Renix long block Vs HO long block

I have a 1990 4.0 Renix long block that is a low milage block. I drive a 1993 HO with 258,000 miles on it and it smokes like crazy. I want to build this Renix block and install it in the cherokee with my HO head. The only difference between the two long blocks that I can see is there are 2 sensors on the driver side near the motor mount. I checked RockAuto.com and all the parts from the camshaft down to the gaskets are the same part numbers (head excluded). Is this a doable thing?

Have you considering just replacing the valve stem seals first, or doing a compression test first? You may just need some cheap easy to swap valve seals.

Desertdave35 said:

I have a 1990 4.0 Renix long block that is a low milage block. I drive a 1993 HO with 258,000 miles on it and it smokes like crazy. I want to build this Renix block and install it in the cherokee with my HO head. The only difference between the two long blocks that I can see is there are 2 sensors on the driver side near the motor mount. I checked RockAuto.com and all the parts from the camshaft down to the gaskets are the same part numbers (head excluded). Is this a doable thing?

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Very doable. But, valve stem seals are way more common of a problem than rings on these 4.0s.

Ecomike said:

Have you considering just replacing the valve stem seals first, or doing a compression test first? You may just need some cheap easy to swap valve seals.

Click to expand...

I still wnat to be able to drive this one while I rebuild the other one.

Valve stem seals are an afternoon project, so is a compression test.

LOL, I spent most of the afternoon cleaning and swapping the valve cover gasket while I had it off to do the 4 valve seals that were bad, and about 30 minutes swapping the 4 valve seals, on the leak that were leaking like crazy and fouling the #1 and #2 spark plugs before I could empty a gas tank.. (my first time, I spent half that 30 minute time shoving rope into the spark plug hole to hold the valves up, compressed air would have been faster)

Summary, it is far easier and faster to do than I ever suspected.