what does everyone know about the a13 are they worth rebuilding or what?

Rare and yes worth rebuilding

Used by most Japan-market B310 Sunny 1980-1982. So the A13 would be rare in AUS or USA.

has anyone seen a quick a13 iv got one in garage or what there worth?

Here in the states, the A13 was used only in 1974 B210s (120Y). It is a new style block, as in center distributor, with a 73mm bore, and a 77mm stroke. Basicly you could make your own by taking an early A12 block and putting an A14 crankshaft in it. You would end up with an engine of 1288cc. Small bore long stroke is great for low end torque, but not too good for top end horsepower. There are a few other differences, but those are the major ones. Basicly put, it wouldn't be my first choice for a hopped up motor. You would get more bang for your buck by going with an A14, or A15.