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Old 04-29-2010, 08:42 PM   #1
texasfunk
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any one have experience with the 8.1's?

So i found a really good deal on an 8.1 vortec..im going to put a big block in my 87 and almost bought a 396...but i was wondering if anyone has put one of these in a square? And how hard would it be? Id love to have fuel injection again..im not worried about a/c or anything. Just want it to fit and go! any help will be greatly appreciated!!
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Old 04-29-2010, 09:07 PM   #2
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Re: any one have experience with the 8.1's?

There is a member on here that has one in a square.... and I can't for the life of me remember his name. I'll see if I can find him.
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Old 04-29-2010, 09:11 PM   #3
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Re: any one have experience with the 8.1's?

Dirtly larry
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Old 04-29-2010, 09:17 PM   #4
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Re: any one have experience with the 8.1's?

thanks guys! o'll see if i can get some info, i really want to go this route, if not the same guy that has the 8.1 has a 5.3 for 300, but he's only askin 500 for the 8.1, and i'd really like to get a big block in this thing
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Old 04-29-2010, 09:19 PM   #5
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Re: any one have experience with the 8.1's?

Thanks Adam!! Here is his member profile:

http://67-72chevytrucks.com/vboard/member.php?u=8178

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Old 04-29-2010, 10:49 PM   #6
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Re: any one have experience with the 8.1's?

thanks! im definately looking into this more!
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Old 04-30-2010, 03:09 PM   #7
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Re: any one have experience with the 8.1's?

I have an 8.1 sitting in my shop waiting to be installed in my '86 crew cab. I read some of Dirty Larry's posts regarding his install and found it very interesting.

I hope he sees this and can give us some pointers. One thing I read with particular interest is his statement about Gary Puhls conversion on the street & performance website. I have read that article over and over, and if there is a better way of doing it without so much fab work, I'm very interested in learning about it.
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Old 05-03-2010, 12:03 AM   #8
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Re: any one have experience with the 8.1's?

It is been such a crazy year for me I haven’t been able to spend as much time here as I would like but stumbled across this thread tonight.

In my opinion, there is a much easier way to retrofit the 8.1L into pretty much anything than what Gary did on the article listed on the S&P site.

Here are a few quick pointers from my swap:

1) Use exhaust manifolds or headers from an older big block, as they will bolt right on (454, 396, etc). No need to hack up the frame to use 8.1L manifolds. The engine mounts are also the same as any other GM V8 but you will have to trim off a mounting boss so the driver's side saddle with sit flat.

2) Use a 1996-2000 L29 7.4L or any LS1 cable operated throttle body if you do not want to use the electronic throttle pedal system. It is a hassle to mount a TAC module then the large APS (thottle pedal assembly). Much easier to stick with a cable operated throttle body....unless you are planning to run cruise control.

3) If running a manual trans, use an L18 8.1L pilot bushing and flywheel then use the clutch and pressure plate from your year of truck. You will need to remove dowl pins from the 8.1L flywheel and open up the pressure plate holes in order for the larger metric bolts to pass through.

4) Use accessory brackets from a medium duty truck or RV chassis with an 8.1L in order to have the A/C compressor on the driver’s side up high….like a L29 7.4L. Don’t hack up the frame like the article on S&P. I couldn't beleive my eyes when I saw the other swap and the cut up frame 7.4L brackets are not the same as 8.1L. That may look close but no dice!

5) I used Howell Engine Development for the wiring harness and custom tune. Through their programming they can turn off EGR, electronic throttle, GM’s famous torque management, and they added a 91 octane hot tune. It runs very well.

6) Set your tach to 4 cylinder or it will read 50% of the actual engine RPM. If you run a factory tach there is a gizmo you will need to buy to add in line.

My only regret is using a Marine MEFI-4 engine management system for the first year and 5,000 miles. I peeled that crap off this past winter and went to a P59 automotive style PCM.


Pictures of the swap here….

http://www.flickr.com/photos/1188958...7605630911630/
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Old 07-18-2011, 06:50 PM   #9
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Re: any one have experience with the 8.1's?

Good info here. My dad and I are discussing the possibility of a swap in our '88 CC dually. A guy he knows was talking about the Vortec 6.0 or the 8.1. This truck will be used for towing, so my vote goes to the 8.1L. He also wants the Allison auto behind it. This all just came up today, so I've got some researching to do, but he's pretty serious about it all.

Would the floor need to be re-shaped for the Allison tranny to fit? The truck has a 5-speed in it now and I think they worked the floor a bit for that swap too.
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Old 07-18-2011, 09:42 PM   #10
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Re: any one have experience with the 8.1's?

I have an 8.1 in my 76, its not running yet. Been working on it for a year or so now. Larry gave me some good points before I made the purchase. I bought it as a crate engine, have a cam and new valvetrain to go in it. Been a slow project. Please ignore the ugly firewall, at some point Im smoothing it, have vintage air for it as well. I used accessory brackets from a 3500 express van they worked perfect.
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Old 07-19-2011, 02:57 AM   #11
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Re: any one have experience with the 8.1's?

Here is basic information you need for a conversion.
http://www.hotrodlane.cc/77chevytruck/77chevy.htm

A/C option: http://www.kwikperf.com/lsx_ac.html

A/C bracket option: http://www.maliburacing.com/forum/vi...hp?=34&t=79059
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Old 07-19-2011, 12:49 PM   #12
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Re: any one have experience with the 8.1's?

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Originally Posted by gchemist View Post
Great links if someone was looking for small block LSX info…..pretty much worthless for this thread topic of 8.1L’s as nothing is similar to LSX engines except for the engine management and fuel delivery systems.

Lookin good 76Stepside!
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Old 07-19-2011, 07:58 PM   #13
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Re: any one have experience with the 8.1's?



The fuel tank info is great. You can buy a direct replacement to fit a stock tank. Just weed out information not needed.
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Old 07-20-2011, 11:47 PM   #14
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Re: any one have experience with the 8.1's?

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Lookin good 76Stepside!
Thanks Dirtylarry... if I can ever find the time I will get her running. Its one of those "simple projects" that just keeps building on itself. But I feel it will be worth it in the end!
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Old 07-21-2011, 10:16 PM   #15
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Re: any one have experience with the 8.1's?

I have an 8.1/Allison in my 01 CC dually. I love it. Id like to put one in one of my ex cabs. I have yet to hook up to something that it had trouble pulling tho I feel theres more power on tap I just havent figured out to get it out. It is a hoss but it is also thirsty....very thirsty.
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Old 07-22-2011, 09:53 AM   #16
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Re: any one have experience with the 8.1's?

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I have an 8.1/Allison in my 01 CC dually. I love it. Id like to put one in one of my ex cabs. I have yet to hook up to something that it had trouble pulling tho I feel theres more power on tap I just havent figured out to get it out. It is a hoss but it is also thirsty....very thirsty.
A custom 91 octane tune can yield you around 425 HP and just shy of under 600 lb ft of torque on the original injectors and through exhaust manifolds. You can get real crazy with an 8.1L with parts from Raylar but it will cost you a fortune. There are a few other marine companies with hop up goodies for the 8.1L but I can't remember who the other guys were. 8.1L's are much more well known in the Marine and RV industry.

My ’78 is running a 91 octane hot tune while my ’01 Silverado is bone stock. The ’78 will run and pull circles around the stock ’01. Both are running manual transmissions with overdrive. Amazing what a custom tune and deleting Torque Management will do for one of these engines. I don’t find either of my 8.1L’s any more thirsty than the 6.0L in my ’05.
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Old 07-22-2011, 10:59 AM   #17
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Re: any one have experience with the 8.1's?

That's awesome. Thanks for the info. Who did your program? My only concern is the Allison which is only rated for 350 hp but its a tow pig so I don't plan on any racetrack time. Its my baby and since I found out it gets better mileage on 91 anyway the program isn't going to matter as far as gas is concerned. I've heard the same thing as far as mileage on the 6.0s and worse with large loads. In my opinion if economy is a concern you probably don't need a truck this big.
Ill be keeping up with this because I really want to put an 8.1 in my 85 k20 excab.
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Old 07-23-2011, 03:30 PM   #18
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Re: any one have experience with the 8.1's?

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That's awesome. Thanks for the info. Who did your program? My only concern is the Allison which is only rated for 350 hp but its a tow pig so I don't plan on any racetrack time. Its my baby and since I found out it gets better mileage on 91 anyway the program isn't going to matter as far as gas is concerned. I've heard the same thing as far as mileage on the 6.0s and worse with large loads. In my opinion if economy is a concern you probably don't need a truck this big.
Ill be keeping up with this because I really want to put an 8.1 in my 85 k20 excab.
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I got my second harness from Howell Engine Development. They did the ECM tuning as well. The first harness and engine management system was a Delphi MEFI-4 ECM, which is basically the same system as the GM Performance Parts RamJet engines as well as GM Marine. The MEFI-4 system is a low tech speed density, batch fire system. That was a mistake! Ran that for a year and yanked it off to replace it with Howell’s harness. Much better now!

The Allison 1000 is like the 8.1L where it is well underrated. It can handle much more than 350HP! Your challenge will be with the installation of the Allison trans. The physical dimensions of that trans are huge where you will have to do some major body modifications at the firewall and trans tunnel and you might even still need a body lift. You’re also going to need to make friends with an Allison dealer with Allison DOC software in order to program the TCM to your specs and that gets pricey! If you already have an Allison lying around, I would sell it and put that money towards a well built 4L80E. The Allison eats up a lot of power to run that beast.
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Old 07-23-2011, 11:40 PM   #19
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Re: any one have experience with the 8.1's?

The Allison is already in my 01.crewcab. definatly plan on running a 4L80e in the excab. I have a friend who works on Allisons so I should be ok when it's time to upgrade the tcm
He said the trans will be ok up to 600 ft/lbs of torque. Said problem is pulling trailers up grade wiith cruise on and letting it downshift to hard. Now to find an 8.1
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Old 10-22-2013, 03:27 PM   #20
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Re: any one have experience with the 8.1's?

How much room you got above the intake to the bottom of the hood?
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Old 10-22-2013, 03:45 PM   #21
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Re: any one have experience with the 8.1's?

Quote:
Originally Posted by rare86 View Post
That's awesome. Thanks for the info. Who did your program? My only concern is the Allison which is only rated for 350 hp but its a tow pig so I don't plan on any racetrack time. Its my baby and since I found out it gets better mileage on 91 anyway the program isn't going to matter as far as gas is concerned. I've heard the same thing as far as mileage on the 6.0s and worse with large loads. In my opinion if economy is a concern you probably don't need a truck this big.
Ill be keeping up with this because I really want to put an 8.1 in my 85 k20 excab.
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my alli is hold 420 hp and about 700 ft lbs i dont think a gas engine would hurt it
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Old 10-22-2013, 06:04 PM   #22
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Re: any one have experience with the 8.1's?

the allisons behind the duramax's hold very well. my 2007 lmm has 365 hp. and 660 ft. lb's. torque... and there are TONS of aftermarket parts to help should a person need more strength. mine will tow 14,500...legally ....... in stock form 3/4 ton 373 gears crew cab 4 x 4 adding a tuner (150hp "street build") on a stock trans is accepted as norm. but things don't break when they twist the tires, they break when they get traction..
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Old 10-22-2013, 06:10 PM   #23
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Re: any one have experience with the 8.1's?

i am looking for an 8.1 for my dually currently
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Old 10-22-2013, 06:45 PM   #24
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Re: any one have experience with the 8.1's?

I don't want to start a **** storm, but is there any advantage to this versus a Cummins swap? I'm asking this to ask this. my truck is gonna need a repower at some point in the future and was just gonna do a Cummins for the power, fuel economy, low cost (relatively speaking.) To me an 8100 swap would be cool on a lot of levels (it's not a cummins or LSx swap, or a built 454, good old fashioned American V8 noises.) How does the 8.1 stack against a basic Cummins 6BTA, or 4BTA based on cost, fuel mileage and power?
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Old 10-22-2013, 07:25 PM   #25
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Re: any one have experience with the 8.1's?

the swap is way cheaper, they have about the same power the only downside to it is it gets 5mpg less than the cummins, but the again around here diesel is 60-70 cents more a gallons so for me its a wash, that and wait until that cummins breaks and see how much parts are!
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