so i was talking to siguel and i asked him if it is possible to use this combination and he said yes and without problems, is there any evidence or proof that the shapes of the rotor housins are different???

 

Only the water seal jackets are different from 85-86. The shapes are the same. Just make sure you use the same counter weight from the 86 rotors on the 85 engine.

 

Front counter weight and flywheel.

 

Allegedly the rotor housings have slightly different shapes, but I put one next to the other and went around with a straightedge and feeler gauges and I couldn't find a difference anywhere.

 

i remembered a link from racing beat claming that it would not work, but i also have a 1974 13b rotor hosing and a turbo II rotor housing and they have the same shape

 

yes it can be done i built my 76 cosmo motor with gslse housings
87 n/a rotors and 84 r12 irons runs great and the lighter rotors from the
87 seem to rev up a little faster than the old 76 rotors.
matt

 

S3 13B and S4 13B rotors are the same... Same weights, Same compression ratio... The only thing to gain on the S4 N/A rotors is the 2mm Apex seal versus the 3mm on the GSL-SE rotor.

I suggest going S5. They are a pound lighter, each and a 9.7:1 compression versus 9.4:1