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.

 

The thought I just read was as a general thing X was used in 2WD and W engines with the beefed up cam +10 HP increase over the X line was used in 4WD or AWD's.

Could some post your drive train and eighth digit VIN to see if there this thought seems to have validity. I can see the logic in that 4WD/AWD is a drag on HP.

 

Mine is 4x4 W, but it's a 95 so it probably doesn't count.

 

The Vin X was only in the 2wd S10. All 96+ Blazers were Vin W.

As far as swapping them, swap away. They were nearly identical and the PCM will not really know the difference.

 

swartlkk I have yet to see much difference between the 4.3 1998 X and W engines. The X does not have the temp sensor on the front of the intake manifold like the W but the 'new' W was out of 1998 4WD automatic Blazer where the X was out of a 1998 S10 2WD.

Good news is that the 'new' used 4.3 engine was very clean when we pulled off the valve covers and the oil pan. As a reminder it was out of a 1998 4WD Blazer automatic with ONLY 119K miles.

However on removing the intake manifold it revealed the intake manifold gasket had not been replaced yet and was nearing the point it was going to start to leak.

We got the old 524K mile engine out of it today and when we pulled the manifold on it the gaskets looked new yet they had about 200K miles on them since they were replaced.

OEM intake gaskets are weak and replacement gaskets are strong is my take from today.

It turned out the oil pans were the same on the 2WD S10 and 4WD Blazer in 1998 in our case so we did not have to touch the oil pump/pick-up. Also throwing a rod through the oil plan did not cause any grief since we did not need the pan from the blown engine.

While doing the job I decided to upgrade to multi-port injector system.

http://www.ebay.com/itm/Delphi-FJ105...sories&vxp=mtr

We ordered ours yesterday from Amazon for $182 and it arrived today. Also order Scan Gauge II yesterday and it came today ($122).

I will not know if the MFI injection system will be a improvement or not since I have never ran this engine before but for $182 I feel better having the 14 year old SCPI injector spider converted to a 2012 MFI system.

 

Another difference is the "X" engine has the injectors at the intake ports and no poppet valves. The 96 & newer "W" engine also has 6 injectors, but they're in a centrally located housing with lines to each intake port and a poppet valve in each one. The injector you got from Amazon is a nice improvement. Make sure you use the Felpro intake gasket set MS98002T and follow the instructions that come with it. Cleaning and sealing the threads is a must, along with proper torque and tightening sequence. If the intake bolts are over torqued it can, and usually does, tweek the block and bind the crankshaft..... not somewhere you want to go

 

Thanks. I will look at the spider the 1998 4.3 X VIN today and note any spider differences.

Our heads and block are cast and while the intake manifold gaskets may not seal well and last a long long time it am certain there is no way to 'tweek the block and bind the crankshaft' with the intake manifold gasket installation.

I do know after 14 years/119,000 miles the OEM intake gaskets were right at the point of failure where the long since replaced ones on the 524K 1998 engine still looked like new. The OEM intake gaskets looked more like wet cardboard.

Now I think the 524K mile 1998 engine was switched back to the old green antifreeze from the Dexcool which the engine was not initally designed to use when it got new intake gaskets long ago. That may be part of the reason even with more miles on the replaced manifold gaskets than the OEM gaskets in the 1998 119K mile engine they still look like new.

Keeping Dexcool out of GM products that do NOT have a pressurized coolant overflow tank seems to be critical to this generation of GM coolant systems.

Today we are going to be working in the gease pit so our 'new' engine so it will not be installed into a grease pit. :B After 14 years/524K miles an engine bay can get nasty for sure. We are going back with new Power Steering and Oil cooling lines to help reduce future leaking and all new engine gaskets other than the head gaskets.

 

Straight out of the GM factory shop manual:

 

I will look that up today and see if I can grasp how that can be. The bore alignment thing is a new twist on my mind.

For others jCaptain Hook's graphic can be found on page 6-559 of volume TWO of the 2002 GM shop manuals.

 

After getting the old engine and transmission out we got the used 119K engine stripped down to a long block, cleaned well and started back together with it using FelPro Problem Solver gasket set.

We have not found any physical differences so far between the old 524K 1998 4.3 5-speed 2WD eighth digit VIN X engine and the 119K mile 1998 4WD with an eighth VIN digit of X. Hope to get it installed and running by the weekend.