L31 (Vortec 5700) swap

[benjaminearle]

Turned over for the first time tonight. Found purples in the transmission harness (cut) that went to and from the safety switch and jumped them together. Used the old coil wire to the main C100 pink (may need to tie in the other C100 pinks to this) for keyed 12V and ran a dedicated new constant 12V to the UHFB input lug. So far, so good. Can't go a lot further until i get the oil filter housing sorted out. For simplicity, I'd like a sandwich that eliminates the cooler altogether.

 

[foamypirate]

Nice work! Not sure exactly how you are doing your harness, but for my TBI, I ran a relay off of an ignition source to power up a fuseblock where I made all my ECM power connections. I used a 4 space fuse block, and ran one fuse to constant battery hot, and the rest switched on by the relay tied to the ignition hot.

 

[benjaminearle]

I have the complete L31 harness so I'm just tying in where i need to to the '79 harness and jumping out things that aren't present on the '79 like park safety switch, etc. I got a universal VSS unit from Dakota and everything else is factory sensors. I'm keeping it OBD2 for diagnostics so as much as possible needs to stay stock.

 

[kleedus]

just get an oil filter adapter off a 85 and older small block without the cooler it will bolt right to the block

if you need to know what a wire is on your vortec harness let me know. I have a painless harness and the harness out of a 96 Tahoe that I had oneluckypops work over for me he labeled everything for me. I can look at them and tell you what wires are what

oneluckypops did an awesome job on my harness built it as a standalone harness and I was able to keep the 96 cruise control. he basically custom built my harness to my needs and for a great price.

 

[benjaminearle]

Thanks Kledus,

I have an old-style oil filter adapter coming tomorrow from Jegs. $27 shipped - didn't seem too bad when it would cost $10-$15 at pull-a-part and i'd get greasy.

Main things I'm missing in the wiring are:

what to splice into my '79 harness for oil pressure gauge and temp gauge

what to do with the red/brown alternator plug from the '79

I think I have everything else done up with the exception of the brake off 12V relay setup (figure that can wait) and cruise (can definitely wait).

I wired up the OBD2 port tonight and also the brake circuit +12 in the C100 and extracted a bunch of constant 12V pins from C100 - didn't like them sitting there ready to arc off something.

Tomorrow is gas tank day - I've been dreading that - mostly because I don't want to get it all together and have to take the tank down again. Also I'm not looking forward to bending fuel line. Maybe I'll install the VSS instead and do my EGR line and lower radiator hose. Oh, and pick up a throttle cable.

 

[benjaminearle]

Gas tank is now plumbed in and wired but not lifted (just in case something's screwy). Tried to use steel line but couldnt get it to bed (yes, using a bender) without folding so i broke down and spent the money on good soft line. So far the fuel system is the most expensive thing besides the engine itself. Verified with a test light that the 2 second prime is happening (at least the power is being sent) so the fuel pump relay is getting its power.

Swapped out the oil filter adapter for the one that came from Jegs today and filled up with oil. THAT's a good feeling - and filled the power steering reservoir - well, overfilled. NAPA said "oh yeah - you need 2 qts, the reservoir is at least a quart." I'm pretty sure i was completely empty and less than a quart overflowed and ran over my pretty clean engine bay. Argh!!!

I think next is to make sure the fuel lines are tight, run the plug wires and give it a go.

 

[benjaminearle]

Fuel - check
Oil - check
Water - check

Crankety crankety VROOOOOM!

Making an awful squeal so it only got to run for 30 seconds or so (it was 12:30AM).

Now to get all the intake stuff on (MAF, IAT, etc) and make sure the oil pressure sender is plugged in (how long should i be able to run on the 2-second prime pulse?)

Also, before i lift the fuel tank in I'd love to figure out why the gauge shows slap full (overly so) when there only about 3 gallons in the tank. It's a TBI sending unit - did I need to wire it some fully way beside taking the purple sender wire to the orange chassis wire?

 

[foamypirate]

Fuel - check
Oil - check
Water - check

Crankety crankety VROOOOOM!

Making an awful squeal so it only got to run for 30 seconds or so (it was 12:30AM).

Now to get all the intake stuff on (MAF, IAT, etc) and make sure the oil pressure sender is plugged in (how long should i be able to run on the 2-second prime pulse?)

Also, before i lift the fuel tank in I'd love to figure out why the gauge shows slap full (overly so) when there only about 3 gallons in the tank. It's a TBI sending unit - did I need to wire it some fully way beside taking the purple sender wire to the orange chassis wire?

Sweet, it's always nice when it fires up! I had some struggles with my TBI swap initially (PO had distributor off by about 1 plug tower, so my correct firing order was no longer correct).

For the fuel gauge issue. make sure the sender is well grounded.

 

[benjaminearle]

I'll check the ground, but it shares a ground with the fuel pump, and that's working. There's at least one splice in the signal wire - i'll check that too.

Any idea which wire in the Vortec harness gives me block temp and oil pressure for the dash?

A whole plug tower off - THAT's impressively bad.

 

[kleedus]

oil pressure wire is a tan colored wire and the coolant temp is green on the inside part of my firewall plug going to the gauges


sounds like a bad sending unit or a bad connection


oneluckypops does great wiring harness work these are pics of my harness I had him modify for me just throwing that out there

 

[benjaminearle]

I found the temp line and think I've found the oil pressure line. I don't have the sensor plugged in right now (but never lose fuel pressure) because it restricted access to that giant bundle i needed to do some splicing in.

Figured out the sender unit - it must have hung on something because the moment i took the sender out the needle fell and after putting it back together it seems to work just fine. So, the tank is now lifted in place.

Wired in the OBD2 port and bought a bluetooth transmitter for it ($15) so it's under the hood as is the Check Engine light (for now). I have a hole in the dash from the PO's manual choke that will be convenient for the CEL.

Haven't re-plumbed the vacuum lines yet so it wants to idle at about 2,000rpm but it cranks every time i turn the key.

I see i never wrote about the terrible belt squeal. Turns out the alternator was frozen (engine rode home in the rain) so i pulled it, whacked the shaft a could times and viola, turns freely. Spliced both of my '79 red alternator wires to the battery post on the '97 alternator and spliced the '79 brown wire to the '97 brown wire. Charges and shows charge in the dash great now.

I made a new EGR line with a couple lengths of 5/8"OD copper tube, 2 45s a 90 and two 1/2"MIPx5/8"compression fittings, finished off by re-wrapping in the old fiberglass heat shield. Should have taken a picture before i covered it with FG but you'd all have seen my terrible soldering job.

Things left to do before the first drive:

• Install VSS
• Install vacuum lines
• Install Intake plumbing with MAF/MAT
• Install new brake booster vacuum check valve (Pull A Part - free)

Things still further down the list:

• Install new '87 TBI right side exhaust manifold (no heat riser, pulled from a TBI Van, Pull A Part - $25)
• Install new '87 Coolant tank (used a '97 Radiator and '79 tank was in the way) (Pull A Part - $5)
• Re-wire my '97 C100 splice using the 10-way weatherpack connector i got with pigtails (Pull A Part - $1.25)
• Swap existing tires to my Outlaw II Wheels

 

[benjaminearle]

Figured out the 2,000 rpm idle - wasn't the vacuum leaks (which are still a-plenty). I had hooked up the cruise box and it had enough cable tension to crack open the throttle. I pulled it's cable and now have a very pleasant idle. The Dynomax mufflers may actually be enough now that i've actually heard it idle down.

Let it run for a while last night to get the trans warm and check fluid -was 3 qts low before it touched the dipstick. Yikes.

 

[gxb930]

Very Exciting!!! You've inspired me! Starting my swap this week!

I have a 73 GMC LB. Factory air. (42 degrees in the Texas summer!) Second owner. Had it 14 years now. The past several years I've been restoring it. (And driving at the same time.) I've always wanted to perform a conversion. I've already converted the TH350 to a 700R4. It's now time to update the engine. I purchased a 96 Suburban 4 days ago. Ready to start pulling tomorrow! Keep everyone posted and thanks for all the great info on this site!!

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Old Faithful

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Ready for new Transplant

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Donor

 

[benjaminearle]

I have a 73 GMC LB. Factory air. (42 degrees in the Texas summer!) Second owner. Had it 14 years now. The past several years I've been restoring it. (And driving at the same time.) I've always wanted to perform a conversion. I've already converted the TH350 to a 700R4. It's now time to update the engine. I purchased a 96 Suburban 4 days ago. Ready to start pulling tomorrow! Keep everyone posted and thanks for all the great info on this site!!

I wish you success in your transplant. If i can offer only ONE piece of advice at this point it would be - label label label and document document document. Take way more pictures from way more angles than you ever think will be necessary and add labels to every wire you cut (both ends) or connector you unplug.

Oh, and clean everything as thoroughly as possible while it's apart.

 

[benjaminearle]

IT DRIVETH!

But, it shouldn't have.

Searching for the giant vacuum leaks I capped off the two evap lines and still had a giant wooshing sound. Kept looking and finally found that the brake booster was leaking like a sieve. Not sure if it was a failed diaphragm or just a rust hole in the body, but i pulled the line, plugged it and viola, no more vacuum leaks.

At that point I couldn't help myself so i decided to take a short trip on manual brakes. WOW, BAD IDEA!!! Way too much steel for that, but it did make me notice that i couldn't shift into second. Yes, you guessed it - I forgot to make a new vacuum line to the TH350 (I didn't even know it needed one, but that explains the wonky long tube that I extracted with the old engine). Made one up out of 1/4" aluminum tubing we had lying around and teed into the brake booster line since that's the only source of constant vacuum I know of on this engine.

Found a booster (Cardone 50-1008) in stock locally so I pulled mine and went to get it. Got it mostly in only to find out that the pushrod won't fit over the brake pedal pin. Appears to be about 9/16" pin and a 17/32" hole. Anybody know the size for sure?

Once that's installed I can at least drive to top the tank off with premium and more SeaFoam. It fires up before the engine can turn over once so I'm very pleased about that.

Computer problem 1: I'm getting is a Trans Temp Voltage code. I don't have a trans temp guage so is there a resistor I can plug in to somewhere to fake a fully hot trans?

Computer problem 2: I wired in a magnetic pickup for VSS but Dakota gives terrible installation instructions. I have two wires from the pickup coil and I took one to VSS High and one to VSS low. a)is that correct or should one have been +12 and the other to one of the VSS wires b)if that is correct, any idea which is high and which is low?

Getting so close and of course this week I'm 3,000 miles from the truck!