Ran in a NEW K&B Veco 19 , needed a second 1 1/4 litre of 30 % Castor , or ' sagged ' rather badly . no guts . On a TWIN . ( both the twin ball race ones )
Usually use 10 % nitro , but they start howling on 15 or 20 % . 8 x 6s timed at 88 mph , in speed . With a stunt twin .
Usually use 9 x 4s , or 8 x 6s . they ' fatten up ' rich nicely on the higher nitro . Tho 5 % is o.k.
The Vecos were set up pretty tight - new . So can require plenty of oil for a good while . So 25 for starters if ' a bit used ' Just in case .
Incidently were Two Venturie Sizes & two heads , high & low comp , in the veco days at least . The ' Hemi/ squish band ' is the usual .
The Enya 3 plug etc is o.k. . they dont seem overly fussy there .
incidently the case on the R. C. ones are shorter above the N V A hole , for the Carb .
Look at the sceptre flight engine tests for them . Typically you loose say 1.000 rpm muffled , but for stunt your not running it flat out .
I use the old 70s Fox 19 / 25 bush ( & 35 ) mufflers , as the outlets twice the size of the Veco ones . The end fastening ones, with a strap, home made .