Frankenstein M311BM+ Boost-Monster+ 286cc LS3 CNC Ported 11 Degree Cylinder Head, 68cc Chambers, Bare

Frankenstein's Boost Monster+ 286cc LS3 CNC Ported Cylinder head. Frankenstein redefined performance with The Monster—a game-changing cylinder head built with precision and power in mind. Featuring 5-axis CNC-ported intake and exhaust chambers, each head is hand-blended, deburred, and quality-checked to exacting standards. Built for 400ci+ stoker engines with higher compression applications (13:1+). Higher rpm (7500+). Higher boost levels (30psi+).

Fit all standard equipment such as valve covers, headers, LS3 Intakes, and OEM-type LS3 rocker arms. (Billet Rocker Stands Required to fit OE-Style LS3 Rocker Arms. Click on the product options button to add the stands.)

Note: Head comes completely bare, no parts. Pictures are for reference head would come bare, no parts. Sold as a single piece, 2 pieces required per engine.

*Notice, See Bottom of page for General Recommendations for Frankenstein Cylinder Heads

**All areas may not be fully cnc ported as the porting only hits the areas that are needed for the head to work as designed.

 

Description	Specification
Min. Bore Dia.	4.000”
Intake Port Volume	286cc
Exhaust Port Volume	112cc
Combustion Chamber Volume	68cc
Intake Valves	Not Included Bare Head.
Exhaust Valves	Not Included Bare Head.
Valve Springs	Not Included Bare Head.
Retainers	Not Included Bare Head.
Valve Locks	Not Included Bare Head.
Valve Seals	Not Included Bare Head.
Billet Rocker Stands	Not Included But Required for OE Style Rockers, PN: 913001 or see the product options
Head Gasket Bore Size:	4.125” Bore
Head Bolts:	6 Bolt
Head Studs:	7/16″ Stud Size (1/2" Stud Size Available)
Pushrods:	8.100 – 8.250” Length x 3/8” Diam.
Lifters:	Standard
Rockers:	Standard LS3 w/FED Rocker Stand *Otherwise Shaft-Mount Rockers

General Recommendations for Frankenstein Cylinder Heads:

Pushrods: Verify pushrod length and ensure at least .030” wall clearance. Do not enlarge pushrod holes further.

Surfacing: Milling affects flow and may require thicker intake gaskets and port alignment.

Boosted/Nitrous: Use Inconel exhaust valves and upgraded valve springs for reliability under high stress.

Marine: Use Inconel exhaust valves and consider hard-anodized coating for corrosion resistance.

Valve Guides: FED sets proper clearance, but boosted/nitrous/marine setups may need more—verify before use.

Valve Springs: Aggressive cams or power adders may need higher spring pressure. Check spring/cam compatibility before assembly.

Piston-to-Valve: Verify clearance (.080” intake, .100” exhaust, .030” radial). FED or TRE not responsible for damage due to improper clearance.

CNC Porting: Minor “as cast” areas are normal and don’t affect performance.

Installed Height: ±.015” variance is acceptable and harmless.

Rockers: Stock GM rockers aren’t suited for aggressive setups—use CHE trunnion kits.

O-Rings: Inspect and replace worn O-rings during service.

Head Studs: Confirm correct diameter and length for your setup.