So, about 8 months ago I fried the 4.0 in my 01 D2 when the front crank seal went and dumped all the oil out....not all, but enough to make the lifters tick. Pressure light never came on, but something happened in cylinder 8 that caused it to eat a ton of oil and constantly foul the plug. It ran fine besides the oil consumption which led to plug fouling, and smoking. I opened the thing up and couldn't find much other than a lot of carbon in that hole.

That's water under the bridge.

Now I'm gearing up to build an engine for the truck, hopefully before the snow starts to seriously fly in these parts. The rest of the garage is BMW stuff that can't handle a light dusting.

I have two 4.6s....one a short block, methinks a GEMs engine, but I'm not sure....one from a 03 that was "rebuilt" but wouldn't turn over. This "rebuild" consisted of headgaskets, etc, oil pump, water pump,....all those goodies. Come to find out the thing had spun a rod bearing on #6 (I didn't do the rebuild, but got it after the owner gave up and parted the truck, paid $0 for the engine) The rest of the bearings were worn, but the crank has some scoring on it that should be able to be taken out....but I don't plan on using that crank anyway.

My plan, keep in mind budget, hopefully stacks the odds in my favor enough to make this thing last a good while.

To start, the block. I've been bouncing back and forth on which block to use. I'm kind of leaning towards using the Thor 4.6 block. The next option being the 4.0 block from my truck, and lastly the older GEMS 4.6 block. My determination will rely on pressure testing them and making sure the vitals are in spec. I do not want to replace the liners. Time and $$ do not allow for it. Maybe later I'll get into having one of the spare blocks top-hatted, but now it not the time. After said pressure test, the selected block will have the liners pinned. Then I'll run a ball bearing hone through them and be done.

The above is my main concern. The rest is fairly straightforward.

The rotating assembly will be from the GEMS engine. New bearings all around, rings, etc. Cam and lifters as well.

Oil pump and heads will be used off of the Thor 4.6 since they were all replaced/refreshed and never ran.

Thoughts?

 

I'm in the middle of doing a full rebuild myself, and here are some of the key things I've learned:

- I've read somewhere (forget) by a guy who has done 100-1000s v8 rebuilds, and if the block is not top-hatted, he observed 50% failure rate on rebuilds.
- The problem is that a pressure tested block still may not reveal cracks behind the liner, since the block at room temp is not heated to allow for the crack behind the liner to be revealed. Need to pressure test with the block heated up, and put soapy water at the liner rims. I'm not even sure if this 100% reveals a problem if there is one
- were any piston heads steam cleaned? If so, top hats are a must.
- Slipped liners is not actually a problem on our engines. It was on the older LR blocks. With our blocks, they added a retainer at the bottom that prevents the liner from moving.
- I do not recommend pinning liners, either don't pin it, or top-hat it. It's the only method worth its beans
- Top hats can be had for about $600 from Turner + there is a black friday 10% off right now. Expect to pay a machinist another $1000 to install them - and only qualified experienced machinists who has done this before. OR simply ship the block off to Q&E in LA for $1500 all in. I know you said you don't want to tophat, but do you want to run the high risk of a failed rebuild?
- MEASURE everything. Get a dial bore guage, accurate micrometers, magnetic DTI, plastigauge.
Cylinder bore diameter, out of round, taper
Piston diameter
Piston to bore clearance
Ring gap x 3 rings x 8 cylinders clearance to bore
Crankshaft journal diameter, out of round x 9 journals
Crankshaft run out - very important, if failed, crank is trash
And more... all in the 4th edition of the overhaul manual

I would not do a rebuild without getting some machine work done: valve job, head warpage/resurfacing, block decked, new cam bearings fitted, oil galley & cam plug replaced, crank polish or regrind, bored/honed (if necessary). If you don't do this, all your really doing is cleaning and re-assembling the block. Any issues it may have are not really addressed.

My 2 cents. Probably not what you wanted to hear, but I've done an insane amount of research on our blocks before starting the rebuild, and those are my conclusions.

Buy all your engine parts (new bearings, rings, etc) from Turner in the UK. They have the best prices by far. Main, rod, and cam bearings are like $20 bucks each.