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Frankenstein Engine Dynamics Monster M311 273cc LS3 Rectangle Cylinder Head-Complete Set w-Billet Rocker Stands
  • SKU: 299-FEDM311

Frankenstein Engine Dynamics Monster M311 273cc LS3 Rectangle Cylinder Head-Complete Set w-Billet Rocker Stands

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Frankenstein Engine Dynamics M311 273cc LS3 Rectangle Cylinder Head-Complete Set

Set of two (2) FED Monster-Series M311 (LS3 11°) 273cc rectangle port cylinder heads. Heads are complete and assembled.


  • 6 Bolt Head
  • 0.750″ Deck Structure
  • OEM/Factory Style Water Crossover Ports
  • 7/16″ Stud Size For Main 10 Bolts
  • 8mm Stud Size For Outer Tabs and Deck Studs

Casting outsourced overseas. Engineered and Machined by FED in the USA.

Our Process:

  • 5-Axis CNC Ported Intake Ports, Exhaust Ports, and Combustion Chambers
  • Precision 5-Angle CNC Valve Job
  • PCD Deck Milled
  • Hand Blended and Deburred
  • Final Wash
  • Final Assembly with Spring Heights Checked
  • Quality Control at every stage of manufacturing


  • FED Billet Rocker Stands For Stock LS3 Rockers
  • Intake Valve Guides – Bronze
  • Exhaust Valve Guides – Bronze
  • Manley Polished Nextek HP Dual Spring 1.295″ 155# @ 1.800/405# @1.150/.660 lift (Hydraulic)
  • FED Titanium Retainers
  • ¼ x ½ Dowel Pin – Rocker Stand Dowel Pins
  • Exhaust Port Silicone O–Rings
  • Intake Valve Seats – Ductile Iron
  • Exhaust Valve Seats – Ductile Iron
  • FED Steel Valve Spring Locators – .565 Guide
  • Stock Style 7° Valve Locks
  • US Seal Viton High Heat Valve Stem Seals
  • US Seal Hardened Spring Shims

Parts Included (standard):

  • O-Ringed Exhaust Ports
  • Manley Custom Stainless Steel Intake Valve – M-Series LS3 11deg – 2.165 / .3135 stem /
    5.400 OAL / .290tip
  • Manley Custom Stainless Steel Exhaust Valve – M-Series LS3 11deg. – 1.600 / .3135 stem/5.415 OAL / .290 tip

General Recommendations for Frankenstein Cylinder Heads:

  • Pushrods – Please make sure to properly check pushrod length and wall clearance. We recommend a clearance of at least
    .030” between the pushrod and the wall. Please do not clearance the pushrod holes any further. We have a minimum port
    thickness required to pass QC and that is set at our facility. Every lifter brand and style use a different pushrod length, so make
    sure to properly check the length needed for your application. We also recommend a minimum pushrod diameter of 3/8” with a
    wall thickness of (.120”).
  • Surfacing – Flat or angle milling will affect flow numbers and may require a thicker intake gasket.
  •  Boosted/Nitrous Applications – With any power adder applications comes increased stress and longevity issues for the
    valvetrain. We highly suggest the use of Inconel exhaust valves in any power adder combos. We also suggest our upgraded valve
    spring kits to help properly control the valve train in these stressful conditions.
  •  All MARINE Applications – We strongly recommend Inconel exhaust valves & also offer a hard-anodized coating to slow the
    effects of corrosion. Please see note on guide clearance below.
  •  Stock GM Rocker Arms – GM Rocker Arms are not designed/engineered to endure aggressive aftermarket cams or higher
    spring pressures/rates. At a minimum FED recommends using CHE Bushing Trunnion Kits. Without the proper parts you will
    experience accelerated guide wear over an extended period. If you are using GM stock rockers you must use ARP# 234-7207 or
    GM# 12560961 rocker bolts.
  •  O-Rings – O-rings will wear out over time. Removal of components, such as headers for example, may cause O-rings to wear
    faster. We highly recommend a thorough inspection of any O-rings during removal and prior to installation. Worn or damaged
    O-rings should be replaced.
  •  Valve Guide Clearance – Your FED Heads come with proper guide clearance (.0014″-.0016″) for most applications.
    Boosted/Nitrous or marine applications might require additional clearance and it is the customer’s responsibility to verify proper
    clearance in these applications.
  • Valve Springs – Forced induction, nitrous oxide and cams with aggressive ramp rates may require additional spring pressure.

We offer upgraded valve springs for these types of applications. FED also recommends the use of billet 8620 cam cores and short
travel Johnson Hydraulic Roller lifters which tolerate higher spring loads. VALVE SPRINGS MAY NOT BE COMPATIBLE WITH YOUR

  •  Piston to Valve – FED assumes no responsibility for damage if the end user builds an engine without properly verifying, he
    has enough piston to valve clearance (depth and radial clearance both checked). We recommend a minimum depth of .080″ on
    the intake valve and .100″ on the exhaust with a radial clearance of .030″ minimum around the perimeter of each valve. Just
    checking depth is not enough, the position of the valve pocket must also be addressed. It is the customers responsibility to
    verify proper piston to valve clearance.
  •  CNC Porting – Occasionally a 100% CNC ported head might have a very small area left “as cast”, this in no way affects
  •  Valve Spring Installed Heights – FED valve spring installed height spec is +/- .015” which is the smallest shim available for
    adjustment. This small of a difference will have no issues and should be of no concern.
  •  Head Stud Sizes- The M311 Monster Series (M-Series) heads come standard with clearance for 7/16” studs or smaller for the
    center 10 bolts and the outer tabs and the deck studs are machined for 8mm standard. Studs may vary depending on the engine
    block used.

Contact Us Now to Speak with one of our Professionals in High Performance!
PHONE: (586) 294-4404
FACEBOOK: @FullThrottleSpeed
E-MAIL: steve@fullthrottlespeed.com