Mopar LA Small Block Torque Specs

Intro

The LA small block became so common that familiarity eventually became one of its bigger hazards. Everybody has seen a 318. Plenty of people have worked on a 340 or 360. That does not mean every LA bolt gets whatever number somebody remembers from the last one.

The 273, 318, 340, and 360 share the same basic LA family, but Chrysler did not give them one completely interchangeable torque chart. The 273 and 318 use an 85 lb-ft cylinder-head value. The 340 and 360 call for 95. Factory rocker-shaft bolts belong at only 17 lb-ft, despite the 30 lb-ft figure that has been copied into enough bad charts to become its own mechanical hazard.

Then there is the 360. Its external-balance hardware does not change the head or rocker torque, but it does mean flywheels, flexplates, dampers, and converter weights deserve more attention than somebody saying, “It came off another LA.” A part can bolt on beautifully and still be the wrong part.

The LA is simple enough to encourage confidence and varied enough to punish lazy confidence. Read the engine, read the hardware, and then read the number.

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General Torque Specs

¹ 273 / 318 cylinder-head bolt value.

² 340 / 360 cylinder-head bolt value.

³ Factory-style LA rocker-shaft bolts are 17 lb-ft. Do not use the common wrong 30 lb-ft chart value unless the actual aftermarket parts call for it.

⁴ Thin covers, carburetor flanges, and cork-style gaskets distort easily. Tighten evenly and do not turn seep control into bent metal.

⁵ Cast-iron-head factory-style intake value. Aluminum heads, aftermarket intakes, and special gaskets use their own instructions.

The head-bolt split is not decorative fine print. Chrysler calls for 85 lb-ft on the 273 and 318, then 95 on the 340 and 360. Ten pounds is enough difference to retire ‘all LA heads are about the same’ before the wrench comes out.

The rocker-shaft row deserves even more attention because bad information has been breeding for years. Factory-style LA rocker-shaft bolts are 17 lb-ft. Not 30. A wrong number does not become correct because it survived three photocopied manuals, six websites, and somebody’s laminated shop chart.

The oil-pump cover is another place where the unit matters as much as the number. Ninety-five inch-pounds is a little under 8 lb-ft. Read 95 in-lb as 95 lb-ft and that little fastener will teach the lesson before the wrench finishes the sentence.

Factory-style intake hardware is listed at 35 lb-ft with the cast-iron-head combination represented here. Aluminum heads, aftermarket manifolds, different gaskets, studs, or replacement bolts can change the instruction. Once the factory parts move out, the factory chart stops getting the last word.

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Important Notes

• The 273 and 318 use the 85 lb-ft cylinder-head value; the 340 and 360 use 95. Same family, different answer. The LA badge does not get to average them together.
• Factory LA rocker-shaft bolts are 17 lb-ft. The often-repeated 30 lb-ft figure is not harmless folklore when the threads, shaft, and bolt are the ones paying the bill.
• The 360 is externally balanced. Correct torque on an incorrect neutral-balance flywheel, flexplate, damper, or converter arrangement still leaves an incorrect engine assembly.
• The oil-pump cover value is in inch-pounds. Eight cylinders around it do not magically make the little bolt any bigger.
• The 35 lb-ft intake figure belongs to the factory-style combination described by the chart. Aftermarket aluminum heads, manifolds, gaskets, studs, or replacement fasteners follow the instructions supplied with those parts.
• Seven pounds on a valve cover or carburetor flange is restraint, not weakness. Bent rails and warped flanges have never been improved by another quarter-turn.

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Common Mistakes

• Using the 273 / 318 head-bolt figure on a 340 or 360 because four LA engines were reduced to one remembered number.
• Torquing factory rocker-shaft bolts to 30 lb-ft because an old chart was trusted more than the actual LA specification.
• Mixing 360 external-balance parts with neutral-balance hardware and then wasting time looking for the vibration somewhere else.
• Reading the 95 in-lb oil-pump-cover specification as 95 lb-ft. Missing two letters can be remarkably expensive.
• Using factory intake torque after aluminum heads, an aftermarket manifold, different fasteners, or a special gasket have changed the clamped joint.
• Tightening valve-cover or carburetor hardware harder after a thin flange has already distorted. The leak is asking for a flat surface, not a stronger arm.

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Bottom Line

The LA small block earned a reputation for being straightforward. Somewhere along the way, too many people translated straightforward into “all the same.”

They are not. The head-bolt value changes between the 273/318 and the 340/360. The rocker shaft wants 17 lb-ft despite a stubborn wrong number floating around the hobby. The 360 brings external-balance hardware into the job. The oil-pump cover quietly switches the wrench from pounds to inch-pounds.

None of this makes the LA difficult. It just asks the mechanic to pay attention long enough for four familiar engines to remain four actual engines instead of one blurry memory.

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Related Links

Engine Specs

• Mopar LA 273 V8 Engine Specs
• Mopar LA 318 V8 Engine Specs
• Mopar LA 340 V8 Engine Specs
• Mopar LA 360 V8 Engine Specs

Engine Family

• Mopar LA Small-Block V8 Engine Family

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