OK, the truck is 28 years old (1986) but it is still running and I can't afford a new anything right now ( the wife and I are in the middle of building a house and I need this work truck to keep going for a year or two till we can get back on our feet).

I have no shop so I am working on a sand/mud driveway. We are living in an RV on site while building ( saved us $1000 per month rent ... even survived winter in VT ... inside of the RV had ice in it).

I have a leaking rear main and a "rumbling" sound deep in the bottom end when the engine rev's up.

The odometer says 37,000 ( could be 137,000 or even 237,000 ) and the truck was used for plowing.

I was thinking about looking for a "good used" engine and swapping them out but am afraid I may end up with just more junk ( how can you tell if a used engine is any good)?

I see they have rebuild kits with just gaskets, main and rod bearings for $100.

Is it possible to pull off the head and pan and replace these parts while in the truck?

Also is it possible to put in a new rear seal while in the truck?

Thanks ...... Mike

 

You didn't say what engine, but I'll assume it is the 300 six as you said "head". It is possible to pull the pan with the engine in the truck to replace the rear main, but it isn't easy. The fan shroud, if you have one, has to come out and maybe the fan to ensure it doesn't hit the radiator. And then you have to pull the bolts to the mounts and lift the engine up high enough to pull the pan, and support the engine on the harmonic balancer. But the balancer isn't a good jacking point and your support can slip, so I cannot recommend it.

It is much safer to beg, borrow, or rent an engine hoist and lift it up that way. But, if you are that far then why not pull the engine. And the head is heavy on those engines so the engine hoist would be a huge advantage for it as well.

If you do pull the pan you could then check the main and rod clearances. You'd need to have a torque wrench and a stick of Plastigage, which is cheap. But, the inside of the engine will be nasty dirty and it'll be raining oil for days, so working under there is going to be a mess.

You might be better off to run this one, gently, as far as it'll go. The 300's are said to be a very tough engine and seem to live for a long time with lots of noise.

 

Sorry, yes it is a 300 six.

Rebuilding "in frame" and/or swamping out an old motor for an old motor both go against my better judgement .... I am just trying to find a "cheap way out".

In the past I have rebuilt performance engines. I am fanatical about assembling them in an almost "clean room" environment.

I am a machinist by trade but my shop is sitting beside me packed up in a tractor trailer waiting for me to build the shop.

I love the six and have had good luck with them in the past so maybe I am worrying for nothing.

I figured new bearings even if out of spec would be better than what is in there now ..... but maybe I am just opening up a can of worms.

Other than being told "it is good", is there a way of judging a used engine?


Thanks again ...... Mike

 

The only way I know of is to hear it run and take some readings. In running, listen for piston slap and bearing knock. On the readings look at the oil pressure. Pull the dip stick and see how black and thick the oil is. If the oil is "new" then someone just changed it and may be trying to hide something. If it is BLACK and thick then it may not have been changed for a long, long time and that's the way the engine's been treated.

The best, by far, test is a leak-down on each cylinder. In that you put a regulated pressure, typically 100 psi, into each cylinder via the spark plug hole while the piston is at TDC on the firing stroke. But in the air line there are two gauges separated by an orifice, frequently .060". That way if there's any leakage out of the combustion chamber the pressure on the downstream side of the orifice will be lower, indicating a loss.

You check each cylinder and record the pressure differential. Plus, you listen to the intake, exhaust, sump, and cooling system on each cylinder. If there is leakage via a valve you'll hear it in the intake or exhaust. If the rings are bad you'll hear it in the sump, and if the head gasket is blown you'll usually hear it in the cooling system.

That'll tell you far, FAR more than a compression test, which I don't even bother with since I have the leak-down tester. Actually, I built it.

 

300 has a 1 piece rear main seal. It isn't access thru the oil pan, but by dropping the trans.

Is it possible to drop the pan, remove the head, and push the pistons out? Yes. Is it easy? No. And, it won't allow access to the rear main seal.

A noise from the bottom end *typically* leads to needing the crank reground. Removing the crank requires lifting the engine out of the chassis.

 

Good points, RW. Obviously I don't know much about 300's. Glad you chimed in.

 

Exactly what I needed to know.

If I can't fix the rear seal without pulling the motor or transmission then I may as well plan on pulling the engine.

There is a huge amount of room ( I love this truck ) to work around it and pull it out.

Since it is a 4 x 4, I think it will be actually easier pulling the engine than the transmission.

So now my question still remains .... I can't afford to "properly" rebuild this unit ( grind cranck, size rods, grind valves, replace guides, .....), at least right now ... maybe in a year or so when the house is done.

I know it will not be "right" but is it better to just though in a "fresh up" it ( new bearings, rings and seals ) or look for another engine?

If I find another engine ( I found one last night on Craig's list .... 1985, was running when pulled, $200 ), how can I tell if it will be any better than I one I have?

Thanks so much for all the advice!!!!!!!!!!!

Mike

 

Used engines can be risky, if you cannot hear them run. Case in point, I pulled out a 300 that run, but it has a serious rattle in the rod/piston meeting area. No smoke, and great oil pressure. Just made an awful lot of noise.......

However, if you can find one that someone is able to fire up and let you hear it run before buying, or comes with a written "money back" contract, you should be able to get a good one.

That said, it is quite possible to toss in a re-ring kit with bearings, and get another few years out of the current engine, so long as the crank isn't hurt.

 

Sorry Gary, didn't see your post.

I agree, best is to see it running ( unfortunately both I have found have already been pulled).

I have a portable air compressor and a "dead" compression tester.

I like the idea of checking the differential pressure.

I may try putting together a tester like you did.

Thanks again for all the advice !!!!!!!!!!

Mike

 

If you have to pull the engine I would at least flip it over and check the crank journals for scoring.

I don't know how long you want it to last but it seems you are short on time and money ATM.

If the bores aren't obviously scored and the crank looks okay with just some smearing I would polish and throw in a new set of bearings and an oil pump.

Forget about rings unless you have a set of bore gauges and know how to use them.
Ii just won't pay off and you likely need to bore/hone/new pistons & rings anyhow.

With the head off you can check for recession and do a solvent test.
If the seats are good you might just lap the valves in and be done.

Check the timing gears for slop and replace the seals and gaskets.
These engines are tough.
Keep it going until you can afford to really go through it or don't need it anymore.

jm2c

 

This was my thinking exactly ......

If I can't find an engine I "know" is good, and mine is still running, then a quick once over might keep me going for the next year or so.

By then I will have a shop up an with luck a little more money in my pockets.

I see kits with bearings, seals and such for about $120, like you said, a new oil pump, chain and gears and I would hope it would hold together for a while longer. Since I have it apart, I may even splurge for a clutch disk ( seems fine but if I have it all apart then it would be nice to put in now).

I have just started asking around to see if I can find a "back yard" mechanic or say a mechanic who wants to work at home on the side.

I figure with my help we could pull the engine one night, rebuild the next and one night to get it back in.

If he would be willing to say work for $100 a night and say $200 - $300 in parts then I would say $500 - $600 would keep me running for now.

I hate doing things "half way" but the timing is just bad.

Just FYI ..... my wife is paralyzed and needs care every 4 hours, thus she had never traveled. Just before we got married (I was living in SC and her in VT), I modified an old motor home (cut a new door, built two lifts, put in hospital beds, ....) so we could travel away from home and I could do her care on the road. We have now been living in it for almost two years while we build our house.

Here is a link to the project: http://mcsele.shutterfly.com/2299

It has a ford V10. My biggest problem so far on the engine has been broken exhaust studs! I machined a jig to fit of studs that were not broken and guide my drill straight. So far so good .... I have repaired about 5.

Thanks again ...... Mike

 

for $200 it is well worth the risk to put in your truck. by the sounds of it, yours is DONE.

You can run the "new" engine while you properly rebuild yours. Or just rebuild the "new" one before it goes in for a couple hundred and take NO RISK

 

Can't hurt to look.
That's what I meant when I said "if the bores and crank aren't scored".

Otherwise put the $200 engine in and cross your fingers.

BTW, your truck has no timing chain.
The Ford inline six series engines use gears only to drive the cam.

 

I concur 100%...

Yes, the 300 has gear to gear drive for the cam, it turns the opposite direction as the crank.
Many of these had a fiber tooth cam gear from the factory, to help keep it quiet. This is the only real weak link in the entire engine.
Changing cam gear usually requires pulling the cam, since the gear is a press-fit.

 

Another option is to buy a parts truck. I've seen a few running, driving 2wd F150's with 6-cylinders for pretty cheap. Not $200 cheap, but you could hear it run.

Also, if you have to pull the engine, since you're working on dirt a trick is to roll the truck back vs rolling the hoist.