Cat 931 engine mystery....

[Welder Dave]

I think confusion reigns between sources that quote Gross Power and those that quote FWHP.........
From the earliest model to to C there is only 5 BHP of difference.

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I have that same chart. The next listing is a 931C Series II at 70 flywheel HP. My mistake the 75 HP is the gross HP rating but the 931C Series II brochure lists the flywheel HP at 69. Another interesting note is the 935B is 75 FWP, the 935C is 78FHP and the 935C Series II is 80 FHP. I'm curious if the IP is just turned up or there's different pistons or a combination of things to go from 62 HP up to 80HP?

 

[Welder Dave]

Nige, I believe all the 931's were built in Japan.

TnTrouble, I see no reason to bypass the standard 931 fuel pump, the system works just fine if the lines and tank are in good condition.
But the tank and lines can end up with internal corrosion (and external corrosion will cause pinholes and create more trouble) - and both these conditions will create fuel flow problems.

Also, tanks often have a buildup of debris inside them, such as fluff from rags, foreign materials accidentally dropped in the tank - and dirt and water (from condensation).
So a fuel tank cleanout and new fuel lines are always a good start when rebuilding - particularly if the lines display any form of corrosion.

You don't have to buy Cat fuel lines as a part, you simply manufacture new ones with some new steel tubing, and a small cheap tube bender.

Re the transmission, seals and o-rings go hard and cause leaks and shifting problems, so replacing as many as you can get at without a complete transmission disassembly would be a good move.
Check the transmission oil pump for wear levels (clearances), and the pump screen for debris and trash and look for metal. The oil pump gears should not need replacement if they fall within wear specifications. As a general rule, .003" to .005" clearance is good, .006" to .008" clearance is getting into the region where you probably should replace the components that are required to produce and hold oil pressure.

There is a bushing that supports the transmission valves control shaft where it goes into the transmission.
Replace that bushing and the seal on it, as wear here allows dirt entry. Check the shaft condition, to ensure the seal seating area, and bushing support area, are not severely worn.

The injection pump should not need attention, these old style injection pumps have a very long life as long as the filters have been working properly.

I don't have the injection timing degrees readily to hand for the PC engine, but the DI engine injection timing runs at 21° BTC.
There will most likely be a difference in timing between the two engines, the service manual advises the injection timing under "Engine Specifications".

A simple way to see if the transmission in decent order is to look at the screen (3F 1R)or the filter (3F 3R) to see if there are black particles in it. When my engine was done they checked the screen and said it was really clean indicating it was in good shape. It's great they checked and I'm very glad it didn't need to be taken apart. The engine was expensive enough!

 

[OzDozer]

The level of engine accessories can affect engine HP output, and the figures are always a bit "rubbery", anyway.
Cat and Allis-Chalmers used to have verbal and sales brochures wars, over engine HP claims, as A-C used to strip all the accessories off their engines before they tested them for output, and thereby claim more power output, than what the engine actually produced in the tractor.

Cat HP variations are usually related to injection pump tweaking and different injector designs.
The Cat Rack Setting chart or Fuel Setting chart is your best indicator of HP and injection pump settings.

Here's one for sale on eBay -

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[Welder Dave]

I was kind of wondering what changes were done to get up to an 80 FHP rating on the 935C Series II? I'd think comparing Cat's own brochures would be apples to apples.

 

[Nige]

I have seen some Cats with the engine S/No stamped into the metal of the lower front left of the engine block, just above the oil pan join line

IIRC that is only for D300/D330 series engines.

 

[TnTrouble]

Started to build the 3204 di. Have the block back bored .020. Crank turned .020 ay the rod lobes, standard at mains. Resurfaced the top plane to the limit without having to modify pistons. Checked the rod pin bearings and they are to spec. Also checked out the rod bolts but opted to change them and the main bolts. Also went with the 3 ring piston from Mcbee. I have some more photos for review, if you all see something amiss let me know.

Based on what Nige said regarding the differential of arrangement and seeing as how i have a 3f/1r transmission I think the flywheel I have will work out. Should be the same for either arrangement option.

Thanks for all the input. so far

 

[TnTrouble]

More Photos

 

[TnTrouble]

More

 

[OzDozer]

Looking good there, TnTrouble. Does it say on any of the McBee parts boxes, where the components are made? On a few forums, end-users are not happy with McBee components and have been getting variable results from them. Some seem to think a lot of the McBee components are from China.

I'm getting ready to re-assemble the 3204 in my 931B as well. My block was bored .020" oversize, but the crankshaft was in excellent shape, it stayed at standard bearing sizes for both big ends and mains, and it just needed polishing.

I went with IPD 3-ring pistons, IPD out of frame gasket kit, IPD camshaft bearings, and a full set of new IPD conrod bolts/nuts. I don't trust those old conrod bolts, even though mine specced as re-useable.

I did go with a set of genuine Cat little end bushings. I was surprised to find these were still made in Japan.
All the IPD components were made in the U.S.A., that makes me feel better than installing Chinese components with their often dubious QC.

I'm re-using my oil pump rotors, they look just fine and are still well within specifications for wear.
The price of new oil pump rotors kind of stuck in my throat, I think US$700 for aftermarket and US$1200 from Cat, is the worst reaming out I've encountered in many years.

I'm in the process of fabricating a new heavy duty engine stand, that little engine is heavy! - and I don't trust the weight ratings on Chinese engine stands.

 

[TnTrouble]

Looking good there, TnTrouble. Does it say on any of the McBee parts boxes, where the components are made? On a few forums, end-users are not happy with McBee components and have been getting variable results from them. Some seem to think a lot of the McBee components are from China.

I'm getting ready to re-assemble the 3204 in my 931B as well. My block was bored .020" oversize, but the crankshaft was in excellent shape, it stayed at standard bearing sizes for both big ends and mains, and it just needed polishing.

I went with IPD 3-ring pistons, IPD out of frame gasket kit, IPD camshaft bearings, and a full set of new IPD conrod bolts/nuts. I don't trust those old conrod bolts, even though mine specced as re-useable.

I did go with a set of genuine Cat little end bushings. I was surprised to find these were still made in Japan.
All the IPD components were made in the U.S.A., that makes me feel better than installing Chinese components with their often dubious QC.

I'm re-using my oil pump rotors, they look just fine and are still well within specifications for wear.
The price of new oil pump rotors kind of stuck in my throat, I think US$700 for aftermarket and US$1200 from Cat, is the worst reaming out I've encountered in many years.

I'm in the process of fabricating a new heavy duty engine stand, that little engine is heavy! - and I don't trust the weight ratings on Chinese engine stands.

I will have to shoot some pics of the stand I made. I used a frame from a dunnage cart set on two 6 wheel equipment rigging skates. The Mcbee parts I have received are mixed bag. Pistons and rings say USA, Pins and snap rings say China. Rod bolts and main bolts came from Off Road of Alcoa Tn. I will be digging into the oil pump gears tomorrow. The face of the outer ring appears grooved and therefore I am hesitant to reuse it. The head has all new springs and exhaust guides, the intake guides speced out.
All the Valves were relapped. I hope to get the head set and lifters and push rods installed in the morning.

 

[Welder Dave]

Hopefully no issues with the Mcbee pistons.

 

[OzDozer]

For my cylinder head, I went with machined guides to take K-Line bronze inserts (the original heads have no guide inserts), all new valves from IPD (no indication of origin), and new valve springs from SB International (U.S.A. made).

The 8 new valves cost me a total of AU$208 (US$138), and the springs were AU$93 (US$62).
At that money for the new valves, I didn't consider it worth grinding the old ones, even though it appears they could have been re-used.

The important spec on the oil pump is the rotor lobe clearance. Cat allow up to .011" clearance as the re-useable dimension, my rotor lobes measure up at .008" clearance. Look for bad scoring on the tops of the lobes, mine only show minor scratches. I replaced the outer bushing that supports the outer lobe.

Don't forget to check and clean the suction pipe and screen for the oil pump, nasty metal contaminants can hide in there, and be resistant to washing.

 

[David C Wier]

Good evening, anyone have a head for the pre combustion engine or the whole thing? I need to replace the head on a old D3 and it used the same engine with pre combustion.

 

[Welder Dave]

I'd check with rebuild shops and dismantled machines on Machinery Trader.

 

[tctractors]

Bit of a heads up chap the injector pump gears are not marked so before you get to keen on unbolting things remember this as you might need to do some thinking.

 

[TnTrouble]

Good evening, anyone have a head for the pre combustion engine or the whole thing? I need to replace the head on a old D3 and it used the same engine with pre combustion.

I have a pre-combustion head sitting on the self. I would not use it without getting it checked out and new guides. What part of KY you in?