8.1 Converstion

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DTrain

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As my trucks mileage has been getting up there(350,000), and starting to show it’s gray hair, I have been looking around and talking about motor replacement and swap options.

The truck is a ‘99, cclb, K3500, 4x4, nv4500, 350 truck. All factory and all original.

So, this last week, out of no where, a buddy of mine fell across a very clean, low mileage 8.1 and snatched it up. He’s has no plans for it persay, and mentioned it going in my truck. I really think it’d be absolutely awesome, but I do know it’d be a chore.

I am wondering if anyone has experience with this swap and what all is involved? This motor has everything but an alternator.

D
 

454cid

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As my trucks mileage has been getting up there(350,000)

Wow, that's more than me.... 280K plus.

I really think it’d be absolutely awesome...

Yes!

I am wondering if anyone has experience with this swap and what all is involved? This motor has everything but an alternator.

No real knowledge on it. I would think you'd want the wiring harness and computer, but I'm not sure how that would work with the rest of your truck. Maybe this would be where one of the wiring harness companies would come into play?
 

Christian Steffen

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If you cant get the harness from the donor truck, you could probably 0411 swap your truck and tune for the 8.1. youd probably want to check over a wiring diagram for an 8.1 to verify the sensor wiring and make any necessary changes. Since it's a manual that is a little easier. An 8.1 and a manual would be awesome, especially with the 8.1 being tuned.

I say go for it.
 

letitsnow

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If i were gonna swap out the 350 in my truck, an 8.1 is the only motor I would swap to.
 

BNielsen

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As beefy and beastly as an 8.1 is, I don't know how I feel about the parts availability such as sensors and what not; still interested in the swap though, a tuned 496 with an NV4500? Can you say Cummins killer?
 

454cid

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As beefy and beastly as an 8.1 is, I don't know how I feel about the parts availability such as sensors and what not; still interested in the swap though, a tuned 496 with an NV4500? Can you say Cummins killer?

Speed parts are not super common, or are very expensive. I've never heard of stock parts being a problem. I would think the sensors are mostly used on other GM engines too.
 

94burbk1500

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You already have the perfect transmission and suspension for it, do it! As much as he annoys me at times @L31MaxExpress could be of some use here, he says his tahoe has one.
 

L31MaxExpress

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Even a stock 8.1 runs great with nothing more than a decent tune. Boosting the power of a stock 8.1 is not that difficult. Even though there is not a huge aftermarket for them, there is an aftermarket. I have 2 of the 8.1s. 1 is in a 1983 G20 van and the other is in my 1999 Tahoe. Both of my engines came from a G-van application. One was a single rear wheel 3500 van and the other was a dual rear wheel cut-away party bus. The engine in my G-van has a GMPP 454/502 HO camshaft in it and 2nd generation camaro long tube headers. My Tahoe engine has a GM 420 HP Marine camshaft in it and long tube headers for a TBI 454. The wiring is LS based although the sensors have slightly different locations and it would be best to start with a GMT400 8.1 or an Express/Savana van 8.1 harness. On the Tahoe I ended up using the 0411 swap spreadsheet to connect the 99 Tahoe's wiring to the van engine harness. I used the DBW setup and a pedal from a 6.5 diesel GMT400. The TAC module from the van that controls the throttle body bolted directly to the firewall in place of the cruise control module. The $$$ and hard part of the swap for me on the Tahoe was sourcing all the GM parts to convert the engine from the van application to the truck application. I had to buy the correct dipstick tubes and dipsticks as well as the oil fill tube and numerous other items. I also installed oil cooler lines for a 454 Vortec and added all the OEM transmission fluid cooler stuff for a 1-ton.
 

L31MaxExpress

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How are you running the older cam when the firing order is different?

Because the cam dictates the firing order and changing the cam changes the firing order. Changing the firing order dictates some repining of the coils and injectors at the PCM and some tuning changes but it is a very straight forward process. The 454/502 roller cam drops right into the 8.1 with only a spring change. I did not even have to convert to an adjustable valve train. Will also say it was hard to beat a steel billet roller cam for $170.00.

https://www.summitracing.com/parts/nal-24502611
 
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