For all us old guys and/or novices, please explain the 383 ci mod(s) that are so often discussed. What are the pluses and minuses of this mod? What does it cost - in general, etc?

Thanks, John
95 LT1 6M

 

Very basic:
383 is a 350 block that has been bored to .3 and a 400 crank built specifically to be used in a stroker motor. Next depending on heads and pistons your compression may increase or decrease.
Do a search in google for 383 stroker kits. The kits can include everything you need except the block and required boring.

 

it gets even better when you move up to the 396 mod! :D

 

pretty much that is it. 400 ci block's crankshaft in your 350. the standard bore seems to be .030". however, anysize can be done up to about .060".

there are a few things you have to be careful about. the main bearing journals of the 350 and 400 block are slightly different; however, many manufacturers make a 400 crank that is designed to fit the 350 main journals without any modification. there are other things that may have to have a little spot grinding done on the inside of block - dont worry i mean a little.

advantages are more then just 33 extra ci's. the longer stroke of the 400 crank also gives a longer counter arm for the piston/pushrod to push down on. this little increase ( i think it is .125" or 1/8" but im sure someone here can give you exact numbers for everything...) over the 350 crank gives a longer counter arm, hence more torque.

by the way, torque is a force; horsepower is a measure of energy produced per minute (or it can be measured in secs, hours, etc but standard is minute -at least if i remember from physics correctly...)

oh yeah, one other problem with a 383, severe traction control problem caused from tire frying torque :hurray:

:steering:

 

In a standard 350. the piston moves up and down the cylinder, from the top of the bore, down to the bottom (nearly), and back up again. This is a revolution of the engine, and produces a certain amount of power.

In a 383 "stroker " motor, by having a different crankshaft (and pistons to suit), the piston now moves from the top of the cylinder bore, to further down the bore at the bottom, making a longer stroke, which produces more power per revolution than before. (This power per revolution of the engine is referred to as torque, by the way)

So if you want more power from an engine, you can either do more RPM, or increase the power for each rev, by making the cylinders bigger (as in this case), having more cylinders, or generally tuning the thing.

This is why a big cube motor will have more torque (more power for one revolution), but it may have no more total power than a small cube motor, which can make up for it by spinning faster. All big horsepower small cubic inch engines rev up to ridiculous figures, (compared to our relatively large V8's) for this reason.

So to summarise - if you want more power either increase the power from each revolution of the engine (torque), or increase the revolutions of the engine per minute(rpm).

Or preferably both.

If you look at EVERY tuning modification, it is an attempt to increase torque (power per rev) or increase revving capability.

:)

 

The minimum to get from a 350 to a 383 is a new crank and pistons. It can be done with just that.
Most everyone takes the opportunity to redo a host of other things that are easier to do with the engine apart. (Head porting, valve job, block boring, new HotCam, etc). Add a good exhaust setup and the end result is usually a fire-breathing engine.

The cost is directly proportional to how many things you choose to upgrade at the same time. Whatever it is, however, it will be worth it in the smile on your face as your eyeballs flatten. IMHO, the 383 is how the Vette should have come from the factory. With an all aluminum 427 as the upgrade option.

 

I am totally new to block modification, but have been told you lose some RPM when going to a 383, but will get more torque.

I am a bigger fan of ZR-1 style high-revving power plants. Something about the zing sound that gets me going.

Down low, your not spinning your tires, and when the big cube guys go to shift, you are still winding your stuff out!

 

The pistons will all be weighed seperately and they will try to get them all to weigh the same. Can remove a little material. Then the rods will be weighed separetly. They will weigh the small ends and try to get them all close in weight, and then the big end also. Then assemble the pistons to the rods and weigh those. The crank may or may not have mallory metal or "heavy" metal added or some drilled out of the counterweights. I think the mallory is like $90.00 a pop. Sometimes need one or several. Then assemble rods to crank and then add the harmonic balancer and flywheel to the crank. Dynamic balance as a whole. You would need to keep that relationship in tact if ever switching parts. So that is called externally balanced.
Every .030 over bore equals roughly another 5 CID.
383 bore is at .030 over as mentioned, and usually the next rebuild they will bore it out an additional .010 for total of .040 over. On our production blocks, I find that .060 over is generally accepted as the most you wanna go although you could still go to .080. That's really pushing it tho.
I can think of NO minuses to this "mod" :D
An all AL 427? Yeow! Sounds like a ZL1 from back in the old days.

 

And a Fartpipe in a pear tree...... :lol:

 

http://www.sdpc2000.com/cart.asp?act...tart&catid=452

http://www.sdpc2000.com/cart.asp?act...art&catid=1580

 

Take your current block, have a machine shop bore it out .030", put a 3.75" crank in, you have 383ci.

You can have it built to rev to the same rpm as a 350, it just may not do it quite as quickly, depending on the characteristics of the motors (cam, heads, intake, etc.).

Only con would probably be cooling problems (which should not be a problem if the 383 is built correctly) and fuel economy losses (which can be mostly made up for by a good reprogram).

 

Mr Mojo, regarding those links to the crank assemblies. do you know if those are actually worth the $$ or should one shop further? I think when i play with my block this christmas i may pull my lower rotating assembly and replace it. I want a new one to hold 500hp at 6000RPM, do you know if this will do it?

Im serious here, so if you know of a better place to buy one prebalanced let me know please.

 

Hear is a nice small block from world. I am not sure what you would need to convert to EFI but I bet someone on the board could help. They also have a 454 with 600 HP. 427 @ 9K, 454 @ 10.5K
955-101006
MoTown 427 c.i., 530 H.P. - Complete Engine
TECHNICAL SPECIFICATIONS
Block: MoTown cast iron with 4-bolt mains
Bore: 4.125''
Stroke: 4.000''
Cylinder Heads: MoTown 220 aluminum
Crankshaft: Scat 4130 forged steel
Pistons: JE 4.125'' forged aluminum flat-top (9:1 compression)
Connecting Rods: High performance H-Beam forged rods
Camshaft: Crane hydraulic lifter profile with Speed Pro lifters
Intake Manifold: MoTown aluminum
Carburetor: Modified 870 cfm Holley 4-barrel
Valves: Manley Severe Duty stainless steel (2.055'' x 1.600'')
Timing Chain: Manley True Roller
Lubrication: Speed-Pro oil pump and Milodon stamped steel pan
Rings & Bearings: Speed-Pro ring set and Clevite bearings
Ignition: HEI distributor, 8mm spark plug wire, Accel spark plugs
Valve Train: Aluminum roller rocker arms, Manley 4130 pushrods
Balance: Internally balanced, Hardcore CNC Balancer
Assembly Components: Fel-Pro, ARP and Manley
Accessories: MoTown chrome valve covers, chrome timing cover
Warranty: 2-years or 24,000 miles.

:party:

 

:lol:
:lol:
:lol:
:lol:


EDIT: 'Tis getting to be the season isn't it ?


[Modified by edsalinas, 6:46 AM 10/7/2003]

 

Very :cool:

Check out the prices????

 

The limiting factors of RPM's are typically the rotating inertia of the engine and it's breathing capabilities. For example the stock L98 intake starts to run out of air around 4500 RPM's in stock form. If you make a stroker out of it and put the same intake back on top you will run out sooner. Every revolution is going to require more air, so if you run out at 4500 RPM's on a 350 you might run out at 4000 on a 383. These are just made up numbers BTW, the loss could be more or less than that.

Assuming you can flow enough air into your engine you will need it to be able to spin that fast. The longer stroke crankshaft is covering a larger arc and will therefore have more material. The pistons are traveling a greater distance down the cylinder as well. So for any given revolution there is really more movement going on inside the engine. As the movement goes up the RPM's go down before the engine starts ripping itself apart.

This really isn't much of a problem though, in fact most people with stroker motors easily turn as many if not more RPM's as they did with the 350. They can get away with it by using top quality light weight components. Remember that from the factory the engine was made with a budget in mind, a good compromise between performance and cost. If you've got about $10k to spend on your engine alone you can use much better components. If you use all light weight forged components and top quality fasteners you can actually end up with a stroker motor that has significantly less rotating weight then the stock motor. Strokers can also be internally balanced. This is harder to do but very nice. It means that you can use a neutrally balanced flywheel, etc. A light weight, properly balanced motor will be able to rev until it reaches the next restriction, usually the valve train.

The same tricks work for the valvetrain. Light weight titanium retainers, higher spring pressures, lighter valves. If you've never seen a titanium valve, let me tell you it's AWESOME! You expect it to just float in the air.

If you give me the budget I'll give you a 396 stroker that'll turn 7500 RPM's all day long and it'll look exactly like your stock motor on the outside.

:cheers:

 

Can't think of a better way to spend 10 grand. Wonder if it would pass emmisions. Would definately go with the 427 though, that way you can bore the cylenders through a couple of rebuilds and still have some sylender wall thickness. 9.5:1 on aluminum heads could even take a little bit of boost.

Anyone want to make a donation to the Bob-Goes-Fast fund? :smash: :lol:


[Modified by rkessel, 5:33 AM 10/13/2003]