Chevy 350 Main Cap Torque Specs: Two-Bolt and Four-Bolt Blocks
Chevy 350 main cap torque reference for Chevrolet Performance four-bolt blocks, with inner/outer values, sequence, lubricant, and bore checks.
For the cited Chevrolet Performance 350 HO and 350/290 four-bolt-intermediate-main blocks, the crankshaft bearing-cap fasteners are specified at 70 lb-ft (95 N·m) for the inner bolts and 65 lb-ft (88 N·m) for the outer bolts. Aftermarket studs, splayed caps, and alternate lubricants require the fastener or machine shop specification.
The main caps locate and support the crankshaft. Correct clamp load and housing-bore geometry are essential for bearing crush, oil clearance, and crankshaft alignment.
A 'four-bolt main' Chevy 350 generally has additional outer fasteners on the three intermediate caps. The front and rear cap arrangements differ, and aftermarket splayed-cap conversions are a separate machining system.
Interactive main-cap tightening layout
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Work from the center main toward the ends in stages, tightening inner fasteners before the corresponding outers unless the exact procedure says otherwise.
Chevy 350 Main Cap Torque Specs
| APPLICATION / ITEM | SPECIFICATION | NOTES |
|---|---|---|
| Inner main fasteners | 70 lb-ft / 95 N·m | 350 HO and 350/290 guides |
| Outer main fasteners | 65 lb-ft / 88 N·m | Four-bolt intermediate caps only |
| Two-bolt block | No outer fasteners | Confirm exact block/service data |
| Aftermarket studs/caps | Manufacturer + machinist spec | May require align-hone verification |
Main fastener torque is part of the block's machining state. Changing from bolts to studs or changing lubricant can alter housing-bore geometry, so align honing may be required.
How to use this specification correctly
- 01
Confirm the block casting, cap positions and orientation, fastener type, lubricant, and machine-shop build sheet.
- 02
Clean the main saddles, cap registers, fasteners, and holes; never mix caps or reverse their orientation.
- 03
Install upper bearings and crankshaft with assembly lubricant on bearing surfaces but keep bearing backs clean and dry.
- 04
Seat each cap squarely in its register and start all fasteners by hand.
- 05
Tighten in several stages from the center main toward the front and rear, following the exact inner/outer sequence for the hardware.
- 06
At final torque, verify crankshaft rotation and measure bearing clearance and crankshaft endplay with appropriate tools.
Why studs can require machine work
Studs load the block threads and caps differently from production bolts. A block machined with one fastener system may not hold the same housing-bore geometry after a change. The machine shop should torque the exact final hardware during align-hone measurement.
Essential measurements
- Main housing-bore size and alignment
- Bearing oil clearance
- Crankshaft journal size and taper
- Crankshaft endplay
- Crankshaft rotation after each torque stage
Stop if the crank binds
The crankshaft should not suddenly become difficult to turn as one cap is tightened. A misplaced cap, bearing shell, burr, journal problem, incorrect clearance, or distorted housing bore must be corrected before assembly continues.
Chevrolet 350 Small-Block (5.7L V8) specifications can change by model year, engine, platform, wheel, and installed component. Confirm the VIN or engine identity, part numbers, fastener condition, and the current manufacturer instructions before service.
Chevy 350 Main Cap Torque Specs: Two-Bolt and Four-Bolt Blocks FAQs
What is the main cap torque on a Chevy 350?+
Chevrolet specifies 70 lb-ft inner and 65 lb-ft outer for the cited four-bolt 350 HO and 350/290 crate-engine blocks.
Does a two-bolt main Chevy 350 use the outer-bolt value?+
No. A two-bolt cap has no outer main fasteners. Use service information for the exact block and bolts.
Can I use the factory torque with ARP main studs?+
Use the instructions and lubricant supplied with the exact stud kit. The block may need align-hone verification with those studs installed.
What order should main caps be tightened?+
Work from the center main toward the ends in staged passes, while following the exact inner/outer sequence specified for the block and hardware.
Why check crank rotation during tightening?+
A change in rotating effort can reveal cap, bearing, clearance, or alignment problems before the engine is fully assembled.
Technical sources
TorqueSheet favors engine- and component-specific manufacturer instructions over unsourced universal values.
1Chevrolet Performance 350 HO Base Engine guide (P/N 12366576)Primary Chevrolet Performance installation and specification manual for the 350 HO crate engine.↗2Chevrolet Performance 350/290 Long Block guide (P/N 19172591)Primary Chevrolet Performance guide for the pre-1986-style 350/290 long block.↗