Load image into Gallery viewer, 6840-4090 6.1 Small Block Mopar Hemi Gen III FX Series -1.5cc  Flat Top  Gen III Hemi Forged Piston Set 4.090 inch bore   COMP HEIGHT:  1.21"
Load image into Gallery viewer, 6840-4090 6.1 Small Block Mopar Hemi Gen III FX Series -1.5cc  Flat Top  Gen III Hemi Forged Piston Set 4.090 inch bore   COMP HEIGHT:  1.21"
Load image into Gallery viewer, 6840-4090 6.1 Small Block Mopar Hemi Gen III FX Series -1.5cc  Flat Top  Gen III Hemi Forged Piston Set 4.090 inch bore   COMP HEIGHT:  1.21"
Load image into Gallery viewer, 6840-4090 6.1 Small Block Mopar Hemi Gen III FX Series -1.5cc  Flat Top  Gen III Hemi Forged Piston Set 4.090 inch bore   COMP HEIGHT:  1.21"
Load image into Gallery viewer, 6840-4090 6.1 Small Block Mopar Hemi Gen III FX Series -1.5cc  Flat Top  Gen III Hemi Forged Piston Set 4.090 inch bore   COMP HEIGHT:  1.21"
Load image into Gallery viewer, 6840-4090 6.1 Small Block Mopar Hemi Gen III FX Series -1.5cc  Flat Top  Gen III Hemi Forged Piston Set 4.090 inch bore   COMP HEIGHT:  1.21"
Load image into Gallery viewer, 6840-4090 6.1 Small Block Mopar Hemi Gen III FX Series -1.5cc  Flat Top  Gen III Hemi Forged Piston Set 4.090 inch bore   COMP HEIGHT:  1.21"
Load image into Gallery viewer, 6840-4090 6.1 Small Block Mopar Hemi Gen III FX Series -1.5cc  Flat Top  Gen III Hemi Forged Piston Set 4.090 inch bore   COMP HEIGHT:  1.21"

PART #: 1-6840-4090D

6840-4090 6.1 Small Block Mopar Hemi Gen III FX Series -1.5cc Flat Top Gen III Hemi Forged Piston Set 4.090 inch bore Pin Dia.: 0.927" Comp Height: 1.21"

Regular price $669.95
Sale price $669.95 Regular price
Sale Sold out
Unit price
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Piston Series Option:
Piston Ring Kit Option:
Ships in 1 - 8 days

Ships in 1 - 8 days

Made in the USA

Made in the USA

Secure Payment

Secure Payment

This is a pre order item. We will ship it when it comes in stock.

376 Small Block Mopar Hemi Gen III, FX, Comp Height: 1.21, -1.5cc Flat Top , PIN: .927", Full-Floating or Press Fit, Ring Groove: 1.2/1.2/3MM, Stroke: 3.578", ROD: 6.243, Approx Comp Ratio: 65cc-11.2, 74cc-10.11, 85cc-9.06


Piston Top Aprox. Comp. Ratio:

-1.5cc Flat Top Gen III Hemi
ChamberComp Ratio
6511.2 to 1
7410.11 to 1
859.06 to 1

For accurate Comp Ratio info use the calculator below.

Engine Brand: Mopar

Engine Family: Small Block Mopar Hemi Gen III

Engine Size: 6.1

Cylinder Bore Size: 4.090 in , 103.804 mm

Ring Groove Width: 1.2/1.2/3MM

Compression Height: 1.210"

Pin Diameter: 0.927"

Connecting Rod Length: 6.243"

Crankshaft Stroke: 3.578"

Cylinder Head: Gen III Hemi

TDC Assembly Height: 9.264" ( Zero Deck Height )

Download Piston Instructions

 
Features: Piston Series
 

E series

 SX series  1-FX series  2-FX series  3-FX series
Broached pin oiling slots

x

x

 

 

 

Drilled, forced wrist pin oiling

 

x

x

x

x

Forged drain-back windows

x

 

 

 

 

Drilled bottom ring land intersecting oil groove drain-backs

 

x

x

x

x

Slightly larger, deeper valve reliefs than OEM

x

 

 

 

 

CNC machined valve reliefs for moderate performance heads and cam combinations

 

x

Larger, deeper CNC valve reliefs for more aggressive cylinder head and cam combinations

 

 

x

x

x

Premium Aircraft spec. 4032 low expansion alloy

x

x

x

 

 

Premium Aircraft spec. 2618 alloy

 

 

 

x

x

Blower, Turbo, NOS ready

 

x

x

x

x

Brushed piston crown

 

 

x

x

x

Turned dishs

x

x

 

 

 

Max Quench milled dishs

 

 

x

x

x

Additional CNC milling for weight reduction in non-critical areas

 

 

x

x

x

Patented “X Groove” skirt for superior cylinder and ring life

 

 

x

x

x

Thinner/shallower Ring grooves for maximum ring seal and land strength

 

 

x

x

x

Low volume contact reduction grooves    

x

x

x

2nd ring land accumulator groove prevents ring flutter    

x

x

x

3rd ring land scraper relief    

x

x

x

Oil ring groove relief reservoir    

x

x

x

Inner and outer pin boss weight reduction radiusing    

x

x

x

Tighter control of crown thickness yields consistently lighter parts    

x

x

x

Dynamic skirt milling controls skirt thickness for consistently lighter parts  

 

x

x

x

Diamond-turned high strength skirts

x

x

x

x

x

High-strength piston pins

x

x

x

x

x

Extreme Duty XR wrist pins      

 

x

Horizontal Gas Ports enhance ring seal        

x

Forged and machined in the USA

x

x

x

x

x

Piston Specs

Piston Top Aprox. Comp. Ratio:

-1.5cc Flat Top Gen III Hemi
ChamberComp Ratio
6511.2 to 1
7410.11 to 1
859.06 to 1

For accurate Comp Ratio info use the calculator below.

Engine Brand: Mopar

Engine Family: Small Block Mopar Hemi Gen III

Engine Size: 6.1

Cylinder Bore Size: 4.090 in , 103.804 mm

Ring Groove Width: 1.2/1.2/3MM

Compression Height: 1.210"

Pin Diameter: 0.927"

Connecting Rod Length: 6.243"

Crankshaft Stroke: 3.578"

Cylinder Head: Gen III Hemi

TDC Assembly Height: 9.264" ( Zero Deck Height )

Download Piston Instructions

Piston Series Comparison Chart
 
Features: Piston Series
 

E series

 SX series  1-FX series  2-FX series  3-FX series
Broached pin oiling slots

x

x

 

 

 

Drilled, forced wrist pin oiling

 

x

x

x

x

Forged drain-back windows

x

 

 

 

 

Drilled bottom ring land intersecting oil groove drain-backs

 

x

x

x

x

Slightly larger, deeper valve reliefs than OEM

x

 

 

 

 

CNC machined valve reliefs for moderate performance heads and cam combinations

 

x

Larger, deeper CNC valve reliefs for more aggressive cylinder head and cam combinations

 

 

x

x

x

Premium Aircraft spec. 4032 low expansion alloy

x

x

x

 

 

Premium Aircraft spec. 2618 alloy

 

 

 

x

x

Blower, Turbo, NOS ready

 

x

x

x

x

Brushed piston crown

 

 

x

x

x

Turned dishs

x

x

 

 

 

Max Quench milled dishs

 

 

x

x

x

Additional CNC milling for weight reduction in non-critical areas

 

 

x

x

x

Patented “X Groove” skirt for superior cylinder and ring life

 

 

x

x

x

Thinner/shallower Ring grooves for maximum ring seal and land strength

 

 

x

x

x

Low volume contact reduction grooves    

x

x

x

2nd ring land accumulator groove prevents ring flutter    

x

x

x

3rd ring land scraper relief    

x

x

x

Oil ring groove relief reservoir    

x

x

x

Inner and outer pin boss weight reduction radiusing    

x

x

x

Tighter control of crown thickness yields consistently lighter parts    

x

x

x

Dynamic skirt milling controls skirt thickness for consistently lighter parts  

 

x

x

x

Diamond-turned high strength skirts

x

x

x

x

x

High-strength piston pins

x

x

x

x

x

Extreme Duty XR wrist pins      

 

x

Horizontal Gas Ports enhance ring seal        

x

Forged and machined in the USA

x

x

x

x

x

Engine Power TV

The DSS FX, X-Groove Feature