C3 Engine Swap
Thread Starter
Intermediate
Joined: Aug 2021
Posts: 49
Likes: 6
From: Elko, Nevada
C3 Engine Swap
Hey there! Im looking to get some advice and possibly any tips or ideas as I’m pulling the 350 out of my 81’. I had a bad engine knock on cylinder 6 and I was thinking of either rebuilding or possibly engine swapping to maybe an LS. I’ve been trying to do some research because I’m on a bit of a tight budget being 16, but I wanted to see if maybe it’s even possible to put a C4 engine into my C3. And if anyone else has done any engine swaps and what they would recommend I do in terms of electrical and other problems I might run into. Thank you so much!
Race Director
Joined: Nov 2006
Posts: 13,195
Likes: 7,795
From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
Your 16 years old. And about to do an engine swap.
I am hoping you have someone to help and guide you.
I too was once 16 and changing out an engine.
I had little help. OK. I had none help.
But no time like the present to learn!
An early C4 engine is basically the same engine and will bolt right in. Put your old intake manifold and carb on it and your running.
Any Gen 1 small block chev V8 will bolt straight in and your running.
A LS swap is definitely possible but will require much more work in terms of custom motor mounts. Rearranging accessories Etc. Not to mention fuel supply and wiring.
If I were you, and many years ago I was. I would keep it simple for your first engine swap. Find a good used 86 or older gen 1 Chev V8. Use your original intake, carb and distributor. All your original accessories will mount up.
No additional wiring will be needed.
On a budget and limited experience, Remember KISS!
Keep It Simple Stupid!
I am hoping you have someone to help and guide you.
I too was once 16 and changing out an engine.
I had little help. OK. I had none help.
But no time like the present to learn!
An early C4 engine is basically the same engine and will bolt right in. Put your old intake manifold and carb on it and your running.
Any Gen 1 small block chev V8 will bolt straight in and your running.
A LS swap is definitely possible but will require much more work in terms of custom motor mounts. Rearranging accessories Etc. Not to mention fuel supply and wiring.
If I were you, and many years ago I was. I would keep it simple for your first engine swap. Find a good used 86 or older gen 1 Chev V8. Use your original intake, carb and distributor. All your original accessories will mount up.
No additional wiring will be needed.
On a budget and limited experience, Remember KISS!
Keep It Simple Stupid!
Race Director
Joined: Nov 2006
Posts: 13,195
Likes: 7,795
From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
And then of course there is fixing your current engine.
Knock you say? Rod bearing? Or took a lobe off the cam?
Any idea as to what your Knock is?
When I was 16 going to the junk yard and buying a second hand engine out of a crashed car was almost always the cheapest way out.
Maybe not so today. Depends on what is wrong with your current engine and how cheap you can get a used good running gen 1 small block.
On a 16 year old budget, forget the fuel injected LS idea.
Great idea mind you. But you may wish to drive this car sooner rather than later.
Knock you say? Rod bearing? Or took a lobe off the cam?
Any idea as to what your Knock is?
When I was 16 going to the junk yard and buying a second hand engine out of a crashed car was almost always the cheapest way out.
Maybe not so today. Depends on what is wrong with your current engine and how cheap you can get a used good running gen 1 small block.
On a 16 year old budget, forget the fuel injected LS idea.
Great idea mind you. But you may wish to drive this car sooner rather than later.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
do an autopsy on current engine. drop the pan and see what you have. a crank kit and a couple of rods will most likely be best budget way to go. or a whole used set of flat pistons and rods from ebay. but you gotta be able to measure and inspect the parts. 2 used sets will most likely get you 8 good ones. i have also gone to core buyers and bought short blocks out of wrecked trucks for dirt cheap. they will be vortec blocks these days so you will need to do electric fuel pump.
Thread Starter
Intermediate
Joined: Aug 2021
Posts: 49
Likes: 6
From: Elko, Nevada
And then of course there is fixing your current engine.
Knock you say? Rod bearing? Or took a lobe off the cam?
Any idea as to what your Knock is?
When I was 16 going to the junk yard and buying a second hand engine out of a crashed car was almost always the cheapest way out.
Maybe not so today. Depends on what is wrong with your current engine and how cheap you can get a used good running gen 1 small block.
On a 16 year old budget, forget the fuel injected LS idea.
Great idea mind you. But you may wish to drive this car sooner rather than later.
Knock you say? Rod bearing? Or took a lobe off the cam?
Any idea as to what your Knock is?
When I was 16 going to the junk yard and buying a second hand engine out of a crashed car was almost always the cheapest way out.
Maybe not so today. Depends on what is wrong with your current engine and how cheap you can get a used good running gen 1 small block.
On a 16 year old budget, forget the fuel injected LS idea.
Great idea mind you. But you may wish to drive this car sooner rather than later.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
all your compression numbers are low. get a different compression tester. but rings are failing on 6 faster than the others. or burnt valve. drop the pan and see if the 8 rod bearings are tight or if one can be wobbled by hand. best bet is replace all rods and mains if crank doesn't look hurt. pull the heads and leak test the valves. quickie method is lay head on it's side and fill exh and intake ports with water and see if it pours or barely drips past the valves. you want more power, you want different heads and long tube headers and the cat mysteriously falls off the car. the electronic carb and crappy computer control (that is the real meaning of CCC) distributor go on ebay and get replaced by any 80-earlier q-jet that Lars approves of and rebuilt. and most any 75-80 HEI distributor. they range from 30 bucks on ebay to 400 from DUI.
Thread Starter
Intermediate
Joined: Aug 2021
Posts: 49
Likes: 6
From: Elko, Nevada
all your compression numbers are low. get a different compression tester. but rings are failing on 6 faster than the others. or burnt valve. drop the pan and see if the 8 rod bearings are tight or if one can be wobbled by hand. best bet is replace all rods and mains if crank doesn't look hurt. pull the heads and leak test the valves. quickie method is lay head on it's side and fill exh and intake ports with water and see if it pours or barely drips past the valves. you want more power, you want different heads and long tube headers and the cat mysteriously falls off the car. the electronic carb and crappy computer control (that is the real meaning of CCC) distributor go on ebay and get replaced by any 80-earlier q-jet that Lars approves of and rebuilt. and most any 75-80 HEI distributor. they range from 30 bucks on ebay to 400 from DUI.
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Thread Starter
Intermediate
Joined: Aug 2021
Posts: 49
Likes: 6
From: Elko, Nevada
Your 16 years old. And about to do an engine swap.
I am hoping you have someone to help and guide you.
I too was once 16 and changing out an engine.
I had little help. OK. I had none help.
But no time like the present to learn!
An early C4 engine is basically the same engine and will bolt right in. Put your old intake manifold and carb on it and your running.
Any Gen 1 small block chev V8 will bolt straight in and your running.
A LS swap is definitely possible but will require much more work in terms of custom motor mounts. Rearranging accessories Etc. Not to mention fuel supply and wiring.
If I were you, and many years ago I was. I would keep it simple for your first engine swap. Find a good used 86 or older gen 1 Chev V8. Use your original intake, carb and distributor. All your original accessories will mount up.
No additional wiring will be needed.
On a budget and limited experience, Remember KISS!
Keep It Simple Stupid!
I am hoping you have someone to help and guide you.
I too was once 16 and changing out an engine.
I had little help. OK. I had none help.
But no time like the present to learn!
An early C4 engine is basically the same engine and will bolt right in. Put your old intake manifold and carb on it and your running.
Any Gen 1 small block chev V8 will bolt straight in and your running.
A LS swap is definitely possible but will require much more work in terms of custom motor mounts. Rearranging accessories Etc. Not to mention fuel supply and wiring.
If I were you, and many years ago I was. I would keep it simple for your first engine swap. Find a good used 86 or older gen 1 Chev V8. Use your original intake, carb and distributor. All your original accessories will mount up.
No additional wiring will be needed.
On a budget and limited experience, Remember KISS!
Keep It Simple Stupid!
Safety Car
Joined: Dec 2012
Posts: 3,801
Likes: 1,712
From: Summerville SC
You might also want to put up where you live. There are lots of us old guys looking to share our years of knowledge with younger people who are not afraid to get their hands dirty. And good luck with your first project. Someone once told me you never forget your first time...
Thread Starter
Intermediate
Joined: Aug 2021
Posts: 49
Likes: 6
From: Elko, Nevada
You might also want to put up where you live. There are lots of us old guys looking to share our years of knowledge with younger people who are not afraid to get their hands dirty. And good luck with your first project. Someone once told me you never forget your first time...
Safety Car
Joined: Dec 2012
Posts: 3,801
Likes: 1,712
From: Summerville SC
Between the knowledge here on this forum and you tube, you should be able to handle this. Stick with the simple small block chevy engine and maybe pick up a book on whatever part of the restore you are working on. The best way is to ask questions, understand how the thing works, then start to take it apart. It is already broken, right, how much more damage can you do! Seriously, we all started someplace and will be glad to walk you through. Have a plan as to what you want the engine to do. DOn't get carried away with the buy a cam, bigger carb, yada yada. Stick with a simple stock rebuild at first. As you begin to take it apart, take pictures ( I wish we had cameras in our phones back in the day,, but we didn't have phones either) and try to understand the part and what it does. I pretty much know I don't know everything, but if I take it apart, I know I can put it back together. You can do this.
Burning Brakes
Joined: Mar 2022
Posts: 1,159
Likes: 491
You might also want to put up where you live. There are lots of us old guys looking to share our years of knowledge with younger people who are not afraid to get their hands dirty. And good luck with your first project. Someone once told me you never forget your first time...
Last edited by Corvette-ZL1; Nov 11, 2022 at 06:49 PM.
Thread Starter
Intermediate
Joined: Aug 2021
Posts: 49
Likes: 6
From: Elko, Nevada
Between the knowledge here on this forum and you tube, you should be able to handle this. Stick with the simple small block chevy engine and maybe pick up a book on whatever part of the restore you are working on. The best way is to ask questions, understand how the thing works, then start to take it apart. It is already broken, right, how much more damage can you do! Seriously, we all started someplace and will be glad to walk you through. Have a plan as to what you want the engine to do. DOn't get carried away with the buy a cam, bigger carb, yada yada. Stick with a simple stock rebuild at first. As you begin to take it apart, take pictures ( I wish we had cameras in our phones back in the day,, but we didn't have phones either) and try to understand the part and what it does. I pretty much know I don't know everything, but if I take it apart, I know I can put it back together. You can do this.
Thread Starter
Intermediate
Joined: Aug 2021
Posts: 49
Likes: 6
From: Elko, Nevada