vacuum readings

[351w fastback]

i put a vacuum gauge on my car today and it read between 14-15. i drove it for awhile and then the rockers started to make noise so i adjusted them. i put a vacuum gauge on again and now it goes between 10 and 15 very fast. also a little bit of grey smoke with maybe gas comes out of the exhaust. it did not do this earlier. what could be the problem?
thanks

 

[mustangdave]

Readjust your rockers. Your valves are not opening and closing correctly beacuse of improper rocker adjustment. That is why it's smoking and letting gas past.

 

[MitchGT]

if you over tighten the valves (like when you were trying to get rid of noise), then they can hang open. 14-15 inches at idle is pretty good with any sort of performance cam is pretty good. Also, I would think the valves would be noisier at start-up, rather than after it warms up. Sometimes a small exhaust leak can make the same type of ticking noise. Try tightening all of the exhaust bolts.

 

[351w fastback]

im pretty sure it wasnt a header leak because ive been tightening the bolts for the last couple of days after i have ran it. how much noise should roller rockers make?

 

[grego37]

what type of rockers are you using, and what meathod of adjusting are you using?

 

[351w fastback]

im using trickflow roller rockers. ive got it on tdc of the #1 cylinder, did those valves, turned it a quarter and did the next one in the firing order.

 

[MitchGT]

hopefully thats TDC compression! Most people I've read recommends doing each valve seperately( when the intake valve is closing, do the exhaust.When the exhaust is opening, do the intake).I think thats right.In any case you want to adjust the valve when the lifter is on the round part of the cam lobe(zero lift).It is almost impossible to see the first few degrees of opening with the naked eye, so you have to adjust when you know the valve is closed by what the other valve is doing.