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Main Studs
Pontiac V8 Main Studs
Hold the Bottom End — Main Studs for Pontiac V8s
Main studs replace the factory main cap bolts with a stud that stays threaded in the block and a nut that does the clamping. The block threads see a straight pull instead of being twisted every time the caps come off, and the cap is held more consistently — which is why studs go into almost every Butler short block that makes real power.
Butler stocks ARP 2-bolt and 4-bolt Pontiac main stud kits, the Butler TorqueMaster 220 ksi 4-bolt kit built by Opti-Torque, and an ARP 7/16 splayed outer stud kit for splayed main caps.
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1. Match the Kit to the Main Caps
Count the bolts per cap before ordering. Two-bolt and four-bolt blocks take different kits, and a splayed-cap block takes a third piece.
| 2-bolt mains | ARP-194-5401 is the Pontiac 2-bolt main stud kit — the common upgrade on a factory 350, 400 or 455 that is staying two-bolt. |
| 4-bolt mains | ARP-194-5601 covers four-bolt caps. |
| Higher tensile four-bolt | the Butler TorqueMaster 4-bolt main stud kit is built for Butler by Opti-Torque from 220 ksi steel, an upgrade over the 190k ARP studs, aimed at high horsepower combinations. Opti-Torque rolls the threads after heat treatment and uses domestic steel throughout. |
| Splayed outer caps | the ARP splayed outer stud kit supplies 7/16 studs and nuts for the outer holes on splayed main caps, where the standard kit does not reach. |
2. Torque, Clearance and Machining
Studs change how the cap loads and how the bottom of the engine gets assembled. Plan for it.
| Factory-style torque | Butler's Pontiac chart calls for main caps at 95 ft-lbs with engine oil on the threads, and the rear main cap at 120 ft-lbs. If the kit is ARP, use ARP's specification and their lube instead. |
| Nut clearance | 12-point nuts are used on the front studs on Butler's kits so the oil pan clears. Check pan rail and windage tray clearance before final assembly. |
| Machine with what you will run | a stud pulls the cap differently than a bolt, so the main bore should be checked and align honed with the same fasteners that are going in the finished engine. |
| Dowel the caps | main cap dowel pins are a separate item, and the holes have to be reamed — the 5/16" (.3125") pins are slightly larger than the original .310" hole, and driving them into an unreamed cap is how caps crack. |
If the block is going to a machine shop, send the main studs with it. Clearancing, align honing and cap dowels all want to be done once, with the hardware that stays in the engine.
Not sure what your Pontiac needs?
Email our tech team at tech@butlerperformance.com. Tell us your engine, heads, car, and power goal, and we will put the parts together as one combination that works.