Choosing Bottom End Bearings and Rings

[Pollarican]

Hey guys,

Ordering some of the last few parts I need for my full 4.0 Overhaul - Last three things I really need are:

- Main Bearings
- Connecting Rod Bearings
- Piston Rings

After inspection and measuring, the crank journals and cylinder bores are all still within OE spec - the engine had 135,000 on it. Going to be ordering OE sized Main and Connecting Rod Bearings, as well as OE bore Piston Rings. Block will get a hone before hand.

Some Questions:

First question, as far as fittament, It seems all "Standard" fit connecting rod bearings are .002" oversize - Is this common practice?

Second, Is there any real difference between a "Moly" material vs. a standard steel for piston rings? Should I be looking towards Summit for a premium quality supplier for piston Rings?

Lastly, Is Sealed Power the brand I should go with? It seems DNJ offers a these bearings at a cheaper cost - but I am skeptical.

These parts are all going in a fully overhauled 1991 4.0, with SI valves, 410 cam, new 93tm heads, smithbros pushrods, new lifters/springs etc. The truck will be a daily driver seeing some somewhat regular, mostly hillclimbing/trailriding offroad use. The goal of the build is a good all around off/on road motor that can pull a decent weight trailer if need be, yet have bulletproof reliability and better mpg than stock.

 

[renesisx]

I would love the answers to the above questions too.

Seems like there is a big overlap between what you are doing and what I want to do.

I want to rebuild my 4.0 for maximum reliability and longevity, so I'm very interested in recommendations for parts for the rebuild.

 

[Pollarican]

A little Update:

Briefly spoke with my machinist. His input on everything was:

1) Crank connecting rod journals were all within spec with no sign of wear. Recommended going with standard sized connecting rod bearings, not the .002" oversized. I was reading about plastigauge and possibly test fitting old bearings but he still has my block, and I trust his input.

2) As far as rings, he recommended Moly. Through some of my own research, these seem to be a little more resistant to wear, and between what I've read and he said, I'm going to spend the extra $30 or so on a Moly set.

3) Researching branding, It seems most of the mainstream engine rebuilders (Jasper, etc.) favor Clevite bearings. I'm going to go with these, since they are only marginally more money and seem to have the best reputation among the aftermarket crowd.

Hope this helps whoever shared the same questions I had. We'll see how they all work out installed in the end!