vnt boost problems `again`

[90DodgeVNT]

Irony just bit me in the butt...
Now I am having a problem similar to GLHShelby...

Car has run 21 psi no problem
16 psi FWD/ND SBEC
3 inch exhaust
stage 2 ported head
ported intake
ported exhaust mani
underdrive pully
52 mm TB
VNT28 TUrbo
Magnecore wires
NGK plugs
ARP studs
180 deg T-stat

NO vac leaks at all



Just got it running...timing is set to 14 deg
Runs nice...all the way up to 12 psi and then I get cutout.

Nothing has changed since with the engine internally or with the head.

Swapped a ported intake (FM) with another during the rebuild (FM again)
Changed the waterpump
Changed all the vac lines
Changed all the intake/exhaust gaskets
Added a front mount
Changed TB gasket
retimed engine

All I can think of is the cheapie cap/rotor I got from advance auto (old ones were cracked and dealer was closed at the time) and maybe a bad pcv valve...

Thoughts?





p.s. didnt mean to hijack thread, just curious if issues are similar... ?

[sdac_guy]

Quote:

Originally Posted by sdac_guy You should have vacuum on the line to the top actuator nipple at idle. The larger bottom line should (and most likely does) have boost pressure under boost.

Uh, I had these bass ackwards here. The top is for boost & the bottom is for vacuum.

But for a good reference on how the VNT boost controls work & a sensibly drawn vacuum diagram see Donovans Dodge Garage Under the Turbo Tech section items #19 & #49.

Barry