Ford 640 compression

Ramseyer35 · Nov 11, 2022

I have a ford 640 that I replaced the rings in. And it has 65 pounds of pressure in cylinder 1. 0 in cylinder 2 and 3. And 5 pounds in cylinder 4. The pistons are all moving like they should. The head was redone 10 years ago and the tractor sat. Does anyone have any ideas where to start on fixing the compression issue?

grandpa Love · Nov 11, 2022

Valves.....

rustred · Nov 11, 2022

u missed the most important thing... set the valves to spec. BUT, it is unclear if you just re-ringed it now as it appears . i have had tractors with no compression from sitting due to the cylinders being dry. belt them up and spin them over to get things lubed up and the compression came back and they started. my last 282 was like that.

old · Nov 11, 2022

Any time you have had the head off the valve HAVE to be readjusted so good chance you have a valve or 2 that doesn't close

Janicholson · Nov 11, 2022

Grandpa is probably correct. Sitting as long as it did, the valves are probably not totally frozen it their guides, but rusty enough to stick open when pushed open by the cam. another alternative (common) is bent pushrods from valves that are in fact stuck and immobile. Pull the valve cover and look at the valve train. Spraying a good penetrant on the stems (through the sides of the springs) then tapping the rocker with a plastic or brass hammer (repeatedly, but gently) can free them. Some may need assistance moving back up using light prying and tapping. PB Blaster is good, as are others. WD40 is not, it is not intended for penetration or lubrication either one. Jim

Steve@Advance · Nov 11, 2022

Did it ever run after the head was put back on? Were the valves adjusted?

Since it has been sitting, chances are the cylinders are dry, and the valve seats are rusty, maybe the valve stems are also rusty and may be stuck open. Usually stuck valves can be freed up with some oil on the stems and prying between the spring coils. Just be careful to pry evenly on both sides so not to bend the stems! If the valves were not adjusted after the head was put back on, that must be done!

Try putting a teaspoon of oil in each cylinder, let it sit a day or so, then spin it out. That should raise the compression enough that it will start.

Once running and up to temperature, if this is the first start, the head bolts will need to be retorqued and the valve lash set again.

Geo-TH,In · Nov 11, 2022

Where to start?
Pull the head.
Valves, blown head gasket between 2 & 3, possible rings.

showcrop · Nov 12, 2022

Remove both the valve cover and the push rod cover. Then as others have said go to work on the ones that aren't moving. You may need to remove the rocker arm assy. but you shouldn't need to remove the head. The valve cover comes off without removing the tank, but it is easier if you slack the mounts off.

Geo-TH,In · Nov 12, 2022

Get a good Flexable shaft camera Stan is asking about above and look inside for a stuck valve, burnt valve or hole in the piston. Look for cylinder wall scarring.
You will have to remove the head if you have a blown head gasket or a burnt valve.
Doubt if a camera could spot a blown gasket..

Ford 640 compression

Ramseyer35

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grandpa Love

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rustred

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old

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Janicholson

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Steve@Advance

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Geo-TH,In

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showcrop

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Geo-TH,In

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