Heat exhangers

[scalino65]

Hi. Can anyone confirm my thinking on heat exchangers please? Am I right that carb equipped cars can run the sames ones as CIS cars? i.e for a carb swb car, you can use any non-mfi version through to the last of the SCs? Also, probably a daft question, but why do the mfi and later cars need heat exchangers with oil pipes attached?
Whilst I'm at it, are all flapper boxes the same across the years? I've think I've seen long and short versions - can someone explain the difference please?
Also, should an swb car have red coloured flapper boxes?
Many thanks
Will

[Lightweight_911]

Any pre-'74 heat exchangers will fit but the non-mfi ones would be preferable - the extra outlets on the left hand mfi heat exchangers are to supply warm air up to the thermostat on the mfi pump (effectively acting as a choke) & for the intake warm-up valve (on the 2.4/2.7 mfi) models.

If you fit mfi heat exchangers to a carb-equipped car you would need to blank off these outlets.

[scalino65]

Many thanks Andy, that makes sense. I also see talk about "thin flange" and "thick flange". My uderstanding is that thin flange is the correct fitting for teh early cars. Does it actually make any difference as to whether it will fit a swb car?

Thanks for the explaination of the necessity of the extra outlet for the mfi version. That had been confusing me
Best
Will

[Lightweight_911]

As far as I remember, fitting 'thick flange' SSI's to an early car requires additional work - fitting longer exhaust studs to the heads & modifying the silencer mounting bracket which attaches to the back of the gearbox (to enable the silencer to mount slightly lower down).

In addition, the mount on the right hand heat exchanger which bolts to the bottom of the crankcase won't line up so needs some 'attention' ...