RobH,
I've found the RCJI issues about .21 Car engines D/F aircraft. Danny Starkey is the man who has yield good results in this area.
These RCJI issues are : Dec-2001/Jan-2002 and Feb-2002/Mar-2002
He used a Novarossi .21 car engine + RK-20 and RK-720
Kress fans.
His website used to be ....
http://www.dannystarkey.freeserve.co.uk/