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Butler Performance 383-388 ci Balanced Rotating Assembly Stroker Kit, for 350 Block, 4.000" str.

  • New Cast or Forged Crank 4.000" Stroke
  • Choose Desired Bore Size and Ring Type
  • Forged Flat Top Ross Pistons, Dish, or Dome Available
  • Specify Desired Compression Ratio
  • Aftermarket 990 wrist pins
  • Bushed/Full Float H-beam 6.700" rods
  • Pin Fitted
  • Total Seal Classic Race Rings
  • Federal Mogul or Clevite Performance Main & Rod Bearings
  • Butler Process- Balanced Internally
Availability: Custom piston assemblies ship in 9-10 weeks
Pricing: $3,195.00

Customize Your Item

- Choose Your Main Bearings -
 * required
- Choose Your Piston -
 * required
- Choose Your Bore & Ring -
 * required
- Choose Your Rod -
 * required
- Choose Your Rod Bearings -
 * required
- Choose your Flexplate or Flywhee -
 * required


Our longrod assemblies offer the ultimate in durability and performance!

These assemblies utilize the lightest, strongest pistons and pin design available. We use only the highest quality ROSS Pistons in all of our long rod assemblies, not the cheaper pistons that many retailers sell at a similar price. Our ROSS pistons have the best weight to strength ratio on the market, and use our own proven Butler Performance designs. Nitrous Safe.

These Butler Performance rotating long rod assemblies come standard with H-beam 4340 forged steel rods from Eagle or SCAT (unless otherwise noted), two of the best names in the business! Bolt upgrades also available.
  • Forged Crank 4.000" Stroke
  • Choose Desired Bore Size and Ring Type
  • Forged Flat Top Ross Pistons, Dish, or Dome Available
  • Specify Desired Compression Ratio
  • Aftermarket 990 wrist pins
  • Bushed /Full Float H-beam 6.700" rods
  • Pin Fitted
  • Total Seal Classic Race Rings
  • Federal Mogul or Clevite Performance Main & Rod Bearings
  • Butler Process- Balanced Internally

All assemblies are internally balanced and require a neutral balanced flexplate or flywheel and harmonic balancer. All our assemblies come standard with Total Seal Classic rings. Our assemblies can be upgraded and customized to your project.


We offer crankshafts from leading manufacturers such as Scat, Eagle, RPM, and Ohio. These crankshafts come in cast steel or 4340 forged steel.

Cast crankshafts are an excellent alternative to O.E. Cranks. These crankshafts are new cast pieces made with modern material and casting processes to be a great alternative to 30 year old factory cranks. Recommended for use in street engines without power adders. Many factory cranks we check have stress cracks, so even though your crank has not broken yet, you may have a problem developing that could destroy your engine.

Butler Performance also offers Pontiac 4340 forged cranks from from many of the same manufacturers in a variety of sizes, and include the latest in oiling technology. Forged Cranks offer a tremendous advantage in strength and durability over cast cranks. This is very inexpensive insurance to protect your engine and even if its not needed at your current horsepower level now. Upgrading to a forged crank to build a solid bottom end will give you the option to safely upgrade performance and increase horsepower without having to worry about costly breakdowns in the future.

Most cranks offer standard oiling while some may offer Straight Shot Oiling. (noted in crank description)


After many years of working closely together, Butler Performance and ROSS Racing Pistons have developed a new line of Performance Forged Pistons for traditional Pontiac engines base on a new Butler exclusive forging.  For years piston forging designs used by performance piston manufacturers have been based off Small or Big Chevy, Ford, etc.  When making Pontiac pistons, these companies would typically use a raw forging originally designed for a small block Chevy, being the closest thing to Pontiac bore size, valve spacing and order, etc. This has worked for many years but sometimes resulted in pistons being heavier than needed because the Pontiac designs didn't "fit" the Chevy style forgings perfectly.Now ROSS Racing Pistons has designed a true "Pontiac" forging exclusively for Butler Performance.These pistons are some of the lightest and strongest available, with no special internal milling required to get the reduced weight.

These are the latest "strut-style" design, which lends to the reduced weight as well as increased strength.  These pistons can also be run at tighter piston to wall clearance so they are great for performance street applications as well as all-out racing.

Piston Selection- Based on your desired compression ratio, our techs work closely with Ross Racing to design a custom piston for your application. Many sellers limit you to only a few piston options, Butler Performance working in conjunction with Ross Racing can design thousands of different pistons for almost any application.


Butler Performance chooses to start Bore Size options for rotating assemblies, short blocks, long blocks, and engines at .030" over. Most engines have normal wear and machining the block and honing the cylinders to .030" over will ensure that you have a good foundation to install your assembly into. This ensures the pistons and rings will seat properly and be within specs and tolerances for building an engine capable of performance, horsepower, and longevity usually found in a Butler Engine.


Butler Performance uses Total Seal piston rings in most of our engines and assemblies. The main reason for this is their ability to build ring sets for us using rings from most of the major ring manufacturers as well as their own rings. This gives us a huge selection and Total Seal will custom build ring sets for almost any application if it's not an in-stock part. We offer Total Seal rings in several different styles: 

  • Classic Race (CR) sets are traditional, non- gapless sets using plasma-moly top rings. 
  • AP Advanced Stainless Top Ring (CS) are manufactured from 440B stainless steel and use a C33 face coating which cylinder wall wear. Stronger, Longer life and Most Precise Tolerances
  • Gapless Top (M) sets use a 2 piece gapless top ring. These are the latest design by Total Seal and were made possible by the better ring materials developed over the last few years. The top gapless sets are designed to prevent trapping pressure between the top and second rings.

We also offer TNT, stainless, dykes, and diamond lapped sets from Total Seal. If you don't see what you need, contact us and we can get it for you.

Std Rings- The rings are normally "Drop-In" Style rings. These still may require additional filing for your application.

File Fit- The rings are usually .005" over the desired bore size so they can be filed to fit.

Example; Total Seal CR, .030 Over, File Fit, 4.150+5 Bore
This is a Total Seal brand, Classic Race Series ring used in a .030" over bore application. The stock bore is 4.120" plus the .030" making it a 4.150" bore size. The ring will actually measure 4.155" so that there is an extra .005" so it can be filed to fit the desired ring gap.


We offer a wrist pin upgrade for all rotating assemblies and short blocks. Standard wrist pins that come in our rotating assemblies are rated up to 800hp naturally aspirated. Standard Pins are Ross Racing 5115 Chromoly, .150" Straight wall/128 gram.

Upgraded wrist pins are Ross Racing Bearing Steel .220 Straight Wall Bearing Steel /195 gram. Rated for use in higher horsepower applications.


We offer rods from several major manufacturers such as Scat, Eagle, Callies, Compstar, Oliver, and more.

Most rods in our rotating assembly's are high tensile 4340 Forged H-beam or 5140 Forged I-Beam. All rods are full floating, bushed unless otherwise noted.

Most rods come with stock ARP8740 rod bolts are rated at a tensile strength of 190,000 psi. Upgraded ARP2000 rod bolts rated at 220,000 are also available.


Our rotating assemblies come standard with Federal Mogul bearings with an option to select Clevite main & rod bearings

Most Forged crankshafts require narrowed Performance or Race bearings because of the larger radius’s on the cranks main and rod journals.

  • Federal Mogul (FMP)- M series main bearings
  • Federal Mogul (FMP)-CH series rod bearings
  • Clevite (C77)- H series main bearings
  • Clevite (C77)- HN series narrow rod bearings

The Butler Process

All rotating assemblies sold by Butler Performance, regardless of brand, are balanced in our shop by our experienced machinists.

We don't take anyone else's word when it comes to the parts we stand behind. We put all rotating assemblies through the Butler Process for quality and performance. Our internal balancing process ensures each part of the kit is put through a multi-step inspection process. We then weigh and pin fit the rods and pistons as needed. We computer balance the crankshaft to the rest of the assembly. This process ensures that all the parts of the assembly are matched to form a "Butler Performance" worthy assembly. We then document all weights and information on a balance card that ships with the assembly.

Compression Calculator

Compression Calculator

Simply fill in the form below to calculate your compression ratio

*BP Flat Top pistons normally include +8cc valve pockets. When selecting dish piston from list, do not add valve pocket cc volume. Valve pocket cc is already included in the dish piston volume*

Bore: (diameter)
Cylinder Head Volume:
Effective Dome Volume:
Use (-) for Dome and (+) for Dish.
Deck Clearance:
Compressed Gasket Thickness:
Number of Cylinders:
Compression Ratio :  
Total Displacement (in.3) :  
Total Displacement cc's :  

Listed is an example of a 461 cu.in. with a 72cc head.

If deck clearance and head gasket sizes are not known, enter 0 and .040 as shown below.

*Chamber volume cc should be entered as a (+) number for dish and (-) negative for dome*

Cu. In. Chart

Pontiac Cu.In. Chart

350 Block Stroke
Bore 3.75 4.00 4.21 4.25 4.50
Stock 3.875 354 377   401  
+.030 3.905 359 383   407  
+.040 3.915 361 385   409  
+.050 3.925 363 387   411  
+.060 3.935 365 389   413  


  • BPI-4000-300-350
  • BPI-4000-300-350
  • Butler Performance
  • Custom piston assemblies ship in 9-10 weeks
  • New

Shipping Information

  • Item Requires Shipping
  • 120.0 lbs.

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