Modifying Robert Goldman's Alloy Midget Head.
Robert's car was one of the two test mules used to develop Moss's new supercharger kit for Sprites and Midgets. After getting used to the nearly unbelievable increase in performance brought on by the blower kit installation, Robert (like all true enthusiasts) decided that too much was never enough and he needed more! We figured a thoroughly reworked cylinder head would help that situation along and so the project began in earnest.
Robert's head received complete re-working, just like our typical "Fast Road" heads for MGBs. This involved complete porting, guide prep, valve job and assembly. With the emphasis on boosted performance, the head was indeed ported to the max.
These heads have a generous inlet port size at the manifold face, requiring only minor efforts in this area. The area near the port divider and valve guide however received significant re-working before we were done. As with all Pierce heads we do, the short side turn radius was also increased appropriately.
Supercharged engines have more exhaust to expel from their cylinders than do naturally aspirated ones of the same size, so the exhaust ports had better be up to the task. Pierce gave us plenty to work with and a complete port and polish job did them well.
Our combustion chamber work focused primarily on getting more flow into and out of the chamber, essentially making the best use of the valve size we had to work with. Because we did not have to worry about killing the compression ratio (Robert said they would make a drive-pully to increase the boost as needed) we de-shrouded the valves however needed.
Robert also sent the blower manifold along with the head. We felt the quality of the manifold was high and for it's intended purpose, an excellent piece.
The first modification we did to the manifold was to remove the port location rings. With a stock engine and boost levels, this would not have been totally necessary, but we were planning to get the most from this effort, as well as those undertaken down the road.
Removing the location rings required that the manifold be located somehow. We drilled location holes in the manifold and installed 1/4" setscrews in the cylinder head as "dowels" for this purpose. These "dowels" locate the manifold relative to the ports for easy installation.
The stock inlet runner entries were retained because they did not present a flow restriction at this stage of tune. Additionally, modification to this area would have required the manifold to have been cut apart and re welded, which was considered unnecessary.
CFM flow numbers at 28"Wc for the above cylinder head.
|Stock Flow||Modified Flow|
You can read more about Robert's car at his personal website at:
|Stock Flow||Modified Flow|
More information on the Moss Supercharger Kit for Sprites and Midgets can be found at:
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