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-> RS+ Cylinder Heads

RS+ Castings: AMC Chambers: 51.5cc’s Hand shaped modified Lima Bean Chamber Step: 95.0 x 1.0mm * Plug angle: 2.0 914 Valve sizes: 42 x 36 Springs: Premium dual Crower set for 190lbs seat pressure & 330lbs at .500” valve lift. Retainers: Crower chromoly Keepers: Hardened and ground for clearance Intake Ports: Stock AMC to valve guide, with extensive re-shaping of bowl and short turn radius. Exhaust Ports: Long side radius machined with in-house designed cutter, then extensive hand work. Short side radius chamfered. These heads are easily the most versatile in the line-up. They were developed for serious 2.0 engines with autocross and spirited driving in mind. The intent was to develop a port shape that would have extremely high port velocities in the mid lift range. Peak flow was targeted for around .420 lift. The earliest efforts showed great promise as flow data indicated we were close to the target. Subsequent tweaks combined with seat profile testing have produced a head whose adaptability to a variety of engine combos has surprised both Jake and I. These heads have proven themselves at home on 1911’s and even 2270’s. On the smaller engines with mild cams, they have excellent response and cruising characteristics. On 2270’s with more aggressive cams, that excellent low end response is still there along with incredible mid range and cruising characteristics. The key to what makes these heads so special is a combination of the chamber shape and port velocity. Compare the flow data to a stock 2.0 914 then consider that the RS+ blows them out of the water with smaller intake throat diameters as well as smaller upper port dimensions. This produces extremely high velocity earlier in the lift range which continues to the upper lift ranges. This high velocity combined with the strategic use of a variety of port wall finishes yields amazing mixture quality and swirl characteristics that allow the use of increased deck heights, making these heads adaptable to larger displacement engines. It’s worth noting that during flow testing the intake ports on these heads produce a nice, even, steady tone free of whistling and undulation throughout the entire lift range, even up to .100” after peak flow has been reached. That is an extremely important variable in the assessment of a port that is impossible to reveal with printed data. Having spent 100’s of hours flowing heads, I have come to recognize that the best performing heads share this characteristic, whether it’s a 50 year old 356 or a modern 4 valve head. The RS+ heads have one of the most efficient intake port shapes I’ve ever seen on an air-cooled 2 valve head. We’ve even borrowed lessons learned from them for the latest version of our top of the line LE-200’s. It’s also worth noting that the intake flow gains from port matching are very slight and only show up on the upper end of the lift range. For that reason we only recommend it for large displacement engines and competition engines where every last drop of performance is needed. Another important feature of these heads is the solid low lift exhaust port flow. This is very beneficial for air-cooled engines as it improves evacuation during the critical blow-down period. Compared to the stock 2.0 914 ports it’s like adding extra exhaust cam duration. This is done with out removing material from beneath the exhaust valve seat as is the case with the 2.0 914 head and many heads ported by our competitors. This leaves a much stronger head that will hold a valve job longer. The addition of premium Crower springs and retainers allow for long life even at elevated revs. Spring coil bind clearances are set to accommodate up to .510” lift.* Lower lifts typically require less open spring pressure so these springs will give that with no shim adjustments. This adds to the versatility of these heads. I’m not aware of any .500” lift solid flat tappet cam that these springs won’t effortlessly handle to 7,200rpm’s. • The step may be machined out upon request. This is an optional service, though there is no additional charge. If you would like the step removed please mention this when the order is placed. Orders placed with no reference to the step will be shipped with the step in place. *If more lift is needed we can accommodate that, but you’ll need to indicate your valve lift when the order is placed. If no mention of valve lift is made, coil bind clearance will be set to accommodate .510” lift.

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  1. RS+ Cylinder Heads

    RS+ Cylinder Heads Item#:07607

    • Castings: AMC
    • Chambers: CNC machined 2.0 914
    • Chamber Step: 95.0 x 1.0mm*
    • Plug angle: 2.0 914
    • Valve sizes: 42mm x 36mm by Manley
    • Standard Springs & Retainers: Crower HD Single springs for 122lbs of seat pressure and 222lbs at .460" lift & Chromoly retainers
    • Upgraded Springs & Retainers: Premium dual Crower set for 150lbs seat pressure & 320lbs at .530” valve lift & Crower Chromoly retainers ($200 upcharge)
    • Keepers: Hardened and ground for clearance
    • Intake Ports: Fully CNC machined with hand finished details.
    • Exhaust Ports: Fully CNC machined with hand finishing.


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