Author Topic: '76 C10 3spd manul to 5.7 vortec and 4l60E swap help!  (Read 482 times)

Offline DIG

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'76 C10 3spd manul to 5.7 vortec and 4l60E swap help!
« on: February 24, 2022, 02:15:41 PM »
I have a 1976 C10 Stepside with a 250 straight six and a 3 on the tree manual transmission that I want to swap a 1996 5.7 vortec and 4l60E out of a 1996 Chevy express 1500 Van. I have the entire van for any parts I may need. My vortec engine does have the mechanical fuel pump block off plate which I believe means it can be carb'd in the future as long as I swap the cam with a lobe on it. So I was going to swap a 700R4 behind it and go full mechanical but I cannot find a used 700R4 to buy (700R4's new are extremely expensive, worth more than my truck is!). I may have to go to the junkyard and get one to rebuild but I really dont feel comfortable rebuilding an auto trans. Right now I just need to get the truck driving so I thought using the vortec and 4L60E as is would be my best bet.

I need to know what all I am going to have to do/buy to swap the 5.7 vortec and 4L60E into my truck.

Will I need to buy a specialty wiring harness or can I use the existing one without too much hassle?
Will I need any transmission mounts?
Will I need a new or custom driveshaft?
Will I need a new steering column or is there an adapter kit I can use to use the existing 3 on the tree column?
Will I need an aftermarket fuel pump or can I use the vans fuel pump?

Anything else I need to know will be greatly appreciated!


1976 Chevy C10 250 I6 3 speed manual > Future: 350  V8 th350 Trans with Hurst shifter

Offline VileZambonie

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Re: '76 C10 3spd manul to 5.7 vortec and 4l60E swap help!
« Reply #1 on: February 24, 2022, 05:01:51 PM »
If it truly is an L31 350 there should not be a block off plate as there was no provision for the mechanical fuel pump. If you plan to use the 4L60E, you will need to use a controller. Are you going to use the PCM and wiring harness from the van? If you want to run a carbureted setup and standard HEI, you will need a return style regulator and just use an in tank pump TBI pump/sender. You would need a vortec intake manifold as well. Yes you will need a driveshaft and steering column for an automatic truck with shift linkage.

I am actually building an L31 from a 96 Suburban right now that is going in my K5.
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline DIG

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Re: '76 C10 3spd manul to 5.7 vortec and 4l60E swap help!
« Reply #2 on: February 25, 2022, 06:46:36 AM »
It is definitely a vortec and I've seen reference to the mechanical fuel pump block off plate and milled port on several vortec blocks. This engine is the original for the van from the factory. As for the pcm and wiring harness I am unsure if I can use it. My truck is a 1976 c10 so it has vary little in the way of electrical. Do I just simply hook up the required electrical for the new engine and trans with the vans harness then plug in my trucks  lights, blinkers, windshield wipers and battery to the new harness? Would they be cross compatible or do I somehow run both harnesses, one for engine and trans, distributor, pcm, alternator etc and the original truck harness for the rest? I know painless sells a swap harness but it's $600 and I don't really want the electrical components anyways. So if it was just gonna be a relatively simple and easy swap I was just going to leave it in for now. But if I'm having to spend that kind of money I'd just try harder to find a 700r4 and begrudgingly rebuild it. I've also seen a linkage kit that can be used to utilize the original 3 on the tree steering column for an automatic transmission. So I'll be trying that before I buy a new or used tilt auto column. Id like to keep the ability to quickly swap back to the original manual transmission if needed. As for the drive shaft I doubt either the trucks original or the vans aluminum one will fit. Is that something I can custom order by length online or do I need a shop to make a custom one? I'd like to spend as little as possible as the van was free. Too bad I want overdrive otherwise I'd just order a brand new th350 and rebuild the engine haha. I'm going to eventually restore most of the truck but for now I just need it to drive.
1976 Chevy C10 250 I6 3 speed manual > Future: 350  V8 th350 Trans with Hurst shifter

Offline wz7u

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Re: '76 C10 3spd manul to 5.7 vortec and 4l60E swap help!
« Reply #3 on: February 25, 2022, 08:40:12 PM »
Seems to my noggin if you want to run early model electronic engine and trans control, you're going to have to give those systems something to work with from the original system. I see another sub harness being the option, consisting of all the parts that feed and manage the replacement drive train (computer too) spliced into the rest of the chassis wiring. I doubt you will be able to put the van harness in place of the pickup harness. This isn't a simple modification to do properly. There are many facets to be considered at the same time. Physical fitment concerning drive lines and mounts need to happen as you go since you are creating a new thing altogether. Lots of this will most likely require a bit of re-engineering of things and their location relative to each other.

Your signature line doesn't give much inspiration towards a satisfactory conclusion, sorry. But, if done with care and precision, this is a doable project at home.
'79 C20 454/th400 "Pearl"

Offline VileZambonie

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Re: '76 C10 3spd manul to 5.7 vortec and 4l60E swap help!
« Reply #4 on: February 26, 2022, 07:17:35 AM »
Quote
I've seen reference to the mechanical fuel pump block off plate and milled port on several vortec blocks

This was common in the 87-95 era, you would need to check the pad on the front of the deck to see if the serial number matches the van. The van wiring harness for the PCM & Trans can be added to your trucks existing wiring harness if you safely add the correct power and ground distribution. You would need to get an adapter or a different speedometer to make that function. You'd need to replace your fuel lines, fuel sender, pump and all of the prior things mentioned. You may think you are saving money but I doubt it and in the end your truck will be viewed as a highly molested truck, not going to help its value if that matters to you. I think you should reconsider doing this swap altogether since you have direct fit options that will ultimately cost less and not require all of the work arounds. A 700R4/4L60 is a direct drop in with minimal effort. The engine might be a great specimen for a new powerplant, but maybe you'd be better off selling or parting out the van to fund getting more direct fit parts.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10