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Evolution - Big Twin | 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 dyno 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 dyno 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!

Evo-Stage-II

STAGE II

This head features our upgraded intake and exhaust port design and is CNC ported for optimal efficiency. The ports are then fully hand finished and have proven to provide a more efficient flow rate. 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 80” to 96”.

Evo-Stage-IIB

STAGE IIB – High Torque Heads

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. Great upgrade for all EVO heads including SE, S&S and other aftermarket heads.

STAGE IIIB – High Torque Heads

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

STAGE IVB – High Torque Heads

Ultimate modification for 3 3/4″ & up bore engines. We install 1.990″ intake & 1.580″ exhaust valves and enlarge the ports accordingly. We recommend a manifold/throttle body with 1.800″ runners to take full advantage of these heads.

HEAD WORK OPTIONS

Evo Manifold

MANIFOLD PORTING

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

Evo 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.

Cooling Fins HiLiting

COOLING FINS HILITING

To give that CNC finish on heads and cylinders.

To download our Evolution – Big Twin machining services catalog or our head work sheet , click here:

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