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Twin Cam | JPrecision
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Unmatched Performance & Durability since 1983

JPrecision specializes in high performance machining of engines components. We let your local qualified mechanics to do the final assembly. Contact your local dealer for more details.

It only takes one pass on a dyne or a quick ride on an open road to fully appreciate the exceptional performance offered by JPrecision heads. Cylinder heads modified and upgraded by JPrecision are simply the most powerful and reliable that money can buy.

Find Dealer_EN

Unmatched Performance & Durability since 1983

JPrecision specializes in high performance machining of engines components. We let your local qualified mechanics to do the final assembly. Contact your local dealer for more details.

It only takes one pass on a dyne or a quick ride on an open road to fully appreciate the exceptional performance offered by JPrecision heads. Cylinder heads modified and upgraded by JPrecision are simply the most powerful and reliable that money can buy.

Find Dealer_EN

Adrenaline and Satisfaction Guaranteed!

TC-Stage2

STAGE II

For stock castings

This Stage features our upgraded intake and exhaust port design and is CNC ported for optimal precision and repeatability. We use only top quality components from the company AV&V™ for outstanding reliability. This is a perfect performance upgrade for your street performance needs.

It features a 1.700 inlet opening, and the chamber is left in its natural state, making this head a perfect fit for any motor combination from 88” to  107”.

SC-Stage2b

STAGE IIB – High Torque Heads

For stock & aftermarket castings

Same as Stage II except  for the intake port which is redesigned and raised by welding to increase velocity, allowing for a crisper throttle response.

  • The chamber is CNC contoured and finished by hand to a satin finish.
  • Great upgrade for all TC heads, including SE, S&S and other aftermarket heads.

STAGE IIIB – High Torque Heads

For stock castings

Same as stage II plus we install 1.940″ intake valves & oversize seats and increase the  intake port area, resulting in peak horsepower increase.

STAGE IVB – High Torque Heads

For stock castings

Ultimate modification for your factory casting. We install 2.000″ intake & 1.580″ exhaust valves and modify the ports accordingly. Makes the most power from bigger throttle body or carbs. We recommend a manifold/ throttle body with 1.800″ runners to take full advantage of these heads.

TC-Stage5
Pin-Stage-5

STAGE V – High Torque Heads

For stock castings

We install 2.150″ intake & 1.650″ exhaust valves and modify the ports accordingly. Intake valve angle is modified and rocker arm geometry is corrected

  • Designed for 131” / 4,250” bore engines
  • Must be used with SE 120R Hurricane oval port manifold
  • Up to 175 rear wheel HP potentiel.

HEAD WORK OPTIONS

Manifold

MANIFOLD PORTING

We port the manifold to optimize the airflow and to achieve a better fuel atomization through our proprietary finishing process.

Compression Release Valve

COMPRESSION RELEASE VALVES

We machine the heads to install the compression release valves in line with the spark plug for an easier access and a better look. We also machine heads for automatic compression release valves.

valvepocketmachining

PISTON VALVE POCKETS MACHINING

We machine the pistons to re-establish a correct  valves to piston clearance after installation of higher lift cams, larger valves or head shaving. (Usually, all TC cast pistons require clearancing)

Cooling Fins HiLiting

COOLING FINS HILITING

To give that CNC finish on heads and cylinders.

JPrecision offers the full range of machining services. From casting repairs to
combustion chamber renovation we have the equipment, tooling and expertise.

To download our Twin Cam machining services catalog or our head work sheet , click here:

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