The Eliminator Big Block Ford cylinder heads were designed for the serious performance enthusiast. Its larger ports and valves along with the unique combustion chamber design can yield a very high horsepower output. Below, you will find some technical information regarding the Eliminator cylinder heads. If you still have questions after reading through this information, do not hesitate to call us at (810) 395-8056.

Valve cover and gasket
• Standard Ford Big Block valve cover that provides clearance for a roller rocker arm, which can be purchased through IDT Racing or Ford Motorsport

Rocker arms and locking nut
• Standard Ford Big Block stud roller rocker arms (1.73:1 ratio) that can be purchased through IDT Racing, Crane Cams or Comp Cams
• If shaft rockers are preferred, Jesel KCS-19187 or T&D 7000 can be used. Variable ratios up to 2.00 can be ordered

Rocker arm stud girdle
• The Eliminator stud girdle kit can be purchased through IDT Racing, Jomar and Probe Industries

Rocker arm stud
• Utilizes standard Ford Big Block 7/16” diameter studs available through IDT Racing or ARP

Valve springs and pocket
• The valve spring design is dependant on your camshaft selection. Consult your camshaft manufacturer for spring specifics. (When purchased in a bare state.)
• The spring pocket has been machined to accept a 1.75” O.D. steel spring cup. These spring cups can be purchased through IDT Racing, Ford Motorsport, Crane Cams and Comp Cams.

Valve guide information
• The valve guide material is AMPCO 45
• The O.D. of the guide is .502” in diameter. (About a .002” press fit to the cylinder head). The overall length is 2.400” for both intake and exhaust.
• The I.D. of the guide is undersized and must be reamed to final diameter for proper valve guide to valve stem clearance (when purchased in a bare state)
• The valve guide has been machined for a .531” diameter valve seal. (If you choose to use a .500” diameter seal, then the guide will need to be re-machined)
• Valve guides can be purchased through IDT Racing

Intake valve seat information
• The standard Eliminator intake valve seat is made from ductile iron
• The ductile iron seat material is compatible for both stainless steel and titanium
• A special alloy material valve seat can be ordered for an additional cost
• The standard O.D. is 2.505” (About a .005” press fit to the cylinder head machining)
• The intake valve seat arrives in an UNFINISHED state, which requires final machining. (When purchased in a bare state)
• Every cylinder head specialist has a “special” style of valve seat machining. This why we sell our bare heads in an unfinished state.
• IDT Racing cylinder head specialists feel that for higher lift camshaft (over .750” lift) that a 38° top angle that blends into the combustion chamber is preferred.
• Working down from the top angle, IDT feels that a 45° contact angle with a .040” width works best
• After the contact angle, a 60° angle is machined with a width of .050” to .070”
• Newen makes a standard cutter to machine the above 3 angles, cutter number B1-068
• A final 75° angle is machined that intersects the throat
• The throat diameter is machined to 2.260” to 2.275” when using a 2.42” intake valve head diameter
• Minor hand blending of the throat to the port will be required for improved airflow
• Again, please note that cylinder head specialists have their own “tricks”. The above information is a guideline.

Intake valve information
• The standard intake valve head is 2.42” in diameter. These valves can be purchased through IDT Racing, REV, Ferrea or Manley.
• The standard valve material is stainless steel. Titanium can be special ordered at an additional cost.
• The valve stem diameter is 11/32”
• The overall length is 5.855”
• Tip height of .250”
• A hardened tip or a lash cap is required
• Single groove for retainer lock is preferred

Exhaust valve seat information
• The standard Eliminator exhaust valve seat is made from ductile iron
• The ductile iron seat material is compatible for both stainless steel and titanium
• A special alloy material valve seat can be ordered for an additional cost
• The standard O.D. is 2.005” (About a .005” press fit to the cylinder head machining)
• The exhaust valve seat arrives in an UNFINISHED state, which requires final machining (when purchased in a bare state)
• Every cylinder head specialist has a “special” style of valve seat machining. This why we sell our bare heads in an unfinished state.
• IDT Racing cylinder head specialists feel that for higher lift camshaft (over .700” lift) that a 35° top angle that blends into the combustion chamber is preferred.
• Working down from the top angle, IDT feels that a 45° contact angle with a .070” width works best.
• After the contact angle, a .50” radius tangent from 55° to 85° machine cut is performed
• A final 85° angle is machined that intersects the throat
• Serdi makes a cutter to perform the above machining, Serdi part number SC-610
• The throat diameter is machined to 1.74” to 1.75” when using a 1.88” exhaust valve head diameter
• Minor hand blending of the throat to the port will be required for improved airflow
• Again, please note that cylinder head specialists have their own “tricks”. The above information is a guideline.

Exhaust valve information
• The standard exhaust valve head is 1.88” in diameter. These valves can be purchased through IDT Racing, REV, Ferrea or Manley.
• The standard valve material is stainless steel. Titanium can be special ordered for an additional cost.
• The valve stem diameter is 11/32”
• The overall length is 5.800”
• Tip height of .250”
• A hardened tip or a lash cap is required
• Single groove for retainer lock is preferred

Spark plug information
• The standard spark plug is a 14 mm with a .708”/.750” reach tapered
• The heat range for a high compression race engine is very dependant on the engine tuner but IDT Racing suggests an AG 901
• PLEASE NOTE THAT IF THE COMBUSTION CHAMBER HAS BEEN MACHINED (or hand ground), ONE SHOULD HAND INSTALL A SPARK PLUG TO CHECK ELECTRODE DEPTH INTO THE CHAMBER. DEPENDING ON MACHINING (or hand grinding), A 14 mm WITH A 5/8” REACH COULD BE REQUIRED.

Combustion chamber information
• The cylinder head chambers are supplied in a semi-finished state. (When heads are sold bare.) Every engine builder has a view on combustion chamber shape and burn rate. Since these heads can be used on bore diameters of 4.44” to 4.625” the chamber is supplied in a semi finished “figure eight” design. The chamber can be machined into the chamber shape of choice. Once the desired chamber shape is achieved, the desired chamber volume is determined. IDT’s experience with this chamber has yielded a volume is about 82cc’s without decking the cylinder head. If you wish to have a larger chamber, then remove more material. If a smaller chamber is desired then deck the cylinder head. We have found that a good rule of thumb is that for every 1.0 cc is about .005”. Please check the chamber volume in the end to determine the correct compression ratio.

Engine block information
• The Eliminator heads were design to bolt to a standard 429/460 block (385 series) that has been over bored. (Standard bore diameter is 4.360”.)
• IDT recommend that the block should be bored .080” oversize or larger (4.440” or greater).
• In the event that you are using a smaller bore block. Please install the head onto the block and check for valve to wall clearances. The block may require notching or a smaller diameter valve may need to be installed to provide adequate valve to bore clearance.

Guide plate information
• The guide plates used on the Eliminator cylinder heads are a special design. The guide plates use a 3/8” pushrod. These plates can be purchased through IDT Racing.

Cylinder head gaskets
• We recommend using a high performance cylinder gasket for an oversized bore configuration. These gaskets can be purchased through IDT Racing or Felpro. SCE copper gaskets also work very well.

Intake gaskets
• IDT Racing manufactures a special intake gasket for this application. The gasket is uniquely designed with a bead seal around the intake ports. These gaskets can be purchased through IDT.

Exhaust gaskets
• Since exhaust flange is a standard Big Block Chevy bolt pattern, a Big Block Chevy gasket can be used. Remember that the gasket may need to be sectioned between the ports to allow for the larger Big Block Ford bore spacing of 4.900”. These gaskets can be purchased through IDT Racing or Felpro.

Exhaust header flange
• Since exhaust flange is a standard Big Block Chevy bolt pattern, a Big Block Chevy is used. Remember that the flange may need to be sectioned between the ports to allow for the larger Big Block Ford bore spacing of 4.900”. These flanges can be purchased through IDT Racing or Hedman Headers.

Manifold information
• Since there are so many intake manifold requirements from a single 4-barrel to a tunnel ram. Please call IDT and they can help you sort your needs.

Cylinder head bolt torque
• The fastener sequence is the same as production Ford. Please follow the fastener supplier’s torque specifications.