the two times I put X-heads on a smogger-teen, with a 340 cam, that low-compression 318 turned into a sleepy marshmallow, and didn't wake up until waaay up in the rpm band. I never tried just the heads. But I don't think the heads were the issue, cuz as far as I could tell, the chambers looked very similar.
Somewhere around 4500, this combo began to wake up, but with 2.94s this was too far up the mph scale to be useful to me. This combo was hungry for more stall and much more gear.
A 2800TC helped get her off the line, as did the 3.23s I installed (because I had them), but it wasn't near enough.Honestly the cylinder pressure was just too low.
I still have that engine, now with it's 318 cam/top end back on, and the 2800, and an A999, and 4.30s really woke her up, but she normally runs 3.55s.
We did put some better springs on her tho, and headers, and a TQ, and she revs sweetly to 5000.
