I just picked up an engine & transmission from a B210 for my 1200 Coupe. The transmission is a 63A#2 5-speed. The engine however was an older A12, not the A14 I was expecting. I'm thing about using the A12 as a starting point (cuz I now have two of them ). This will be for a streetable vehicle, 6,500ish redline, using pump gas.

This is the direction I'm going (for now anyway):
- Boring the block out to 76mm or 76.5mm with a 70mm stroke (~1300cc)
- 9.0 to 9.5 compression
- Using Motorcycle Carbs (I picked up a set from a Kawa ZX-9R)
- Headers

Any thoughts on Cams & heads? I'm looking for stuff that is available in the US.

The new engine could be an early closed chamber if I'm lucky. Any idea on how this could be checked externally? I'd prefer not to remove the head from the new engine, as I may just drop it in the coupe as is. I'd then have a drivable car while the other motor is built.

Thanks

A12 stock revs to 6500, and already has that compression ratio.

it will be cheaper to obtain a good used A14 which will have more power than the modified A12.

Mate some good info in the tech wiki link <-. Personally I think these motors desire turbocharging; one told me once when I was out driving.

If you tune it carefully you can get 69 HP at the flywheel
While a stocker A14 is 80 HP. 1975 models were 75 hp, and 5-speed A14s were only 65 HP.

older A12 -- distributor under #1 spark plug:



newer A12 -- distributor under #3 spark plug

Frcm the outside the closed-chambr and open-chamber heads are identical

same compression ratio too

you could take out a spark plug and shine a flashlight in there and compare the too, but without a comparision it would be hard to tell

The difference was rated 1 peak HP, but supposedly the closed-chamber drive better at less than peak.

turbo is the cheapest way to make the most HP -- if you fricate the plumbing yourself


Camshaft is available anywhere. Just call any camshaft company and they'll sell you a custom cam. They don't list them in their catalogs but they make them on order.

The GX cam was the best factory cam, better than the A14/A15 cam, but all of them of low-lift. Ordering a new cam from Isky will get you a better performing one

Nismo used to sell several high-lift cams, but no longer...

If you want an off-the-shelf cam, you can buy them in america from mail order japan. But they are hugely expensive like $400.

boost is the cheapest way to hp

Thanks all for the input. I'm not looking for the most HP (I have other vehicles for that). My intention is more for a daily driver. Something that is unique, fun to drive, deliver 20+ MPG and the over square dimensions (76mm x 70mm) appeal to me in a fast revving kind of way.

Having heard the motorcycle carbs on an A-series, I really want to use them.

Regarding the A14... I hear what your saying, however, I'm not seeing the 30+ year old A14 motors in the local wrecking yards. And since I have the extra A12, the bigger piston installation has some advantages as it doesn't require the H150 diff.

Thanks for the cam info. I was thinking about having my cam reground to GX specs. I'll definitely check out Isky.

BTW.. both of the A12s I have are the early front distributor type. My understanding is that the earliest A12s in the US had slightly higher compression due to the 'closed' combustion chamber. If I'm lucky, the head of the new engine would be that type. But It appears I won't know that until I take the head off.

I'm also planning on doing some minor head porting, more clean up actually. Making sure the gaskets don't protrude into the intake/exhaust stream. I've done this before with good results.

Sounds like a plan.

Quote:
They are the same compression ratio with 27cc combustion chambers. The 1971 heads are closed-chamber, while the 1972-1973 are open chamber.

The change was made to lower NOx without reducing compression ratio.

Regarding the the open vs. closed head on the A12.
I remember reading that in the techwiki (great source if info BTW).

What I'm not clear on is this quote from the "A-series Cylinder Heads" section:
"A12 H39 Head

* USA B110, from April 1971
head has no casting numbers
* Same as H10 head, but with open chambers
* Compression ratio 9.0:1 with dished pistons"

From the "Engine Mechanical">"A12 Engine" section:
"Specifications:
* Bore: 73mm
* Stroke: 70mm
* Connecting rod: 121.5mm
15725.jpg
* Block Height: 189.1mm
* Displacement: 1171cc
* Compression ratio: 9.0:1 or 9.5:1
* Power: 68hp or 69hp (depending on year and country)"

I thought this (Compression ratio: 9.0:1 or 9.5:1) implied that the USA B110 Early 1971 model had higher compression. Most likely a result of the closed chambered cylinder head.

Thanks for the clarification.