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Modular Head Shop 5.8L GT500 1200+ HP Rotating Assembly - Cobra Jet Crankshaft, Molnar PWR ADR Rods, Diamond 5.8L Series Pistons, King XP Bearings

Cobra Jet Crankshaft, Molnar PWR ADR Connecting Rods and Diamond 5.8L Competition Series Pistons
Pricing: $2,399.00

Customize Your Item

- Select Piston Bore / Volume -
 * required
- Select Wrist Pins -
 * required
- Add Ceramic Dome Coating? -
- Add Lateral Gas Ports -
 * required
- Balance Rotating Assembly? -
 * required
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Modular Head Shop 5.8L GT500 1200+ HP Rotating Assembly 

  • Cobra Jet Forged 4130 Crankshaft - 4.165" Stroke
  • Diamond 5.8L GT500 Series Pistons 
    • Full Round Style Forging 
    • 1.315" Compression Distance 
    • .320" Down Top Ring Land 
    • Moly Coated Skirts 
    • .151" Intake, .050" Exhaust Valve Reliefs - Will accommodate +1mm Valves 
    • Forced Pin Oiling 
    • .180" Wall 8620 Alloy Wrist Pins 
    • 1.2mm x 1.5mm x 3.0mm Ring AP Steel Top, Napier 2nd Ring Set
  • Optional Piston Upgrades
    • Lateral Gas Ports - Suggested for 20lbs + Boost 
    • .200" H-13 Tool Steel Pins - Suggested for 800 HP +
    • Ceramic Dome Coating - Thermal Barrier helps with piston fatigue  
  • Molnar 5.4L / 5.8L PWR ADR Connecting Rods 
    • Forged 4340 H-Beam Design 
    • 6.657" Length 
    • Supplied with 7/16" ARP 2000 Rod Bolts
    •  Approx weights:
      • Big End 487g
      • Pin End 207g
      • Total 694g
  • King XP Series Main Bearings - 5.4L / 5.8L Aluminum Block specific 
  • King XP Series Rod Bearings 

This Diamond Piston / Molnar Connecting Rod Combo for the 5.8L GT500 is an excellent choice when looking to upgrade the bottom end components. Whether you are looking to hold 800 HP reliably, or looking to get close to the 1400 HP mark, this kit has the best components for the price. 

The Pistons included are from the Diamond 5.8L GT500 Series. These are built for boost. Forged from 2618 Alloy Aluminum, they are supplied with a very nice Total Seal AP Steel Ring Set and premium 8620 Alloy Wrist Pins. The Piston Ring set includes a Napier 2nd Ring, which helps with oil control. Pistons are available in the standard 5.8L Plasma Arc 3.681" Bore, as well as 3.650" and 3.670" Bore for blocks that have been sleeved. Our recommendation for sleeved applications is to start with a 3.650" bore. This gives you some extra material for future rebuilds. Available in 8.5:1, 9.0:1, 9.5:1, 10.0:1 and 10.5:1 Compression Ratios. 

Optional Lateral Gas Ports are suggested for boost levels over 20lbs. The gas ports allow combustion gasses behind the top ring, pushing it out harder against the cylinder walls for better sealing. 

While you will not break a .180" Wall 8620 Pin at 800 HP or even 1000 HP, we suggest the H-13 Tool Steel Wrist Pin upgrade at 800 HP for one reason...rigidity. The H-13 Pins are more rigid. We have seen plenty of wrist pin flex around the 800-900 HP mark with standard 8620 or 4130 alloy pins. The flexing wrist pin will gall up the pin bores of the piston and damage the pin bushing in the connecting rods. This simply shortens the life of both components. 

This assembly will come un-balanced unless that option is selected. There is no option for not balancing an assembly. It MUST be professionally balanced either by us or another machine shop. 
It is recommended to have us balance the assembly in house as we pay very close attention to details to get you the most accurately balanced crankshaft possible. 

Note: This assembly will require one large slug of heavy metal to be added to each end of the crankshaft for proper balancing due to the additional weight of the rods and pistons. Most machine shops will charge $50-$100 per slug added. This is built in to the balancing option already so you can be certain there will be no additional charges added. 

The Pistons in this kit are not always in stock. Please allow around 4 weeks for delivery. Add 7-business days for balancing option as the pistons must come here first. If you are in a rush, please check with us for availability before placing your order. 


Shipping Information

  • Item Requires Shipping
  • 35.0 lbs.
  • W14.0000” x H14.0000” x L28.0000”
  • Free Shipping!

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