Here are a couple of comments about the 36 taken from Bob Allan's compendium on all things Enya.
"The 36 being listed seems to date this sheet (Enya catalogue) to the first half of 1955. This engine was only produced for a short period, which explains its status, alongside the later 29 Racing Special and the 3-bolt 19 as one of the three rarest, air cooled, production Enyas of all time."
"The decision by Enya to make a 36 size engine probably the result of rival OS releasing their 36 in 1953 (apparently, around this time, Fuji had a 36 as well), specifically for distribution in the US by the (Bill) Atwood Company. One theory on why the 36 was so short lived is – during 1955, it was discovered that quite a few 35 size engines in the States actually displaced more than the 0.350 cu. in. limit set by the AMA. As an example (when discussing this anomaly) Chinn revealed (in MAN April 1956) that both the FOX 35 and Sabre 35 were actually 0.3519 cu. in., the K&B Torpedo 35 was 0.3529 cu. in., and the OS Max 1 35 was at 0.3555 cu. in. Possibly these discrepancies in “pushing the boundaries” were small enough to overlook initially, but eventually perhaps it was thought wise to curb this trend of ever increasing illegal capacity, thus Enya had to more or less scrap their 36 immediately. One other theory is, the capacity was reduced to comply with a 0.35 cu. in. limit on C/L Combat engines, yet another that maybe OS were confused in the first place by the 0.349 cu. in. McCoy 36."
The 36 was only in production for a year, being replaced mid '56 by the 35 model 5001.