350's are internallly balanced.

the other way to get almost 400 cubes is to get a 350 engine and put an 3.875 stroker crank. this will net you 396 cubes. the draw back to this is that you will have to buy a forged crank to get there. i don't know of any companies that sell a 3.875 stroker crank that is cast. and you will also have to get the rest of the rotating assembly. on top of that you will have to take the block into a machince and have it clearanced for the stroker crank. and the cam will ahve to ahve a small base circle. all of this is pretty common for sbc engines. imo this is too costly of route to go. if your goal is 400 horse power, the crank, rods and pistons are going to be overkill for this combo.

if you i were you, i would take any 350 and put in a 3.75 stroker crank and rotating assembly. it is fairly cheap, about 1000 bucks for everything you will need and will net you 383 cubic inches. a fairly mild cam will get you the 400 hp you are looking for. the 400's are getting harder to find in the junk yards.

pm me if you have more specific questions.
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Old 06-01-2006, 05:53 PM   #9 (permalink)
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well i just put a 383 in my camaro and it put 405 at the wheels and 425 torque
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Old 06-01-2006, 06:28 PM   #10 (permalink)
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I run a 383 stroker 350 in a K5 with 42s and 4.56 gears. Its more than enough engine to run in a 4WD truck. It will white smoke all 4 tires if ya like that sort of thing.
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Old 06-01-2006, 06:46 PM   #11 (permalink)
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i am thinking of going with the 383, what performance parts would i need for 400 hp and what parts should i have beefed up to handle that? i am thinking of buying a full rotating assembly for about 1000 what else would you guys recommend? i am trying to not spend more than 1500 on parts because im probably gonna rebuild the whole thing. thanks

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Old 06-01-2006, 07:35 PM   #12 (permalink)
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. 383 will be the way to go. i was planing on this till i scored a 454 bbc.

P.A.W lists the 383 "kit" at $1066 with crank,pistons,bearings,rings, and rods and long block kits up to $2100
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Old 06-01-2006, 07:49 PM   #13 (permalink)
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I bought an Eagle rotating assembly from a local wholesaler. After the machine work on the block and an good internal balance job I had about 1600 in the short block. It was well worth the extra money spent on quality parts and machine work. I run a set of vortec heads for a while and they made great power. I bought a set of Darts from a friend and it was a whole new world of power.
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Old 06-01-2006, 07:53 PM   #14 (permalink)
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383 is prolly the best bang for the buck. I got the 383C kit from powerhouse for $799 balanced and it was assembled using decent parts. One thing I did not like about it, and would ask them to make substitutions if I ordered again, was the gasket set was cheapo paper type from the 1950's and that they added weight to the flexplate and harmonic balancer instead of doing it the "right way" by balancing internally so you can use off the shelf parts in the event you trash the flexplate/balancer. Most builds with a decent set of heads and a mild performance cam will make 400 ft lbs.
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Old 06-01-2006, 07:54 PM   #15 (permalink)
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I run a SBC 400 in a '53 CJ-3b, long rods, flat tops, and decked large chamber heads. The torque is incredible!

But if I had to do it again, I would find a stock 6.0L out of a HD Chevy and have a fuel injected beast for just a little more money.
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Old 06-01-2006, 09:44 PM   #16 (permalink)
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go big block... you will love it.. a decent complete 454 can be scored for $500-$800 or cheaper if you look long enough... personally i Love my Caddy 500 and it gets better milage than my small block did since i dont have to have the hammer down all the time to make good power. if you have a 350 already you can put and intake, carb cam and headers on it and it will do fine... if your dead set on a SB 400 steer clear of any that have been rebuilt already. the cyl wall is simesed on these and can only be bored over so much before thay get pretty thin... anything over .030 over (406 ci) is proably asking for trouble although i have seen them .060 over on a all out drag engine (solid block no coolant passages)
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Old 06-01-2006, 09:48 PM   #17 (permalink)
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they make a 4.0" stroke for a 400 CI that will measure 427 cubes, about the same cost as buying a stock 400 crank, there is no replacement for displacement. Built Vortecheads and the proper cam will easily make 425 hp from a 427 engine. If you can find the 2 bolt main 400 they are actually stronger then the 4 bolt add an arp stud kit to the main bearings and can be even stronger thena 4 bolt 350.
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Old 06-02-2006, 12:25 AM   #18 (permalink)
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Quote:
Originally Posted by botiejeep
Dude, I run 40 inch iroks with 4.56 gears and I have a bone stock 350 that is like 250 hp. It gets up and runs great. If reliability is what you are looking for just get a good stock motor.
You also wheel a glorified go-cart. No disrespect intended, but a stock engine just doesn't push a fullsize, 6000 lb truck all that well.
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Old 06-02-2006, 04:55 AM   #19 (permalink)
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Originally Posted by read306
I bought an Eagle rotating assembly from a local wholesaler. After the machine work on the block and an good internal balance job I had about 1600 in the short block. It was well worth the extra money spent on quality parts and machine work. I run a set of vortec heads for a while and they made great power. I bought a set of Darts from a friend and it was a whole new world of power.
which dart heads did you go with? i'm planning on building a 383 for my truck, and have no clue yet on what heads to run.
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Old 06-02-2006, 08:42 AM   #20 (permalink)
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383, 6"rods, vortec head's set up for hydralic roller cam. Around .470' lift. Pretty close to 400 hp and very driveable.
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Old 06-02-2006, 04:00 PM   #21 (permalink)
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which dart heads did you go with? i'm planning on building a 383 for my truck, and have no clue yet on what heads to run.
The heads are the older 220cc Iron Eagles,2.05 intake and 1.65 exhaust.They have 72cc chambers.
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