Standard 16-bolt or vertical 6-bolt or 10-bolt GM style intake manifold pattern configuration, or 16 & 6 or GM & 6 patterns. Raised exhaust port only. Head bolt sizes 1/2", or 9/16". Single or Dual spark plug versions. For Nitrous engines stainless steel exh guides and chrome-moly int guides are recommended. Copper alloy valve seats available.
These heads were designed for very competitive normally aspirated engines needing a smaller combustion chamber for higher compression ratios and lighter pistons. Made from a superior grade of aluminum C355-T6 which is 21% stronger than 356 commonly used by other manufacturers. The valve angle has been "flattened out" to decrease the chamber size. The intake port runner has been raised considerably. The shafts and intake and exhaust rockers are the same as the big valve head but the rocker stands are M2000 head specific. The other part that is different are the 3/16" longer spark plug tubes.
The smaller chamber coupled with the much longer intake port short turn seems to increase power level output by achieving a more complete burn with less lost during overlap. It is not uncommon to see a 200 Hp increase over a very competitive big valve standard chamber hemi.
The hemi is a large engine that is a tight fit in the engine compartment, so rather than raising the valve cover straight up we rotated it up 2 degrees leaving the exhaust side of the head unchanged. The exhaust valve can be standard hemi, but the intake valve is now longer to accommodate the raised runner.
All Millennium / M2000 heads have the external water option as they are generally used for serious all out racing.