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Discussion Starter #1
Anybody have any success or horror stories in regards to mating an 8.1L to a SM465? Which pilot bearing did you use? I will be beginning this swap next weekend and will be using an 8.1L flywheel and hopefully the Centerforce clutch from my 454.

Thanks
 

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I'm swaping in a sm465 behind a 5.3L, I got a flywheel fom an 04 gto and the clutch that fits the tranny. You prolly don't need that info but you might have to do a little measuring to get the right TO bearin here's a good write up under Sequence of linkage setup http://www.novak-adapt.com/knowledge/clutches_etc.htm You can read about the pilot bushing and the can polly help you out here to. This might be what you need http://www.novak-adapt.com/catalog/pilot_bushings/gm2_to_gm1.htm but I'm not sure if it applies to the 8.1. I would research it a lttle more cause I'm not sure how accurate this info is :flipoff2:
 

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No horror stories. My 8.1L to SM465 swap is still in the works.

The factory 8.1L pilot bushing will work just fine I think.

We swapped a bunch of info in this thread http://pirate4x4.com/forum/showthread.php?t=631745

Progress has been very slow but I've got the transfer cases rebuilt and I'm in the middle of cleaning up the wiring harness. If work and other projects wouldn't keep getting in the way I'd be done by now. :shaking:
 

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Discussion Starter #4
Mudbug,

Thanks for the info but the 8.1L big block engine architecture is an entirely different animal than the Gen III small block info that you linked….although the engine management systems are similar.

J Bruce,

Dude, where the hell have you been?? I have reached out to you on a couple different occasions on the thread you posted and never heard squat back. I am aiming to stab my 8.1L with in the next week or so and I was hoping you were fifty paces a head to give advice. My MPI 7.4L pissed me off so OUT it comes an in with the 8.1L. I guess we will see how well the 8.1L clears the ORD HD engine crossmember here shortly. LOL. I am still running this engine on the MEFI-4 Delphi controller as the MPI 7.4L albeit a different engine calibration.

Hopefully, I will be able to report back with successful info before too long.
 

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J Bruce,

Dude, where the hell have you been?? I have reached out to you on a couple different occasions on the thread you posted and never heard squat back. I am aiming to stab my 8.1L with in the next week or so and I was hoping you were fifty paces a head to give advice. My MPI 7.4L pissed me off so OUT it comes an in with the 8.1L. I guess we will see how well the 8.1L clears the ORD HD engine crossmember here shortly. LOL. I am still running this engine on the MEFI-4 Delphi controller as the MPI 7.4L albeit a different engine calibration.

Hopefully, I will be able to report back with successful info before too long.
Sorry man. Work keeps getting in the way of my fun. Between deadlines and travel I haven't had much time for the stuff that makes it all worthwhile :(

Looks like you'll be the one to give advice next LOL. I want pics of the progress :D

The EMFI-4 setup is starting to look pretty attractive. I've probably cut about 10lbs of wiring out of the factory harness so far. I've got a few connectors left that I still need to ID but it's almost there. Then it's relocating the computer to the other side of the motor. Buying a harness is getting more appealing all the time LOL
 

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Discussion Starter #6
Sorry man. Work keeps getting in the way of my fun. Between deadlines and travel I haven't had much time for the stuff that makes it all worthwhile :(

Looks like you'll be the one to give advice next LOL. I want pics of the progress :D

The EMFI-4 setup is starting to look pretty attractive. I've probably cut about 10lbs of wiring out of the factory harness so far. I've got a few connectors left that I still need to ID but it's almost there. Then it's relocating the computer to the other side of the motor. Buying a harness is getting more appealing all the time LOL

I hear you Jon….I am in the same exact boat….actually in Indiana tonight. I see the inside of more airplanes and hotels than my own house. I haven’t really been able to play with my project in about 5 weeks. If anybody ever asks you to be a service rep for a truck manufacturer tell them NO because your personal life will vaporate. When I was young I had plenty of time to spend on projects and didn’t have two nickels to rub together. Now I have no time and the project budget isn’t much better but more flexible than it was when I was 21.

If you seriously decide to go the MEFI-4 route I have a good connection on the harness, controller and software side.

Harness and MEFI-4 controller: ~ $1000

Todd Blake
Electric Wind
www.mefistuff.com

8.1L specific calibration file: ~ $ depends

Bob Radke
OBD Diagnostics, Inc.,
www.obd2allinone.com

Fine tuning might still be necessary after the 8.1L calibration is uploaded. I’ll keep you posted on my debacle.
 

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Discussion Starter #7
Well, the verdict is in….

The 8.1L mates up nicely to the SM454. The recipe is to use an 8.1L flywheel and pilot bearing. Then you will need to open the pressure plate mounting holes just a tad to allow for the larger metric pressure plate to flywheel bolts to pass through as well as remove the two dowel pins from the flywheel. The only other mod was the driver side engine mount had to be slightly messaged to clear an extra mounting boss that is cast into the engine block. The 8.1L also clears the ORD HD engine crossmember with ease. I would recommend removing Cylinders #5 and #7 coil packs before stabbing the engine as they get pretty close to the power booster.

I still have a ton more fine details to work out yet but hope to have it running within the next few weeks or so depending on my work schedule.

Here are a few pics and a picture of the MEFI-4 wiring harness from Electric Wind (not pictures is the small relay pack).








MPI 7.4L that pissed me off and got yanked out and tossed in the corner.
 

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Well, the verdict is in….

The 8.1L mates up nicely to the SM454. The recipe is to use an 8.1L flywheel and pilot bearing. Then you will need to open the pressure plate mounting holes just a tad to allow for the larger metric pressure plate to flywheel bolts to pass through as well as remove the two dowel pins from the flywheel.
[MrBurns]Excellent![/MrBurns]

Glad that worked out as well as we expected it to. I think I'm running the same clutch too LOL.

The only other mod was the driver side engine mount had to be slightly messaged to clear an extra mounting boss that is cast into the engine block. The 8.1L also clears the ORD HD engine crossmember with ease. I would recommend removing Cylinders #5 and #7 coil packs before stabbing the engine as they get pretty close to the power booster.
That motor looks like it belongs in there. :D

I was looking at the pics of the 8.1L thinking wow he really cleaned that thing up well, then I saw the truck and thought wow same with the engine bay.

Then I saw the old motor. Holy crap man don't these things ever leave the driveway? :flipoff2:

Here are a few pics and a picture of the MEFI-4 wiring harness from Electric Wind (not pictures is the small relay pack).
Have you decided how you're going to hook up guages? Since you're running the MEFI-4 stuff I guess that means you're ditching the drive-by-wire and going with an aftermarket unit?

Looks the MEFI-4 is much easier to work with than the factory stuff LOL. I've got mine sorted out now. Spent some time yesterday relocating the computer to the passengers side, removing all the stuff for the Allison, the A/C, and cruise control. Just cleaning up the power connections and putting the wireloom back on.
 

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Larry, what exhaust manifolds are you running? Are the the factory 7.4 manifolds? I am in the process of stickin an 8.1 in my 84 and the factory manifolds are a bit on the wide side to fit in my frame. I would like to avoid notching my frame if possible but also dont want to shell out the skrilla for a set of decent headers.
 

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Larry, what exhaust manifolds are you running? Are the the factory 7.4 manifolds?
Yeah those are the factory 7.4 manifolds (no EGR port so they're not the 8.1L units). The bolt pattern for the exhaust hasn't changed so any BB chev manifolds should work. You just need to watch the knock sensors and make sure they clear.
 

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Discussion Starter #11
Yeah, that 454 left the driveway many times when it was carbureted. :D It never left but on a few test drives with the MPI system though. :mad3: It appears there is an internal problem with the MPI intake or the fuel rail that prevented it from running properly. I could have fixed but for the same amount of money I decided to toss the 8.1L in instead. I’ll fix it later and probably put it in my old tow truck.

You are correct, the MEFI-4 does not use the drive by wire which cleans up a lot of the wiring. I am actually using the L29 454 cable operated throttle body. You can also use LS1 or 1999-2002 C/K small block truck cable throttle bodies as well if you ever go the MEFI-4 route.

The MEFI-4 is only a 3 wire system. Battery power, ignition, & analog tach so no changes have to be made with the instrument cluster.

As far as the exhaust manifolds go……you can use any big block exhaust manifold on the 8.1L as they are all compatible. If headers are your thing they should fit as well. However, on the driver’s side of the engine towards the back there is a casting boss that needs to be slightly trimmed to clear the exhaust manifold (on my manifold anyway). That was easily done with a file and 5 minutes of elbow grease. My exhaust manifolds are actually a mix of years. One side is 1996-2000 7.4L and the other is a 1987?? I had to use the older manifold on the driver side to clear the clutch Z-bar. I’ve been using these manifolds since I first put the Gen VI 454 in back in 2003.

And you are right…there where clearance issues with the manifolds and knock sensors so I had to purchase a pair of knock sensors for a mid-90’s Buick 3.8L (small metric thread end on sensor) so they would thread into the smaller holes vs the large holes the originals were mounted. You would not be able to use these older style sensors as the connector ends are different from the stock GM truck PCM-32 and MEFI-4 systems.

One other item…. You will need all new metric fastners for the engine mount saddles to block as well as bell housing to block….and a ton of other places.
 

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Yah I knew about the metric hardware issue I had to buy the bellhousing bolts from the dealer and have been scrounging metric shit from anything else I can find. I guess its off to flea-bay to find me some earlier model manifolds.
 

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Got it running yet DirtyLarry?

I got mine bolted up to the tranny and tcases and have it slung between the frame rails. Working on engine mounts now.

Unfortunately I screwed up and used the wrong bellhousing so now I've got to pull it all apart again :shaking: I've got a nice hydraulic bellhousing that was supposed to go on instead *sigh*. Ah well it gives me a reason to pull it out so I can weld up the mounts properly.
 

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Not trying to hi-jack, but seems like a few of u guys are pretty familiar with these 8.1's. Since the exhaust manifolds are interchangable, what is the chance that a carbed intake would possible fit? Probably a long shot, and sorry for butting in.:)
 

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Discussion Starter #15
Got it running yet DirtyLarry?

I got mine bolted up to the tranny and tcases and have it slung between the frame rails. Working on engine mounts now.

Unfortunately I screwed up and used the wrong bellhousing so now I've got to pull it all apart again :shaking: I've got a nice hydraulic bellhousing that was supposed to go on instead *sigh*. Ah well it gives me a reason to pull it out so I can weld up the mounts properly.
Well, that is a drag about the bell housing. Things could be worse! Who knows what will happen when we try to fire these things up. :grinpimp:

I am getting real close Jon. Other than waiting on the controller to come back from the tuner I just need to run the fuel lines from the pump to the engine and a few small things.

Here is how it is sitting now as well as a shot of the controller and relay bracket that I fabricated the other night.



 

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Discussion Starter #16
Not trying to hi-jack, but seems like a few of u guys are pretty familiar with these 8.1's. Since the exhaust manifolds are interchangable, what is the chance that a carbed intake would possible fit? Probably a long shot, and sorry for butting in.:)

No dice Red….

The 8.1L heads are entirely different from previous big blocks. While I had a few of them apart I took a family photo of the last 3 generation of big block heads. Nobody builds carburated intake for the 8.1L yet. I wouldn't want to polute this great engine with a toilet on top anyway.

The far left is a 1991-1995 7.4L head
Middle is 1996-2000 L29 7.4L
Right is the 2000 – current 8.1L

The last picture is the height difference between a 7.4L (Left) and 8.1L (right). The 8.1L head is huge!







 

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Damn those intake ports on the 8.1 heads are enormous! Just out of curiosity, did you measure the valve size?
 

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Thanks Larry, those pics tell it all. I was just curious cause a guy was asking me the other about this. He manage to get a complete warranty engine from the local chevy dealership as a core and only needed a set of rings and bearings(I think it was an inside buddy deal with the shop manager).
 

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Discussion Starter #20
The 8.1L is ALIVE!

Wholly cow is all I can say. This thing runs like an absolute animal even through the fuel calibrations still need fine tuning. I still need to figure out something with the dual fuel tanks as the OEM Pollak fuel tank switch valve too restrictive on the return side causing the fuel pressure to run around 100 psi when it should be around 44 psi max for on the MEFI-4 system. Way too much fuel pressure. So, it got bypassed for now and I am constrained to only the right tank.

Here are a few videos with poor audio quality.

The weird thing is the 8.1L is quieter through the exhaust even though nothing changed on the exhaust system other than a firing order change between the 7.4L and 8.1L.

http://www.youtube.com/watch?v=avyjEr4bnGA

http://www.youtube.com/watch?v=SAYW1OXyEIU
 
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