L31 (5.7 Vortec) in 2001 S10 4.3 - S-10 Forum
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post #1 of 15 Old 06-09-2012, 11:05 PM Thread Starter
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L31 (5.7 Vortec) in 2001 S10 4.3

I have a few questions. Please forgive me. I have searched and searched. Some answered. Some not. And mostly, confused lol.

1. What all is added to the harness? The 2 injectors and extra 02 sensor? Other than that everything from my original harness should plug in. Including all the accessories.

2. Read the L31 is limited to super power gains compared to other options. Is there other intake manifold options? And you cant go too big a cam. Whats the number I need to know NOT to go over? Or is there a recommended cam for the motor in stock form? Motor would be dynotuned with HPTuners by the way.

3. Im not familiar with the mounts. Simply because I have not broken into these trucks that deep yet. The 4.3 mounts wont work for V8 correct? So Id need... adapters or mount brackets relocated and welded to the frame? Im not fully understanding the motor mount language yet with these trucks. Can someone break it down?

4. The 4L60E will bolt up and work just fine with this motor I read. But which torque converter? The 4.3 or the 5.7? Same with the flex plate.

5. My truck is lowered 3 in front, 4 in rear angled blocks. You can see pics of my ride Im sure if you look me up. The drive axle play is close to none now. How would this effect the installation of the L31 to the front near the fans, the drive axle play and the whole rear end, and the height of its position to the hood?

Uhhh.... I think thats everything... Thanks in advance.

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post #2 of 15 Old 06-10-2012, 04:32 PM Thread Starter
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

No one? Unbelievable...
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post #3 of 15 Old 06-10-2012, 07:18 PM
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

1: most buy a conversion harness from cpp

2: I have used a stock LT4 cam and LT1 cam in these motors before. I have read you can use the LT4 hot cam also and have even suggested t b4 on here.

3: conversion mounts from JTR work.

4: the 4.3 convertor will have a higher stall than the 5.7. it really up to you and what cam you decide to go with. but your trans prob wont last long if you beat on it since it came from a 4.3

5: this conversion has been done lots of time under a stock hood. you will have to use elec fan in frt of the rad or recess the rad in the core support and install fan behind it.

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post #4 of 15 Old 06-10-2012, 08:39 PM Thread Starter
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

Thanks for the input. I digged a little more and got some more questions answered.

My harness will work. Just need to repin the 2 extra injectors and have the pcm flashed. The extra 02 is not that necessary as far as driving conditions. Im sure it can be removed from HPTuners I hope.

Thanks for the cam input. I will look into those.

Just so I understand. For the mounts I dont have to reweld anything. These are adapters that bolt to my stock mount brackets on the frame, and the motor bolts to the adapters correct?

Looks like I would reuse my 4.3 torque converter and flex plate. Check.

I think I have an electric fan. But if not enough room, move it to the other side of the radiator. Got it.

Now out of curiosity (Ive searched everywhere) does anyone have a quarter mile time with this setup? Stock, or cammed, or headers, any combo. I cant seem to find confirmed quarter mile times anywhere. Just one site that had a guess of mid 13s if you can hook up.
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post #5 of 15 Old 06-12-2012, 01:42 PM
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

The L31 has the same fuel injection setup as the 96+ 4.3's do so it is limited in the same manner really, "limited" being subjective. There is no reason you couldn't have a healthy 300-325hp L31 with the stock injection setup in my eyes.

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post #6 of 15 Old 06-12-2012, 06:20 PM
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

My old 97 Blazer with an 2000 5.7 engine from a 2500 Van.

Had to replace the Spider in it once.
Walbro fuel pump
Used long tube headers and cat/cons
Custom Radiator and dual puller fans
4.3 air cleaner assembly with bottom opened up
4L60e from S10 fully rebuilt
2,400 Stall converter
3.42 gears
27" tires

"Red-light runners" should lose their license for 30 days.

Blazer was sold! Now in Michigan!
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post #7 of 15 Old 06-14-2012, 12:33 AM
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

Not to be a highjacker but im looking at doing the same. Already have owned multiple v-8 dimes so the swap is no problem, but what im wondering is if you have a 97 4.3 truck and you get a 97 or close 5.7 motor with harness and computer could you just not plug it all in? I havent looked at the 5.7 trucks that close so didnt know if the plugs are all the same or not. Just seems if they were it would be easier than repining a couple of wires assuming you have the harness and ecm.
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post #8 of 15 Old 06-16-2012, 02:28 PM
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

Phil, do you have any more pictures of that blazer?

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post #9 of 15 Old 07-14-2012, 01:54 PM
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

Let me throw this out there about the harness. Remove it with the entire 4.3 and do your wiring that way. Run two wires from the V8 injector pod to the PCM. Also two pink wires at the injector pod need to be spliced into two other pink wires to give them power. Since you already have a 411 have your tuner turn on the e-fan pins and run two wires from your e-fan relays to these pins. Works much easier and better than a kit. Cheaper too.

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post #10 of 15 Old 08-04-2012, 05:53 PM
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

i just did the l31 swap in my 01 xtreme it was a breeze pm me with any questions i used stock harness it was a breeze and all accesories worked exhaust trans etc had to buy mounts and hedders thats all i did the whole swap for about 400 bucks oh and i bought 2 fans and put in front of stock 4.3 rad
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post #11 of 15 Old 08-06-2012, 02:08 AM
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

mounts wont have to be welded. buy the slider mounts. o2 sensors are not needed once its tuned. your 4.3 wiring harness will work. if u choose to use the v6 accessories you shouldnt have to change many plugs but you can do the v8 acc and just splice the v8 ends in the wiring harness. yes its just 2 wires to re pin and i believe they are ground wires that run to the pcm. also you ll have to add to more wires for the injector pack which they are all hot. knock sensor is behind the dizzy on the v6 and on the bottom of the v8. and if u use the sanderson shorty headers youll have to do some beating on the passenger side fire wall. thats all i remember. its pretty easy. this was my first pull and install of a motor and it was swap.

yes these are limited to power b/c if the injection system but if u dont mind being under 400whp then u should be fine but they do make a marine intake manifold which is kinda high dollar.

cam sizes is the same limitation as the 4.3. 500 lift max but if you do 918 valve springs you can do a little higher

98 4.3 ext cab auto transgo shift kit 1, 266 cam, 1.6 full rr, 2.02 and 1.6 valves, pcm"shit"tuneforless, .030, 10 cr flat top forged pistons, balance shaft removed, msfi upgrade, accel distributor, msd wires, lt hookers and true duels to a delta 40
1/8 is 9.7@ 74mph 1/4 miles 2.3 60ft 15.3@ 88, and 14.4@ 98 w/ a 75shot99 sonoma scfs w/ 99 350, stock, fi, painted black 1st gen zq8s 2.3 9.5@ 76 14.6@ 95
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post #12 of 15 Old 08-11-2012, 01:45 AM
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

Do a search for my name, I have an a very detailed build thread somewhere on swapping an L31 into a four-by. But to answer your specific questions...

1: Yes, the original harness will "plug-in-play" into the L31, but you will need to add a few wires to the injector pod and repin the wires going into the PCM to accommodate the change in firing order. Depending on some trucks you may need to extend the lead for the AC compressor and the knock sensor. I relocated my knock sensor to the driver's side because I was worried about heat soak from my custom headers on my truck, the amount (and if an extension is even needed?) will vary from truck-to-truck

2. If you are running stock Vortec heads, the max lift is roughly .475 and will vary depending on who you talk to. Some say it's .450 and others will say it's .490 and anywhere in between. The only way to tell is to measure spring bind on YOUR SPECIFIC heads. And if you need more lift, you can call up Scoggin Dicky and spent ~$30 on some "Z28" springs that will drop onto the Vortech heads with absolutely no modifications or expensive machining and will net you ~.525 lift. The LT4 cam is a decent cam, but I've heard from a few tuners that its difficult to tune. Check with your tuner first and ask for a cam recommendation for your particular setup. And if you are planning to run the simple stock EFI, the only intake option is the stock intake. If you want to spend some money and do some custom plumbing/wiring then any "Vortec" intake will bolt up.

3. You can use either the 4.3 or 2.8 mounts. I have(had) a 4x4 that has 4.3 mounts integrated into the frame. But from what I've read you have a 2wd truck. Which means you can swap out your mounts. If you run the 2.8 frame mounts then you can use the JTR mounts that allows the engine to sit ~1 inch lower than stock. If you reuse the 4.3 mounts then you can use the Advanced Adapters "plate" mounts that raises the engine ~1/2 inch which can - and will - interfere with any some headers since the steering shaft runs through them. Since you have a 2wd, I would highly running Hooker's mounts that allow the use of real V8 clamshell type mounts. These will clear up tons of room for any header option and wont require relocation the knock sensor.

4. As S15vortecpwr said, the 4.3 converter has a higher advertised stall than the 5.7 converter. The 4.3 converter is actually a physically smaller converter with a higher fin count, which will make the 4.3 converter "stall" higher with the 5.7's increased torque. The 4.3 tranny will bolt up the the 5.7 with zero modifications. You may need a different dust cover depending on if you have a 4x4 or a 2wd.

5. I would highly recommend you get rid of the blocks and use a shackle/hanger lowering kit. Blocks act as "levers" and increase leverage on the leaf springs that induce crazy amounts of spring wrap. The amount of fan/radiator clearance will depend on the mounts you use. The JTR/Advance Adapter's mounts give you roughly 1/2 inch either forward or behind the stock position. The Hooker mounts will place the motor in the stock position with almost no adjustment. Running the JTR/AA mounts may require you to notch the bracing in the hood to clear the AC compressor.

I've done many first gen V8 swaps, and one 2nd GEN 4x4 swap, so if you have any questions feel free to PM me. Since I sold my truck I don't get on the site much anymore. And sending me a PM is linked with my email, so I'll get it even if I'm not logged in.

Current owner: '99 ZR2, 383 Vortec L31
Previous owner: '93 GMC Typhoon #2025
Might still own: '88 GMC S15 with SBC, I don't know where it is now or who has the title.

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post #13 of 15 Old 08-11-2012, 03:42 AM
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

5. I would highly recommend you get rid of the blocks and use a shackle/hanger lowering kit. Blocks act as "levers" and increase leverage on the leaf springs that induce crazy amounts of spring wrap.
Blocks will be fine as long as they're not 4" and he has the proper pinion angle. There's no such thing as a shackle/hanger drop kit for s-10's

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post #14 of 15 Old 08-11-2012, 02:44 PM
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Talking Re: L31 (5.7 Vortec) in 2001 S10 4.3 ('91 S-10 Free!)

I was lurking on your post. I am an S-10 fanatic but my health is slipping and I had a minor accident (hit a suburan with the square type of trailer hitch mount) needless to say it mess up the front end and had to pop off all of the bumper and cosmetics just to pop the hood open. The Radiator has a leak but it was drivable the 5 miles home. I looked at LMC catalog and all the front end cosmetics are ~$1200 but the radiator leaked a bit before the accident, believe it or not the ins co. did not total it.

Anyway, if someone is looking to drop an engine in an S-10 ext. cab ('91) then I have one for the taking. Por notta, FREE. I just want to give this to another S-10 owner or a first time owner.

Just respond to this post.
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post #15 of 15 Old 08-11-2012, 03:17 PM
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Re: L31 (5.7 Vortec) in 2001 S10 4.3

Forgot to mention, the '91 S-10 is an Ext Cab, needs paint. 4.3L Z engine with Auto w/OD tranny (in good shape), the 4.3 works but it must have either gotten too hot or blown through an oil filter because about 6 years ago I had to take the valve covers off and lifter springs and clean it up as the oil returns were clogged up pretty bad so when I stopped all of the oil stayed up under the valve covers and then made its way down to the cylinders. At the time I was working at a State University here is San Antonio and parked in the garage. When I would come out after work and start it up and it would cover the whole floor with smoke.

no mods, all stock.
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