A question about vacuum retard

Hello everyone,

After having searched this forum I can see that the question about vacuum retard and ignition timing on the 117.982 US spec engines has been discussed in the past. However, I have not managed to find an answer to the fundmental question whether it can be disconnected and the port at the throttle housing sealed off. Sure, it would advance the timing to around 5-9 degrees BTDC in idle, but absolute timing at 1500 and 3000 rpm should be unaffected. I’m asking because the idle behaviour would ideally become better if you advance the timing a bit compared to the factory spec of 5 degrees ATDC. But is there any risk in doing so as it only affects the idle situation? For the purists, this is probably a no-no, but what about the pragmatics?

Any views?

best, Peter

Hi Peter,

it is not a black and white. Sure, when u run AC compressor, retard is anyhow disconnected to lift engine rpm. However retard vacuum box does not sharply only affect idle. It takes a slight overlap before it closes completely.

TO be pragmatic: Try out by closing the vacuum switch that bocks retard on AC running and check.