Engine 306 to 331


Founding Member
Jun 9, 2002
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Lately, i have been poisoning my mind and reading up on going from a 306 to 331 in my 93 GT.

Can i get the block bored to 331 while keeping the existing parts?

Engine mods below:

306 Dart SHP engine block; DSS Dished Forged Pistons; hardened pushrods; Scat Crank; 8.6:1 Compression; TFS Stage-II CNC Ported heads; 1:6 Crane Roller Rockers; Stage II Camshaft (duration unknown. Specs lost during a move); Vortech SQ-trim Supercharger 12lb boost; Vortech Intake Manifold; Accufab 75mm TB; 90mm SCT BA-3000 MAF; Anderson PowerPipe; K&N air filter (in fender); Crane Hi-6 ignition; MSD distributor; NGK plugs gapped .032”; FMS spark plug Wires; MAC H-pipe (no cats); Smog plumbing removed- EGR still hooked up but not functioning; JBA 1 5/8" titanium coated shortie headers; Flowmaster 2-chamber mufflers; 60lb Injectors; 320 lph Aeromotive fuel pump; T-Rex Fuel Pump (came with Vortech Kit), Moroso 7-Quart oil pan, new motor mounts, AEM methanol injection; SCT Chip w/ Custom tune.

Since the engine will be torn part, i will have the head ports matched and polished same with the lower intake. The heater core replaced as well . I also have a custom cam i that i bought back in '97. Unfortunately, the specs was lost during a move. I will probably get a new cam as well.

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Mustang Master
Aug 18, 2017
Looks like the parts you have would work well on a 331 build but is the effort/expense worth 25 cu in ?
You'll need to get the correct stroker crank and rods .
If you're going to invest the time and money why not go 347 at that point, imo your parts would support it.