Have a 1986 na 13b that i wasnt planning on using for a while but i found a 1991 tII motor missing a housing and rotor. Would the 86 work for the 91? does it matter that its na not turbo? Can i use them with a little modification? And answers are greatly appreciated.

 

Short answer is no.
Yes
Not really. One could use the 86 n/a rotating assembly( E-shaft, rotors and front and rear counterweights). The rotors are different weights between S4(86-88) and S5(89-91) so they can't be mixed. Also since the 86 n/a is 9.4cr and the 89 TII is 9.0cr the stock computer may not compensate very well. So it's generally not recommended.

 

[QUOTE=Dak;12400608]Short answer is no. Thanks man

 

Adding a comment on how the spark plug locations are different between s4 and s5, therefore you cannot use mismatched housings.

 

I disagree. I'm actually running an engine right now that has probably 20 some k on the rebuild and I'm using a n318 housing in front. As far as spark plug placement, TDC is TDC.

EDIT: I am however using two s5 rotors and also turbo. Matching your rotors is more important than anything. It's not something I would do if I had the option of having identical housings or if I had high hp goals.

 

No hard feelings, but still want to disagree. I just looked up older threads asking about this and s4 and s5 have different locations for their leading plugs.

 

You’re correct in that the spark plugs are in different locations, but this doesn’t affect timing. Timing is the correlation between eccentric shaft angle and when the spark plug fires. Moving the spark plug alters where the flame front propagates from, not ignition timing.

if this was an all-out, high strung motor, i’d be more concerned about using matching housings, but for a mild build, it’ll be fine.