In the great Ideas hall of Fame, the first builder to develop the ubiquitous 383 stroker combination is right up there through whoever created s"mores and also Philippe Kahn, the guy who stuffed a camera in a cabinet phone.

You are watching: How to make a 383 stroker out of a 350


Along through the 33 added cubic inches over a 350 engine, the 383"s complementing advantage is torque. The bore/stroke proportion of a stock, oversquare 350, through its 4.000-inch bores and also 3.480-inch punch is 1.15:1. The 383 is tho oversquare, through a larger bore measurement than the stroke, but it comes lot closer come square v an boosted stroke proportion of 1.07:1, which boosts torque production.


Let"s take a watch at another example because that comparison: Chevrolet"s new 6.6L gas V-8, uncovered in the latest heavy-duty trucks, matches the 6.0L engine it replaces. Almost all of the 6.6L"s better displacement comes via a much longer stroke: 3.860 inches versus 3.620 inches. That"s a almost 7 percent increase, while the bore measurement is basically unchanged. The an outcome is 401 horsepower and also 464 lb-ft that torque, compared to 360 horses and also 380 lb-ft for the 6.0-liter engine.


*
See every 19 photosThe 383 small-block recipe is one virtually every enthusiast knows: mix a 0.030-over 350 block v the 3.750-inch crankshaft indigenous a 400 engine to deliver the long-strong combination. By the way: The typical 4.000-inch bores the the 350 to add the 3.750-inch stroke create a 377-inch stroker.

That"s virtually 11.5 percent greater horsepower and 22 percent an ext torque for the 6.6L. It"s necessary to keep in mind that, thanks to direct injection, the 6.6L has a greater compression of 10.8:1 matches the 6.0L"s 9.4:1, however it primarily improves horsepower. It"s the far-reaching increase in stroke the really amplifies the torque output.


In fact, the stroke proportion for the 6.6L is 1.05:1, i m sorry is ~ above par through the 383. So, that original builder was on come something through that first stroked small-block.


And in ~ a glance, building the 383 seems virtually as an easy as mashing a toasted marshmallow and a item of chocolate between a pair of graham crackers. A 0.030-over 350 block, to add the 3.750-inch stroke indigenous a 400 small-block (versus the 350"s 3.480-inch stroke) equates to 383 cubic inches. Fine the precise displacement is about half a cube shy of 383 inches, however it"s to be rounded up for decades.


Simple, right? no exactly. Since of the unique design and production attributes of the 400, dropping the crankshaft right into a 350 ain"t as simple as all that; and that"s what we"re right here to discuss.


*
See every 19 photosAlthough the 350 block is the foundation of the 383, it"s reasonable to questioning why the larger displacement 400 just wasn"t built into an ext performance engines. Its unique design features were the greatest factors, due to the fact that the aftermarket was set up to company small-blocks through the 350 key journal size, connecting pole length, etc.; and also because castle were additionally comparatively rare, there simply wasn"t much of a market for 400 performance parts. There to be an city myth about 400 overheating problems, too, which kept contractors away, specifically when 350 cores to be plentiful and cheap.

Stroker ChallengesThe challenges for building a strong 383 space due, mostly, come the geometry that the rotating assembly and the parameters that the cylinder block. All production small-block castings have a 9.025-inch deck height, which way the compression elevation for the pistons—the distance between the wristpin centerline and also the flat portion of the top of the piston—is a an important factor. The determines just how the piston fits family member to the deck surface at the optimal of the stroke.


To preserve the exact same compression height for the 400 small-block as the 350 engine, Chevrolet offered a shorter, 5.565-inch connecting pole length. All various other small-block variants supplied 5.700-inch-long rods. Beforehand 383 builders logically do the efforts the 400 rods in your combinations, because they were already matched with the crankshaft and its bigger journal, yet quickly found it produced excessive side-loading ~ above the cylinders through the 350 block"s smaller sized bores (a 400 has actually 4.125-inch bores).


*
See every 19 photosInternal clearance is an concern with a long-stroke small-block and also notching the bottom the the cylinders and often the pan rail is important to provide adequate room for the connecting rods. Care must be required to grind away just the material important for enough clearance since the water coat is right listed below the surface.

As the pistons moved up, the geometry that the comparatively lengthy stroke/short rods (the rod/stroke ratio) to be pushing them also hard versus the cylinder wall, developing performance-robbing friction that affected performance and also the engine"s high-rpm capability. Store in mind the the 350 engine had a much shorter stroke than the 400, however a much longer connecting rod.


So, the following logical move was to usage the longer 5.700-inch rods from various other small-block combinations, including the 350. That compelled machining the 400 crank journals to accept them, and also it also required tradition pistons v a shorter compression height. That relieved lot of the side-loading that the pistons but included cost and complexity to the build. Additionally, in ~ the bottom the the long, 3.750-inch stroke, the pistons had (and have) a tendency to extend past the bottom of the cylinders. If the piston skirts room too long, that can, in ~ the least, develop an annoying and disconcerting slapping noise as the pistons are propelled upward; at the worst, the can influence the engine"s longevity.


*
See every 19 photosWhen utilizing an yes, really 400 crankshaft, the main journals must be cut down native the manufacturing 2.65 inches to the 350"s 2.45-inch specification. Aftermarket crankshafts because that the 383 counter come v the journals already sized because that the 350 block. The 400"s larger mains likewise make that block unique and also incompatible with various other small-block cranks.

Today, a 6.000-inch connecting stick is a pretty typical solution because that the 383. It more reduces side-loading however the trade-off is a an extremely short piston to attain the appropriate compression height. And also it way the wristpin is driven up and also into the ring land, which calls for special accommodations because that the rings. Fortunately, with several years of 383 building, there are a variety of aftermarket 383 rotating kit to pick from, with each supplying matched pistons that room sized even for decked blocks. That means all the math required for determining the compression elevation is unnecessary, which conserves time.


*
See all 19 photosAnother thing around the 400 crankshaft, and also a variety of the aftermarket stroker crankshafts, is that it"s externally balanced, prefer a 454 big-block, with balance out weights at both ends. That method the engine should use the appropriate offset-weight harmonic balancer and also flexplate/flywheel.

A concern of Balance and also SealingHere"s another thing about the 383. The 400 crankshaft (and countless aftermarket cranks designed for a 383) is externally balanced. That"s because of the vital crankshaft counterweights forced for the longer stroke, yet to ensure block clearance, castle were added to the end of the crankshaft.


That means the flexplate/flywheel and harmonic balancer are details for one externally balanced engine. The wasn"t such a big deal for the 400 in production kind since it to be designed much more as a low-rpm speak engine for larger cars and also trucks. It"s less ideal in a high-performance mix that"s designed to rev, as it deserve to introduce detrimental twisting force on the crankshaft at higher rpm. Admittedly, it"s not that big of a transaction for many street/strip engines, however it"s other to save in mind.


*
See every 19 photosInternally well balanced aftermarket crankshafts are available for the 383 combination, yet to administer the appropriate mass for the counterweights they room typically balanced with Mallory, a very dense Tungsten alloy. The adds cost, however the trade-off is a typical internally well balanced small-block and also the innate durability advantage that comes through it.

A number of aftermarket 383 crankshafts and/or rotating assembly kit are available in the standard externally balanced design, and also internally balanced. We"d go with the internally balanced crank, given the choice.


The rear main seal must also be thought about when selecting a crankshaft or rotating kit. Older, pre-1986 small-block castings supplied a two-piece seal and the 1986-and-later castings have actually a one-piece seal that alleviated many of the small-block"s leaking tendencies. It"s crucial to know which you have since crankshafts used with the two-piece architecture have an counter weight the cranks because that the one-piece design do not. The one-piece seal crankshafts, in turn, combine the weight on the flywheel or flexplate.


There room aftermarket 3.750-inch crankshafts and also 383 rotating kit designed for one-piece seals, yet using them requires the removal of the load for balancing. Save that in mind when spec"ing a crankshaft or engine kit.


*
See every 19 photosMost rotating kits perform not encompass a balancer, so once ordering one because that a 383, it"s vital to clues one because that the traditional externally well balanced crankshaft or one internally well balanced one. And because that the lengthy stroke and unique counterweight characteristics of the engine, stick with a standard 8-inch balancer. There"s no real benefit for a street/sometime strip engine to use a smaller, 6-inch balancer.

Camshaft SelectionThe variables involving choosing the optimal camshaft for any kind of engine construct are practically endless, yet rod length in the 383 is critical factor that should be contained when spec"ing a camer or stating it through the tech line that a camshaft manufacturer.


Generally speaking, the goal is to open the valves to enable the best port flow (volumetric efficiency) when the pistons are relocating at their highest velocity ~ above the corresponding intake strokes. The rod length affects piston speed and the time it spends both at height dead center (TDC) and bottom dead facility (BDC); and also consequently, the valve timing via the camshaft must be accommodated commensurately.


*
See all 19 photosEven the rear main seal is a crucial component of the 383, and also it have the right to be a small confusing. Making use of an aftermarket, internally balanced crankshaft for the engine with a later-style one-piece main seal (shown) needs eliminating the unique offset weight from the one-piece-specific flexplate or flywheel. The weight is generally welded in location on flexplates, if weight should be removed from a one-piece-compatible flywheel by drilling feet 180 levels from the original holes.

Again, in an extremely general terms and also compared come a stock-displacement engine, a stroker combination will want an ext duration come help process the much more air delivered by the larger displacement, yet piston speed is a direct result of the rod length and affects the optimal duration in crankshaft degrees. To store things from gaining unnecessarily complicated, a good rule of thumb is that, because of the rate of the pistons and also the dwell time in ~ TDC and also BDC, a combination with a longer connecting rod—6.000 inches matches 5.700 inches, because that example—will require a small less duration to accomplish optimal volumetric efficiency. The camer would likewise likely advantage from a slightly tighter lobe separation angle, too: 109 degrees rather than 110 degrees, because that example.


The bottom line is, when ordering a camshaft for a 383, the rod size is a an essential specification that can significantly influence performance.


*
See all 19 photosWhen it comes to connecting rods, the length is crucial for a top-performing 383. In short, walk long: usage either 5.700-inch-long or 6.000-inch-long rods because that a less-severe stick angle the reduces the thrust, or loading, versus the cylinder wall. The reduces friction and enhances the engine"s rev capability, specifically at greater rpm.

Like us said, there"s an ext to structure a strong 383 보다 just adding a big-swinging crankshaft. Get it wrong and it will autumn flat, however get the right and the natural torque that the small-block multiplies and brings through it a satisfying rush of horsepower.


*
See every 19 photosAlthough much longer rod lengths sell the best rod angle, piston stability have the right to be an problem if the piston dress is long enough to expand too far below the cylinder bore in ~ bottom dead facility (BDC). It deserve to rock and smack the edge of the bore as it travel upward, possibly affecting ring seal and also ultimate engine longevity. For that reason, the pistons in a 383 need to be selected carefully.
*
See every 19 photosIt"s all around getting the compression height correct for the pistons. The is the measurement between the centerline of the wristpin and also the flat part of the optimal of the piston; and it determines the place of the optimal of the piston at peak dead facility (TDC) in relationship to the block"s deck surface. It"s identified by separating the punch by 2 and adding the connecting rod length to the quotient. Climate subtract the sum from the deck height. Because that a standard-deck (9.025 inches) 350 block using 6.000-inch rods, the formula functions out like this: 3.75 / 2 = 1.875; and 1.875 + 6 = 7.875. Finally, 9.025 7.875 = 1.15 inches for the compression height, which put the piston ideal at the height of the engine block.
*
See all 19 photosWhen the compression height pushes the wristpin right into the ring land, similar to the piston shown, the bisects at least the oil ring. As soon as that happens, oil rail supports are compelled to administer a heavy oil ring floor foundation. Alternatively, a pin button may be offered to "fill in" the gap in the ring land wherein the pen bore to be drilled. They replace the traditional locks.
*
See all 19 photosBecause a much longer connecting pole pushes the wristpin higher on the piston, there"s a suggest where the goes too far. The basic guideline is the compression height shouldn"t be less than 1 inch, which makes the 6.000-inch rod the valuable limit for the 383, particularly when decking the block is factored right into the build"s in its entirety machining. The 1.15-inch compression elevation is decreased to only 1.125 inches when a 350 block is decked come 9.000 inches.
*
See all 19 photosAnother consideration for rod size is even if it is the engine is normally aspirated or has forced induction. It"s important since the length of the rod determines the overall height that the piston and also the wristpin"s place on it. Contrasted to the 6.000-inch rod, using a shorter 5.700-inch rod means the piston will certainly be a tiny taller and the pin place a tiny lower, allowing a thicker, stronger head and optimized ring pack to better withstand a raised engine"s cylinder pressure.
*
See all 19 photosThe rod length can additionally create clearance concerns for the large end around the camshaft. Factory 5.700-inch rods will virtually certainly must be ground down about the pole bolt. The problem can be an especially acute as soon as using a higher-lift roller cam. I-beam rods, such together those shown, generally offer an ext clearance and also are easier to modify, if necessary.
*
See every 19 photosAnd speaking of camshafts, there are plenty that options, yet a hydraulic roller works an extremely well, an especially with a tighter lobe separation angle (LSA) that 108-110 degrees. That accentuates the engine"s torque-building capability at low rpm. Various other factors, such as the cylinder heads, will help determine the optimal lift and duration specs, yet generally speaking, one engine utilizing the much longer 6.000-inch rods will most likely do well with a small less duration and a tiny less LSA 보다 one through 5.700-inch rods.
*
See every 19 photos383 rotating assembly kits room plentiful and comparatively affordable, such as this Scat kit accessible from Summit Racing. Budget-minded, gentle street systems with a cast crank and also hypereutectic pistons are obtainable for much less than $800, when kits v a forged crankshaft and also forged pistons will certainly run up towards $1,300. These kits don"t include a camshaft or the crucial balancer, etc., yet they"re tough to beat when it come to starting a develop project through all the crucial parts already spec"d.

See more: Does Dawn Dish Soap Kill Grass ? Does Dawn Dish Soap Kill Grubs


*
See all 19 photosWhoever developed the very first 383 short-block to be on to something great, however it to be no accident. Doing it correctly ago then compelled forethought and much more than a little math. That"s quiet the instance today, even with aftermarket kits. Obtain all the number right, however, and also the power potential is precious the fuss.
*
See all 19 photos
*

By clicking sign Up, you agree come the terms of Use. Your information will be accumulated and provided in accordance with our Privacy Policy