Hi. I have a 1997 chevy blazer with the 4.3 in it. We were thinking about changing the engine as my head gasket went and I can get a used engine cheaper then fixing mine. I was wondering if someone could tell me if a engine from a 1999 blazer its also a 4.3 would work in mine or where to go to find out if it will. If it would work would it be a straight swap? The 8th spot in both vins is a w if that matters. Thanks for reading

 

I've made that swap and iirc the only difference was the temp sensor which can be swapped out, no problem. Is it possible you have a bad lower intake gasket and not a head gasket? These engines are notorious for bad lower intake gaskets which cause symptoms similar to head gaskets.

 

How do you go about swapping the temp sensor out? We are not positive but was told head gasket. We are having rough idle getting code p300. Losing antifreeze without a visable leak. Overheating issues as well as white smoke out the exhaust and the check engine light on and flashing. We changed the plugs wires distributor cap rotor thermostat water pump and radiator

 

The temp sensor just unscrews from the head. You can just replace it with the one from the original engine. It sounds most likely to be head gasket in your case.

 

Thanks for responding. Do you have any tips on making the process easier? We've never done it before and are getting a manual.

 

4WD or 2WD? and yes the 1999 engine will work just fine in your 1997.

 

It is a 4wd so is the other one

 

Manual will probably be of little help, though. You should be aware that GM installed the engine before the body was put on the frame. Because of this on a 4WD (I have no experience with a 2WD) the bolts holding the transmission, a fuel line clamp on the back of the driver's side head, and the ground straps on the back of both heads are very difficult to remove with the engine in it's normal place. GM manual wants you to remove the driveshafts, transfer case, and transmission crossmember - then lower the back of the engine/trans assembly in order to get at the bolts and remove the tranmission. Most people reject doing all this extra work to get a few bolts out.

Removing/reinstalling the engine can be done with the transmission in place, but nothing is easy about it on a Blazer (and I have done many engines in a ton of different GM models). Biggest problem being the middle bolt on the drivers side of the transmission bell housing. There is not enough room for the bolt to come out of the hole - it just backs up against the firewall. Some people have taken the body mounting bolts out and jacked the body up for clearance (doubtful to be feasible on a rusty blazer). Others say that removing the engine mount on the driver's side (not easy with the engine in place) allows the engine to come down enough for the bolt removal. When I did mine, I cut a little 1.5" flap in my floor with a dremel cut off wheel behind the accelerator pedal and bent it back to access the bolt. To access the top two trans bolts, remove the distributor (plug the hole so nothing falls in), oil pressure sending unit, and the section of fuel line going into the top of the injection spider. Then use a combination wrench and a lot of patience to turn those top bolts out, sometimes 1/12 of a turn at a time. Plan on losing at least one wrench on top of the transmission when you drop it (seriously), so have an extra wrench ready. You can retrieve your lost wrench once the engine is out. The remaining trans bolts can be removed with a swivel socket and a long extension. The ground straps and fuel line clamp are best left until the engine is actually coming out. When the engine is disengaged from the trans and comes forward, then you have an extra inch to work on the back side of the engine and it make a BIG difference. Don't forget to remove that fuel line clamp on the back of the driver's head or you will ruin your fuel line - it clamps to both the engine and the transmission. Hopefully this explains the unusually tough stuff.

So here is how I would proceed to remove the engine from a 4WD (in this specific order): take lots of photos so you know where things go.
Disconnect battery and drain fluids
Remove hood.
Remove radiator, shroud, and serpentine belt. Be careful with clips holding trans and oil cooler lines into the radiator. Cover oil cooler lines so nothing gets inside.
Unbolt/remove water pump with the fan still mounted.
Remove alternator and then remove mounting bracket from engine
Remove P/S pump from bracket with hoses attached, and zip tie into the corner of where the radiator sits.
Remove A/C compressor from its bracket with hoses attached, then turn over and tie on top of the evaporator case.
Remove the A/C compressor bracket and the A.I.R pipes from the engine.
Unplug main wiring harness going across engine from the block on the drivers inner fender, and lay back on top of the A/C compressor.
Disconnect drivers side exhaust manifold from the exhaust pipe. Do not try to remove EGR tube from the exhaust manifold itself - it is not necessary
Remove the passenger side exhaust manifold completely (it will hit on evap case during engine removal, and when removed the starter has easy in/out access.)
Remove the starter and dont' forget to disconnect the transmission line clamp on the oil pan.
Working through the starter hole, remove the torque converter bolts.
Remove the bellhousing bolts using one of the methods described above.
Disconnect the motor mount through bolts.
Place floor jack under trans and jack up against trans tunnel (with wood to prevent bending pan).
Hoist engine upwards until engine mount ears disengage and then pull engine forward about an inch until oil pan hits front axle assembly.
Disconnect all ground straps and the fuel line clamp from the back of the heads.
Look engine over carefully and remove or disconnect any small things I have forgotten to mention that will prevent it from coming out.
Engine should now come straight up and out as long as the trans guide pins clear the transmission. If not you can loosen the front axle mounting so the engine will go forward a touch more. I did not have to on mine.

I would replace lower intake manifold gaskets on whatever engine will be going in. Good time to do it. Use the Felpro rubber/metal ones - not the plastic type. LIM gaskets is the failure these engines are known for, and it ends up ruining the engine bearings. Either wire brush the bolts until clean and apply new Teflon sealer, or replace the bolts. New bolt sets are available with the sealer already printed on them. Clean the threads for all LIM bolt holes using a tap and torque bolts with an INCH POUND torque wrench (inch pound not foot pound - go buy or borrow one, its important) in sequence - let sit overnight and go over one more time with the torque wrench in sequence.

Don't forget a crank sensor relearn will need to be done once new engine is installed and running. The crank sensor calibration in your PCM is for the old engine. The SES light will probably be on and flashing until you have that done.

Hope this helps.

 

That's a nice write-up by Lesmyer! As noted the upper bell housing bolts seem to be the most troublesome part of the job. I remove the upper and lower intake making all but the left corner bolt removable from the top with a wrench. The left corner bolt can be removed with a 14mm 6pt swivel socket (not a 14mm socket and a swivel, it will be too long) and the proper length of extensions.

 

Thanks for all the help and info it's greatly appreciated. I'll let you guys know how it goes. Thanks again.