L18 8.1L swap resource thread

[Larry]

My friends did an 8.1L swap to his 72' K20 with 4l80e and np241 case recently.

Things they used
- Denali radiator
- Stock Intake
- 8.1 with comp cam
- Blackbear tune (they are datalogging it right now, to send in)
- Used stock motormounts that were in the k20
- Suburban fuel tank with in tank pump
- Lokar shifter


Overall this thing is a monster, if the truck could handle going over 105mph safely it would do it with ease. It's on 35's and 4.10's gears but this thing has some diesel torque. Can't wait till they program the stupid torque management out of the motor. After riding in this I think that i'm gonna do a 8.1 swap myself in the K5.

Cool!

Yeah, just having some ECM tuning done and removing TM makes a huge difference. My stock 2001 Silverado with an 8.1L and my ’78 K10 with a stock 8.1L run night and day different from each other just due to ECM tuning. Now my ’89 Suburban with a RayLar cam runs entirely different than the ’78 K10. The Suburban is also in the midst of getting tuned so it will run even better once the chop gets tuned out. It has a date with a Dyno Tuner in late May. I can’t wait!

Hopefully your buddy didn’t really retain the stock 67-72 engine mount design as I doubt those will hold very long with an 8.1L. My ’68 GMC 2wd with a bored and whored 396 has habitually ripped apart the driver’s side engine mount over and over. In fact, back in the day GM even had a recall to add a cable from the frame to the driver’s side exhaust manifold because the engine mounts breaking were so common. The reason they tied the engine to the frame was because when the engine mount broke it would jam the throttle linkage rod and stick the throttle wide open. What most people do to fix the sucktastic engine mounts on 67-72 trucks is to install 73-87 engine mount frame brackets then use the 73-87 clam shell type engine mounts. The clam shell mounts are much more durable than the old single bolt design. Safer too!

 

[Tncumminsguy]

Cool!

Yeah, just having some ECM tuning done and removing TM makes a huge difference. My stock 2001 Silverado with an 8.1L and my ’78 K10 with a stock 8.1L run night and day different from each other just due to ECM tuning. Now my ’89 Suburban with a RayLar cam runs entirely different than the ’78 K10. The Suburban is also in the midst of getting tuned so it will run even better once the chop gets tuned out. It has a date with a Dyno Tuner in late May. I can’t wait!

Hopefully your buddy didn’t really retain the stock 67-72 engine mount design as I doubt those will hold very long with an 8.1L. My ’68 GMC 2wd with a bored and whored 396 has habitually ripped apart the driver’s side engine mount over and over. In fact, back in the day GM even had a recall to add a cable from the frame to the driver’s side exhaust manifold because the engine mounts breaking were so common. The reason they tied the engine to the frame was because when the engine mount broke it would jam the throttle linkage rod and stick the throttle wide open. What most people do to fix the sucktastic engine mounts on 67-72 trucks is to install 73-87 engine mount frame brackets then use the 73-87 clam shell type engine mounts. The clam shell mounts are much more durable than the old single bolt design. Safer too!

Stock 8.1 mounts not the K20, I was mistaken! I'm starting my hunt for one right now, he paid around 1100 for his complete so thats what i'm after

 

[Larry]

Stock 8.1 mounts not the K20, I was mistaken! I'm starting my hunt for one right now, he paid around 1100 for his complete so thats what i'm after

Yeah, it seems $800 on up to $1800 seems to be the going price for an 8.1L. The best and worst thing about the 8.1L is nobody knows anything about them which can yield some decent purchase prices. Meanwhile, Ls engines are starting to go for stupid money. Here is an example of some a-hole asking $4000 for a little 5.3L!

 

[-stew-]

I'm into mine for $5-600. And I left money in the van when I scrapped it. The sister to the van I bought is gonna be coming up on the auction block this summer. I might grab it and strip it for future use.

 

[Upstate]

Yeah, it seems $800 on up to $1800 seems to be the going price for an 8.1L. The best and worst thing about the 8.1L is nobody knows anything about them which can yield some decent purchase prices. Meanwhile, Ls engines are starting to go for stupid money. Here is an example of some a-hole asking $4000 for a little 5.3L!

Here in NY 5.3 are going for $500-800.

 

[Larry]

Here in NY 5.3 are going for $500-800.

As they should.....

 

[Upstate]

As they should.....

I see in your signature you are the man on NV 4500. I just bought a '94 with bell adapter and a 208 hooked up to it. My bell only had a fork, interested in pointing me the way on what I need and where to buy the rest of the parts for the bell?

Also, no one and I mean no one around here wants to mess with sticks (rebuild) .Alternative?

 

[Larry]

I see in your signature you are the man on NV 4500. I just bought a '94 with bell adapter and a 208 hooked up to it. My bell only had a fork, interested in pointing me the way on what I need and where to buy the rest of the parts for the bell?

Also, no one and I mean no one around here wants to mess with sticks (rebuild) .Alternative?

What else do you need? What are you putting it in? If you’re installing this into an old square body truck (or older), I suggest using the Advance Adapters bell 712576 along with their slave cylinder bracket 715535 that way you can run off the shelf 85-91 square body hydraulic parts (slave, m/c and hose). If you are putting it in GMT400 truck then just find 92-94 pieces. Napa sells new forks and pivot balls.

Yeah, I don’t blame anybody for not wanting to touch a NV4500 to rebuild. They are finicky transmissions to dick with. The one in my Suburban has been gone through twice and still won’t go into 5th gear unless you get into a fist fight with it and punch it in 5th. The guy doing the work is a well-respected GM master tech but if you don’t do these 4500’s everyday they are hard to get really good at building. I would suggest doing an exchange with someone on Ebay or something like that. The one in my K10 is actually a NOS trans from an Ebay seller in Texas. $1000 exchange but that was 4 years ago. I don't know the sellers name off hand but I recently saw he was still on Ebay.

 

[Upstate]

So my components from my hydro bell SM465 with work with the AA bell?

Do you mind if I pm you with questions?

 

[Larry]

So my components from my hydro bell SM465 with work with the AA bell?

Do you mind if I pm you with questions?

If you have an 85-91 square body, then yes you’re existing hydraulic components will go right on the AA bell when using their hydro bracket. Yes, PM me so this 8.1L can stay on track

 

[Upstate]

I got to ask, what are the negatives of installing a 8.1 in a K5 other than weight? Frankly I don't see to many.

 

[Larry]

I got to ask, what are the negatives of installing a 8.1 in a K5 other than weight? Frankly I don't see to many.

Me neither . I find them much cheaper and easier to install than a LS small block with greater rewards in the end. Many times one can find an 8.1L for less money than a small LS engine because most people don’t know anything about the 8.1L whereas the demand & knowledge base (and price) for used LS engines has gone crazy. An 8.1L is even an easier swap if you’re going from an older BBC to an 8.1L as there would be no exhaust work needed to be done. The only downside I can think of is finding an 8.1L, although they seem to be popping up more and more lately. As with any late model engine swap don’t be surprised that the install bits and pieces (harnesses, fuel lines, air induction, etc.) cost more than what the engine costs itself. It is not uncommon to for an $800 engine to end up being a $4000 engine swap by the time everything is all said and done. As I’ve said many times before, I am not a promotor of using a donor truck harness. Pony up the money and buy a fresh stand-alone harness. It would be the best $600 a person could spend on a late model engine swap.

You will hear a lot of people whine of the lack of aftermarket support for the 8.1L but in reality, what does one REALLY need from the aftermarket?? In bone stock form with some minor ECM tuning the 8.1L can run very close to 400HP and 500 lb. ft. of torque. If that isn’t enough, any older BBC header will fit an 8.1L and RayLar has plenty of hop up goodie$. In my opinion a bone stock 8.1 with gobs of torque is what is needed in a big 4x4….not high end HP like little LS produce. Let the tuner crowd play with those cute little windup engines

 

[Upstate]

Me neither . I find them much cheaper and easier to install than a LS small block with greater rewards in the end. Many times one can find an 8.1L for less money than a small LS engine because most people don’t know anything about the 8.1L whereas the demand & knowledge base (and price) for used LS engines has gone crazy. An 8.1L is even an easier swap if you’re going from an older BBC to an 8.1L as there would be no exhaust work needed to be done. The only downside I can think of is finding an 8.1L, although they seem to be popping up more and more lately. As with any late model engine swap don’t be surprised that the install bits and pieces (harnesses, fuel lines, air induction, etc.) cost more than what the engine costs itself. It is not uncommon to for an $800 engine to end up being a $4000 engine swap by the time everything is all said and done. As I’ve said many times before, I am not a promotor of using a donor truck harness. Pony up the money and buy a fresh stand-alone harness. It would be the best $600 a person could spend on a late model engine swap.

You will hear a lot of people whine of the lack of aftermarket support for the 8.1L but in reality, what does one REALLY need from the aftermarket?? In bone stock form with some minor ECM tuning the 8.1L can run very close to 400HP and 500 lb. ft. of torque. If that isn’t enough, any older BBC header will fit an 8.1L and RayLar has plenty of hop up goodie$. In my opinion a bone stock 8.1 with gobs of torque is what is needed in a big 4x4….not high end HP like little LS produce. Let the tuner crowd play with those cute little windup engines

The 5.3 have their place. I done a couple in a TJ and they work great. I am also a strong advocate of MSD Atomic set ups and prefer tuning them over factory FI when it comes to performance applications. In this case other than headers I would leave the 8.1 alone.

I been looking at Pacific Fabrication mostly because they sell a complete 8.1. I realize it isn't cheap but around here they sell the 8.1 for 3 times a 5.3.

 

[y5mgisi]

The only downside I see to the 8.1 is the parts availability. Larry, even you had trouble finding something like cam bearings if I remember right. And in a stock ish k5,i bet the 5.3 would get a couple mpg better. But I bet something like a burb or a bigger truck it would start to even out a bit. My burb with th400 and 5.3 does 12 in town and 14 on the highway. I bet with od it would do 16. But it sure doesn't move like it has a big block! It cruises any grade I have encountered so far here in Oregon at whatever the highway speed is pretty easily. With a weekend worth of gear in the back, passing people is no problem like it used to be in with the tbi 350. But, I think if I did more towing or had it weighed down more often, I bet I would start to find the 5.3 struggling. I think a pair of quads on the trailer would be about the maximum the 5.3 could handle and still maintain 55-65mph up any Hill. With an 8.1, I bet you could haul another burb and still maintain 55-65mph with fair ease!

I definitely want to own an 8.1 some day! It's just hard when buying one costs about as much as a 5.3 swap does complete.

 

[Larry]

True, the LS have their place and a little TJ is a perfect place for one or even a light K5. I’m helping build a 5.3L K5 for my buddy Rob as we speak. I trust it will work fine for something light like that.

That is odd, you are finding 8.1L prices that high. Most of the guys on the 8.1L Facebook group are picking them up from $500 to $1500. Majority of them under $1000. There can be some internal 8.1L parts that are hard if you want to stick with OEM pieces. Cam bearings and rod nuts are perfect examples that I struggled to find but I am the kind of guy that pretty much only uses GM parts. I could have settled for cam bearings from Napa and found rod nuts elsewhere if I wanted to dig into the aftermarket side but I was trying to keep the build cost down.

I’ll be away until after Memorial Day. Heading out on our annual desert trip for 8 day starting tomorrow morning. Loading up the truck now

 

[Upstate]

Enjoy the trip. As for me I have 4.56 riding on true 37s with a soon to be NV4500. I really like the fact that the 8.1 can use BBC exhaust were the 5.3 is a pain with headers. Got some time to figure it out. The K5 has a new crate motor with 1 hour on it. But I am always planning for tomorrow.

 

[olive-drab]

Larry, what are you having problems with in NV4500? I keep flip flopping between it and the zf6.

I briefly thought about the allison, but prefer manual and don't want to deal with vss or anything like that.

 

[Upstate]

Larry, what are you having problems with in NV4500? I keep flip flopping between it and the zf6.

I briefly thought about the allison, but prefer manual and don't want to deal with vss or anything like that.

Exactly why I am going 4500. Not really any cheaper but in my position I can easily swap motors without headache.

 

[Larry]

Larry, what are you having problems with in NV4500? I keep flip flopping between it and the zf6.

I briefly thought about the allison, but prefer manual and don't want to deal with vss or anything like that.

Exactly why I am going 4500. Not really any cheaper but in my position I can easily swap motors without headache.

I had problems with both NV4500’s but they are behind me now….hopefully. We’ll see! The problems were not related to the fact it was behind an 8.1L but more due to the fact I foolishly used an Advance Adapters kit to mount a 27 spline 205 behind a 4500. The kit requires trans tail shaft to be cut off and the only thing that hold 5th gear is their cheesy collar and the pressure of the tcase bolted to the trans. I took that crap off and got a round pattern 205 and did away with the AA pieces except the bell housing. The other problem was the fact I mismatched parts between a low tower 4500 and a GMT880 Silverado/Sierra HD NV4500 which has a taller cover to compensate for the 2" body raise used on HD trucks. That is explained HERE, which not a single person found the information interesting enough to comment

As far as the ZF, piss on that trans. It is huge and miserable to row around. I have on in my 2001 Silverado HD behind an 8.1L. I hated that trans when I drove it off the lot 15 years ago and hate it more and more each year. Very awkward bastid to shift.

That’s it for a while. I am loaded and ready to roll out around 7 AM. THIS LINK will go live once we hit the road. You all can watch us like ants in an ant farm all week. Planning on 7 to 9 days roaming the Utah back country. White Rim, Lockhart Basin, & Needles District then start working our way home.

 

[coloradoblazers]

Larry,
I have some questions on what you are doing to remove and install the engines.

the manual says to attach J36857 to the heads using 9428217 and 15650963.

Do you have an alternate method that might be more easy to procure?


Thanks