Swapping in an 8.1BB

[Beadlock]

I have read, perhaps on here, that the new 8.1L BB will bolt up to my T400 Trans in my 89 burb. Does anyone know if this is true?

If so, can someone point me to a website or other resource where I can get additional information about this possible swap.

Thanks for any info.

Lee

EDIT: I might also be willing to entertain the idea of getting Allison 1000 Trans and swapping it in. But then can I get an adapter to mate this combo to a dual T case setup? Thx again

 

[pauly383]

Well I would assume it would , same belhousing pattern on the new motors as on the old . And motor mounts would be easy too , as its just a new glorified big block .

Your issues will be wiring , fuel , and exhaust . With exhaust being the easiest I imagine .

 

[Pvt. Maggot]

You won't be disapointed in the motor, thats for sure. we have one in our 02 2500hd with the allison tranny, man that thing has some balls hah. The wiring is going be a pita for sure. good luck

 

[Russell]

8.1L is basically the easiest new style engine you can bolt in. It literally bolts straight in.

You can use a 14" 168 tooth flywheel or flexplate from a 396 or 427, just as long as it is a neutral balance unit. They bolt straight up to the crank, which is spaced the same as the old big and small block chevy engines. You can then bolt your original transmission up, using a normal torque converter, or clutch kit.

The 8.1L has both the newer style 4 bolt engine mounts, and the old style 3 bolt engine mounts cast into the side of it. You can literally bolt your old engine mounts on the side, and drop it straight in

As mentioned the only issues to overcome will be electrical, getting an adequeate fuel system, running exhaust, and getting the PCM flashed to remove a couple of un-needed emissions systems / VATS & to change the tach signal to something your truck can use.

You will need to switch to an electronic speedometer, the 8.1L will need a 40 tooth reluctor ring speed sensor (NP241s, or rare NP205s) to run properly, which replaces your speedometer cable drive.

Two things to keep in mind though -- All 8.1L engines are fly by wire, so you'll need the wiring, pedal and module for the swap, and some 8.1Ls have problems with oil consumption & bad piston slapping when you start it in the morning. Make sure you can cold start the engine, and find out how the oil consumption is before you buy one.

If I could find an 8.1L at a reasonably affordable price, which I knew was in good shape, I'd drop one into my truck in an instant

 

[Beadlock]

Ok this is great information, I just a few more questions.

As mentioned the only issues to overcome will be electrical

This is not an issue, by biz partner and long time pro wrench can handle this kinda electrical without missing a beat.

getting an adequeate fuel system

What exactly do you mean? Is it plausible that I could use an external fuel pump that can be regulated to the correct PSI? What other info do you have on this particular part of the build?

running exhaust

No problem, got a great exhaust shop in town

and getting the PCM flashed to remove a couple of un-needed emissions systems / VATS

I assume this will be a GM deal. They will need to use something like a Tech2?

to change the tach signal to something your truck can use.

If I go to aftermarket gauges all around then this won't be an issue right?

You will need to switch to an electronic speedometer, the 8.1L will need a 40 tooth reluctor ring speed sensor (NP241s, or rare NP205s) to run properly, which replaces your speedometer cable drive.

What year of NP205 am I looking for. This is a swap I wanted to do anyway so I might as well get it done right.

Two things to keep in mind though -- All 8.1L engines are fly by wire, so you'll need the wiring, pedal and module for the swap, and some 8.1Ls have problems with oil consumption & bad piston slapping when you start it in the morning. Make sure you can cold start the engine, and find out how the oil consumption is before you buy one.

I am working with a close friend at the local auto recycler and if the engine craps out I know I will get it warranteed. And removing and reinstalling the engine is not that big a deal to me. I may even consider rebuilding the motor after a year of running cause I know I am going to want to put go-faster parts on it.

Which brings me to my last question. How much aftermarket go-faster parts are available for this engine?


Thanks for taking the time

 

[Russell]

Fuel system will basically be a 3/8 supply line, and 5/16 return line. You'll need to provide approx 60 PSI to the fuel rail, and a reasonable amount of volume too.

Since you have an 89 Suburban, you're already way ahead of the game as far as the fuel system goes. You can replace your stock TBI pump with the Walboro 255 litre in-tank pump, and use the factory sending unit / fuel lines right up to where they change into stainless steel braided line then head up to the stock throttle body. You can buy fittings that convert the factory o-ring saginaw fittings over to -AN fittings, then buy a set of fittings that convert the factory fuel rail quick disconnect fittings into AN fittings as well. Then it is just a matter of running two lengths of high pressure fuel hose inbetween.

Getting the PCM flashed is not quite as bad as you may think -- I'd definitely avoid going to the dealership with it. The cheapest I've found so far is www.pcmamerica.com who does the flashing for like 25 bucks plus shipping each way. He'll change everything you need done right off the bat, not just VATS like some places, then paying extra for other stuff.

As far as the tach goes, if you don't want to have the tach signal output modified in the PCM, you'll have to run a tach for a 4 cylinder engine. GM standardized all of their PCMs to put out the same tach signal, regardless of the number of cylinders so they could standardize their tachs as well. There are little modules you can buy that double the tach signal if you want to go that route instead.

The NP205 you'll be looking for is found in 91 Crewcab trucks in a 4l80e / NP205 or SM465 / NP205 combination. They are quite tough to find, but you can bolt the 205 up to a normal 32 spline TH400 with the normal adapter, then you have your NP205 with the reluctor ring.

Another option is to run the 4l80e. All 4l80es, 2wd or 4x4, have a reluctor ring built into the case. You can then put whatever 32 spline t-case on the back that you can get an adapter for, and run the factory cable drive off the t-case for the speedometer while using the reluctor ring in the transmission for the PCM.

As far as aftermarket support goes, I'm not really sure. I haven't done a ton of searching... I know that there are camshafts available, but at 455 ft lbs of torque at 3200 rpm stock, I'm not sure how much more power you'll need

 

[Beadlock]

I want you to know that this tech help has brought a tear to my eye. Its that beautiful. Thanks Man.

Seriously though. You are a plethora of useful information on this subject and I really appreciate it.

I will have more questions, and I will get back to you as I come up with them.

I love this forum.