New 2018 paint colours(retro serca 1970s Datsun 1000 sport sedan )
Still running the 1322cc motor unfortunately.

Attach file:

---

  FB_IMG_1521357726493.jpg (53.48 KB)


  FB_IMG_1522362888477.jpg (51.04 KB)

The bottom pic was last race last year it broke 2 rings hense its a bit smokey
A quick rebuild for this year.Have to put some thought into what to do with the blown 1510cc motor????

I'm in the same boat with my A15, I've got the added dilemma of the spare head having been milled 2mm. The head off the A15 would need extensive welding to be useable.

The GX head I am still using was one of Peter Zekerts damaged units.He fixed it before I bought it and I have repaired it once more a few years ago it has a chamber of 20cc and 39mm inlet 33mm ex.They are worth repairing here as they are $1000AU for a bare head approx. PS any damaged heads freely accepted 😆😆😆

Tom there is an incar video on Facebook. Just type in Greg Sutherland you may find it because I can't put it up here
PS if you are on facebook let me know

I'm not on Facebook but my wife is, I'll get on her account and check it out.

I was mulling over some more options; I could use the existing cam and just replace the couple lifters that are rough (they have lines around the circumference like a clock face) basically slap it in the stock A15. Then have my buddy weld up the trashed head and call it a day.

I could find some flat top pistons for the A12A to get the compression up. This motor has very few miles on it since it was rebuilt. The guy that had it rebuilt had it in his Lotus of all things. I'd put the milled head on that as is but even with a .6 head gasket the compression can only be brought up to 9.6-1.

I'll likely live with the motor I'm putting in it now for a while and focus on the handling, getting some more weight out of it (I can pull about 60lbs out without spending very much) and possibly work on the aerodynamics. I'm also doing a improvements to the brakes and exhaust.

The A12GX isn't likely to put out more than about 85hp at the wheels. When I had this motor on the dyno previously it made 73whp. In current trim it has 1 point higher compression, larger valves (37/30), more aggressive porting and less restrictive exhaust. I did some rough calculations and the compression was worth 2 horsepower, the exhaust 2-3,the valves 4-5 and the porting maybe 4-5. Regardless it's going to be down at least 10hp over the A15. It's going to cost me at least a second per lap but I'm expecting it to be as much as two or three seconds slower. I may be able to claw that back with the improvements mentioned previously.

The eventual goal is to get the weight down to 720kg and have a motor puts out 120-125hp at the wheels.

Not sure what you are allowed to do to your motors for the class you run.
We are allowed to do anything we like as classes are 0-2000cc...2001.etc etc.
My A12 has A14 77.5mm semi flat top 3cc dish pistons,ithas com ratio of 12.8=1...on E85 fuel.I had the little ends reemed out 2mm to take the A14 pin(been reving the crap out of it for 8 years with no problems.
Cam starts to work 5500 and flat lines at 8600.was able to rev to 9500 if needed without loss of power.Has 39mm inand 33mmex valves.2x45mm webbers.
Last time on dyno 99bhp at wheels.
E85 fuel is bowser fuel and easy to get and is cheap HP but you use a lot more of it(about 1 litre per kilometre)but the power is fantastic.what else can I say I have been building Datsun motors for over 50 years and only 1 blowup(and it was big time and big money).I will just use old faithful 1321cc this season much to my disgust as I am up against 2000cc cars.GREG.
PS if you want to know anything else just ask.
PPS What bore and stroke is an A12A and littelend size.We don't get to many of them here'

Quote:1980-1982 A12A (1237cc) is basically a bored-out A12
Bore: 75mm (A12 is 73mm)
Stroke: 70mm (same as standard A12)
Rod little end: 19.7 mm (same as A14/A15)
Block, crank and rods are H85 parts
Only available in B310 Japan/Asia and North America

Attach file:

---

  H8500_A12A.jpg (24.60 KB)

Thanks for that

Greg the class I'm currently in is a catch all class. Under 2.0 liter and I could even run a full tube frame car. With a few small mods I could run B-sedan which was one of the Sports Car Club of America classes from the early 70s. B-sedan is a very popular class in vintage racing. The biggie is B-sedan doesn't allow motorcycle carbs so I'd have to switch from the flat slides to weber DCOEs which isn't going to happen. Additionally the other cars in B-Sedan are all 1.8 to 2.0 cars sporting between 165 to 195whp. Theses cars weigh 200-300lbs more than my car it doesn't make up a 65-95hp gap. The cars are also sporting $8,000 to $10,000 engines. Most of my engines have never had more than $1500 in parts and I put them together. The motor that broke is one I went all out on it had $1600 in parts and $400 in machine work plus $200 in additional bits to accomadate the installation. When I put it together I thought I must have lost my mind to have a $2200 race engine.

The A15 was making 99hp at the wheels. It had GX head with 37/30 valves, 39mm flat slides, 76.5 JE forged pistons, Delta 278 cam (278 duration .420 valve lift, Isky double valve springs, 14lb flywheel, 11.89-1 compression, headers, 1.75 exhaust and porting done by me. The powerband was similar to your motor. Pulls from 4000 rpm, makes most power above 5500 and pulls to 8200. The motor will rev to 8600. The reason I went with an A15 is to keep the refs down. The A12 I had in the car was revving to 8600 all the time and as you would expect it wore the rings out very quickly. I got 8 weekends out of the A12 before it was really tired (80 psi cranking pressure). By contrast I got 5 years out of the A15

So cost wise I can put together the spare / stock A15 using the head that's on the A12, regrind the cam, do rings bearings and gaskets for about $225 U.S. This set up would get me close and possible even match the 99whp with a slightly more aggressive cam.

For $150 more I could have the block bored to fit the JE pistons and by adding a more aggressive camshaft maybe get upwards of 110whp. So figure $500 to put that set up together.

I'll be instructing at a track day in 4 weeks and I'll know if the various mods to brakes, rear suspension and exhaust keep my lap times close to what they were.

If I pick up an A14 crank and stuff that in the A12A it would probably put out the same 99whp but it would seem to be a lot work for no real performance gain. It does open up access to another class.

At the moment I'm leaning heavily towards the stock A15 with more aggressive camshaft then the Delta 278/.420 camshaft with the 27cc head. This may make 110whp. This also allows for the option of fitting 37/33 valves to the repaired head. This might get me to the 120whp mark.

For $1000 I could likely install bigger valves 38/33, bore the motor out to 1598cc but the big issue is going to be how to get the compression down. With the 27cc head compression would be 14-1. Carefully selecting a camshaft could bring the dynamic compression ratio down but even with that I'm not sure I could still run the readily available 100 octane.