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

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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?

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