After about 6 years of owning a 2002 Blazer I still knew little about the 4.3 V6 but that started to change after buying the 1998 Step-Side S10 with 524,000 actual miles then blowing it up the next day instead of just blowing it out.
From other posts here I knew they were interchangeable yet the junk yards were saying an 8th digit X needed to be replaced by a 96-98 X and that a W would not work but no one knew why. In fact the WWW info was all over the board on the subject.
Last night we picked up a 119K mile 1998 4.3 with the eighth digit VIN of W to replace our 1998 X and I could see they were physical differences when we got home. WHY, WHY, WHY was on my mind.
Found this on s10 forums.com:
*****1996 - 1998 VIN "X" WITH BALANCE SHAFT: The VIN "X" engine replaced the VIN "Z" in '96. It is identical to the '96 VIN "W" engine except for a milder cam and 10 less horsepower. The cam is a p/n 10241692.
1996 - 1998 VIN "W" WITH BALANCE SHAFT: The VIN "W" engine has a 10541691 camshaft and makes 10 more horsepower than the VIN "X" engine. There is also a special roller cam for the VIN "Z" turbocharged engines (p/n 10214714) along with a couple more with a fuel pump lobe for marine and industrial applications, but these are the common ones that were used in most of the cars and trucks. All of these cams can be identified by the last three digits of the part number that is stamped on the barrel of the cam, just behind the last lobe and in front of the distributor gear. *****
There are physical differences I can see but they seem to be application specific. Oil pan shape is different between either the X or W eighth digit VINs depending where it is 2WD or 4WD, exhaust manifolds are different between a 4.3 mated with manual or automatic transmissions I have been assured by the seller of our 'new' W. He has added a lot of 4.3 and Chevy V-8's to Jeep's and seemed to be knowledgeable.
I have noticed temperature sensor usage varies and I am guessing that may depend transmission type or maybe emission controls. Of course bell housings vary of physical reasons but from the best of that I can understand at this point the long blocks are physically identical except for the more mild cam in the X vs W eighth digit VIN difference.
The 1998 W is out of a 4WD automatic Blazer and is still setting in the rear of the Nissan pick-up covered with a silver tarp (really hate the look of the blue ones
). The 1998 X is still installed in the Step-Side long WB S10.
After the swap I expect I will find the simple understanding stated above will need to be made more complex after the swap is completed at some future date.