347 Windsor Stroker Guide: Build Recipe, Parts, Power

347 Windsor Stroker Guide: Build Recipe, Parts, Power

347 Windsor Stroker Guide: Build Recipe, Parts, Power

The 347 is the most-built Ford small-block stroker for good reason. 302-based, uses the factory bellhousing pattern, drops into a Fox, SN95, or classic Mustang with no unusual parts, and gives you 45 more cubes than a 302 for the price of a rotating assembly. It's the answer for most 5.0 HO owners who need more than a cam-and-heads combo but aren't ready to go 351W-based.

Why 347 Beats 331 and Often Beats 363

The three common 302-block strokers:

  • 331 = 302 block + 3.250" stroke, 4.000" bore (or .030" to 4.030")
  • 347 = 302 block + 3.400" stroke + 4.030" bore (.030" over)
  • 363 = 302 block + 3.400" stroke + 4.125" bore — thick-wall aftermarket block required

331 is the conservative build. Stock-bore, shorter stroke, less rod-to-bore geometry drama, and easy pump-gas pistons. The problem is it gives up 16 cubes to a 347 for essentially the same parts count. If the block sonic-checks good for a .030" cleanup, spend the extra money on a 3.400" crank and get the displacement.

363 buys more displacement (16 more cubes than 347) but requires a Boss 302, Dart SHP, or Ford Performance aftermarket block — a stock 302 block will not safely take a 4.125" bore. The cost jumps dramatically at the block, and for street builds the return on 16 cubes isn't there. 363 makes sense when the customer is already buying an aftermarket block for durability (boost, high RPM, repeat-offender builder) — the extra bore is "free" relative to having bought the block anyway.

The 347 sweet spot: existing stock 302 block, sonic-checked .030" overbore, 3.400" stroke. Done.

Piston Skirt Clearance and Valve-Relief Depth — The 347 Trade-off

The 3.400" stroke on a 4.030" bore forces compromises. The wrist pin lives high in the piston — high enough that on most 347 pistons the oil ring sits below the pin bore and the skirt above the pin is short. Result: piston rock if piston-to-wall clearance isn't spec'd tight. Typical targets:

  • Forged 2618 (Wiseco, JE, Diamond, Manley) — the loosest piston-to-wall clearance of the three, per the manufacturer spec sheet
  • Forged 4032 (Mahle PowerPak, Icon) — tighter than 2618, per the spec sheet
  • Hypereutectic (Probe SRS, KB) — the tightest of the three, per the spec sheet

Too tight and the 2618 scuffs cold; too loose and the skirt rocks and slaps the wall. This is why a 347 needs an honest machine shop with a torque-plate bore + hone.

Valve relief geometry: at 3.400" stroke the piston comes up to or slightly above deck at TDC with a zero-deck build. Valve reliefs have to clear whatever cam lift and head combination you're running. Most shelf 347 pistons are cut for a 2.02"/1.60" valve on a Twisted Wedge or Edelbrock RPM chamber. Step up to a 2.08" valve (AFR 205 Competition, TFS 205) and a .600"+ lift cam and you may need custom valve-relief machining.

Rod Length and Rod-to-Stroke Ratio

Stock 302 rod is 5.090". 347 kits run a 5.400" H-beam or I-beam rod to keep the wrist pin out of the ring pack and preserve rod-to-stroke ratio (5.400 / 3.400 = 1.588). That ratio is friendly to street manners — strong torque, tolerant of duration, doesn't punish the pin boss.

Rod options by tier: - Budget street — Scat 4340 I-beam 5.400" - Mid-grade — Eagle ESP 4340 H-beam 5.400" with ARP 8740 bolts - High-performance — Manley H-Tuff or Callies Ultra H-beam with ARP 2000 or L19 bolts - Boost/race — Oliver, Molnar billet H-beam

Rotating Assembly Tiers

Cast-crank street — 450-500 hp NA tier — Scat 9000-series 4340 cast, Scat I-beam 5.400", Probe SRS forged or Mahle PowerPak, Hastings rings, Clevite H bearings. Cheap, honest, pump-gas friendly. Good in a Fox Mustang or a sportsman track car.

Forged street/strip — 500-650 hp NA tier — Eagle ESP 4340 forged, Eagle H-beam 5.400" with ARP 2000, Mahle PowerPak or Wiseco Pro Tru forged 2618, Clevite H bearings, Total Seal gapless or Mahle moly rings. The volume 347 build.

Boost-capable forged — 600-900 hp — Callies Compstar crank, Manley H-Tuff or Callies Ultra rods, Mahle Motorsport or JE forged 2618 with lower static CR for blower or turbo. ARP L19 rod bolts, main studs.

Cam Pairing with TFS Head Flow

The Twisted Wedge series is the default Windsor head because the revised valve angle clears stock-piston valve reliefs without machining — which matters on a 347 where the reliefs are already deep.

  • TFS Twisted Wedge 170 (170cc intake runner, 61cc chamber) — stock-style small-runner. Pairs with hyd-roller 220/226° @ .050", ~.550" lift. 400-450 hp with a short-runner intake. Good for a truck build or a mild Fox.
  • TFS Twisted Wedge 185 — the mainstream 347 head. 185cc intake, 61cc chamber, 2.02"/1.60" valves. Pairs with Comp Xtreme Energy XE274HR or Lunati Voodoo 60103 (228/232° @ .050", ~.570" lift). 450-500 hp pump-gas capable.
  • TFS Twisted Wedge 205 — enthusiast-tier. 205cc intake, 58cc chamber, 2.08" intake. Needs more cam — 232/240° @ .050", .600"+ lift — and a better intake. 500-575 hp range NA.

AFR Renegade 165/185/205 are the alternate line. Port volume is similar but the AFR valve job and CNC chambers tend to favor high-RPM flow. AFR requires valve-relief depth check with shelf 347 pistons — TFS does not.

Intake Selection

  • Edelbrock Performer RPM II (#7121) — dual-plane, 1,500-6,500 RPM. The right choice for a street 347 with TFS 170 or 185 heads. Broad torque, tolerant of a big cam.
  • TFS Box-R Series — single-plane with plenum expansion, 2,500-7,500 RPM. Pairs with TFS 205 heads on a strip-biased build.
  • Edelbrock Victor Jr #2975 — straight single-plane, 3,500-7,500. Race intake on a street 347 gives up low-end; only the right choice if you're spending most of the time above 3,500.

For EFI Fox / SN95 cars keep the factory-style upper/lower intake swap path — Ford Racing Cobra, Trick Flow Track Heat (EFI). The Track Heat (confirm the current Trick Flow SKU) is a bolt-on gain over the two-piece stock intake.

5.0 HO to 347 Build Recipe — Fox Body Pump Gas

  • 1989-93 5.0 HO block, sonic-checked, .030" over
  • Eagle ESP 4340 3.400" forged crank, Eagle H-beam 5.400" rods, Mahle PowerPak dished pistons (10.2:1 CR)
  • Clevite H main + rod bearings, Total Seal AP Steel rings
  • TFS Twisted Wedge 185 aluminum heads assembled, 2.02"/1.60"
  • Comp XE274HR hydraulic roller cam, 228/236° @ .050", .565"/.574" lift
  • TFS 1.6 roller rockers, hardened pushrods sized to installed height
  • Cloyes true-roller timing set
  • Edelbrock Performer RPM II dual-plane intake, 650 CFM Holley vacuum secondary, or a factory-style EFI with Pro-M mass air and 42 lb injectors tuned
  • ARP main studs, head studs, oil pump driveshaft, harmonic balancer bolt
  • Melling M-83HV high-volume oil pump, Milodon pickup matched to pan

Expected at the flywheel on 91 octane: ~475-500 hp, ~460-475 lb-ft torque with a broad, streetable torque curve from 2,000 to 6,200 RPM.

When 363 Makes Sense Instead

Skip to 363 if: - You're already buying an aftermarket block (Dart SHP Windsor, Boss 302, Ford Performance) for durability reasons — boost build, high-RPM road race, builder's shop engine - You want the same 3.400" stroke but the extra bore (4.125") for more area under the valve - You need the beefier deck for studded heads at high cylinder pressure

363 is a 347 build with a different block. Everything else — rods, stroke, piston geometry — scales the same. The delta is mostly the cost and durability of the block.

What to Do Next

  • Sonic-check the 302 block before committing to .030" over
  • Spec the rotating assembly around the head you plan to run
  • Match the cam to the TFS head port you chose
  • Verify piston-to-wall, valve-relief depth, and installed spring height before final assembly

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