Thread: Need information on fitment of 95-96 4.3 Chevy engine

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I figure that there is someone on the forum that knows this. What is different between the 1995 and 1996 Chevrolet 4.3 V6 engines that they won't interchange?
My Nephew has a 94 Chevy truck with 4.3 and it has a problem, what I don't know. I found a 2008 4.3 V6 very cheap. I have been around Chevy engines all my life but haven't kept up on this particular issue. I am told that a 96 4.3 will not work on a 95 or older period. I don't understand this. If I take the intake and distributor from the 94 and put it on the later model it should work. I have been told by a dozen people that it won't work but no one can tell me why. I have been told that even a 1996 engine won't work in the 1994.
Any information will be most appreciated. I can make anything work in anything, but I don't want to get involved in something that is not worth the trouble of fooling with, especially if it is not mine. I will help him change the engine if it is pretty much plug and play.

Thanks, Ed

I thought the 4.3L went down with the Astro.. in any case. '96 would be a Vortec block, which I know 350 vortec heads are 64cc, so the pistons are diffrent than the earlier heads with 76cc. swapping heads would probably work, but it may not have as much power as it should

Let's see....where do we start? The Vortec motor is a roller cam motor with no fuel pump lobe....so you have an electric pump to deal with. The intake manifold bolt pattern is differerent.....you would have to go with an aftermarket manifold (assuming a carburetor). The old manifold will not bolt on. Depending upon what the new engine came out of, the pan may be different as may the flywheel ring gear with the converter bolt patern. The serpentine belt bracket bolt pattern is probably different since Vortec heads have a different pattern in the ends of the heads. The changeover can be done....it just is not a cheap bolt in deal. By the time you buy another intake, fuel pump, and whatever else, you've blown your "cheap engine" advantage.

Mike in Tucson

Mike is absolutely right, in 96 Chevy made major changes to the 4.3, parts from 95 back are mostly different. I ran into EXACTLY this problem with a boat I once owned. It was a 95 Chris Craft that I bought with a blown 4.3 in it. I found a low milage 96 4.3 engine and rebuilt it to install. When time came to put the accessories on it almost none of it fit, like the intake manifold. So I had to buy brand new 96 parts to make it complete, and they were not cheap because my 95 had a carb on it and all the 96 up engines I could find in the junkyard were injected. So I had to buy a special marine intake that was something like $ 500.00. As I remember there were also differences in some of the ways things mounted.

The engine ended up costing me a whole lot more than I planned on but I was over a barrel as I had already spend a bunch of money rebuilding it. I think Mike is right that your cheap engine might end up like mine did.

Don

My '93 has a Vortec CPI 4.3 in it, and my brothers '92 Jimmy had a Vortec CPI 4.3. In '94 they used the same CPI (center port injection) if it didn't have CPI it was TBI and not a Vortec 4.3. In '95 the went to MPI instead of CPI, a different intake setup.
I don't know what comes in boats, but my brothers boat has a 4.3 with a carb.

Pat

Yep, all the boat 4.3 engines I have seen use either a 2 barrel or 4 barrel carb. That was my problem, only boats used a carb in those years, and the 96 intake had a different bolt pattern than the 95 one I was replacing. Had to buy it from Volvo marine and it was $$$$$$$$$$$$.

Here is a little more info from Wikipedia on the 4.3 engines:

The Vortec 4300 is a 90° V6 truck engine, replacing the Chevrolet 250 in light trucks and 200 cu in (3.3 L) and 229 cu in (3.8 L) 90-degree V6s in passenger cars. The 4300 is based on the 350 cu in (5.7 L) Chevrolet small-block V8, and first appeared in 1985 with the throttle-body injected LB4 in passenger cars; light trucks and vans used Quadrajet carburetors for 1985. In 1991, the limited-edition GMC Syclone featured a 280 hp (210 kW) and 350 lb·ft (475 N·m) turbocharged and intercooled LB4 with the first use of multi-point fuel injection on a Vortec V6. The central-port injected L35 (Vin 'W') debuted in 1992; the cylinder block was slightly changed, a balance shaft was added to remove minor vibrations, and better breathing yielded 200 horsepower (150 kW). Another CPI engine, the LF6, joined in 1996 with the introduction of Vortec cylinder heads, while the LB4 was retired after 1998. In 2002, GM introduced a new multi-point injected LU3 engine, and a LG3 variant appeared soon after. This engine's origins date back to 1955, when the original Chevy small-block V-8 was introduced.

All Vortec 4300s use a cast iron block and heads and 4 in (101.60 mm) bore and 3.48 in (88.39 mm) stroke, both of which are the same as a 350, which gives them a displacement of 262.39 cubic inches (4,299.8 cc). Connecting rods still measure 5.7 in (144.78 mm) although the rod journal diameter is 2.25 in (57.15 mm). 1992 and later cylinder blocks used a different timing cover since these engines used a balance shaft (some 1992 production cylinder blocks for the LB4 with TBI induction used the 'traditional' front timing chain cover from the small block Chevrolet). This change created a situation where most after market timing chain alternatives do not fit. This is true of gear drives and double roller chains. They are OHV engines with two valves per cylinder and are produced in Tonawanda, New York and Romulus, Michigan. Power output of the new LU3/LG3 engines is 180 hp (130 kW) to 200 hp (150 kW) and 245 lb·ft (332 N·m) to 260 lb·ft (353 N·m).



Don

This is not what I was talking about. My Nephew has a 1994 Chevy full size pick-up. It has about 130,000 miles, which is really not that much by todays standards. He was told that it had burned valves. I really don't know how the mechanic determined this because he didn't do a compression check, he just pulled the spark plugs and looked at them. He wants $1100 for a valve job.
I found a complete 2008 4.3 V6 with less then 10,000 miles coupled with the transmission. Both engines are fuel injected. I considered getting the 08 engine and putting it in his truck.
After extensive checking, I found that it could be installed in in as old as as 1996 by drilling the crankshaft position sensor hole beside the distributor and tapping it out to 1/4" pipe threads for the older CPS. This no biggie. I have been told that it will not work on vehicles 1995 and older, no matter what because everything was different. What is so different that it won't work?. The engine mounts are the same and the transmission bolt pattern is the same. The flywheel is different but that can be changed.
People tell me that it won't work and they won't even talk about it. At the worst case, I figured that I could take the intake manifold and distributor from the 94 and install it on the newer engine. I was first looking at a 1998 engine and get the same story about it not working.
This does not make sense to me. If something will bolt up it can be made to work. On the 98 engine I was going to get the complete engine, harness and computer but was still told that it would not work. My idea about the 08 engine is that since the 98 would work as far back as 96, what is so different that it will not work with the 1994? When you ask why it won't work people act like you just asked them about VooDoo.
I am considering finding a 305 or 350 and putting it in place of the 4.3. The 4.3 was a decent engine but in a full size truck I would prefer a V8. I just want to know what is so special from 1995 to 1996 that the engines won't work? When I talk to sellers with the later model engine they clam up and say that it won't work and refuse to talk about it anymore. If I try to install a 96 or later engine in the 94 truck is a gremlin suddenly going to appear and eat me or something?

OBD I on 94 and earlier engines and OBDII on later than 1995 with 1995 being a transitional yr using parts from that yr only.Speedo controls are different.The wire harness's are completely different and no plug and play even with engine harness.Can you over come these things???.Sure,but you said you didn't want to get that involved.

About 10 years ago I could have quoted chapter and verse to you about all the differences because I was knee deep in that same swap myself, but today I just can't remember everything I had to do to make it work. I do know that I was painted into a corner because I rebuilt the new motor before I realized so much was different about it, so I had to continue on. In the end I had a whole lot more money in it than if I would have simply gotten the same year engine to start with, not to mention weeks and weeks of poring over parts books to find parts to make it work.

You are right that the bell housing and motor mounts are the same, and being hot rodders we have this optimism that if it is mechanical we can MAKE it work. What you are not seeing is that Chevy developed groupings of 4.3 engines and all they shared in common was the displacement. They changed the heads, internals (balance shaft vs non balance shaft) pulleys, pan shape, timing cover, damper, flexplate, etc, etc. There are so many differences that it becomes expensive to try to make a newer one fit where an old one once lived. I understand only too well what you are saying about "it doesn't make sense" because I was saying those same words when I was trying to salvage my boat engine swap back then.

You would be far better off buying a rebuilt long block 94 engine, or rebuilding yours than trying this swap. I think your quote of $ 1100.00 for the valve job is nuts. We had lots of these heads (and 350's too) redone and the bill never was higher than $ 500.00, and that included ss valves. Plus, if you do get this engine down in there you will have to contend with two different computerized systems, and we all know how much fun that can be. Finally, we are talking about a 1994 pickup with 130 K on the clock. With all due respect, it isn't worth the amount of money you are going to lay out to make this thing work.

Just trying to save your sanity bud.

Don

set of rebuilt heads shouldn't bee too expensive.. rockauto lists heads at $329 each w/o core and $269 each with core

+ a 2008 engine would be a marine engine ( possible reverse rotation ) as the last vehicle to use the 4.3L was the 2005 Chevy astro

I will be the first to admit that I haven't been too much into the 4.3 engine. I have had a couple in boats that have unexplained vibration that I wasn't crazy about. I later found out why.
Personally, I would not put $1100 in a valve job on a 4.3. I am just looking for alternatives for my nephew. I could pull the heads and do the valve job for him since I am a Journeyman Machinist. I even have most of old school equipment to do it with, but I am not looking for any work to do.
It is one thing to do something for yourself, especially when you need it. His truck would be easier to drop a small block V8 in than fool with the 4.3 but he is unsure what he wants to do. I ran across a really good deal on 2008 4.3 and was told about the impossibility of exchange into a 94. This just didn't ring a bell with me
I will wind up either rebuilding his 4.3 or dropping the small block in it's place to help him out. I can grind his valves, seats and resurface his heads for a little of nothing other than the trouble of doing it and the price of the gaskets providing they are not cracked. I think $1100 is way too much for the valve job anyway.
I have had three open heart surgeries, three heart attacks and two small strokes. Like I said, I am not looking for too much work right now. My main reason for asking about the 2008 4.3 was that I could find a use for the 4l60E that was attached and split the cost with him. I have found that the 4.3 doesn't really get much better, if any, mileage than a small V8 because they have to work harder to keep up. I am thinking that it would be just about as easy to install a 5.3 and better mileage too. 21 MPG in a 4X4 pick up truck. I haven't seen a 4.3 that will do that. Same transmission bolt pattern, different mounts but that is no problem.
I have found that in my case, it is easier to do something when you are interested than when you have to and not interested. Know what I mean?
Heck, I told him of another truck that I could get for $1000 that was 4X4 extended cab with a bad fuel pump. He is still thinking about it. Not too much to think about in my opinion, but it is his decision. It is a lot more fun to build a street rod anyway.
Thanks to all for the information. It is much appreciated.

Hope you are doing well with the health issues. I've had a couple of each one of those too (heart attack and strokes) so know how you feel.

I also understand what you mean about not wanting to immerse yourself in another persons project. There have been times when I have tried to help someone out by doing some mechanical job for them and most times they end up becoming a nightmare and biting you in the end. On your own projects you can accept that problems and additional expenses arise, but that isn't always the case when you are spending another persons money. Both of you end up wondering why you ever got into that mess in the first place.

The other thing Ed, no one is 100% sure what is going on with that engine. The mechanic simply looked at the plugs and proclaimed bad heads. I would do a proper compression check and leakdown test. It could be something much more simple and different. You are also right about the 4.3 not being a gas sipper. The marina I once worked at sold new boats, some with 4.3's in them and customers were always complaining they should have spent a few bucks more for the V8 as theirs wasn't as good on gas as they thought it might be.

Good luck with whatever decision you make.

Don

Hi Itoldyouso,

Looks as though we are in the same boat, or at least in the same lake. Sometimes it feels like a whirlpool. I questioned him about how the mechanic knew the heads needed a valve job just by looking at the plugs. He must be a lot better than I am. I have worked at 4 different GM dealerships before I became a Journeyman Machinist.
My Nephew is a good kid and I want to help him save some money. He is self employed in home construction and needs his truck. Like I said, I would prefer to replace the engine with a 305 or 350 of similar vintage. Most of the wiring will hook up with a few changes and the exhaust. Being self employed money counts so I can see why he needs to try and do it his self.
Not necessarily in this case, but most of the time when I try to help someone out I wind up doing all the work, they are gone and I am still wondering how I will get my own stuff done. Seems it is vastly one-sided.
The 4.3 is a good engine but it stands to reason when it has to work so hard and require more throttle to keep up that sometimes the larger engine is a better choice.

Hurst... STOP !!!! It might not need a Valve job... I was a GM line tech in the 80's-90's and 00's. The 94 engine used a Linear EGR valve that gave us a fit. Sometimes the valve itself would be bad, OR a hunk of carbon would get hung up in it and stick it open. Now, it gives the syptoms of a fried valve. So, pull off the EGR, check it for chunks of carbon stuck in the printle valve. If nothing there, then get the valve checked. Also, if there is a hunk of carbon in it, pick it out, then cap the hole going to the intake side and start it up with the valve off, this will blow any other loose carbon out. then reinstall valve. It would also explain the sooted up spark plugs. It can cause, low power, bad or no idling, excessive black tailpipe smoke, and a miss. The problem was so bad, a service bulletin was issued to address it;

( I stole this off another site )
Repeat failure
Repeat failure is a common problem. You can recommend a top engine clean to the customer and attempt to clean loose carbon from the upper intake. GM has noted the problem and come up with a software update for the PCM. Essentially, what the update does is periodically command the EGR to 100 percent opening to prevent or flush out carbon chunks. The new prom numbers were in a "special policy" procedure bulletin and not a regular TSB. The special policy number is 96067(A). It refers to '92-'94 S/T, M/L and C trucks with the 4.3 V6 engine and linear EGR valve. The bulletin number is 67-65-38. It refers to '95 C, S/T and M/L trucks with the 4.3 V6 engine and linear EGR valve.

Weasel Diesel,

Thanks for the information. I have not seen the truck for almost a year. I was planning to have a look at it later this week. I would not have just yanked it apart without checking it though. No way I would take someone's word for something like that, too much work. If I pull it apart it is because it needed it.
I was unaware of the bulletin that GM had put out on the 4.3. It has been several years since I worked for GM. It was far enough back that we were not called Techs. I certainly appreciate you taking the time and trouble to post this information, it will give me a heads up and I will check it first thing.
I have always found this to be a pretty decent site to find information.