MSefi.com read only forum (Jan.15,2018)

Ms2 v3 on 2.890
350 sbc in a 85 s-15 jimmy
Tpi intake 19lb injectors have a set of 22 or 24s for when i do my fuel pressure regulator swap. Pulls about 13 in of vacuum
Frame mounted pump and it seems to be keeping up no way of logging it yet.

Removed a performer rpm with a tbi and a plate kit. Pulled close to 18 in of vacuum.

Ive sprayed the intake for leaks and i never heard it change. Seems like my entire table is rich though and my milage is suffering compared to the tbi as well right now.

If you went from 18 to 13 vacuum reading, you have a vacuum leak or a hose off somewhere. The low vacuum will cause the MS to richen the mix. Billk

c_10,

Yep, I agree with Bill. Assuming the tuning has been optimized for minimum MAP kPa (which it should be before doing any troubleshooting, of course), a vacuum leak is the most likely suspect.

Note that a rich mix will cause a low vacuum, and a low vacuum can cause a rich mix, so sometimes a little bit of tuning can make a big improvement.

Small block Chevys have an annoying tendency to leak from the valley into the intake ports at the gaskets, so if there are no internal leaks, that would be my first guess.

You can try removing the PCV valve (oil oil filler cap) and see if the is air flowing into the valve covers (or put your thumb over the hole and see if you can feel a vacuum) - if you can, then the intake gaskets aren't sealing properly.

Lance.

Ill get another set of gaskets. I have all but the intake to head gaskets. While im in the next time ill swap injectors to some 24lbs and my adjustable fpr. Im playing with the timing now alot as well and its helped. Ive gotten a vac reading of 16in now after some playing with it.