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| * 1967-1973 motor mounts vs 1974-up mounts | * 1967-1973 motor mounts vs 1974-up mounts | ||
| * increased deck height raises exhaust pipe | * increased deck height raises exhaust pipe | ||
| - | * and 3-bolt vs 2-bolt exhaust flange | + | * 3-bolt vs 2-bolt exhaust flange |
| * A14 & A15 call for stronger transmission | * A14 & A15 call for stronger transmission | ||
| * Call for stronger differential than 1967-1974 H145 type | * Call for stronger differential than 1967-1974 H145 type | ||
Revision as of 22:56, 26 January 2012
Contents |
A-series Nissan Engines
The A14 and A15 engines are "tall deck" engines, and are 3/4 inch higher than A12s. However, they fit in the 1200 with only minor changes. This also applies to the 1974 A13 engine. The A14 and A15 are by far the most popular swapping candidates since the bigger displacement of the A14 and A15 means both more power (peak HP) and more low-speed power (torque) than the A12, A13 or A12A. Remember: "There is no replacement for displacement" (aka "theres no substitute for cubic inches").
Swap Factors
These factors are different when swapping:
- 1967-1973 motor mounts vs 1974-up mounts
- increased deck height raises exhaust pipe
- 3-bolt vs 2-bolt exhaust flange
- A14 & A15 call for stronger transmission
- Call for stronger differential than 1967-1974 H145 type
A14T Engine
A15 Engine deck
A15 Engine (left side)
Like all 1974-up engines. the A14/A15 have the motor mount bosses in a different place compared to the 1971-1973 A12 engines. So the engine mounts are a bit different. This photos illustrates the difference:
Stock left-side mount in Datsun 1200, but Newer A12 engine. A better way is to move the brackets on the engine, to get the engine lower. You could also 1) use the 1974-up 1200 crossmember or 2) modify the crossmember.
Engine Mounts
The easiest thing to do is use a matching set:
- Late Engine
- Late Engine mounting brackets
- Late Crossmember
Or the complete set of early items if swapping an early engine into a later 1200. For more details and comparison photos, see Engine Mounts.
Early vs Late Engine crossmembers
RH engine mount brackets (old) 55mm bolt center (new) 50 mm bolt center
Lower bolt is 5mm higher on new engine, so mounts actually bolt at the same level.
Perhaps a 3mm difference. Then add thickness of your adapter plate.
Late Engine onto Early Crossmember
When fitting a 1974-or-newer engine into an orginal Datsun 1200, and using the original crossmber, modifications to the engine mount brackets are needed.
There is no need modify the crossmember, although that can be done. It is easy to modify the brackets.
Left Side Mount Location
Left Side (manifold side) of A-series engine
- Engine mount bolt bosses were moved back 35mm (1-3/8") on the late blocks
- Front rubber mount fitted with roll stopper, to prevent excessive engine roll
- Rear rubber mount (transmission mount) fitted with roll stopper, which helps prevent engine from moving forward in an accident
Engine mount boss is 35mm farther back on newer blocks
5mm higher from bottom of block
Remove this Late LH bracket:
And obtain another RH bracket, and then fit it to the LH side. Old A12 brackets won't fit, but new A12/A14/A15 brackets will:
The mounts are also 35mm (1-3/8") further back. So drill two holes in a flat plate and mount it like this:
If the engine is centered and the plate holes drilled correctly, it will fit straight as above.
If the engine is not centered, the plate can be skewed:
There are three different RH mounts, some allow the engine to sit higher or lower than the others. If the mount is now up too high, slot the bolt holes for the engine bracket, and slide the mount up on the block the thickness of the plate, then tighten. This will lower the engine a bit.
Three different RH mounts. Which is best for a swap?
154 mm: Early block front face to center of mount
189 mm: Revised block front face to center of mount
Alternatively, you can put the mount on the last accessory bosses (as in the photo of the Yellow A14 block), which is 26mm (1") farther forward. To do this, you will need to redrill the lower hole on the engine mount bracket, 8mm over. And you will still need to slot the mounts and use a flat plate. Nothing gained, but it takes a little more work this way.
Right Side Mount
Right side (spark-plug/oil pump/starter side) engine mount bracket is practically the same Late vs Early.
Two types of right-side brackets:
The only thing you might need to do is Measure engine installed angle and if you need to lower it a little bit, slot the bracket bolt holes (where it bolts to the engine) slow you can mount it slightly higher.
Custom Brackets
For the cleanest look, you may cut and re-weld the brackets so they fit just so. You can fabricate the LH and RH brackets to have the 35cm offset and be a bit lower.
Discussions and Details
The simplest way to fit the motor mounts is a flat plate:
However, this might makes the engine sit about 5/16" too high. You could slot the bolt holes in the engine bracket so it will slide slightly to level the engine. Or if you use the correct new bracket it will be very close as-is. Only about 4mm higher.
- cheater_5 wrote up a detailed conversion here: Cheaters a15 into 1200 conversion
- An A14 installation Mildman undertook has been quite significantly detailed at the following web link: Mildman's A14 Installation
- There is also a technical article at the datsun1200.com site that discusses this installation too: Datsun1200.com Tech Section
Early Engine onto Late Crossmember
You can either fit an early crossember to the newer 1200, OR just use the newer mounts with simple metal plates on each side.
Crossmember Swap
Swap the crossmeber? Swapping crossmembers is fairly easy. There are two bolts on each side, plus the LCA bushing mount. But you don't have to swap crossmembers.
Use Newer Mounts
Or use newer engine mounts? You can modify the engine mount brackets to fit an early A12 engine (GX, anyone?) into your later 1200.
The only trick is to drill a flat plate to bridge the 35mm difference in back-to-front location.
- Use Datsun 1200 RH mount
- Use 120Y A12 or B210 A14, or any B310 LH mount with a longer bolt
- Drill two holes in 4mm flat plates
4mm thick plates. The mount bracket overlaps the insulator so it is partially supported by it.
Use the 1200 lower radiator hose to clear the alternator.
Right Mount Bracket
The original A12 RH bracket is very similar to the newer bracket (but the newer RH bracket doesn't fit the old engine).
Left Mount Bracket
On the LH side, use a LH engine bracket from a late engine. The newer LH bracket will match the newer or older LH crossmember horn. The height is perfect and no adjustment is needed.
Old A12 uses stepped bracket (upper boss is set back). To fit New A12 bracket, remove the stud and use a longer stud, or a bolt.
To fit the new A12 bracket, use 19mm worth of washers and a longer bolt or stud. Bolt centers are the same for the original A12 stepped bracket and the revised A12 flat bracket.
Swap Notes
- Distributor wiring will reach either dizzy (under #1 or under #3
- Alternator fits on opposites sides
- Can refit alternator to other side, but not necessary
- use extension wires to reach across (Ground, Battery, and FN/LS wires). Be sure to use the same thickness (gauge) as original.
- If you newer 1200 does not have a voltage regulator, fit an Internally Regulated alternator. Later Datsun 620/720 is a direct bolt on. See Hitachi LR Alternator
- Radiator hoses are different for the original 1200 low-mount alternator.
HB210
B210 with A14 engine pan changed to mid-sump (USA B210 only). So if swapping this engine in, swap the pan and pickup tube with the newer B310 A14 unit (or, perhaps the A12 pan will fit).
Questions
- What's Better? A14 or A15?
- But isn't the A15 stroke to long to rev high?
- Isn't the rods too short in the A14?
For answers, see: Engine Swaps, section "A-series Nissan Engines"