I have a bunch of parts. This includes a complete 1999 4wd Blazer, most of the parts from a 1998 2wd Blazer, and my daily driver truck-a 2001 GMC Jimmy 2wd. The motor is seized in the Jimmy, and I will be using the engine from the 99 Blazer. I have some questions though. I am going to do the gaskets while the engine is out (probably not the head gaskets, even though I have them and the new head bolts). Supposedly, the engine in the 99 was rebuilt 60k miles ago, but the previous owner had no paperwork on it. I really don't think I will do any performance upgrades, and I don't do any off-roading. I may occasionally tow with it though. I just want a reliable daily driver.

1. Should I put the stock roller rockers from the 01 engine in the 99 motor (that I assume has the stamped rockers)?

I noticed the timing chain in the 98 was a lot beefier (I think they are called a Quiet chain-it has been a while since I looked at it, but it is a double roller chain if I remember correctly).
2. Should I put the bigger chain from the 98 on the 99 motor if it doesn't already have it?

3. Can I ditch the AIR pipes coming off the exhaust manifolds, the air valve, and the extra vacuum lines on the 2001 Jimmy without messing with the PCM? It is not that I have performance issues or anything with it. It has just gotten in my way a couple of times, and I don't want to work around it if I can avoid it.
Thanks in advance!

 

1. NO
2. NO
3. NO - all original things from the 2001 will need to be there and working or the PCM will not be happy. If they are different, then transfer them to the new engine. If they won't transfer, then you have a problem.

As far as I know the only problem with 99 into 2001 would be the mounting for the knock sensor in the block may (will probably) be different. Also I believe certain threads in the block were already changed to metric by 1999 (ie starter, etc). Someone else may be able to coment on this better than I.

You do know that you will need to replace the timing cover, now that you have removed it? Also you will definitely need to do a crank sensor relearn after installing any new engine or the SES light will certainly be on.

Don't forget to replace the radiator (oil cooler) to ensure metal particles that have been circulating in the oil do not damage the new engine (if your 2WD has an oil cooler built into the radiator).

Oil pan might be different for the 4WD engine you are installing. Check it out.

Not sure why you need any parts from a 1998? worries me.

 

I have worked on several 4.3s, so they aren't new to me. Every 4.3 is pretty much the same from 1996 on up. As long as it is an OBD-II system, there are no issues with swapping stuff from year to year. The 4wd oil pan is different. I will be using the 2wd oil pan and oil filter adapter (the 4wd Blazers have a remote oil filter mount). I know all the threads are the same, as well as the knock sensors, etc. I already have the new timing cover, and will definitely flush out the coolers and lines. The crank sensor relearn is not always necessary. For example, when I changed the head gaskets on the 01, I had a starting issue. Turned out that the balancer was shot, so the timing marks were not correct. The outer ring on the balancer had spun around 120 degrees. When I had that off, I checked my timing chain. When i put it all back together, I didn't have ANY codes, including anything indicating a crank sensor issue. I know that sometimes the crank sensor relearn is necessary, but it is not a definite. My questions were more geared to making the strongest set up I could with what I have available. I know roller rockers and double roller timing chains are usually better, but I was curious if it is even worth my time to swap them over while I have the engine out. Thanks for the reply though.

 

That's correct, but there are certain conditions when it is necessary.


The crankshaft position sensor creates a unique magnetic field that is precisely focused in the "general vicinity" of the tone ring on the crankshaft. When the tone ring passes through the magnetic field, the sensor sends a pulse to the PCM. The pulse is mainly used for ignition timing and injector timing, but it is also used along with other data, for detecting and identifying cylinder misfire. When the engine is originally installed in the vehicle at the factory, the crankshaft position sensor relearn is performed to "tell" the PCM precisely where the magnetic field is focused, in relation to the position of the crankshaft, hence the name "crankshaft position sensor". The relearn data is burned to a file in the PCM where it remains until the next relearn overwrites it. If the timing cover, and or crankshaft position sensor is moved, removed, replaced, or disturbed in any way, the relearn MUST be performed because the "focus area" changed. Also needs to be done if the PCM is replaced. If the relearn is not performed, no bells or whistles will go off, the check engine light will not come on, and no DTC's will be set in memory. The engine will still start and run, but, ignition timing, injector timing, and cylinder misfire will all be incorrect, guaranteed. Why? Because the PCM is using incorrect relearn data.


Along this same line, if the distributor hold down bolt is loosened, or the distributor, or camshaft position sensor are removed or replaced, camshaft retard must be checked, and adjusted if necessary. It's part of the job, just like adjusting ignition timing on older engines was.


Both of these procedures must be done using a capable scan tool. The el cheapo $500 jobbies at the auto parts store are not capable of either procedure.

 

The auto parts stores near me use a $100 scanner lol. I use ScanXL Pro, and it does read the cam retard data. Also, a P1345 DTC will set. It is not guaranteed that a relearn will be necessary (for example, mine did not need it-it was dead on). If you Google it a bit, there are others that have replaced crank sensors and/or distributors, and did not need to do a relearn. Even the FSM says to check it first. If it is within specs, no adjustment is necessary. Look, I appreciate the opinions, but no one has really answered my questions. Why wouldn't I want the quiet chain? Why wouldn't I want the roller rockers? What happens if I use the 1998 exhaust manifolds to get rid of the AIR system valve? What code will be set? If anyone knows the answer to these questions, please give me your opinions. Thanks!

 

If you know so much about the 4.3's and OBD2, I'm not really sure why you are coming on here as a newbie, asking us those questions, and demanding only those answers.

There is nothing strong about any of these 4.3's.

1996-1998 takes a GM 12491865 Goodwrench engine L35
1999-2000 takes a GM 12491867 Goodwrench engine L35
2001-2002 takes a GM 12491869 Goodwrench engine LU3 is only one available.

Anyone wanting to interchange engine and parts between these may want to determine the actual differences between these three different engines.

2001 was a year when knock sensor could be 1-wire or could be a two wire. Mounting boss for the different sensors on the block are different. There is a work around, but first you have to realize there is a difference.

What exactly makes you think that you can use the data stored in your PCM for a completely different engine and crank sensor? When your light comes on with a P030x after install, you can do the crank sensor relearn then. ScanXLPro isn't going to do it. Your local Autozone isn't going to do it. I have ScanXLPro and it is the one OBD2 software that I regret buying. Car Gauge Pro does the same for $8 on my Android phone. I use HP Tuners when I need to do a crank relearn.

Best timing gear setup is the single row with tensioner (not original). Gets rid of the timing chain noise in TSB. Never heard of a double row timing chain when a balance shaft is used - no room when the balance shaft gear is there. Melling sells the entire set if the GM is too pricey for you. Used from another engine would be a joke.

Best used rockers for your engine are the ones that are already worn for the pushrods and valves in the engine you intend to use.

I'm done wasting my time on this thread.

 

P1345 is set if/when the distributor gear is off at least one tooth in either direction. If the code is not in memory, it means that the distributor gear is timed correctly with the camshaft gear. It also means camshaft retard is within ~13 degrees, and no DTC will be set for that, (spec is zero degrees, plus or minus 2 degrees). If it's out of spec, it requires an adjustment to the distributor, (it is not a relearn).


Sounds like there might be a little confusion between a crankshaft position sensor relearn, and adjusting camshaft retard. As mentioned, if the crank sensor is disturbed, a relearn is required, (if you want the engine to run correctly). The only way to know if the relearn data is correct, is to perform the relearn. If the distributor or camshaft position sensor are disturbed, camshaft retard needs to be checked, and adjusted if necessary, (it's not a relearn). As for Google searches about others that did not need to do the relearn: It's not that they didn't need it, they don't understand the importance of it, and chose not to do it, for one reason or another. Their loss


If you use 1998 exhaust manifolds on a 1999 through 2002 with secondary air: #1 It's a violation of federal law. #2 The service engine soon light will be illuminated constantly, and P0410 will set in memory, and most likely a few other DTC's as well.