im just a tad confused bc im getting prepared to build my first engine...im planning on doing a 408 cid stroker with a 4" stroke and 4.030" bore...now what i need to know is: Is it necessary to get a sbc 400? or would it be cheaper to just get a sbc 350 and drop the bigger stroke crank in?

if im correct it seems that the sbc 350 and 400 both have a 4" bore and the difference is simple the crank stroke correct?

 

haha, not exactly close at all....

350 has 4" bore and 3.48" stroke 349.8ci(350)
400 has 4.125" bore and 3.75" stroke 400.9ci(400)

So by putting a 400 crank into a 350 bored .030 over... you get
4.030" Bore and 3.75" Stroke, equivilating to 382.7ci(known as 383)

 

No the 350 and 400 bore are not the same. The 350 bore is 4.000", the 400 bore is 4.125".

You will spend probably $1000 less by buying a 400 core and rebuilding it; and it's anybody's guess how much less trouble you'd have as compared to that other.

Then when you get done with that, you'll have basically the exact same displacement as a .030" over 400; except, you'll have a MUCH longer stroke (less desireable) and a MUCH smaller bore (less desireable).

In other words, spend WAY WAY WAY more, get ALOT less.

All in all, not a very good idea. And MOST ESPECIALLY not for a "first engine" build. Build something stock, where there aren't so many variables, so that you don't spend wheelbarrows full of money for something that doesn't work out.

Yes, it happens.

 

4" stroke cranks are available for the SBC, but to fit one of those into a factory block is near impossible, if not absolutely impossible.
Those cranks are intended to be used in aftermarket blocks that have the oil pan rails spread apart to make room for the wider crank. And in many cases a 4" stroke crank will be used in a tall deck block as well, to allow more clearance for some deck height on the piston.
With a 4" stroke and a 4.125" bore you get a 430+ci engine... Sorry I 'm not in the mood for doing calculations right now, so that figure might be off, but you get the general idea I think.

 

WOW thx for clearing that up guys...i was searching all over the web for proper engine specs..so that really helps me out

so i def want to get a 400 block (4.125" bore) and bore it over .030 w/a 3.75" stroke...and id have a 406.77 or so...

but having a stroker motor means increasing displacement by adding bigger stroke correct? so i technically wouldnt have a stroker motor unless i went with a bigger stroke crank?

also, how do you get a 408 CID sbc then?

 

A 400 comes with a 3.75" stroke and a 4.125" bore
A 350 comes with a 3.48" stroke and a 4" bore

To make a stroker you can put a 3.75" stroke crank into a 350 and it will be a 383.

Stroking a 400 is getting into the realm of "specialized equipment". It can be done, but it's something for guys who have good connections with a machine shop, and who know their way around the SBC engine pretty thoroughly.

 

400s have plenty of stroke. Don't even worry about that.

 

a 408 would be a 400 with like a .040" overbore or something. The few cubes between 400 and 408 or whatever the max is, isn't there for power. That won't give you anything. Just bore it enough to get the walls straight enough to seal a piston ring, not a micrometer more. After .030" you are losing strength, etc.

Don't get caught up on the numbers, a 406(or 408 I guess), is just a cleaned up Chevy 400 motor. Still a chevy 400 block. It'll have like 1 percent power difference between that and a virgin 400cid motor, with all the same parts on it.
you're probably about to do some searches on google on chevy 400 blocks, so make sure you do some searches here on this forum. Key thing to note - you won't have cooling problems. You don't want/need a 4 bolt block, etc.

but yea, if this is a first build, might want to do a 350 block. I mean, you can do a 400, but the 350 might be a tiny bit cheaper and simpler. Just a tiny bit though. Everybody and their dog has rebuilt a chev 350, so there's no secrets, tricks, or oopsies left to make. (Like steam holes).

 

i appreciate the advice sonix but i dont really want to go smaller for another 200,000 miles on a 350...a 383 is def a possibility and was my first instinct...did i mention this is going to be a twin turbo motor??? either blow through carb or HSR injected cant make up my mind

i was planning on purchasing some quality engine building dvds and taking everything step by step and confirming uncertainties with a local engine shop

why no 4 bolt mains? arent they stronger?

 

oh, holy cow, you are about to be in a world of hurt.
Those are quite difficult to build eh? Well, your call. I think HSR like you already have would give better driveability, if you can tune the FI setup. Otherwise, blowthrough is how to do it.

4 bolt mains on 400cid blocks have thinner webbing then the 2 bolt style. You can take a 2 bolt and get splayed 4 bolt caps.

If you're doing a 350 block, then i'd highly recommend using a 2 bolt and getting splayed caps. A factory 4 bolt will work however.

Financially, and effortwise, this is going to be one massive undertaking. Hope you know what you're in for.

 

well ive read some more reviews of the 400sbc and i think im gonna stick to a 383 for ease of build...what i plan on doing is building the 383 with a low compression and running the motor while i save for the twin turbo project...i have researched most of this pretty well and understand what is necessary to get the job done...

im having trouble deciding on fuel system tho bc a carb blow through is much cheaper than buying a HSR and Stand alone EFI system ...but id like the EFI drivability and better gas mileage

 

I thought you have the HSR now?

ok, make sure you do searches on the screwups associated with a 383 build. Clearancing oil pan rails, clearancing rod bolts, small base circle cam, internel/external balance, which flywheel to use, which starter to use, which damper to use, piston pin height (383 pistons), trying to lower the CR on a 383.... Just make sure you know it all. Nothing that hasn't been done a fair bit by now (year 2006 that is), but it isn't as simple as a basic rebuild.

The 400 would basically be ; remove, clean, put back. Using stock parts.

Remember, a blower built motor, without the blower, will run like like a fat kid - very slowly I mean, civics-showing-you-who's-boss type of slowly. You won't want to drive it for long like that.
If you motor works ok now, maybe just save up the $$, and buy the parts as you go. Then once you have a shelf (or two) loaded with all the parts you need, go ahead and build it.
Just my

 

hey i def agree...i was planning on building it over the course of 6 months but i want a fresh block bc my GTA is over 200,000 miles old or so and the 350 in it is pretty worn...i actually had two HSRs but i sold them due to lack of time to install them...

hey would you recommend leaving the bore size at 4.00" and stroke at 3.75" making it technically a 382 but leaving more material btw cylinders for longer life and strength for FI?

oh yes, i thought about the FI motor w/o the FI haha ..well with a 9:1 compression it wouldnt be too bad...id bet it would outrun my l98 as of now haha

 

oh, ok, you're going to buy a brand new block? Like a world, dart or something like that?

I think your old block would be just as good as new with a good bore-out. Assuming you can park it for that 6 months.

9:1, then twin turbos? Yea, I guess that'd work. Get a good turbo camshaft for it. It'll run "funny" without the turbos, so might as well put 'em all on at once.

blow through carb should work fine. It's been done before, not by a ton of people on this forum however. Should be able to find some info on it.

 

what about the 382 vs 383 for strength?

well i can get a CSU carb and bonnet (all you need) for about $900 and then its just time tuning a carb...but my concern would be drivability and adjustment to the carb for added boost

 

A virgin block would be slightly stronger then one that's been bored out. Slightly, very slightly. That's not really a weak point, when you put pressure inside a cylinder, the top and bottom see twice the force (pressure) as the walls.
$900??? Holy cow, that's kinda pricey isn't it? I mean, it's still like a $400 carb, a bonnet can't be that much, it's just stamped metal... CSU?

Choke function is tricky to get working apparently. In texas it shouldn't be a major concern to you. If you're using a bonnet, (not completely enclosed) I hear you have a limit of around 10psi before it starts leaking around the throttle blades. Not sure if that's with an old carb, or a brand new one. I remember recently reading in car craft I think, about a guy with an orange 3rd gen, winning some drag races somewhere, with a carbed single turbo small block. Anyway, he must be doing alright, so...

 

well i look at it this way

EFI w/stand alone ECM and tuning...looking at about 2 grand

Blow through $900 and tuning

Custom EFI setup 2-3 grand easy

 

Plus a short block $2-3 k
Plus a set of heads $1.5 - 2k
Plus the turbos themselves
Plus all the exhaust plumbing
Plus a transmission that won't let out all its magic smoke the first time it tries to shift under power $2k
Plus a rear end that will last all the way through the first pass $1.5 - 2.5k
Plus enough suspension to actually hook the tires up, and of course the tires themselves

Plus plus plus plus ......

You're likely biting off more than you can chew. Seems like every n00b that rides in a turbo Supra or 300Z for the first time, gets this same sort of fantasy.

Build yourself a nice normal stockish kind of motor first. Learn what you're doing and where some of the gotchas are and make your newbie mistakes on something where you don't send $10,000 and 2 years worth of motor up in shrapnel the first time you step on the gas. Then after you've gotten REALLY GOOD at it, and know what you're doing, THEN AND ONLY THEN you'll be ready to step up to this mountain motor you'd like to have.

It's a common misconception to people who have never done it, that you can look through a catalog and pick out a couple of shiny things and tell yourself that's how much it's going to cost, and all you have to do is turn a couple of bolts and you get an instant 1000 HP or whatever. The reality is QUITE A BIT DIFFERENT. And that is, you have NO CLUE how much time, trouble, and money a project like you're talking about will take. If you think you do, you don't, because you're too inexperienced. You're asking questions that clearly put you into the "if you have to ask, you don't have enough background or experience" category.

Now maybe you're made out of money, and you just happen to have $15,000 laying around that you can drop on some toy, and you don't have to worry about rent and food and retirement savings and stuff; but I think just building a simple, ordinary, N/A 350 would be a great place to start, and get your feet wet. Give you soemthing to drive in the meantime, and you can sell it when you get this other thing all running and driving.

Call me a jerk or tell me this is what you're going to do and you're going to do it regardless; but you'll see. The real world has a way of straightening out fantasies.

 

If I were in your shoes, and posessing what limited knowledge I have at this time, I would do this:
Buy a 350 vortec truck engine from a 3/4 ton or bigger, I'm pretty sure those are all 4 bolts... (Might be 1 ton or bigger). It will have a hyd roller cam and a 1pc rear seal, to make life easier on you, and with that you'll get some heads that you can work with also.
Then get a forged/balanced stroker bottom end with 5.7" rods. If you shop around, you can find one of those kits that will have "stroker rods" which are already clearanced for the cam.
Buy a kit that has the right dish in the pistons to give you a workable CR with the 65cc vortec heads.
Don't invest a lot of $$ into your vortec heads.
Later when you go turbo, you can buy some larger volume aftermarket heads that will drop the CR.

Also don't be too concerned about the 1ci of displacement that an extra .010" of overbore gives you. Go with .020" or .030" either will be good.
Pay attention instead to getting quality machine work, and be extra sure the block is prepped correctly.

A lot of guys say you can't build a good turbo motor that will be good N/A, it has to be one or the other. But if you build a good turbo shortblock, then switch the heads when you add the turbo, it's feasible. The N/A performance
will be somewhat compromised, but if you're prepared for that slight sacrifice, then you won't be too disappointed.
It won't be a slug with a turbo cam and vortec heads in the N/A setup either, cause there will be some compression there.

 

let me just first off say that I WELL UNDERSTAND the extremes of my ideas cost, time, money, etc...I could pay someone to build me a boost ready motor for 5k and have it but i thought it might be nice to work with others and build it myself for 3k and in the process made a mistake when researching block dimensions

TAKE IT EASY with the "noob" etc. comments...i dont appreciate it...i dont particularly want a stock 350 rebuild thats gonna be the same thing for the next 5-10 years of my life that i have now...SLOW...i have no doubts that i could build and piece together a 383 sbc by myself with the help of friends that have BUILT plenty of motors and engine shops if need be if i run into snags

furthermore, if i built it for turbos then i wouldnt be racing it while it waited for them...it would be driven rarely and just enough to be necessary to be put in while waiting for a kit...i dont get how a 9:1 compression with a mild cam would be all that weak and as mentioned before its VERY feasable to build the 383 for a semi aggressive setup and then later tear it back apart and swap pistons and cylinder heads to drop the comp ratio

 

as far as the original idea of the thread goes, i have decided against the larger 400 block due to design flaws and difficulty in building and will definately go with a 383 (382) fresh virgin block and build from there over a 6 month period TAKING PLENTY OF TIME TO RESEARCH and BUILD IT RIGHT (i take pride in my car and make sure the $h*ts done right i.e. hand sanding my entire car for paint job)

there is a very good posibility that i will build a decently aggressive motor and then later when the turbo funds are available and ready...swap a diff cam, heads, and pistons retard the timing etc...to prepare it for boost...this is all brainteasing as of now...the only thing im putting money into somewhat soon is a fresh (or possibly) used block to build what i want