Manifold Vacuum

[64drtGt]

I rebuilt my carb yesterday, and when i put the vacuum gauge on it to tune the idle in. I noticed it jumped around quite a bit. I have never had a engine with anything but a factory cam in it so is that normal for a cammed engine or should it stay steady?

 

[TrailBeast]

It will jump around depending on the cam duration and overlap, and the bigger the cam the worse it gets.

 

[64drtGt]

Alright my cam is 206/212 duration at .050 .512 .522 lift 107 LSA. Vacuum jumps around 3-4 inches. I got it adjusted fairly steady at around 15".

 

[Inertia]

If you go to this site, and clik on the green tabs,, you'll see diff vacuum patterns, to help diagnose probs.

http://www.secondchancegarage.com/public/186.cfm

hope it helps

 

[64drtGt]

Alright mines normal then thanks guys Just wanted to make sure.