Author Topic: K20 engine sizes  (Read 1740 times)

Offline TheBigHat

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K20 engine sizes
« on: February 09, 2021, 05:14:13 PM »
I'm trying to figure out if my engine has been swapped or not. The previous owner claimed it was a 350 in my 78 K20 but I read an article online that showed that the K20 didn't come with a 350, it came with a 400. The front of the head looks like a ski slope design kind of like [\ , aren't those 400 smog heads? They aren't great I know but I'm just trying to figure out what I'm starting with. Also, I should be able to tell what it came with by the VIN too right? Any information would be appreciated. I'm so tempted to yank it but I always to that and end up with a 5 colored, rusted out, flying gas can because I put my budget all into the drive train! LOL! Save me!

Offline SilverMiner

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Re: K20 engine sizes
« Reply #1 on: February 09, 2021, 05:39:41 PM »
There were no less than 3 engines available for the K20 in 1978 - the 292 inline 6, the 350, and the 400. Your VIN would be a definitive source to confirm whether or not your truck originally had the 400. If it had the 400, the first three letters of the VIN would be CKR which translates to C = Chevrolet, K = 4wd, R = 400.

But after more than 40 years and multiple owners, it can be a real hunt to decipher what changes may have been made over that span of time. Engines, transmissions and of course entire axles can be swapped out easily in these trucks so simply knowing what it came with originally doesn't guarantee that is what the truck has today.

If you're curious to know every specification available in 1978, the Vehicle Information Kits at the GM Archives are a great resource and allows you to download a PDF describing everything from paint and interior options to engines, gear ratios, GVW figures, etc. https://www.gmheritagecenter.com/gm-heritage-archive/vehicle-information-kits.html
If you really want to nail down exactly what options your truck had at the time of delivery you can order a build sheet and invoice for the low price of $50.

Offline TheBigHat

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Re: K20 engine sizes
« Reply #2 on: February 09, 2021, 05:47:21 PM »
Thank you! I was just thinking of putting some rockers on it for a little more lift but then was wondering what cam it came with to do the math on what ratio to use. I tried looking into it for that purpose when I found a list of possible specs that did not have a 350 as a possibility for my model. I didn't know whether to trust that or not but I do trust the VIN, so thank you!

Offline TheBigHat

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Re: K20 engine sizes
« Reply #3 on: February 09, 2021, 05:58:19 PM »
OK, so got the ol' registration out. Says CKL :( Bummer, I was really hoping! So, is L 350 or didn't they have 307's too. Not that I want a 307 but it would be nice to know.

Offline JohnnyPopper

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Re: K20 engine sizes
« Reply #4 on: February 09, 2021, 08:03:49 PM »
I think you can also reference the number on the block.

Someone recently posted a table that I used to ID the number 14010207.

350, year range, models used in, that I have already forgot.  ;D

It's the casting on the block behind head of even cylinders.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline SilverMiner

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Re: K20 engine sizes
« Reply #5 on: February 10, 2021, 12:59:15 PM »
OK, so got the ol' registration out. Says CKL :( Bummer, I was really hoping! So, is L 350 or didn't they have 307's too. Not that I want a 307 but it would be nice to know.

Yep, the L definitively means your truck originally came with the 350 and not the 400.

BUT...

That still doesn't confirm what may actually be sitting in the engine bay today. Of all the squarebodies I've owned over the past 42 years it's been 33 years since I bought one with an original engine, and all the rest were claimed to have a "350 from a Corvette". I've learned to believe nothing I'm told and to only trust the ID stamped onto the block as JohnnyPopper suggested. And even then surprises can await once you open up the engine.

Offline JohnnyPopper

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Re: K20 engine sizes
« Reply #6 on: February 10, 2021, 07:51:10 PM »
So True Miner, though mine is a 350 it's actually a 383  ::)
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline 1980K20

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Re: K20 engine sizes
« Reply #7 on: February 19, 2021, 09:46:47 PM »
Bought my k20 without reading the engine casting. It was a 305. Sigh. I used a fiber optic camera to read it. Then was worried the th350 tyranny wasn't stock either, but the heritage museum said that was correct. Now I have a nice roller cam 350.  Just can't wait to get her on the road.

Sent from my SM-G965U using Tapatalk

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1952 International L112 - waiting for EV conversion
1967 Camaro - 250 six cyl, 200-4R
1980 K20 4x4 Fleetside - 350 SBC roller Cam, TH350