These Bonneville heads are for the 1940-53 models and for use with our Long Reach Spark Plugs and have a 1/8" relief.
Note: Sold as a Pair (2)
KIWI heads are designed with longer spark plug threads to accept our long reach plugs for maximum performance. Heads have more material on the gasket surfaces in critical areas to reduce the chances of blown gaskets. We have paid close attention to the depth of the combustion chamber to eliminate any potential problems with detonation. Heads are made from high-end aircraft grade A356 T6 (heat-treated to T6) for increased strength over originals so as to not mush out under head bolt torque loads. Competitors' heads are full of porosity and use recycled aluminum. While they are cheaper, they distort under heat and do not dissipate heat well or seal. KIWI heads are the finest heads available for your Indian.
74” was the std engine displacement through to the end of 1948. 1950 was the introduction of the 80" engine. Any engine from 1940 can be upgraded to 80", hence, why we call out the head years from 1940-53.
Stock 74" engines had pistons that came up level with the top of the cylinder. Bonneville 74" pistons protrude 1/8" above the cyl. 80" pistons protrude 3/16". 84” pistons are level. 88" protrude 1/8". 92" protrude 3/16".