Vacuum problems with the 39 120

Posted by David Grubbs On 2014/10/17 20:44:05

I have been having a problem with the 120, with lousy acceleration (especially when compared to the 51 200 with the bored out 327) and mild overheating. I've read that a faulty vacuum advance can cause that so I put the hand operated vacuum pump on the copper tube and checked to see if the vacuum advance would work. Sure enough, no movement and the vacuum bled off quickly. So I pulled the distributer today and put in on the bench to clean up and check out more closely. I took the vacuum advance off and cleaned it up - while checking it out, I noticed that the flared connection that fits into the carb had a crack in the flare. I pushed the connector back, cut off the end and reflared the tube. Upon reinstalling it, the engine now runs smoothly and accelerates well in the garage. I'll take it out for a test drive tomorrow and confirm the findings. Another simple, but goofy issue that was causing me fits.

ps - I took the 51 out for a 200 mile drive last Sunday, and it was cruising fat dumb and happy at 70 mph. Made a few sprints up to 85 just to see how it would do. Sure surprised a few Subarus....