Principle of DG code R.H.S Heat pickup? Mine's missing!

[futurecut]

A previous owner's bodge job methinks! I've been told i can get away with it but it may be responsible for some poor running symptoms.

I presume it increases carb efficiency when cold by preheating inwards air but any more to it than that? (in combi with carb heater).

I've a vac tube from the carb to the in/outake of the pipes that would be fitted to the exchanger (except near cold intake). What do they do then in combination with the normal vac tube to flap near air-filter?

And while we're at it what why does the dizz have a vac and pull down and when is it used?

Ignorance is bliss but the more i learn the more daft questions i can ask....

cheers in adv.

[steve8090]

See this

http://www.club80-90.co.uk/forum/viewtopic.php?t=1959

and this

http://www.club80-90.co.uk/forum/viewtopic.php?t=2109

[futurecut]

Much obliged!