Cat 1693 vs. 3406A

According to the valve cover sticker on my 3406A the highest HP rating was 380. Mine's rated at 375. Whether or not a 400 HP version was also available back then I do not know. CAT reman offered them with a 400 HP rating though I think.

I believe the 1693 was originally a D343 engine and was DOHC. 3406A is a pushrod engine with a single cam.

Don't really know what the advantages of either are but I think the B model is a better option than the A or 1693. Prechamber head design is typically harder on fuel.

 

The 343 was ahead of its time in many ways. Overhead cam rear accessory drive etc. But it’s pros stop there.

Cons

Even being over head cam it used lifters. Setting the overhead is a class A m’fer.

The injection system was #### it uses a capsule type nozzle lower injection pressure. The capsule nozzle was pieces in laymen’s terms so you were basically putting the fuel nozzle itself together in the field or the dirt. The fuel lines themselves are very prone to break. And the govnor is kinda #### too.

Now let’s talk about weight they #### near weigh as much as a 3408. That is also the reason that they were discontinued in favor of the 3406 in 73.

the early A model pre cups used a capsule nozzle as well. The late ones used a pencil type. So not all A’s are created equal as well


They would turn the RPM, for the time they were solid but if you ever believe they were power houses or reliable your fooling yourself. The A fuel system is still not great by today’s standards but well ahead of them. Neither used the best turbo but tech there has come a long way. Both are cool for a toy but would I set out trying to work one today and deal with the hassle of it absolutely not.


Sometimes it’s not so much if you can but if you should

 

I think they also made a 1673 for a while. Other than being a little smaller than a 1693 I don’t know anything about them. I did see a truck on marketplace a while back that had one. They are so uncommon I imagine they are a booger to get parts and service information on.

 

The 1673 was a very underpowered pos. They were worse about cracking heads than the 1693, and that was a fairly common occurrence

 

They didn’t have set screws and jam nuts. The lifters had holes around them with an adjuster inside it that worked like a brake adjuster on hydraulic drum brakes you could tighten it easily but backing it off is a class a m’fer right up until it goes bad backs it’s self all way off and you drop a valve.

The JWAC being smaller isn’t odd in no other way than they were the first motor that was after cooled. They didn’t put a big enough one on it, another sign that there is something better


Don’t get me wrong I have a soft spot for the 343 or 1693 etc. it’s the motor that put the patent on the clatter that CAT is known for. I’ve often said with a better fuel system it could have been in the hall of fame. But you still have the weight to deal with. There is still a lot of hype from the guys who run them but to be fair when comparing it to a 290 Cummins that’s not anywhere near a fair comparison. They certainly are not what most remember them being.


There was a tug company on the island that had several of them they updated from them straight to the E model. Every boat captain made the remark they never wanted to go back. FWIW the E models I rebuilt for them were truck spec so it’s sorta a fair comparison

 

The Caterpillar 3406A is a 14.6-liter (893 cu in) inline-six, mechanically injected diesel engine with a bore of 5.4 inches and a stroke of 6.5 inches. It produced between 310 and 425 horsepower and 1,090 to 1,460 lb-ft of torque, a range that varied by application and configuration. Known for its reliability, it was widely used in heavy-duty trucks and construction equipment.
Key Specifications:

• Engine Type: Inline 6-cylinder, 4-stroke cycle diesel engine
• Bore: 5.4 inches (137.2 mm)
• Stroke: 6.5 inches (165.1 mm)
• Displacement: 14.6 liters (893 cubic inches)
• Valves: 24 valves (four per cylinder) driven by a single camshaft
• Fuel System: Mechanical injection (pre-combustion chamber or direct injection, depending on the specific model and age)
• Applications: Heavy-duty trucks, construction equipment

Performance (Varies by Application):

• Horsepower: 310 - 425 hp
• Torque: 1,090 - 1,460 lb-ft

 

I’m certainly no expert but I think 380 was the highest factory rating for a truck. I’m sure cooter knows for certain