8.1 in a C15

[AP Guy]

Hey all,

New to the forum but have read a handful of posts on swapping in an 8.1 vortec in the k20 trucks but has anyone dropped one in a 2wd half ton?

I own a 3/4 ton suburban with the 8.1 and have grown to love this engine. I was somewhat unaware of these until owning and driving one. The torque is just nuts... anyway... I have a 78 Sierra Classic that I've owned and driven on&off for 15+ years that I want to revive again. Everyone jumps on the 5.3/6.0 swaps but I want to do something a bit different, hence the 8.1 idea.

Im planning on dropping the truck via drop spindles and/or shorter coil springs and an axle flip kit out back. One of my concerns is the weight of the 8.1 on stock 1/2 ton front suspension being the 8.1 is an all iron block weighing close to 800lbs...

Anyone completed a swap on a c10/15? Is it a simular process to what's been done already on the k20's? Will the c10 front end support that weight?

This is all still in the planning stages at this point but just trying to do a little research before I start pulling parts off

Thanks in advance and if this has been done already and I missed the thread please feel free to post a link to it.

 

[Dutch Rutter]

Welcome to the forum!

From everything I have read (all K series) the swap is one of the easier to do. With you wanting it in a 2wd that should make sourcing parts even easier. No need to track down a rare t-case, or swap the front end. Your transmission choice will be important as that may or may not need the crossmember relocated, from here you may need a custom length drive line made up which would be a good idea to beef up along with the rear end. I'm sure the torque from the 8.1l would eat up a stock c10 rear pretty quickly.

As for the weight I'm not very sure. I could see it not being too hard to swap in 3/4 ton front springs along with some other heavier duty items to make up for the added weight. However, I would also be concerned about the frame holding up to the weight and added torque. Another thing to keep in mind is the oil pan to frame and oil pan to ground clearance. This has never been talked about too much in other builds as they have been done on lifted 4x4s but on a lowered 2wd this will definitely come into play.

I am a huge fan of the 8.1l swaps btw, but if you had a c20 (especially an originally diesel c20, as you would have the hydro boost and HUGE radiator already plus the heavier suspension, frame and rear end) it would probably be a better candidate. Not to say the C10/15 would be impossible or anything, just a bit more challenging with more things to overcome. I'll definitely be following your project.

 

[AP Guy]

Welcome to the forum!

From everything I have read (all K series) the swap is one of the easier to do. With you wanting it in a 2wd that should make sourcing parts even easier. No need to track down a rare t-case, or swap the front end. Your transmission choice will be important as that may or may not need the crossmember relocated, from here you may need a custom length drive line made up which would be a good idea to beef up along with the rear end. I'm sure the torque from the 8.1l would eat up a stock c10 rear pretty quickly.

As for the weight I'm not very sure. I could see it not being too hard to swap in 3/4 ton front springs along with some other heavier duty items to make up for the added weight. However, I would also be concerned about the frame holding up to the weight and added torque. Another thing to keep in mind is the oil pan to frame and oil pan to ground clearance. This has never been talked about too much in other builds as they have been done on lifted 4x4s but on a lowered 2wd this will definitely come into play.

I am a huge fan of the 8.1l swaps btw, but if you had a c20 (especially an originally diesel c20, as you would have the hydro boost and HUGE radiator already plus the heavier suspension, frame and rear end) it would probably be a better candidate. Not to say the C10/15 would be impossible or anything, just a bit more challenging with more things to overcome. I'll definitely be following your project.

Great input! I didn't think about the rear end yet...or frame strength. I'm half tempted to see where the front end would sit with it installed before I go throw money at drop spindles and then have it sitting too low. Although drop spindles and k series springs might be the way to go.

Again, this is just an idea that's been in my head for a long time. I'm just now getting around to asking questions lol. I'm sure a 5.3 swap would be fast and easy with endless aftermarket goodies but I'd love to say there's an 496 vortec under the hood when folks ask

First things first... try to find an 8.1 to yank out of something that's not going to cost me an arm and leg.

 

[4WDKC]

Welcome to the forum!

From everything I have read (all K series) the swap is one of the easier to do. With you wanting it in a 2wd that should make sourcing parts even easier. No need to track down a rare t-case, or swap the front end. Your transmission choice will be important as that may or may not need the crossmember relocated, from here you may need a custom length drive line made up which would be a good idea to beef up along with the rear end. I'm sure the torque from the 8.1l would eat up a stock c10 rear pretty quickly.

As for the weight I'm not very sure. I could see it not being too hard to swap in 3/4 ton front springs along with some other heavier duty items to make up for the added weight. However, I would also be concerned about the frame holding up to the weight and added torque. Another thing to keep in mind is the oil pan to frame and oil pan to ground clearance. This has never been talked about too much in other builds as they have been done on lifted 4x4s but on a lowered 2wd this will definitely come into play.

I am a huge fan of the 8.1l swaps btw, but if you had a c20 (especially an originally diesel c20, as you would have the hydro boost and HUGE radiator already plus the heavier suspension, frame and rear end) it would probably be a better candidate. Not to say the C10/15 would be impossible or anything, just a bit more challenging with more things to overcome. I'll definitely be following your project.

The 1/2 ton got the 6.2 and while it was no power house it was heavy, shouldnt it be the same frame as 350 truck?

 

[idahovette]

Didn't GM put 454 -turbo 400's in these trucks ? Shouldn't much if any difference in the 2. Cooling and rear end may be the touchy spots. I would put the engine -trans in and see where it sits, might be ok. Like to watch where this goes, sounds FUN !!

 

[4WDKC]

Didn't GM put 454 -turbo 400's in these trucks ? Shouldn't much if any difference in the 2. Cooling and rear end may be the touchy spots. I would put the engine -trans in and see where it sits, might be ok. Like to watch where this goes, sounds FUN !!

Have read they use the same mounts and exhaust as a 454 so shouldnt be a problem, Im pretty sure you could get a 454 c20 not sure about the c10 though.

 

[Dutch Rutter]

The 1/2 ton got the 6.2 and while it was no power house it was heavy, shouldnt it be the same frame as 350 truck?

I actually was unaware they put the 6.2 and the 454 in them from the factory. I thought that was a 3/4 and up thing. Thank you for the correction! The 6.2 was what 650-700lbs? and a 454 is in that same ball park? an auto trans will also add weight if going to a heavy pig like an Allison. If however, going to a manual a 2wd zf6 or something with an NV-something or other would be awesome in a 2wd retromod streetrod square.

The fun thing about the 8.1, from what I've read, they use the same mounts, headers and placement on the frame as a bbc.

 

[idahovette]

GM put 454's in at least 73 thru 76 C10 mostly with turbo 400's. We had a ton of them come thru our Chev-Cad dealership . Early one's were mostly Cheyenne Super packages with all the bells and whistles. Really really expensive some almost $5500-6000 !!!

 

[4WDKC]

I actually was unaware they put the 6.2 and the 454 in them from the factory. I thought that was a 3/4 and up thing. Thank you for the correction! The 6.2 was what 650-700lbs? and a 454 is in that same ball park? an auto trans will also add weight if going to a heavy pig like an Allison. If however, going to a manual a 2wd zf6 or something with an NV-something or other would be awesome in a 2wd retromod streetrod square.

The fun thing about the 8.1, from what I've read, they use the same mounts, headers and placement on the frame as a bbc.

Wiki says the 6.2 was heavier than the 454 and I thought the 454 was 750 lbs
https://en.wikipedia.org/wiki/Detroit_Diesel_V8_engine

 

[Dutch Rutter]

Wiki says the 6.2 was heavier than the 454 and I thought the 454 was 750 lbs
https://en.wikipedia.org/wiki/Detroit_Diesel_V8_engine

A stock 8.1 specs are listed as 330hp and 450 ftlbs and weighs in at 761lbs. Sounds like weight and frame wont be a big deal, and should work out pretty close to a 454.

 

[AP Guy]

Thanks for all the replies guys! If I can find one, although unfamiliar with the ZF6, I would LOVE to have a manual in a 2WD reg cab. Talk about fun city! A little more realistic, or more readily available would be another 4l80E. Unless I can yank one out of a 3/4 ton roller that already has the Allison mated to it. Definitely don't need an Allison behind it for my application but we'll see what I can find.

 

[Charlie]

 

[malibuman402]

Welcome, here are some pics of my 84 c10 with a built 402. stock from bell housing back to the 10 bolt rear end. lowered front with springs 2.5", lowered back 4" with brackets and shackles. eng has about 460 hp and 500 lb ft torque.

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[malibuman402]

my 84 came with the np833a 4 spd or should i say 3 spd with od. its alot of fun to drive. the 402 is more fun than the 305 that came in it.

 

[AP Guy]

Welcome, here are some pics of my 84 c10 with a built 402. stock from bell housing back to the 10 bolt rear end. lowered front with springs 2.5", lowered back 4" with brackets and shackles. eng has about 460 hp and 500 lb ft torque.

You must be registered for see images attach

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Love it! That looks like it would be a blast to drive!

What tire and wheel size do you have on your truck? Great look.