4.0 ohv mild rebuild

[ckucia]

I picked up a 4.0 from a '94 Explorer over the weekend for a project.

My original intent was to grab the wiring harness and computer since it was a manual trans (and I have an M5od already).

But I had to take the intake off to get to the injector plugs. Once I did that, I figured I may as well take a look under the valve covers. When I pulled them, the valve train was in near pristine condition - no sludge or gunk, just light oil browning.

So I pulled the heads and found them to be in good condition with no cracks and no evidence of fouling, coolant or combustion problems.

I didn't have the tools to get the rest of it apart, so I took a chance and brought the whole thing home. Pulled the oil pan, and there's just a little bit of sludge in the bottom. The donor had around 115k as I recall. Perhaps the engine was rebuilt at some time or it was well taken car of.

I can still see the factory cross hatching on the bores.

So assuming the crank journals are in good shape, I think I can get by with a pretty basic rebuild - new gaskets, bearings, rings, water pump, stat, hoses and belts after a general cleanup.

I read the head bolts are single use, so I'll need to get a set of those.

I ordered a set of FSMs today.

Forgot to look at the rocker tips, but if they aren't worn are there specs in the manual for pushrod length? Any chance I can reuse the pushrods/rockers or should they be replaced as a matter of course?

I'm not really interested in boosting performance, but is there anything I should do to improve reliability on this engine while I have it apart?

 

[RobertFord]

The rods and rocker arms are supposedly prone to wearing out, but if the engine isn't ticking now, and there is no apparent play in the rocker arms/push rods, I would leave them alone. You can easily replace them later on should they develop a problem.

You might want to inspect the hydraulic valve lifters while you have the heads off, as you can not replace them without pulling the heads.

Sidenote: purely theoretical knowledge until now, but I'm about to do a head-replace myself and have been investigating thoroughly.

 

[ckucia]

I found some info that the lifters can be disassembled by popping the plastic cap off carefully. That seems prudent to do so they can be thoroughly solvent cleaned and inspected.

I found pushrods in varying lengths on Rockauto's site, so I assume those can be used in the event they're too short due to rocker wear.

I'm going to try to inspect the rockers tonight to see what condition they're in.

I managed to damage the cam sensor that goes where the distributor normally would be when I was removing it's plug. Had no idea how expensive those things are (yikes!) or I would have been more careful (not that I could really see it). Do those things tend to go bad? I could probably pick up a replacement at the pull-a-part for next to nothing. One of my valve covers is rusted through on the flange so I have to hunt for a better one anyway.

 

[Runnin'OnEmpty]

The fact you can still see the cylinder cross-hatching
indicates the engine has been taken care of, with
regular oil changes, etc.

Since you'll have the engine apart, I'd check the
cam synchro shaft. The upper bushing tends to
run dry of lube and start squeaking and eventually
seize, once the mileage builds. If you do decide to
pull it, it's a good idea to use the tool to reinstall.
(Reason is, the syncro hold-down bolt is inaccessable
with the plenum in place.) If the shaft is rough and
needs replacing, I'd also recommend a genuine Ford
part over the Dorman.

The FelPro Severe Duty headgaskets cost a little more,
but are well worth it. You already know to use new
headbolts.

Also check the flywheel or flexplate for cracking around
the bolt holes.

Good luck and have fun...

 

[ckucia]

Checked the rockers last night. Most showed a shiny spot where the valve stem seated, with just enough wear you could catch the edge with your fingernail.

But a couple were worn pretty badly - almost a dime-thick recession in the rocker tip. I suspect those are worn enough to have caused some ticking.


Pushrod cups looked OK to me, but without some sort of gauge, it's difficuilt to eyeball any wear.
It's going to be awhile before I get to work on the engine. I hadn't planned on getting it, so the workshop isn't really ready and I'm still tied up with some wintertime home remodelling.

 

[Jstcruz]

I took apart an ohv that had 200,000 on it and it still had a like new cross hatch pattern in the cylenders. I was happy anout that! what I wasnt happy about was that all of the lifters and cam was worn pretty bad. I dont remember if it was certain years in particular for the ohv but I read that they have poor oil flow to the upper valvetrain. would explain some of the rocker issues I think.

 

[ckucia]

I took apart an ohv that had 200,000 on it and it still had a like new cross hatch pattern in the cylenders. I was happy anout that! what I wasnt happy about was that all of the lifters and cam was worn pretty bad. I dont remember if it was certain years in particular for the ohv but I read that they have poor oil flow to the upper valvetrain. would explain some of the rocker issues I think.

Thanks for the heads up. I'll have to take a close look at the valvetrain. Unusual to see cam wear on roller lifters in my experience.

Has anyone come up with any solutions for the valvetrain oiling?

First thing that came to my mind was maybe some oil squirters plumbed into one of the pressure cavities and pointed at the rockers to keep them lubed up.

 

[Jstcruz]

what was worn were the sides of the lifters where they move in the block. Im not sure what can be done to improve that. Im sure someone has some ideas/info.

 

[ckucia]

Looking at a 1st gen Ranger this weekend as a potential vehicle for my 4.0. If it's as the seller described, I'm going to get it.

Also picked up a rocker and pushrod from a 2.9 V6. Thinking of going with that design rather than the 4.0 since it's adjustable, but I still have to do some measuring to be certain it's 100% compatible. It appears to me to be a better system, but I'm still researching the pros/cons.