The Blacktop has an inner shape in the manifold in a more of the heart shape compared to the Silvertop’s circular inlets (see “Throttles”). The Blacktop inlets at the head aspect can also be broader to allow for the much larger inlet ports in the head. Remember to see “Throttles”, https://jdmtoyota4a-ge43141.daneblogger.com/33651443/not-known-facts-about-toyota-4age-blacktop-engine-for-sale