Low Vacume, full boost??

[Bmxr152]

My car is freshly rebuilt but has like only a -10 vacume and idles kinda iratically. When i hot boost though everything clears up!???? I have an open downpipe exhuast if that makes a diffrence. Also seems to be running rich, Whats the proper o2 voltage for idle and for WOT?? thanks in advance guys

 

[Bmxr152]

which way do i need to move it to be correct??

 

[chris4g63t]

which way do i need to move it to be correct??

Both sets of marks on the Cam gears have to be line up with the head surface when the motor is at tdc. The way to be exact about it is to pull off the lower timing cover and spin the crank until it lines the notch on the plate behind the crank pully with the mark on the oil pump. Or you can put a screw driver in the #1 cylinder and turn the crank until the screw driver doesn't go up anymore.

 

[oldman]

which way do i need to move it to be correct??

Remove your #1 spark plug, insert a long thin rod and let it rest on top of the piston. Rotate the crank pulley CW until the rod stops moving up when the piston is at the top. There will be two different positions for the piston to be on the top position. 1) TDC, top dead center, when the piston is in between compression and power stroke. 2) In between exhaust and intake stroke. Only TDC will bring both cam marks anywhere near each other. If you're already in TDC in the picture you're off, not only should both cam marks line up, they should also line up with both cam sprocket center bolts.

Edit: beaten to the punch.

 

[Bmxr152]

all of a sudden today its ideling at -16 vac, but now ideling at about 1k RPM and now runs really crappy. It like vibrates through the pedal and backfiring while accelerating. What is going on now. I did =nt even touch the motor. It now has like 100 miles on it.

 

[chris4g63t]

all of a sudden today its ideling at -16 vac, but now ideling at about 1k RPM and now runs really crappy. It like vibrates through the pedal and backfiring while accelerating. What is going on now. I did =nt even touch the motor. It now has like 100 miles on it.

The higher it idles the more vaccuum it will pull. I wouldnt drive it until you figure out the problem. Do you still have balance shafts?

 

[Bmxr152]

yes still have the balance shafts

 

[chris4g63t]

If you oil pump isn't lined up right with the bs then thast could also cause a rough idle. Im not sure if it would cause low vaccuum though.

 

[Bmxr152]

alright i got everthing lined up today... now my car like studders till exactly 3500 rpm then clears up completely and runs great. whats going on. All i did was allign the cams. Is the CAS off maybie?

 

[wickednightmare]

alright i got everthing lined up today... now my car like studders till exactly 3500 rpm then clears up completely and runs great. whats going on. All i did was allign the cams. Is the CAS off maybie?

hey man i got the same problem. tonite i changed my o2 and went for a joy ride becuase it was running pig rich and that solved that now my car is only setting at -10 vac i have been reading threw the thred and see n u have the same problem im goin to go check my tdc my check engine light is comming on and off sometimes now allso put the car still pulls realy hard rock solid to 15lbs no creaping either my mods at 1st ever halman mbc oh ya still works baby and vpc+gcc i know the gcc is over kill but got it in a good deal allso custom uicp ported head full 2 1/2'' buschur exhaust ported 2g 02 housing ported 14b and egr block off and only min vac lines i also did a boost leak check im goin to keep ya posted maybe it will help ya

 

[wickednightmare]

wow do i feel stupid didnt ever look at the dates ha ha oh well ! u guys should take some of this stuff off here

 

[zhjiln]

im not the first to say it.... definitely vacuum leak... and make sure your lines aren't kinked....

 

[wickednightmare]

im not the first to say it.... definitely vacuum leak... and make sure your lines aren't kinked....

i got it my boost gauge took a shit i check my timming and its all lined up and my problem was my 02 sen. and my car cas need set so it would idle after i swaped the o2 car idles and runs great now but i need a new boost gauge

 

[duwackerTSi69]

I didnt take the time to read the whole threah from the OP but I rebuilt my motor a few months back and I had the exact same problem. At Idle I was at -10---15HG, but when I drove her she cleared up untill i let it at idle again. My timing was off basically..Just get ## car lifted in the air some how and put ## timing at TDC and readjust ## cam gears and make sure the cam marks are even when u get her all back together..I bet its ## problem.