73 911 dist vac puzzle

[chauser]

'73 911 w/ mfi

Dist Vac Puzzle:

I checked timing with both L/R vac lines connected, I get ~TDC (should be ~ 5 ATC)

• I pull vac line from rt back and put finger over tube and I get 5 ATC
• I do opposite, leave rt bank connected and pull line from let bank and hold finger over it - I get ~ TDC
• I run just 1 line (no T) from lt bank to distributor - 5 ATC

I put my 70's era vac gauge on each bank separately and appear to be pulling about same from each ~ 200mm Hg
I sprayed cleaner down both vac ports, and each flowed - so no sign of blockage.

So it appears something wonky with right bank, yet vac gauge seems to indicate it is pulling a vac

Jamie Novak has suggested a vac leak on right side.
Other suggestions, how to test - spray carb cleaner at throttle bodies.

This appears to be a new event - not experience previously, but I know/suspect throttle bodies are leaking.

Charles

[rsscotty]

I assume you are using the factory vacuum tee. I have seen these plugged inside with carbon.

[chauser]

It is not stock T, but it is clear - can see and blow thru it.

[cmcfaul]

as long as you are getting 5 degrees of vacuum retard you are ok on that front. May be sign of vacuum leak on the other side