So for some odd reason with this new engine i have a bouncing boost gauge in boost. Vac is smooth but once i get to about 5psi i got a bouncing needle. Im bout to go disconnect it and check the hose for leaks and try tapping into the mani in a different spot and see what happens... seems to pull smooth in boost and i dont think the boost is actually fluctuating.. unless my bov is cracking open... any thoughts/ideas?

 

what brand boost gauge, what bov do you have?

 

I cant recall the brand of the boost gauge.. hadnt had a problem with it till now... turbonetics bov.. Im going outside to mess around right now so ill let ya know if i find something..

 

how do you have your vac lines all tied in?

 

It's highly likely that the gauge like has developed a crack. In vacuum the line does not show a leak as the small diameter of the plastic allows a seal, but when pressure is changed from negative to positive, fluid will follow the path of least resistance and "burps" out of the lines causing fluctuation in the reading. Its a common problem on the gauge lines for the CAT V16's I work on.

 

Yup it was a cracked vacuum hose... I couldnt see the crack but when i pulled the one line off and plugged it and blew through it, it sure wasnt sealed.. replaced it good as new now!