0 hg manifold vacuum @ carb

[phil8825]

Hey guys,

Played with the cj a little today, replaced the heater core, radiator and clutch linkage. Afterwards I decided to take a closer look at my carb setup and dial in my idle mixture with a vacuum gauge. Im still a noob when it comes to this stuff but I figured Ill just learn by doing.

I have an amc 360, edelbrock performer intake and carb (1400). All in all the engine runs fantastic, pulls strong, no oil consumption, stumble etc. only has a couple thousand miles on it.

So I plugged in the vac gauge at the manifold vacuum at the carb, start the car and the needle shows 0 hg. I figured something is not right here so I plug the gauge directly into the intake to see if it actually works and it sure does, gave me a reading at 15, steady.

Also tested it on the ported vacuum and it increases with throttle as it should. Have not checked for any vac leaks yet but even if I do have a leak shouldnt the manifold vacuum port show me at least some reading.

Im a little stumped, any thoughts.

Also took a look at my timing (disconnected ported vac) shot the light at it and wasnt to happy seeing the timing bounce around between 12-15.

As for the camshaft, unfortunatley I dont know whats in there but what I can tell it certainly is not stock..

Any input would be great

 

[Torxhead]

The steady vacumn reading you got at 15 is good, although it is a bit low probably due to a performance camshaft that you suspect that you have. The bouncing timing mark you saw isn't bad either but I would say that it does indicate a little wear on the timing chain.

 

[phil8825]

Thanks for the quick reply. I figured out that my carb only has ported vac in the front, no full manifold.. Took a different timing light to it and now its steady. Did some experimenting today.