LONG ASS POST WARNING!!!! You've been warned...
I see things that you should add and probably some that you should remove, or atleast change. I'll start with the Adds:
Camshaft: Now would be the time. That said the Explorer cam isn't a bad option for a 4wd truck. Being a roller motor stock cam and lifters should still be in great condition.
Valve springs: Stock valve springs weren't good enough for the stock cam when new, with almost 250K they are worn out. You are already pulling them to do valve stem seals, so now is the time to replace them. Check out Alex's Parts, good prices on good drop-in valve spring kits. Pick one for the GT40P and what ever lift cam you decide to use. I was recommended
P/N: Vsk7D49-M for stock Explorer cam with 1.6 (stock) or 1.7 rocker arms.
Valve Train: As I said previously it's a roller motor so cam and lifters should be fine. That said the pushrods and rockers are known to wear. Check them out and replace if necessary. If replacement needed look into the benefits of roller rockers, but they probably aren't worth it if you don't need them.
Now for the removals:
All those gaskets: As far as you are going into the engine, just get an engine rebuild set and replace them all. It'll include all those gaskets you list, valve stem seals, both main seals, and more gaskets you don't realize you need yet. Probably be about the same price too.
Tensioner, idler pulleys, oxygen sensors: If it ain't broke don't fix it, that said you may now something about these that I don't. I'd even include the water pump in that if it looks to be in good shape when you pull it off.
Main bearings: You need to open and inspect the crank before even thinking about ordering bearings. More on this below the following lists
So based on your list my lists would be...
Refresh:
- Engine Gasket Set
- New Oil Pump
- Timing Set
- Thermostat, water pump, and new hoses
- Serpentine belt
- PCV Valve
- Plugs and plug wires
- New Valve Springs
Rebuild:
- Engine Rebuild Kit $279.79 (usually includes * items below)
- Main bearings
- Rod Bearings
- Piston Rings
- Gasket Set
- Freeze Plugs
- Camshaft Bearings
- Timing Set
- Pistons w/Pins
- Oil Pump
---OR---
- Rering kit $120.79 (Better option if don't need pistons)
- Main bearings
- Rod Bearings
- Piston Rings
- Gasket Set
- and (not included)
- Freeze Plug Set $4.31 (if needed)
- Timing Set $17.10
- Cam Bearings $13.70 (if needed)
- Pistons w/pins $175.12 (if needed)
- Oil Pump $28.79
Prices grabbed from Rock Auto.
Plus the following with either kit:
- Thermostat, water pump, and new hoses
- Serpentine belt
- PCV Valve
- Plugs and plug wires
- New Valve Springs
Explanation on main bearings:
Let me start this by saying that I don't know your background working on engines, or the history of this engine. As such I mean no insult by any of what follows. It's time to make a decision. Are you willing to do a full on rebuild of the bottom end, machine work and all. If not willing to do a full rebuild, just refresh the bottom end and carry on, but know that it's a 250K mile engine with new seals. If you are willing, read on...
Personally I wouldn't install main and rod bearings on this engine without also doing new piston rings. With that many miles worn rings are likely to be a bigger problem than any bearings, so that's where I'd start. None of this stuff can really be ordered until you get the engine apart and see what it needs.
First thing I would do is a compression check followed by pulling the heads and visually inspecting the cylinders. Not only will the compression test tell you a lot about condition of the engine it'll let you know if your heads need some attention as well. If you get good results you may not want to touch the bottom end.
More on compression testing here.
Upon pulling the heads, you may even be surprised and find that there is still factory crosshatching visible in the cylinder, I've personally seen it on 180K and 200K mile Ford engines that got regular maintenance. If cylinder walls look good and you don't have a ring ridge, you may be able to hone and install new standard size rings. If they are rough, no cross hatching is visible, deep scratching, scoring or a ring ridge the block probably needs machined for overbore to smooth out the walls because the new rings won't be able to seat properly. At that point if you are carrying it to the machinist, might as well have him check you the crank and rods as well.
After cylinders I'd flip the block over and inspect the crank. No signs of wear on the crank journals then you can probably use standard size main and rod bearings. Any signs of wear and you need to have it checked/machined to determine what oversize you need, or slap it back together exactly like it was and hope you didn't mess anything up. Like I said I'd start with the cylinders because if they are bad you know you will need machine work. If they cylinders are good and crank is bad you can either have crank machined or order a crank kit, which is a reman crank including crank and rod bearings. Looking at Rockauto a crank kit is about $170.
Honestly if you are willing to go that far, your best option would be to pull the engine apart and just have the machinist inspect the block and rotating assembly regardless. Costs a little more, but you'll know what your installing is going to have the best chance of lasting. I'd still do the compression check before tearing it apart to see if the valves need some attention as well. You could also have the block (heads too?) hot tanked while it's there to remove any build up in water jackets and have a nice clean engine to reassemble.
Now I said all that, but I'm installing a 180K mile engine into my 86 without doing more than swapping the oil pan and removing the valve covers. It ran good, had good oil pressure and didn't smoke when pulled from the Explorer. I'm swapping springs and installing 1.7 Rockers (street truck and want a little more from cam) so I'm installing new stem seals while removed. Otherwise the long block is being installed as is. I do know that I will be building a performance motor in a few years to replace it, so I don't much mind if it does die on me.
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