A-15 4th over??? What displacment is possible with A-series?? For Rally I need to have a car pass smog so I cannot get too crazy with engine plus I need car with mid-range. Also for Vintage I have to retain an A-series engine. So when my A12 wears out I plan to switch to "big bore" motor.

Tom

Down the road, I want to Vintage race. Even if I'm just on the pit crew. What "series" do you race in and where can I download a copy of the rules. Are you SCCA? Do you ever get to the Monterey Historics?

I've got an A15 block out to 79mm. and with an A15 crank this will give just over 1600 cc.
You might be able to have a bigger bore, but I'd be scared of striking water.
If you've got the dough, you might also consider increasing the stroke in which case 1700 cc might be possible.
How reliable the engine would be when you start stretching it out is the real question.

Got it...SCCA.ORG

Pitroad sells a 1600cc engine. And there was discussion of similar build up using Justy pistons (not proven yet?). The search box to the left should pull up those discussions.

there are a couple here in NZ who run/declare their engines to be 1640cc I guess they use a 80mm piston

largest i've heard of is 1680cc

No , I have been running SCCA club races since about 1991. I will be running with a vintage group called VARA. The folks that run the Monterey Historics are very selective , unless your Datsun were a factory car you are not likely to be able to run. VARA runs Laguna and Sears Point and they are open to anyone who signs up. Also there is HSR West. Grab a copy of Victory Lane they should have all the west cost vintage schedule. For Rally I will be running SCCA events with California Rally Series.

Tom