3000 Ford

I have a friends 3000 Ford diesel doing some minor repairs to it. He thinks the engine is getting weak and wants me to check the compression on it. What should i see on a good engine? It is a 3 cyl with about 6500 hrs on it.

It looks like they made some changes to them in 1968, dropped the compression a tad.
Pre 7/20/68 it should be 420-510 psi.
After 7/20 420-500 psi.
Anyone venture a guess why and how they did it?

They changed several things on the engine at that time, thicker head gasket is what probably lowered the compression some.
They also changed to a better flowing head, higher lift cam and beefier rods.

To kycase: Mid-300s PSI is what you'll find on a good running Ford Basildon diesel. If it is highly carboned up inside the compression chambers, it might be a little higher than that. The more important thing is that they are uniformly consistent across the board, in other words, they should be the same within about 50 PSI of each other.

To destroked: When Ford started to use thicker head gaskets in 1968, they also machined the blocks lower at the same time. This kept the compression ratio, and consequently the compression pressure, pretty much unchanged.

To ultradog: The 420-510 PSI quoted by Ford in the early manuals is unrealistically high. If you look at later repair manuals for say a 3600 or 4610, you'll see more realistic compression numbers in the mid-300s PSI range. Keep in mind that this is for essentially the SAME engine. The later Genesis engines (also of Basildon origin) run higher compression ratios and show a 375 PSI figure in that engine manual.

To all: I have a book in my hand, published by Ford New Holland in 1987 (SE4653), titled "Diesel Engine Diagnosis". It covers "all Ford built diesel 3,4,& 6 cylinder engines", i.e., all Basildon series diesels. Under engine compression, it says that 6 cylinder turbo engines should have a minimum of 275 PSI of compression pressure, and all others should see a minimum of 290 PSI. It does not give a "normal" figure.

I've compression tested MANY Basildon Fords, and I don't think I've ever seen one crest much over 400 PSI. Most good engines were right around the 350 PSI or so range. Also, when I do a compression test, I don't crank the engine over 100 times waiting for the needle to stop moving. I give about 6-8 puffs for each cylinder, which is consistent with the instructions in the aforementioned book.

One final note: Cummins does not publish compression test figures for their engines. When I asked why not, they said that there were too many different variations in the way service techs performed these tests (cranking speed, temperature, number of puffs, amount of internal carbon in the bowl, etc.), and that it was causing too much confusion in the field. With the electronic engines now, they use "relative compression tests" using a laptop. Older mechanical engines can be tested using a scopemeter and amp clamp while looking at starter motor current draw waveforms.

Would like to have a copy of that book.

I hardly every compression test a diesel, how well it starts with a good fuel system, blowby and oil consumption are good indicators of the engine internal condition.
Had a guy that wanted me to rebuild his engine once because when they checked compression one cylinder was down, it took me about an hour to get good compression on all cylinders.
I adjusted the valves.