Mopar Gen II Hemi Torque Specs

Intro

The Gen II Hemi is the 426 Hemi. Chrysler built plenty of engines with hemispherical chambers before and after it, but this is the one that turned four letters into an argument at every drag strip, dealership, and garage in the country.

That reputation does not make the hardware interchangeable with every other Mopar wearing a Hemi name. The 426 has its own cross-bolted bottom end, its own head requirements, unusually light intake-manifold torque, specific 7/16-inch rod hardware, and separate street and race camshaft cap-screw values.

This is also an engine where a number that looks ordinary can be attached to hardware that is anything but ordinary. The main caps are clamped vertically and tied into the block from the sides. Iron and aluminum heads do not share the same bolt range. The intake bolts call for only 8 lb-ft while the harmonic damper bolt wants 135. Read the row before admiring the valve covers.

A 426 Hemi may be famous enough for everybody to recognize it. The torque wrench still needs considerably more information than that.

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General Torque Specs

¹ Head-bolt value changes by head material. Iron and aluminum heads are not the same row wearing different paint.

² Rocker shaft bracket bolts are listed as a maximum value. Aftermarket rocker gear, stands, shafts, and fasteners follow the part maker.

³ Thin covers, carburetor flanges, and cork-style gaskets distort easily. Tighten evenly and do not turn seep control into bent metal.

⁴ 426 Hemi intake hardware is low-torque hardware. Do not drag wedge intake numbers into this row unless cracking expensive parts sounds fun.

⁵ Street Hemi and race Hemi camshaft cap screws do not use the same value. Match the actual parts.

The bottom end makes it plain this is not an ordinary Mopar wedge. Main cap bolts are listed at 100 lb-ft, while the horizontal tie bolts that finish the cross-bolted arrangement are 45. Same main-cap assembly, different fasteners, different jobs. The torque wrench does not get to photocopy one number onto both.

The head rows are just as fussy. Factory iron heads are listed at 70-75 lb-ft and aluminum heads at 65-70. The head material changes the answer before aftermarket bolts, studs, gaskets, or modern castings even get through the door.

Then comes the number most likely to insult somebody’s big-block instincts: 8 lb-ft on the intake manifold bolts. No digit fell off the page, and Chrysler was not asking for help from a remembered 35- or 40-lb-ft wedge number. Eight means eight.

The street and race camshaft cap screws make the same point from the other end of the wrench. Street hardware is listed at 40 lb-ft; race hardware at 75. Same 426 Hemi family, nearly double the number. The badge gets you to the chart; it does not get to pick the row.

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Important Notes

• The 426 Hemi bottom end uses vertical main-cap bolts and horizontal tie bolts. The 100 and 45 lb-ft values belong to different fasteners, not two mechanics arguing over the same one.
• Iron and aluminum heads get separate head-bolt ranges. Identify the head material before choosing a value, then follow any different instructions supplied with aftermarket heads, studs, bolts, or gaskets.
• The 7/16-inch connecting-rod bolts are listed at 75 lb-ft. Replacement rods and aftermarket fasteners may require a different procedure, especially when the fastener maker specifies lubricant or stretch rather than relying on a generic factory number.
• The 30 lb-ft rocker-shaft bracket figure is a maximum. Maximum does not mean ‘keep pulling until the wrench gets there’ when the rocker system on the heads is no longer factory hardware.
• The 8 lb-ft intake specification deserves to be believed exactly as printed. Familiar wedge numbers can stay with the wedges; the Hemi intake does not need a larger number just because somebody remembers one.
• Street and race camshaft hardware are identified separately for a reason. Determine which parts are actually in the engine before the wrench decides whether 40 or 75 belongs there.

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Common Mistakes

• Treating the cross-bolted bottom end like an ordinary two-bolt or four-bolt main arrangement and overlooking the separate 45 lb-ft tie-bolt specification.
• Choosing the head-bolt number from memory without first determining whether the engine carries iron or aluminum heads.
• Seeing 8 lb-ft for the intake, deciding that cannot possibly be enough for a 426, and “correcting” Chrysler’s number with a wedge specification.
• Using the 75 lb-ft race camshaft cap-screw value on street hardware because the larger number sounds stronger. Torque is not a horsepower rating.
• Treating the 30 lb-ft rocker-bracket figure as a universal target after shafts, stands, fasteners, or the entire rocker system have been replaced.
• Using factory numbers on modern rods, head studs, aluminum heads, race hardware, or other aftermarket pieces whose manufacturers supplied their own torque or lubricant instructions.
• Reading the converter specification as 270 lb-ft instead of 270 in-lb. The Hemi is expensive enough without inventing new ways to damage it.

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Bottom Line

The 426 Hemi earned its reputation by being different where difference actually counted. The torque chart is no exception.

Its cross-bolted mains use two sets of fasteners with two values. Head material changes the head-bolt number. The intake wants only 8 lb-ft. Street and race camshaft hardware can differ by 35 lb-ft. Those are not footnotes around one generic big-block Mopar specification. They are the engine.

Recognizing a 426 Hemi from across the parking lot is easy. Knowing which bolt is under the socket is what keeps all that expensive legend from turning into expensive pieces.

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Related Links

Engine Specs

• Mopar 426 Hemi Engine Specs

Engine Family

• Mopar Gen II 426 Hemi Engine Family

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