2000 Dakota update (Head experiment)

Well, I did an experiment last night:

I took one of the heads (the one with the suspected blown head gasket) and turned it over on its side the the exahust ports on top. I sprayed brake cleaner in the ports to fill them up with fluid. Every exhaust valve seeped fluid out of it, eventually completely emptying the fluid. (Not real fast)

I turned the head over and did the same thing to the intake ports, same result except for number 1 I believe intake valve. It did not leak anything.

Are my valves leaking? If this was fixed, would my compression go up to normal?

It is an extra 60 bucks to have a valve job. If you dont think this engine should have much money put into it, what if I lapped the valves by hand? Would this be advantagous? I could lap them, then do the test again to see if they are leaking then I guess if they leak have a valve job.

If the engine is not going to last i dotn want to spend too much. I have one of those suction cup lappers. I rebuilt an old techumseh engine and bought compound for that. I am not sure if it is adviseable on an automotive engine or not.

Have you ever worked on these 3.9 dodge engines? Are they good engines?

By the way, I bought a Hayes manual last night and it said you could reuse the bolts for the v6, just not the 4 cylinder.

Here were my compression numbers before tearing it down:

6 = 90psi 3 = 190 psi (120 checked later) 5 = 105 psi 2 = 90 psi 4 = 95 psi 1 = 95 psi
Reply to
stryped
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I'd say they are leaking.. If fluid can get through air definitely can. Get some lapping compound and give it a shot. I had a work truck with the 3.9 in it that had over 250k on it and was still running strong.

Reply to
m6onz5a

Should i lap them or just bite the bullet and take them to the shop for a valve job?

Someone said that doing head work without doing anythign to the botom end might cause problems because of the increased stress due to increased compression?

Reply to
stryped

Should i lap them or just bite the bullet and take them to the shop for a valve job?

Someone said that doing head work without doing anythign to the botom end might cause problems because of the increased stress due to increased compression?

**** If you are tight on coins, go ahead and try lapping them. When you disassemble them, you will get a better idea of what you are facing.

I have heard the admonition not to clean up the valves on a weak engine all my life. If you have bad rings or a very weak lower end, you might see some blowby, etc.. Again, if you are tight on money, I would probably try it and see what happens.

The only REAL cure that you can pretty much rely on is to remanufacture the whole engine, and that is costly. Probably run you the better part of a grand. If you dont want to pay that, then fix what you find and trust in God.

Reply to
HLS

I trust in God anyway :)

I have the money. I guess it wont cause too much of a problem with the lower end will it?

Reply to
stryped

I trust in God anyway :)

I have the money. I guess it wont cause too much of a problem with the lower end will it?

******* No guarantees, but probably not. If the rings are stuck or worn or rusted, then you might get a bit more blowby..A lot of cars on the road nowadays have some blowby (Well, all cars have some degree of it..)
Reply to
HLS

What can I use to clean up the rust spots in the cylinders before putting the head back on?

Reply to
stryped

WD-40 and steel wool.

Reply to
E Frank Ball III

snipped-for-privacy@sonic.net (E Frank Ball III) wrote in news:49e65b82$0$1589 $ snipped-for-privacy@news.sonic.net:

No, penetrating oil and scotch brite. KB

Reply to
Kevin

I agree. If you like the truck and it serves a useful purpose in your life and it's otherwise in good shape, might as well pull it for a major overhaul or at least do an in-car rings, valves, bearings sort of minor overhaul as long as the block isn't cracked. BTW, it looks as though a warranted used 3.9 goes for about $1200-1400 and there is some availability of already rebuilt "crate motors" and "long blocks".

Lesson learned: as long as you're going through the trouble of a compression test, might as well do a "dry and wet" test -- the latter is the same routine but with a couple of good squirts of motor oil into the spark plug hole, and gives you an idea about the health of the rings. To really be scientific before teardown, you might additionally want to do a compressed-air bleed-down test.

Some fun stuff about your engine:

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Best of luck,

--Joe

Reply to
jtchew1

Is it aceptable to just replace rings/bearings while the engine is in the car? Dont you have to take the crank out to be ground typically?

Reply to
stryped

Bearings in the car used to be very common. Its not terribly difficult.

Rings in the car can be done, but its not advisable unless the cylinder walls are really in great shape and have no taper at all. In which case, why would you be replacing the rings anyway? It can be done, but its a lot of work for very little gain most of the time.

Reply to
Steve

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