Battery advice

[sunbeam alpine]

Yesterday I recovered a friend's TVR 350i (hardtop 2+2, which I think is quite rare) which has some starting problems.

The battery seems to me to be a bit on the light side - 70AH/315 - on the basis that I've got the same battery in a 4-cyl 1960's Alfa. Even fully charged, it turns over quite slowly and if it doesn't catch quickly, I guess it's flooding. The battery itself is OK.

Can anyone suggest what we should be looking for in terms of battery spec?

[sunbeam alpine]

OK, on the grounds that the only stupid question is the one you don't ask - here goes!

The only good battery we have lying around is from a New Holland tractor, with 1000 CCA! It fits! But can you put too much current through the starter?

Just want to test to make sure it's definitely the battery.

[sunbeam alpine]

Update - still doesn't start! Cranks very fast with the new battery, but doesn't fire. Plugs are wet, so fuel is getting through, and we have a strong spark, so what's going wrong?