454 tbi with 4l85E swap into c1500 350tbi

[someotherguy]

Bloodwater man I am SO SORRY we have totally hijacked your thread. Please pop back in here and keep us posted on your swap project. Don't let anyone discourage you; if you have even half-ass mechanical skills and ambition, your swap is totally do-able without major hassle. Yeah you'll need to source/make a few supporting items but so far the biggest hurdle I see is that 3500HD transmission; if you can spring for a rebuild then the shop can change out the tailshaft and housing from one of their core units, or you could source a non-HD trans elsewhere.

Just as motivation this was a former '94 3500HD 6.5TD/NV4500 that was missing the engine, trans was junk, interior was trash, and pretty much every body panel was shot. I did a Vortec 7.4 swap, full 95-up interior swap, and built the truck almost literally the way the factory would have - using "spare parts" from donor trucks including 93, 94, 95, 96, 98, and 99 and in my "spare time" ...

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Richard

 

[Busted Knuckle]

Yeah they used the 8.1 for several years in the GMT800's but those trucks would only serve as an engine (and possibly PCM) donor; you'd still need to figure everything else out or custom hack the harness. I do believe some of them came with the Allison transmission, too. Talk about your literal can of worms for a swap donor! The 2001-2002 3500HD IMO is a far better donor. (Or 2001-2006ish if you can get one from Mexico! shhhhhh...)

Richard

I've eyeballed the 8.1 as well. There aren't many performance parts as (almost) nothing from the 454 will fit. One of the things to mod is a restrictive intake manifold. I'm linking a company that makes 8.1 performance parts. As the economy continues to crash (until 2026) there will be bargains all over. https://www.raylarengineering.com/

 

[alpinecrick]

I suppose on the GMT 400 line most of the 2500/3500 were long beds, and many folks don't get too excited about long bed project trucks?

RCSB have always been 1/2t, regardless of era.

 

[Sam Cooper]

I've eyeballed the 8.1 as well. There aren't many performance parts as (almost) nothing from the 454 will fit. One of the things to mod is a restrictive intake manifold. I'm linking a company that makes 8.1 performance parts. As the economy continues to crash (until 2026) there will be bargains all over. https://www.raylarengineering.com/

The 8.1 liter gen 6 big block is very interesting from a tech standpoint, as it is essentially a stroker 454 to 496 set up like a LS motor. It has the 7-4 firing order swap, cathedral port heads, and individual ignition coils. Raylar and Dart both offer aftermarket heads for them. Several companies offer camshafts for them and they are torque beasts. I would love to play with one in my hauler rig, just because I can. They are starting to get harder to find. Oh and don't even try to run a 4L80 behind one. Allison 6 speed only. I wish someone would offer a legal manifold for them, aside from Raylar boring out the stock manifold.

 

[454cid]

The 8.1 liter gen 6 big block is very interesting from a tech standpoint, as it is essentially a stroker 454 to 496 set up like a LS motor. It has the 7-4 firing order swap, cathedral port heads, and individual ignition coils. Raylar and Dart both offer aftermarket heads for them. Several companies offer camshafts for them and they are torque beasts. I would love to play with one in my hauler rig, just because I can. They are starting to get harder to find. Oh and don't even try to run a 4L80 behind one. Allison 6 speed only. I wish someone would offer a legal manifold for them, aside from Raylar boring out the stock manifold.

The 8.1L is Gen 7. The Vortec 454 is the Gen 6.

I'd love to get a hold of one of the 8.8L PSI engines.

 

[Sam Cooper]

Bloodwater man I am SO SORRY we have totally hijacked your thread. Please pop back in here and keep us posted on your swap project. Don't let anyone discourage you; if you have even half-ass mechanical skills and ambition, your swap is totally do-able without major hassle. Yeah you'll need to source/make a few supporting items but so far the biggest hurdle I see is that 3500HD transmission; if you can spring for a rebuild then the shop can change out the tailshaft and housing from one of their core units, or you could source a non-HD trans elsewhere.

Just as motivation this was a former '94 3500HD 6.5TD/NV4500 that was missing the engine, trans was junk, interior was trash, and pretty much every body panel was shot. I did a Vortec 7.4 swap, full 95-up interior swap, and built the truck almost literally the way the factory would have - using "spare parts" from donor trucks including 93, 94, 95, 96, 98, and 99 and in my "spare time" ...

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Richard

Nice job on your update! When you did the interior update, how did you handle the wiring issues? I have a beautiful complete 97 interior to put into my 93 crewcab, but the harnesses are totally different at the firewall connection. I guess I can delete the air bag stuff, but then what. The 97 has the ECM on the fender whereas the 93 has it behind the dash. I wonder if maybe I need to find a dash harness from a 95. Thanks in advance.

 

[Sam Cooper]

The 8.1L is Gen 7. The Vortec 454 is the Gen 6.

I'd love to get a hold of one of the 8.8L PSI engines.

Thank you for the correction. The 8.8 is interesting. I quickly looked online but can't yet tell what it is. If I was to do an 8.1, I would consider stroking it to a 540cid, which seems to be the most popular configuration for big power marine use. That is about the same as the 8.8L, or so it seems.

 

[Sam Cooper]

The 8.1L is Gen 7. The Vortec 454 is the Gen 6.

I'd love to get a hold of one of the 8.8L PSI engines.

Has anyone done an apples to apples comparison between the gen 5 tbi big block and the gen 6 vortec big block. I have a nice virgin gen 4 short block and a complete gen 6 mpfi system to play with. I'm just wondering if it is worth the effort to change over. If so I would need to decide on cylinder heads. I know the L29 heads are popular with their 100cc quick burn chambers.

 

[Sam Cooper]

The 8.1L is Gen 7. The Vortec 454 is the Gen 6.

I'd love to get a hold of one of the 8.8L PSI engines.

I just found the specs on the 8.8L engine and I'm with you. They offer a smog legal 10:1 engine with 500 HP and a steady 500 ft/lbs of torque. Oh yeah! That would pull my horses or my 40' fifth wheel. Plus it's a big bore motor, ala 502 style.

 

[someotherguy]

Nice job on your update! When you did the interior update, how did you handle the wiring issues? I have a beautiful complete 97 interior to put into my 93 crewcab, but the harnesses are totally different at the firewall connection. I guess I can delete the air bag stuff, but then what. The 97 has the ECM on the fender whereas the 93 has it behind the dash. I wonder if maybe I need to find a dash harness from a 95. Thanks in advance.

Thanks.. but if you look closer I updated not just the dash, but the engine, PCM, wiring, everything. I did not mate any old and new harnesses. The truck is essentially now serviceable as a 1996 model (the donor truck year for the engine, PCM, harness) although there are minor differences in the 1994 chassis.

Richard