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Old 02-19-2018, 03:33 AM   #1
81SierraGrande
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5.7L Swap Help

Ok guys, I know it's another 5.7L thread. I have seen a bunch on the internet but none that answered my questions completely. I have a 1981 GMC K10, it has the 250 I6, SM465 transmission and im not sure which transfer case, probably an NP 208. I am swapping the engine out for a '97 5.7L Vortec. I am trying to figure out everything that is going to need changed for this swap. The motor was running when disconnected but all I have is the motor, nothing else off of the donor truck. I am doing away with the fuel injection and putting an intake and carburetor on it. I am also lost to what needs changed to get the motor hooked up to the bell housing and if the clutch needs replaced. I have heard so many different things, just trying to get some answers from someone who has done this swap before. I am trying to get as many parts as I can before I pull the motor and start this so I can get it on the road as soon as I can. Any suggestions, tips, tricks or anything are welcome. Just trying to get as much information as possible before doing this. Thanks for the time and all your help!

Last edited by 81SierraGrande; 02-19-2018 at 04:19 AM.
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Old 02-19-2018, 04:09 AM   #2
mongocanfly
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Re: 5.7L Swap Help

bellhousing will bolt right up to engine...id put a new clutch/pp in while I had it apart..i think youll have to get a tbi engine flywheel also
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Old 02-19-2018, 04:17 AM   #3
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Re: 5.7L Swap Help

Would there be a difference in the clutch because of the swap or just put a new clutch, pp, and bearing like what is in it? Does anything else need changed out? Ive heard electric fuel pump needs to happen. This is the first time I have attempted anything like this and it doesn't help that the truck is on it's way to my house in Louisiana from Tennessee so I can't even look at it and try to figure this stuff out on my own yet.
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Old 02-19-2018, 04:32 AM   #4
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Re: 5.7L Swap Help

the vortec has no provision for a mech fuel pump...youll have to use low pressure elec pump with the carb..
im on the LS bandwagon now so the older stuff is becoming a distant [foggy] memory to me
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1981 c30 lq9 nv4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598
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2013 gmc z71. (daily driver)
Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563

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Old 02-19-2018, 08:24 AM   #5
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Re: 5.7L Swap Help

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Old 02-19-2018, 12:12 PM   #6
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Re: 5.7L Swap Help

Thats what I thought Greg. I may consider an LS Swap later. This truck was my grandpa's from the time it was new until about 5 years ago. My brother bought it from him and I just bought it from my brother. Sort of a family truck so it is going to get a full restore lol. The 5.7L my brother gave me, he had bought it for the truck and never had time to put it in so I have no money in the motor. Easier to do that than go out and find a 5.3L and then get into that swap.
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Old 02-19-2018, 12:13 PM   #7
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Re: 5.7L Swap Help

Will the flywheel need changed since Im going from an I6 to a V8?
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Old 02-19-2018, 12:23 PM   #8
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Re: 5.7L Swap Help

The flywheel will need changed because you are going from a 2 pc rear seal crank to a 1 piece (changed in 85 I believe)

If you have the whole truck, take the harness and modify to stand alone, and run the fuel injection. It looks intimidating at first, but really not that hard. I’m doing a harness now for a guy who is putting a Vortec 5.7 in a Jeep. Just waiting to hear back if he wants me to swap to the 0411 PCM or not to finish.

Was in New Iberia recently visiting some people I know
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Old 02-19-2018, 05:30 PM   #9
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Re: 5.7L Swap Help

You're going from the 250 Inline-6 to a 5.7L V8.

The 97 Vortec motors probably do not have the mechanical fuel pump boss machined, or the fuel pump cam eccentric, and definitely don't have the push rod for a mechanical fuel pump.
You'll need an electric fuel pump that provides 6PSI for the carburetor or a bypass-to-return-line regulator.
If you run a frame mount pump it needs to be able dry lift prime without damage so you'll have to do some research to find one.
The easiest thing to do is run the 1987 TBI tank(s), Delphi in-tank pump(s), and modified 1987 fuel pump wiring. You'll need a 6PSI bypass-to-return-line regulator. If you'll eventually be moving to an LS this is a good time to update to the baffled fuel tanks to make that transition a little easier.

The 250 bellhousing will bolt right up.

You can't use the 250 clutch parts on a 5.7L V8. The flywheel is the wrong balance and probably the wrong bolt pattern. You'll need a flywheel for a 1987 and later 5.7L with a one-piece rear main. GM changed it in 1986 but it's rumored there are some one piece and some two piece rear main engines scattered through the 1986 model year. 1987 is a safe bet. I'd stick with good names in the clutch game. Sachs, LUK, and Valeo

The 1987 & 1981 350 pressure plates are the same. I'd just get an LUK, Sachs, or Valeo 1981 350 smallblock clutch kit. The pressure plates are the same but the Hydraulic and Mechanical linkage throwout bearings are different. Complete kits usually have a plastic alignment tool included with the disc, bearing, and pressure plate.

V8 clutches can be had in 11" & 12-5/8". Bigger is usually better. The flywheel has to be drilled and tapped for the clutch disc & pressure plate you want to use so pay close attention to what you order.
You'll definitely want to bolt the flywheel to the engine, install the clutch, install the bellhousing, and turn the crankshaft to be sure there's no interference before you install the engine so you aren't working in an inconvenient position.
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Last edited by hatzie; 02-19-2018 at 05:37 PM.
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Old 02-20-2018, 12:50 AM   #10
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Re: 5.7L Swap Help

Thanks alot guys, sorry for the lack of knowledge but you all have helped out quiet a bit. Like I said main reason why I am asking all of these questions now is so I can have all the parts ready before I pull the I6. I know I always run into more problems along the way but I would like to have all my ducks in a row before I pull it anyway. If you guys can think of anything else please let me know. Is there a certain header yall would recommend? I know certain headers are turned to go around different things and I dont want to order headers that will have issues fitting or that I will have to make modifications for if I can keep from it.
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Old 02-20-2018, 12:54 AM   #11
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Re: 5.7L Swap Help

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Originally Posted by 44th Miss Inf View Post
The flywheel will need changed because you are going from a 2 pc rear seal crank to a 1 piece (changed in 85 I believe)

If you have the whole truck, take the harness and modify to stand alone, and run the fuel injection. It looks intimidating at first, but really not that hard. Iím doing a harness now for a guy who is putting a Vortec 5.7 in a Jeep. Just waiting to hear back if he wants me to swap to the 0411 PCM or not to finish.

Was in New Iberia recently visiting some people I know
44th Inf, Thanks for your service by the way. I have served with 2nd Cav in Germany and 1st Army in Texas, still active duty as a recruiter here in New Iberia.
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Old 02-20-2018, 01:56 AM   #12
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Re: 5.7L Swap Help

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44th Inf, Thanks for your service by the way. I have served with 2nd Cav in Germany and 1st Army in Texas, still active duty as a recruiter here in New Iberia.
My name here is the unit of my 3rd great grandfather. I did my time at Bragg and Wood.

I had hoped to be stationed in Germany, but all they seemed to have been sending over at the time was Trans personnel. Wall was still up, so I wouldnít have been able to meet my grandparents (my father met my mother when he was stationed there in 61-64) but I did go meet them right after the Wall came down. My fatherís father served in both ETO and PTO in WWII while momís father was in Rommelís Afrika Korps.

I grew up with some crazy Cajuns that live in New Iberia
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Old 02-20-2018, 07:03 AM   #13
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Re: 5.7L Swap Help

When you do the swap, could you note if you have to move the motor frame stands? According to what I have seen there 'should' be holes in the frame in the right locations. I 'think' the bell housing to mound distance is different. I can't confirm this as I don't own a SBC. I ma looking at doing the exact inverse, L6 in place of 350, in a K20.
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Old 02-20-2018, 10:55 PM   #14
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Re: 5.7L Swap Help

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When you do the swap, could you note if you have to move the motor frame stands? According to what I have seen there 'should' be holes in the frame in the right locations. I 'think' the bell housing to mound distance is different. I can't confirm this as I don't own a SBC. I ma looking at doing the exact inverse, L6 in place of 350, in a K20.
I will do it. Everything I have read so far is the same, The factory holes should already be there for a sbc.
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Old 02-20-2018, 11:54 PM   #15
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Re: 5.7L Swap Help

You will most definitely need frame mounts from/for a V8. I have a 1986 and went from the 4.3L V6 to a 350 GEN I. All my friends were sure the swap would be a direct fit--WRONG! I ended up pulling some from the junkyard off an '88 model. This is not that big of a deal, it just held up the swap for a few days until I could find some. You can go the pick-a-part route or just order some. Here's a link to this exact problem from the past http://67-72chevytrucks.com/vboard/s...d.php?t=543170
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Old 02-21-2018, 07:14 AM   #16
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Re: 5.7L Swap Help

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I will do it. Everything I have read so far is the same, The factory holes should already be there for a sbc.
I hope it works, but if not, I would be interested in the L6 frame mounts.
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Old 02-21-2018, 09:01 AM   #17
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Cool Re: 5.7L Swap Help

Can you do a build thread on this, I have been wanting to do a 96-99 vortec swap with fuel injection for a while but also like the easiness of carbs like you. People seem to not realize how good the vortec engines were it's always that's a waste you could do an ls swap lol.
I am a fellow Louisianan currently living in Port Barre, squares are a rare sight in Acadiana.
Not sure if you know but there is a carshow I think every first Saturday of the month at pepboys on Johnston in Lafayette.
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Old 02-21-2018, 10:57 PM   #18
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Re: 5.7L Swap Help

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Can you do a build thread on this, I have been wanting to do a 96-99 vortec swap with fuel injection for a while but also like the easiness of carbs like you. People seem to not realize how good the vortec engines were it's always that's a waste you could do an ls swap lol.
I am a fellow Louisianan currently living in Port Barre, squares are a rare sight in Acadiana.
Not sure if you know but there is a carshow I think every first Saturday of the month at pepboys on Johnston in Lafayette.
I can byuld a thread on the build if there is interest for it. Squares are definitely a rare sight down here. Like I said this was a family buy so currently I am figuring out a way to get it from Tennessee to here but once the build starts I can either start a thread here of create something so people can follow the build if they choose. It isn't going to happen very fast lol I am going to chip away at the parts until I get them all before I truly start the process. I didn't know there was a car show up there but I'll definitely be attending it soon.
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Old 02-21-2018, 11:15 PM   #19
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Re: 5.7L Swap Help

project and build section ....that's where you need to do your build thread when you get ready....
we've got lots of squares running around our area...I wouldn't have thought it would be much different where you are...
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1981 c30 lq9 nv4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598
1955.1 ls3 tr6060...(under construction)(on hold)
2013 gmc z71. (daily driver)
Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563
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Old 02-23-2018, 01:28 AM   #20
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Re: 5.7L Swap Help

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Originally Posted by mongocanfly View Post
project and build section ....that's where you need to do your build thread when you get ready....
we've got lots of squares running around our area...I wouldn't have thought it would be much different where you are...
I'm originally from Tennessee, where the truck currently is, and there are squares everywhere up there and they are sought after trucks. Down here in Southern Louisiana they are few and far between. I can only think of one square I have seen in the 1.5 year I have been here.
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