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Old 02-14-2018, 09:12 PM   #1
Chilly178
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5.7 Vortec for 72 C20

Hello, i'm planning on putting a 5.7 vortec in my C20. I think I have a lot of it worked out like plugging the crank sensor and running a carb with it. I'm wondering if my gauges will work as well. I only have a speedo and a fuel gauge, however I do plan on adding a aftermarket tach sometime as well. Thanks
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Old 02-14-2018, 09:29 PM   #2
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Re: 5.7 Vortec for 72 C20

The only problem with gauges would be the temp gauge. The temp gauge sending unit for the 72 will not fit the heads on the Vortec. There is a guy on here who will modify your sending unit to make it fit or you can install it in your intake. A lot of people frown on installing it in the intake but mine works just fine.
Don't forget if you don't have the heater core hooked up you will need to run a by-pass hose from your intake to the water pump.
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Old 02-14-2018, 09:45 PM   #3
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Re: 5.7 Vortec for 72 C20

I donít have a dedicated temp gauge. Are you talking about the idiot light?
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Old 02-14-2018, 09:55 PM   #4
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Re: 5.7 Vortec for 72 C20

Gauge and light both use a sending unit in the head or intake to operate.
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Old 02-15-2018, 09:55 AM   #5
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Re: 5.7 Vortec for 72 C20

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Originally Posted by Chilly178 View Post
Hello, i'm planning on putting a 5.7 vortec in my C20. I think I have a lot of it worked out like plugging the crank sensor and running a carb with it. I'm wondering if my gauges will work as well. I only have a speedo and a fuel gauge, however I do plan on adding a aftermarket tach sometime as well. Thanks
Why not keep the fuel injection? Vortec motors are pretty strong. Just replace the intake gaskets while it's out.

There is probably an idiot light on/off sensor for those heads. Just have to delve into the books at the parts store and find one with the right threads.
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Old 02-15-2018, 05:20 PM   #6
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Re: 5.7 Vortec for 72 C20

Don’t have the engine planning on buying the long block from GM. Carb will be much simpler in this old truck. Nothing wrong with a good carb. Any other things I should know about doing the swap?
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Old 02-15-2018, 07:26 PM   #7
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Re: 5.7 Vortec for 72 C20

You'll need a mellonized distributor gear - the roller cam will eat up a regular gear, an intake manifold for the Vortec bolt pattern, and your block will likely not be drilled for a mechanical fuel pump, so you'll need an electric fuel pump. You'll also need a new flexplate or flywheel for the one-piece rear main seal crankshaft.
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Old 02-15-2018, 07:53 PM   #8
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Re: 5.7 Vortec for 72 C20

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Originally Posted by MARKDTN View Post
There is probably an idiot light on/off sensor for those heads. Just have to delve into the books at the parts store and find one with the right threads.
http://67-72chevytrucks.com/vboard/s...d.php?t=726025
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Old 02-15-2018, 07:57 PM   #9
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Re: 5.7 Vortec for 72 C20

Yup I know about those. What I'm not sure about is what specific distributor I should buy and also what flywheel I need that will hopefully still fit my starter that was rebuilt last summer. I currently have a (junk) 350 with the SM465 so anyone know what will work?

Last edited by Chilly178; 02-15-2018 at 08:02 PM.
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Old 02-15-2018, 08:21 PM   #10
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Re: 5.7 Vortec for 72 C20

Do you have the bellhousing mounted starter or block mounted? The original SM465 would have 168 tooth flywheel with bellhousing mounted starter.

I'd by the MSD Streetfire HEI since it comes with the melonized gear. I think the GM performance parts one does as well, but I like the bushings and spring assortment for tuning that comes with the MSD.
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Old 02-15-2018, 09:49 PM   #11
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Re: 5.7 Vortec for 72 C20

Pretty sure it bolts right to the block. I remember because one of the bolt holes was partially broken so there is only two bolts holding the starter in.
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Old 02-15-2018, 09:55 PM   #12
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Re: 5.7 Vortec for 72 C20

The GM motor should come with a balancer but you need a flywheel for a one piece rear main seal.
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Old 02-17-2018, 02:13 PM   #13
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Re: 5.7 Vortec for 72 C20

Could someone explain what the coolant bypass is all about and how I would have to run my hoses. I was watching this video https://www.youtube.com/watch?v=Y91ut0D0wGo and he was saying something like if you put a older style water pump on the engine somthing about it spinning the wrong way and it shows he has some sort of loop for the intake manifold rigged up he talks about it at 30:00 in the video. I would be keeping the heater core, but I don't have AC, power steering, and use a manual trans. I know his is a square body and my truck is older than his so it would be a little different. He is also using a block he got out of a truck I think I would be just getting the L31-R long block from GM which may be different?
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Old 02-17-2018, 05:37 PM   #14
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Re: 5.7 Vortec for 72 C20

The guy on you tube has some goofy stuff going on. It might work but it sure ain't pretty!

Are you using a v belt setup like the original engine or are you using a serpentine drive system?

original V belt = standard rotation pump, bypass built into pump/block/head
Vortec serp belt = reverse rotation pump, external bypass using hose.

Vortec blocks do not have the bypass hole drilled into the block. The bypass is a hose on top of the water pump & goes into the intake. (see pic)

If you run a stock GM serp belt system, run a vortec pump with a bypass hose & your done.

If you run a V belt system you will need to drill the extra hole in your block for the water pump AND DRILL THE HOLE ON THE DECK OF THE BLOCK & THE CORESPONDING HOLE IN THE CYLINDER HEAD & MAKE SURE THE HEAD GASKET HAS A HOLE THERE ALSO.

If you google SBC water pump & SBC Vortec water pump you will see pics that show the vortec pump has one less hole.

Read this link, Captainfab has some great info & pics:

http://67-72chevytrucks.com/vboard/s...d.php?t=610112
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Old 02-17-2018, 06:31 PM   #15
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Re: 5.7 Vortec for 72 C20

Yes I was planning on using the V Belt. Thanks for the thread. So there is no other way of doing it you need to dril holes? Found some threads arguing about it.
http://www.hotrodders.com/forum/v-belt-5-7-liter-vortec-block-56138.html

http://67-72chevytrucks.com/vboard/s...d.php?t=667071 Post 19
http://www.hotrodders.com/forum/ther...on-161468.html Post 6
http://www.hotrodders.com/forum/vort...ng-233934.html

It sounds like to me if I run a hose from before the thermostat to the heater core then the return to the water pump this serves as the correct bypass instead of having to drill a hole in the block. This article seems to confirm this. http://www.hotrod.com/articles/coola...lly-neccesary/

Last edited by Chilly178; 02-17-2018 at 07:43 PM.
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Old 02-17-2018, 08:02 PM   #16
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Re: 5.7 Vortec for 72 C20

You do not need to drill any holes, just run a heater hose from the intake water jacket to the water pump. If you are going to run a carburetor the aftermarket intake should have a place to connect by the thermostat housing and run it to the water pump, there should be a plug on the top or the right hand side that you can use. If you are going to run a heater that will serve as your by-pass just don't install any shut-off valve in the line.
I have done two vortecs and I used the Summit brand Stage 1 intakes and they worked great.
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Old 02-17-2018, 08:33 PM   #17
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Re: 5.7 Vortec for 72 C20

Thanks Gary! I have a few other questions for you if you could. Could you tell me where/ how you mounted the electronic fuel pump? Thinking of going with the Holley Mighty Mite. Instructions say it has to be within a foot of the tank. Using the original tank in the cab. Also what distributor did you use, and do the stock ram horns work with the vortec heads? Or do you run headers?

Last edited by Chilly178; 02-17-2018 at 08:49 PM.
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Old 02-17-2018, 09:40 PM   #18
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Re: 5.7 Vortec for 72 C20

INline eletric fuel pump can be mounted on the frame rail ,you will want to also mount a filter before the fuel pump, you should be able to be close to that with in 12'' off tank

Also you might want to check out your fuel sending unit for 3/8 feed because they were made 5/16 feed for 6 cyl and 3/8 for 8 cyl ,this will help keeping the pump primed and not starve the pump when you get on the gas.

You also will need a fuel regulater so you can dial in the pressure for the carb (5-7lbs .

Any Hei distributor will work , but you must make sure it comes with a melonized gear ,I belive Accel distrib come with Melonized gear. all Hei distrib have a post/pole for tach option.

And yes you can use your Stock rams horn if you want .

I would also go with a serptine set up you can go to your local junk yard and get a complete set up there, pull one from any 96-99 chevy truck even the 6 cly vortech will work just take everything PS pump and alt, even the belt . everything will line up perfectly and you will never have to tighten up a v belt again
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Old 02-19-2018, 08:20 PM   #19
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Re: 5.7 Vortec for 72 C20

I'm running a Mighty Mite now. I wasn't too sure about it when I first got it but it has worked just fine. I'm still running an in cab tank and mounted the pump on the frame under the cab. There are two versions of the mighty mite, be sure to get the higher volume pump. You shouldn't need a pressure regulator with this pump, I took my regulator off and haven't had any problems.
I'm running a MSD 85551 and a 6AL box left over from a hot 383 I had in my truck for a short while. I have a MSD HEI that I was planning to install but never did, just keeping it for a spare right now. Be sure to get a melonized gear not a melonite coated gear.
I'm running headers but ram horns should work without any problem. You can get ram horns in 2 1/2 inch which is what I was planning to get if I hadn't already had the headers left over from the 383. I've got the Headman headers with the ball flange, they don't use a flange gasket and I have to admit that I do like them.
BTW, I like my GM Vortec crate engine and wouldn't trade it for any other motor out there. Get the L31-R, it's a 4 bolt and has heavy duty valves.

Last edited by garyd1961; 02-19-2018 at 08:35 PM.
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