Hey fellas,
I've just bough my first project, and I'm wondering what options I have and also which ones are the most viable to improve performance. (All while keeping the original block naturally aspirated, so no turbo). I'm already thinking about going for the standard stuff- webers, worked cam- but I have no idea what specific brands are the best, so I look to you for advice. It's a standard 1978 4-door sedan 120Y, with an engine pulled from a 1974 coupe. What ideas have you got?

All suggestions welcomed

Stock 120Y engine: 58hp (39 hp at the wheels). Cost 0
Worked 120Y engine: 80hp. Cost 2,500
Turbo'd 120Y engine: 127hp. Cost 1,200

Turbo'd is something that I won't do for awhile, but 80hp from a Worked engine, how? All I come up with is bigger valves, a header with a high compression + hardened valve seats to run unleaded, and a bigger carb, but that's it. I know that there has to be something more, but what would you have in mind?

Datsun had a factory 83hp A12 engine. It had the large-port cylinder head, twin carburetors and a high-RPM camshaft, 3-into-2-into-1 exhaust manifold. And flat-top pistons gave it that extra 3 hp.

Same size valves as regular A12, same size 1.5" exhaust.

All A12s have hardened valve seats to run unleaded, at least my 1972 owner's manual says so. I haven't checked the 1971 owner's manual

Found this information on a Japan web site. He figures Datsun changed to unleaded (hardened) valve seats during 1972, even lists engine numbers:

Japan-Market Lead-free Transition (~1972)
from engine number
* A12 613858 Sunny (B110) High-octane
* A12 638894 Sunny (B110) regular
* A12 808954 Cherry (E10)
* A10 061133 Cherry (E10)
* A10 828286 Cherry cab (C20)

That being said, we've had no reports of problems running unleaded/ULP in early Datsun 1000 or 1200 engines. The problems would be excessive seat wear, requiring replacement of the seats and perhaps the valves

Quote:The A12 engine makes the most HP at 4,500 to 6,000 RPM. So anything you can do to get the RPM up will improve performance. Of course at higher RPMs your engine will wear out faster. It is a trade-off you need to decide on (the alternative is a larger engine)

Here's what I have done, and would do again:
First, use extra gearing. This 1) gets the RPMs up during normal driving and 2) multiplies torque which is the accelerating force. So it's a double-whammy
* Replace the stock 3.70 gears with 4.11 gears from a wagon. If you buy a good used center section (diff head), it's cheap and easy to swap
* Replace current tall tyres with short, wide tyres. I bought 165/55R12s -- they not only cornered better, but increased the effective gear ratio to about 4.2. This combo allowed a 110 kph crusing speed no problems
* When accelerating, shift at 5,000 for maximum effect

Next step is to free up the breathing of the little A12. Twin carburetors are best, but on a budget a new Weber 32/36 carburetor ($400) or used Weber 32/36 (or Holley G100/5200) makes a huge difference at anything over 5000 RPM. Buy the linkage kit and adapter and it's easy-peasy

Also to improve performance:
* make sure the dwell is correct (49-51 degrees)
* total timing is 32 degrees
* Remove one of the distributor springs so advance occurs sooner
* check that the vacuum advance works. This increases power at low throttle openings

What about larger exhaust pipe? If you change from the stock 1.5" pipe to 1.75" pipe will it make more power? NO, the pipe won't make any horsepower. But if your engine needs to breathe, the pipe size can be holding it back

Consider that 1.5" pipe made 83 bhp with the Datsun A12 GX twin-carb engine. If you go up to 1.75" pipe, it will be sufficient for an engine making 108 bhp (engine dyno hp)

So yes, for a mildly-worked A12, 1.75" pipe is overkill. But for a more aggressively worked engine, 1.75 is a worthy upgrade. What about 2" pipe? If your A12 makes more that 108 hp, get back to us with your advice on how you achieved that on a budget!

I am hoping for this to be a daily driver, so with all of those combined mods to up the rpm, what was your rpm's at 100? (Were you using a 4 speed?)

Yes, I was using a 4-speed. My RPMs at 100kph were 4k (2,400 rpm below redline). It was fun and I made many long trips with it including a 2000 mile trip

Pulling out the engine this week. Seized but hopefully it'll be ok.