Slow cranking speed/no start

[roccit_53 at scirocco.cs.uoguelph.ca (C Boyko)]

I'm trying to get the 16V out to have the headers installed and she will
not start. So I've swapped batteries, and the starter was rebuilt just
before she was parked for the winter. But this car has seldom started well,
and it always seems like the battery doesn't have enough juice to kick her
over fast enough. Sounds like the battery is low. But it does not matter
what battery I put in there. So I tried a direct ground jumper to the block
and to the starter housing, and still it's cranking too slow to start. It
gave one or two tries, but just not enough to start. I used the charger
pack too. No dice. It IS cold here, so the oil will be thick, but what
causes the starter to not turn fast enough? Ground wires were all checked
over too, and are in good shape. I'm charging the battery again, and will
give it another go, but I just hate a car that will not start. The roads
are perfect, she needs to get out of here this morning.
Cathy