Woody, sounds like I'm going to spend some quality time sucking in your exhaust fumes then!! You should get a really nice engine for $10g. Thats two-and-a-half times the price me and Mick paid for our race car, and we went halvies in that!

Errol made a post a long while ago stating that one of the two types of 240Z big end bolts from ARP fit A-series rods. I plan to use these on my next engine. To date, we've used standard rods with new genuine nissan rod bolts and have had no failure (touch-wood). I've largly attributed this to our dedication not to over-rev it. Anyway, it seems possible to use nissan bolts, but I think ARP's are stronger and provide cheap insurance against a nasty failure - thats just my thought.

Do you know how to do compression calculations ?? Static and dynamic?? What about overall piston height (piston to deck clearance)??

I'm sure you would learn alot about your engine if you did strip and measure it all. But if you don't want to do that, I think there is enough wisdom in this group to get away without stripping your engine.


D, about the big strokes, I'm sure you've done a lot of research and know what your talking about, but I'm viewing things from a different angle. I'm concerned only with keeping the total capacity below 1632cc (1600cc + 2%) that our class of racing will allow. Obviously that will be the same for Woody. Saying that, the ideal setup for circuit racing is the biggest possible bore with whatever stroke is required to stay just under this capacity. I'd happily de-stroke it if I could use a bore big enough, but sadly, I don't think its possible within the realms of reality and my budget.

Talking outside the rules of our class...
Power = volume of fuel/air mixture x efficiency
Volume of fuel/air mixture = capacity x rpm.
so, Power = capacity x rpm x effiency.
But RPM is goverened by the forces on the bottom end. As a rule of measure, most engineers use average piston speed. Eg, an A15 at 7000rpm has a average piston speed of 82mm x 7000rpm = 574,000 mm/min or 9.57m/s. Now if we stroke it to 85mm (a stroke increase of 3.7%) and use the same redline piston speed of 9.57m/s we now have a new redline of 6753rpm (a decrease of 3.7%). You can see that the volume of air/fuel mixture for both engines at redline is the same. So the only power increase feasible is due to increased efficiency or increased stress on the bottom end.

A much better method is to increase the bore size. Std stroke, so same 7000 redline rpm. But increased piston area will result in increased air/fuel volume consumed, which in turn produces more power. A secondary benefit is the bigger bore will allow bigger valves which is a major bottle neck. When comparing the A15 with modern engines, compare bore/stroke ratios and also bear in mind that the two-valve-per-cylinder datto head has much less breathing ability than the modern 4-valve heads and also the geometery of the A15 head is not as good.