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What gave the 13A d8 more power?

17 years 2 months ago #2907 by XtremeXcavator
I am working on my 13A and will be reassembling the top end soon. Do I need to know anything different than what the servicemans reference say's about setting the plungers.I want to give her the power she had from the factory.
Thanks, Jim Gangle

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17 years 2 months ago #2910 by SJ
Replied by SJ on topic 13a
If you have the correct book there for your tractor then go by that.The power is effected mostly by the rack travel from inside the governor & the RPM settings & the governor spring used.It takes a rack setting tool to set it up.The old book I have shows 1.716" setting for the lifters with a 3F1668 camshaft in the injection housing. The little later book I have shows with that cam 180 HP at 1200 RPMs full load & 1305 RPMs with no load setting. Also the gov. spring number is listed as 1H2823 & the rack setting of .475 & the low idle setting is 425 RPMs. This info. is from a couple Cat books I have from a Cat dealer I worked for.I have set up many of them & the power always was right there where the specs showed when it was tested on the dyno.

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17 years 2 months ago #3145 by maximan
Replied by maximan on topic Horsepower History?
I have wondered myself about the increasing horsepower through the years of the D13000 engine used in early D8's. Does anyone have a blow by blow description of the horsepower and rpm progression and what corresponding changes to the engine were made along the way? It would be interesting to see the rack setting guide if someone has it scanned.

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17 years 2 months ago #3165 by SJ
Replied by SJ on topic D13000
Without getting into all the details so the changes effecting the power on them were camshafts in the inj. housing & gov. springs & rack settings & lifter settings & the RPM setting & the 13A tractor was the last of the D13000 engines used in the D8s & had the highest power output.The 14A & 15A tractor then went to the D342 engine with the same bore & stroke but all together a new engine but yet similar in looks with some things.

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17 years 2 months ago #3182 by OzDozer
The progression of D8 power ..

1935 - RD8 released, featuring the new D13000 engine .. 108 FHP at 850 RPM ..
1940 - D8 8R released, featuring HP & RPM increase .. 131 FHP at 950 RPM ..
1950 - D8 2U (released 1945) gets a HP & RPM increase .. 148 FHP at 1000 RPM ..
1953 - D8 13A released, featuring HP & RPM increase .. 180 FHP at 1200 RPM ..
1955 - D8 14A & 15A released, featuring all-new engine (D342), rated at 191 FHP at 1200 RPM ..
1958 - D8 36A, 45A & 46A released. D342 is now turbocharged, and produces 235 FHP at 1200 RPM ..
1965 - D8 36A & 46A feature further HP increase, to 270 FHP at 1280 RPM ..

Upon the release of the higher HP 13A model, it was termed the "D8 pusher tractor". This was due to a increased demand for scraper pusher tractors, due to an increase in towed scrapers .. which was due to an increase in road-building activity in the early 1950's in the U.S.
The pusher tractor arrangement came with a #25 CCU and 8S blade, and also featured solid steel chassis frames (chassis members).
At the rear end of the main frames, where they cross-bolted to the rear housing, the frames measured 4½" thick x 14½" deep.

The 13A engine improvements featured ..

1. Replaceable valve seat inserts, for both inlet and exhaust valves ..
2. Valve rotators ..
3. Aluminum alloy pistons with cast-in iron band for the top ring groove ..
4. Stainless steel heat plug in the piston crown ..
5. Chrome-plated top piston ring and oil ring ..
6. Larger capacity oil pump ..

The D8's of 1953 featured numerous transmission changes. The first D8 tractor fitted with the new oil clutch, 2U21513 was fitted with a new transmission, P/N 9F3859, which featured faster reverse speeds.
This transmission was fitted from 2U21513 to the end of 2U production, at S/N 2U23537. An optional transmission (2H1530), with a 6 mph, 5th gear speed was offered.

On the release of the 13A model, there was a new transmission fitted with different speed ranges. This transmission was P/N 3H1906, and featured a 5 mph, 5th gear speed.
This 3H1906 transmission was only fitted to 13A1 to 13A234, whereupon, at S/N 13A235, the earlier transmission, P/N 9F3859 was re-instated as the standad transmission. The 3H1906 became an optional transmission.

The service literature I have examined, does not show any variation from the engine specs as listed in the manual.

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17 years 2 months ago #3187 by Kelly
Replied by Kelly on topic D8 Pusher Tractor.
Caterpillar Service Magazine. Nov. 16, 1953

The D8 pusher was a more powerful track-type tractor that joined the Caterpillar “family”. The machine had been designated as the D8 Pusher Tractor. Its intended use is/was, as the name implies, push loading scrapers. With increased weight and a more powerful engine combined with the low forward and high reverse speed transmission, this machine offers the best in pusher tractors design.

Included as a part of the pusher tractor arrangement was a No.25 Cable Control Unit, an 8S Bulldozer blade with special trunnions and a 1900 pound overweight mounted on the rear of the tractor.

The weight of the complete D8 Pusher Tractor arrangement is 49,940 pounds. This exceeded by approximately 3 tons the weight of a standard D8 Tractor equipped with the No. 25 cable Control Unit and an 8S Bulldozer. The increased overall weight, is the result of a slightly heavier engine and heavier frame than those used on the standard D8 Tractor.

Many of the parts used in the D8 Pusher Tractor are/were identical to those used in a standard D8 Tractor. The track and track components such as roller frame, idlers and sprockets are identical. The main frame engine support frame of the D8 Pusher Tractor is several hundred pounds heavier. Dimensionally, the width and depth of the frame is the same as the standard box section type.

Heavy duty track roller guards, offered as an attachment for the standard D8 Tractor, are included as original equipment on the D8 Pusher Tractor arrangement.

A new two-piece crankcase guard, announced in the Service Magazine of June 20,1953 is assembled to lugs on the inner side of the main frame. This guard provides complete protection for the underside of the engine.

All recent improvements to the standard D8 Tractor, such as the new oil type flywheel clutch, greater capacity steering clutches and new steering clutch controls, are also included in the D8 Pusher Tractor.

The transmission used in the pusher tractor is of the same basic design as that use in D8 Tractors, 2U21513 and up. All of the constant mesh gears on the upper shaft and countershaft have bore bushing pressed into the gears. The complete gear assembly rotates on hardened steel sleeves which are splined to the transmission shafts. Transmission speed ranges available with the D8 Pusher Tractor transmissions are as follows:
1st 2nd 3rd 4th 5th
Forward 1.4 2.3 3.1 3.8 5.0
Reverse 1.9 3.0 5.2

The engine use in the D8 Pusher Tractor is a 6 cylinder 5 3/4” bore 8” stroke Diesel engine. From outward appearances this engine may seem to be the same engine as that used in the standard D8 Tractor. However, many of the internal parts are different as the engine operates at a full load speed of 1200 RPM and develops considerably more brake horsepower.

A damper is used on the crankshaft of the D8 Pusher Tractor engine to reduce torsional vibrations which are encountered at the higher speeds of this engine. Since the vibration damper is mounted on the front end of the crankshaft, all parts in front of the vibration damper have been moved forward about 1 1/2”. A spacer has been added to the fan support to move the fan forward.

The lubricating oil system has a new gear-type, positive displacement lubricating oil pump and maintains a constant pressure with a controlled inlet. The control system is similar to that on the 4”, 4 ½” and 51/8” bore Diesel engines. The oil pump and control valve is mounted inside of and onto the oil pan. Oil pump drive is different from that found on the standard D8 Tractor engine. Drive is accomplished from the crankshaft through an idler gear in the timing gear train. To simplify oil pump removal, the drive gear is connected to the oil pump shaft with a splined coupling. Lines leading to the front and rear scavenge suction bells have been changed.
Pistons, piston rings and piston pins in this new engine are the same as those used in the D397, D386, D375 and D364 Diesel Engines. Pistons have heat plugs in the crater and the piston pins have a heavy wall section. Connecting rods have the same general appearance as those in a standard D8 Tractor engine. There is, however, one important difference: To accommodate the larger piston pins, rods have pin bores which are .070” larger.

Considerable changes have been made to the valve train. Camshaft lobe profile design closely parallels that of the D397 and D375 Diesel Engines. The standard D8 Tractor engine uses an entirely different camshaft. Valves are equipped with rotators and shorter and heavier valve springs. Both the inlet and exhaust valves seat against hardened steel inserts in the cylinder heads.

The fuel system and governor of this engine is basically the same as that of the standard D8 Tractor. Fuel pump rack settings and adjusted governor speeds are different. Engine full load speed is 1200 RPM and the high idle speed is 1320 RPM. Fuel rack settings with the 3H1690 Gauge are 0.475”, with the 1f 7945 Fixture the rack setting is 1.675”. Because of the higher engine speed, governor flywheels are lighter. The capacity of the air induction system has been increased by using a larger inlet manifold, larger air transfer pipe and a larger (13” diameter) air cleaner.

Crankcase lubricating oil recommendations for the D8 Pusher Tractor engine are different form those recommendations for the standard D8 Tractor engine. Because of the higher speed of this engine, at the time, it is recommended that Superior Lubricants (Series 2) be used with oil change periods and filter element change periods at 240 hour intervals when the sulphur content of the fuel does not exceed 0.4% to 1.0%, reduce oil change and filter change periods reduce oil change and filter change to every 120 hours.

When the sulphur content of the fuel is 1.5% or higher, oil change intervals should be reduced to 60 hours. The oil filters which are of the full-flow type must be changed at every oil change. Other lubrication recommendations are the same as those for the standard D8 Tractor machine serial numbers 2U21513 and up.

Offered as a special attachment for the D8 Pusher Tractor is a 3H4171 tandem Pusher Frame Group. This group consists of an additional pair of

trunnions which are weld to the special trunnion plates used with the 8
S Bulldozer blade and a “C” frame which is supported at the rear of the tractor by the drawbar. A dome-shaped block, resembling the pusher block on a scraper, is a part of the “C” frame and is the pusher block for the second pusher tractor.


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17 years 2 months ago #3188 by OzDozer
Kelly - I'm a little short on Service Magazines, Service Reporters and general new model releases in the 1953-1954 period.
Was the 13A available in a "Standard D8" form, as well as the "Pusher D8"? If so, what were the differences?
The reason I ask, is .. that a Service Letter I have, mentions "D8 Pusher tractors from S/N 13A1 to 13A234" .. yet also talks of the "Standard D8"?
Were Cat referring to the 2U series, when they spoke of "Standard D8"?
I presume the 2U ended production upon the release of the 13A model?
I see a production figure of approximately 317 2U series D8's a month for 1953, with a total 1953 production of 312 machines for the 13A series.
That's some pretty impressive production figures .. but they also seem to indicate that there was only around a months production of 13A's in 1953, making the release date around mid November 1953 .. and apparently also ending the 2U series production, at the same time as the 13A came out.

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17 years 2 months ago #3193 by Old Magnet
To add an additional comment it is interesting to note that according to the rack setting charts the 2U-7129-up and the 13A1-up were available normalized (turbo-charged) but still topped out at the same 149 hp on the 2U and 180 hp on the 13A (same as normal aspiration engines)

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17 years 2 months ago #3205 by SJ
Replied by SJ on topic Turbos
OM, I think the turbos were probably an attacment as they were pretty rare around here & we had lots of the 2Us & the 13As here esp. in the coal strippings.I had very few come in the shop to work on that was turbocharged but there were a few around.

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17 years 2 months ago #3213 by maximan
Thanks, Oz and Kelly for the run down on the D8 13000. Some points to be aware of when swapping engine parts!
So to recap, increases in HP before the 13A were accomplished by upping the RPM, using a stronger spring or lighter weights, different injector pump cam and letting the rack open up more.
With the 13A a change to valve timing and beefier pistons on top of these tweaks?
Accompanying the increases were the change to precision bearings, improvements in crankshaft and piston design and metallurgy, oil delivery/cooling as well as the screw-in injector heads. There were defenitely some key turning point changes!

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