Hi Dane,
On NE motors the head can be milled up to .090", but I suggest .060" and use a copper head gasket. The original steel gasket was .010" thick whereas the copper gasket is .020".
The head used on the last edition Ambassador motor and most likely on the NE-R has the spark plug located near the center, and less fins for cooling.
The following comments are just my personal observations, and aren't presented to "bash", "trash", or harm any company, person, persons, etc. The same engineering company in Tiawan that brought us the NE heads with the spark plug way too long, the combustion chamber with many sharp edges and turns, very thin areas around the head bolt holes, is the same firm that designed the current head. The current head has a very, very small surface area near the center rear head bolt, and may present problems with head gaskets leaking. I must admit I am totally confused about Tiawan head designs for the Whizzer motor. I have never understood why 2 different size head bolts are used, re-locating the spark plug over the piston on a flat head motor, a copper head gasket with an obstruction in the middle of the combustion chamber, and a very small surface area near some of the head bolt holes.
I am concerned that milling the head on the current Ambassador motor may cause more harm than good, because of possible head gasket problems, and elevated operating tempatures [less fins to cool]. If you do decide to mill the head, please post pictures, and let us know how it works out. The motor runs best if the combustion is above 110 pounds. The stock compression is usually less than 90 pounds. I have one motor running at 165 pounds, but it uses a modified head from Woodstock Whizzer Works in IL., and requires hi test fuel.
I have milled and reworked hundreds of Whizzer heads including vintage & new edition versions, but haven't touched the last version. If you want to remove it and take a picture I will gladly advise you.
The head with the spark plug located near the center uses a different copper gasket than the NE5.
Have fun,
