C4 vacumn problems?

[iwlbcnu]

Went from the stock 302 to a FRPP 385/351 and now the trans won't shift until 4k. I would think once above 2k vacumn should still be sufficient to shift the trans. You can really feel it down shift now when slowing down too.

 

[broncnaz]

Might want to swap the modulator and make sure all the lines are hooked up and in good condition. Sounds like either its unhooked or just not working. While the big cam in that 351 may generate lower vacuum I think your right it should shift before 4K if working correctly.