The Special’s engine offered 160 bhp, up nearly 50 bhp from the standard model. This was mainly due to the new cylinder head which offered a higher 9.5:1 compression ratio, larger vales, a high-lift cam and individual exhaust ports. Known as the 135J, some of these engines were machined on the exterior to reduce weight.
Many 135 Specials were bodied by Pourtout as dual-purpose road/racing cars. The sweeping fenders were removable allowing admittance into both GP and sports car racing.