Old thread - I know - but what the heck... We block them off permanently all of the time when we convert these motors into track cars and on race car builds, without any adverse effects...
On one of the street cars, I blocked it off with pinch hose-pliers over the summer (but it eventually kinked and cut the hose, so I wouldn’t go that route again...!) If it is still in a 164, then the best is just to simply install an inline ball-valve, so that you (or the next owner in a colder climate), can have access to a fully-functional heater-system at the turn of a valve!
Full-Race 3.7 Litre 24v Milano 6-Speed Getrag; Restored Street/Track 3.0 Litre 24v Milano Verde; 3.7 Litre 24v Turbo Project!
Last edited by junglejustice; 11-17-2010 at 06:08 AM.