While in South East Asia I had the opportunity of spending a lot of time on a D8H 35A Torque Converter 3 speed Bulldozer. I am asking if anyone could assist me - - I know the 2u D8s I operated on a civilian road crew had the D 13000 engine but my main question is what was the motor in the D8H an early 1960s model turbocharged. Some have said the engine developed 235 drawbar HP. Please help me out. Also, as the D8H developed, what was the final Drawbar HP and How did they keep the heads from cracking on the higher HP motors?? SeaBee Mal

I dont know the serial number breaks for the 36A series, The first D8H tractors were 235 flywheel hp and a D342 engine, in the 46A series at about 46A12884 they increased to 270 flywheel hp. Standing near a tractor the 235's had a vertical air cleaner, the 270's had a sloping air cleaner, the later 270's had a scroll fuel pump and heavier final drives. The very early 235's had a fuel converter and at about 46A 3300 they changed to an oil converter. The D8H's were a very successful and productive tractor, had a very good service life, there were many updates throughout the series which ended at about 46A32000/33000. English built tractors were a 68A prefix. The D342 was used in the D8k and started at 300 flywheel hp, at about 77V15000 they were fitted with an aftercooler. I never experienced any head cracking problems in 15 years of owning D8H and D8K tractors, with the exception of an operator running a tractor with the radiator drained.

The early 46A and 68A tractors (68A1-82) were also diesel torque with a power shift transmission and we shouldn't forget the 36A and 22A (Glagow Built) direct drive tractors with a six speed constant mesh gearbox.
The weak point on these was the liner seat in the block, this engine started out around 140hp in the 14A, then 235hp in the D8H, later up to 270hp (apart from some odd 250hp around 22A1025 or just below). The truth was there was insufficient support in the ounterbore and when the factory machine tools got a bit worn, they would leave ripples in the counterbore allowing the liner to settle and cause cooling system pressurisation, although I am positive that many heads were pulled off for repair when the cooling system pressure was quite normal! The fix was a stainless steel insert in the block to support the liners.
The last D8H tractors and the D8k had 'spacer plate' blocks with no counterbores ( or was this just after the D8K came into production?) so the top of the block was a flat surface, a much better set up but still prone to problems if the cooling system wasn't properly maintained and we still sometimes had to fit inserts if the liners had fretted in the block.
I was once running service on a job with over a hundred machines including a D9L, two D8L's and a pile of D6D's, 225's, 215's and 966D machines, when I was told a 'nearly new' D8K was being sent, I ordered a spare head gasket set straight away because I had already written too many warranty claims for mods to the D8K head joints a few years before! They were a great machine if you maintained the cooling system properly.

Thanks to all of you who replied. I operated 35a Cable bulldozer and Push cat, 36a pushcat (this one cracked a head). 46a Hydraulic dozer in the dump in Guantanamo, Cuba. I really liked the D8H series much improvement (for the operator) compared to the 2u D8s which I had plenty of experience on also. SeaBee Mal

The D342 change in HP from 235 up to 270 was not through a simple adjustment, the engines are not the same, the rods,crank and block are different, it was not possible to upgrade the lower HP 235 to the spec of the 270, the Non spacer plate engine was first fitted into the D8K's, these tractors were fitted with the spacer plate motor about a 1/3rd way into their build total but the K's all sat at 300hp, the water cooled turbo and after cooling was to improve the engine not realy the power output, I have worked on a very early D8H with a stumpy set of track frames, that had an engine set around the 195-200hp sat in the hole.

Catsilver. Could the stainless steel insert you are referring to be the same thing we call a Z ring for the counter bore block and L ring for the spacer plate. Would you happen to have any literature re fitting the inserts. I just found out last week the shop that did this closed its doors and it won't be long before no one remembers how to do this. Thanks. Mike.

There was a special Cat tool to do this without stripping the engine past pulling the heads and pistons/liners. It bolted straight on top of the block and as far as I know is still current as there are plenty of 3300, 3400 and even newer engines it can be used on, don't be afraid of dealer prices because they can do it so quickly once the engine is stripped far enough, no need to pull the crank.
Alternatively, any good machine shop would be able to do it on a vertical borer, working out dimensions from a new liner,(inserts are also available under Cat part numbers) but this does mean a complete strip..
I will see if I can find any detail among my old paperwork (its 'buried' in my garage at the moment). I saw most of this work done on 3306 truck engines in the late 80's when I was a service manager, and on a few 3400 motors more recently, but didn't get involved too much because a mechanic/machinist/coded welder I had employed was so good at this sort of job I just left him to get on with it.

Thanks. I'll check my tool catalog for the reamer. No hurry on the info; whenever you get to digging in the garage. I shouldn't have to do one for quite a while. Our dealer was extremely good at this sort of thing but they started subbing it out to the guy who closed his doors. I'm sure their engine shop already has a substitute.

Yes Mike, the stepped insert is refered to as a Z ring by some. It is reasonably sucessful for repairs. The problem with the big bore (D342/353) blocks is the large size of the casting. Most I have repaired have had a crack between the cylinders that leads to an inclusion as you finish the cutting. On another note many of the early hour head gasket failures on the new D8K's and D9H's was not due to cooling system pressurizing but the metal gasket with silicone rubber on it around the push rods coming apart and leaking oil. Back in those days we spent many weekends turning them around for monday morning pick up.
Later Bob

I had a serious collection of tractor literature back in the '50s, and my favorite machines were D8s. IIRC, the 2U and the 13A used the D13000 engine, and were rated at 130 DB HP and 148 belt HP on the late 2Us, 150 DB and 185 engine HP on the 13As. The 14As and 15As used a NA D342, rated at 191 engine HP and 155 DB HP. The D8H, when it first came out in 1958, was 225 engine HP, and was the first of the turbo'ed D8s. The HP rating was soon raised to 235. The first 46As were still at 235 HP, and had the powershift transmission. The powershift later became the only choice, and the HP rating was later raised to 270.