fidelity101 wrote: anyone have a gen IV 6L repair manual? I can only find gen 3. I have a feeling that I actually don't have an LQ4 but an LY6 but I have never seen any displacement on demand or VVT things associated with it...
Check your RPO sticker. Should be in the glove box. In this case you'll literally be looking for LQ4 or LY6.
camaroz1985 wrote: The pictures aren't working for me either, just the RX7....
Interesting. Same here but only on the tablet (Apple). They all come through fine on the laptop (Windows).
In reply to Chadeux:
gotta love GM for that then - looks like I have an LY6.
And if anyone was wondering, yes - I welded a grill to a harbor freight hitch basket.
You can also look at the Gen VI L21 engine. Slightly shorter stroke than the Gen VII engine, but with forged internals ready for a blower... 
L21 Applications:
1998–2001 Chevrolet Kodiak/GMC TopKick/Isuzu H-Series 4500 5500 1998–2001 Kodiak/Topkick 1998–2001 P12 HD Motorhome Chassis. The Workhorse W-20 is a clone of the P12 Chassis.
Nessumsar wrote: You can also look at the Gen VI L21 engine. Slightly shorter stroke than the Gen VII engine, but with forged internals ready for a blower...
not without a cam swap, its a different firing order. plus I'm still stuck spending 500 on a timing cover kit...
next big issue is figuring out if the sensors are "different" are their values the same? it may just be a simple connector change for some of the sensors and everything will operate smoothly.
In reply to fidelity101:
I've also been lead to believe that the cam won't swap, at least not without some machining at the very least.
Anyone have a good site or place with some GM sensor specs? Trying to see which sensors will work on the block and if I have to swap them or just re-pin the connector to work the LY6 computer.
well in case you were wondering, there are updates... as of today:
!!!!
let the "fun" begin! Crank/Cam trigger kit is in the mail and I need to grab a starter and a few misc items from rock auto and we should be all set. Getting it home will be interesting...
EDIT: upon further inspection this engine has come with DEI spark plug shields and MSD 8.5MM plug wires! Now its time to open the oil filter and get an oil analysis done and see what I'm working with since I am kind of afraid to do a comp test with the engine sitting for 3 months.
Got the engine home and used the car hoist to get it off the truck bed (super sketch!) using tow straps. BUT it looks a lot cleaner when you remove the wire harness and brush off the dust, give it a quick de-greasing.
I also managed to find some bosch 4 point platinum plugs in this thing, and I noticed a late November date of 2016 written on the oil filter. The engine had been sitting in the junkyard for about 3 or 4 months before I grabbed it so this may lead me to believe that this vehicles was maintained. Not much oil in the pan or filter but almost enough to fill a blackstone sample - so lets see what they say about the oil/general engine condition in a few weeks.
Some parts are starting to arrive and its almost time to get the truck on the lift and tear out the old motor! (I am excited!) so until then more homework: Big hangups on this is the electrical sensors since the objective is to run the Gen III engine on the gen IV ECM. Coolant and oil temp.
I got a lot of help here from clipless, the big (little) differences between gen III and IV LS engines is that the sensors went from traditional pipe thread to metric straight thread and with his help we discovered that the L18 and LY6 coolant/oil sensors are electrically perform the same. So in this instance, running adapters is more expensive and complicated than re-pinning a simple metri pack 150 series connector.
the L18 uses the coolant sensors on the passenger side head however on the driver side there is a plug in the siamese spot, easy fix then without having to do any crazy wiring and de-looming.
Knowledge is progress and progress is good! (or at least a solid re-assurance) I think the biggest hurdle is going to be the engine mounts since the 8.1 and duramax share the same mounting position/mounts/frames, I am led to believe that the HD gasser frames have a slightly different engine mount frame section but custom engines mounts is a pretty easy task in comparison to other engine swaps.
I may have read what you said wrong and missed the answer to this question. But I always thought the 8100 still used old big block mounts. Which were the same as small block mounts. So if that's true, here's my dumb idea: put some LS-small block adapter plates on backwards. Or if my assumptions are false, get the marker, tape measure and drill press out and make some plates.
This should be good. I really enjoyed the 8.1 in my limited driving of it.
Chadeux wrote: I may have read what you said wrong and missed the answer to this question. But I always thought the 8100 still used old big block mounts. Which were the same as small block mounts. So if that's true, here's my dumb idea: put some LS-small block adapter plates on backwards. Or if my assumptions are false, get the marker, tape measure and drill press out and make some plates.
I'm not sure if they are the same as the old ones or not, but there are definite differences in part number (and price) between the GMT800 L18 and small block LS - this seems to be a current grey area for this swap.
luckily I have 2 small block engine mounts on the truck right now and the engine I bought has a passenger side mount still in great shape, driver side just has a plate with the rubber busted.
might be a little trial and error when it gets time to install these. I did look at the dirty dingo mounts as they have some adjustability to them which looks similar to the one you have shown here. I also picked up a load leveler for this engine swap because this may get tricky...
Goal for this week is borrow a friends HD engine stand and start poking at this thing and take apart the accy drive.
java230 wrote: This should be good. I really enjoyed the 8.1 in my limited driving of it.
Me too. I wish they were still being made. Big torque and compared even with some of the 5.3s in full size trucks not that much worse mileage.
crankwalk wrote:java230 wrote: This should be good. I really enjoyed the 8.1 in my limited driving of it.Me too. I wish they were still being made. Big torque and compared even with some of the 5.3s in full size trucks not that much worse mileage.
Exactly! 3.73 gearing with an even stronger 6 speed (than the 4 speed) an additional 100 ft lbs should do the trick.
Count me among the 8100 lovers. Watching closely to see how this all goes together.
Our 8.1 has treated us well (2006 2500 Burb). I'm sure GM stopped using the 8.1 for smog reasons, but will be nice to see it in a more current vehicle.
my truck threads always get more attention than the rx7 stuff lol. This is certainly uncharted waters for me but that's part of the fun of learning. I don't want to open this engine up but I'm still tempted on putting a raylar cam in it.
EDIT: I also managed to drain the coolant last night and it came out SUPER clean. all good signs so far.
Sad news... the throttle body won't bolt on: upon inspection today I realized that the gen III have a 3 bolt pattern and the gen IV have a 4 bolt pattern - we are gonna have to stop the build thread here...
PSYCH!
Unlike the rotary world, more than 4 companies make things!!!!!!
and its cheap too! ($23+ sh/h)
so in addition to that there is "free" bonus is that now the 8.1 will have a 88mm throttle body upgrade from the LY6 instead of the existing 73mm that the BB came with.
I am following this with great interest. It has become apparent that the 429 in the Cadillac is ill, and I'm weighing engine swaps vs rebuilding a motor that went out production a half century ago. LS swaps have been done - but now I'm thinking I need an 8100. Why put in a smaller motor? 
fidelity101 wrote: Sad news... the throttle body won't bolt on: upon inspection today I realized that the gen III have a 3 bolt pattern and the gen IV have a 4 bolt pattern - we are gonna have to stop the build thread here... PSYCH! Unlike the rotary world, more than 4 companies make things!!!!!!
I'm guessing that's an ICT Billet part? They make a lot of useful stuff for LS engines. I have several of there products on my 4.8 and im pretty happy with them.
In reply to edizzle89:
Yes it is! Found it on summit - glad to hear because It is in the cart now. I'm sure I need a few misc things so I am going to pull the trigger on that soon.
updates! I have the engine on the stand now so its a bit easier to work on stuff, took the accy drive off and begun to tear into the timing cover, probably the biggest unknown part about this swap so to help others in this future swap I will go into detail
So here is a side by side comparison for the gen VII (2004+) BB timing cover next to GM's trigger kit, the cam sensor spot is exactly the same and the crank area has a slightly larger volume. There are some differences for the 01-03 front timing cover but if you're doing this swap for the gen IV ECM it won't matter, but if you have the late 03/04+ style you have an extra cam sensor which couldn't hurt to keep in your box of misc truck stuff just in case you get a failure on road.
The one on the left you can see where the stock oil pan seal seats against and clearly the two seem different in this location but in-fact: this cover bolts right on.
This space is for the large 58x trigger tooth wheel so that the CKP can pick up the correct signal. the extra sensor boss at the bottom is a dead give away, you can install the sensor on after the cover but is much easier to install it first then place the cover assembly on.
When you look at the back side you can see the provision for crank wheel and that they have given it extra space but it looks like it won't fit on because the stock cover has a flat spot whereas the new one has a valley.
You can remove the stock timing cover without loosening the oil pan, but you cannot install/remove the new cover without loosening the oil pan bolts because the seal rides in that valley and you basically have the outer ridge of the cover over-flush to the seal/pan. Instead of just riding along side the seal it wraps it in a C shape, so this may even be less prone to leaking perhaps - which is a bonus.
Here you can see the gap where the ridge will sandwich between.
and this is the engine on a stand with the cover bolted on.
I had to loosen the pan bolts to install it like I mentioned but once you set the cover on and tighten the pan bolts it becomes quite the sandwich and everything fits together perfectly. (sorry for the blurry photo)
no machining or grinding required for this part. So far so good...
Set the engine up at TDC/match the dots. remove the cam timing gear and test install the new double roller, fit fine - all good.
next move onto the crank, so I remove the gear with a 3 jaw puller and then notice this...
which means it is unlike the old big block:
Same GM kit on an older chevy BB.
so right now I have this going on:
its a roll pin instead of a woodruff key?! who the hell decided on that? Right now I haven't installed (completely) the crank double roller gear but it doesn't appear to be any room to have the reluctor wheel and crank gear installed.
So should I just drill and tap it with a hardened bolt or another hardened wrist pin for the wheel? I need to finish cooking dinner (to let the oven gen warm) and then heat the crank gear up to install it all the way to verify if my theory is correct or not. I don't feel like hammering it on right now...
I have heated the crank gear up and it slide perfectly on the crank to its final resting spot small victory!
but the fear assumptions confirmed.
if this was a woodrift key, we would have been installed the crank pulley by now or at least trial spinning the engine over by hand.
Here you can see that the gear totally uses the roll pin, however there is a bit of a gap in the recessed area on the crank so I have a few ideas:
I'm thinking of remove the roll pin, tap the threads put a hardened rod there and then put a key over the rod through a threaded hole but have it long enough to extend outward to support this wheel. The 8.1 service manual says that the crank pulley gets pressed on until it touches the crank sprocket. This makes me wonder if I need to shorten the end of the crank to line up the accy drive then because of the added thickness of the gear and wheel...
otherwise I'm back to drill and tap with some sort of countersunk bolt through the wheel to the gear so its flush then the pulley will prevent the bolts/screws from coming lose.
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