L31 (Vortec 5700) swap

[Jims86]

Thanks, so initially the trans wants heat from the engine, only later does it want to shed heat. Interesting.

Found a factory gauge cluster with big speedo and tach, small voltage, coolant, oil press and fuel. VERY tempting, but it's in wood grain, not aluminum.

New transmissions wont even allow full line pressure until over 100 degrees i think. HRPC would be the guy to Edumacate folks on the subject.

 

[benjaminearle]

Well, I got my new driver's side exhaust manifold today. Found one from an '88 Burb - has an AIR tap which I'll use for EGR and has Oxygen sensor port in the collector. Only have to weld an Oxy port on the passenger pipe now and do some creative Home Depot tubing (in copper for now) to plumb in the EGR. Pics of LM1 and Burb manifolds attached.

Motor mounts came in the morning, too. Need to order the VSS encoder and signal conditioner.

 

[benjaminearle]

And...now I've ordered my VSS encoder from Dakota. I almost bought the SEN-4160 and the 8000 to 4000 conditioner and then saw the SEN-4165 magnet-on-driveshaft kit which will not require the signal conditioner. So YAY, save some money. Maybe in the future I'll get the fancy one, but I'm pleased as punch to have an extra bracket AND and extra $80.

If the majority of engine computers and cruise units want 4000 pulses/mile why is the standard sending unit 8000? Is this a bowtie v. oval thing?

 

[benjaminearle]

OK, maybe someone knows - i pulled the engine mount brackets off my old tired engine and they have some spacer/bracket things behind them which I didn't bother to notice exactly which way they went back on and last night realized they aren't symmetric.

I'm assuming, based on some google, that these are torque rod brackets (which weren't connected to anything) and they shoudl at the very least go back on, if not be connected to the aforementioned nonexistent torque rods (something got left off at the transmission shop I do believe).

Anyone got a picture of how they go back or know if I need the torque rods (and where to get a set)?

 

[benjaminearle]

Well, hopefully the new engine is going in this weekend. Got it all pretty - just need to grab an AC compressor and swap the oil pump (no real need AFIAK, but prudent).

Used a spray ceramic for the block and heads and direct-over-rust ACE grill paint for the manifolds and some frame touch up after a thorough pressure washing and soap/water cleaning. Also used that same black on the engine mount brackets and torque rod (rods not there) brackets / engine mount bracket spacers. It came out a little more blue than I had hoped, but historically the 350 in '79 would have been blue anyway (just a too Ford-ish blue for my taste).

Have a '87 TBI fuel sender/pump on the way and new tank fill hoses and a Vortec pump ready to swap in to the assembly. Think I'll just put the tank in teh bed and run soft hose until i get the fuel supply sorted. Also, I think I'm keeping my un-baffled '79 tank and will use a silicone loaf pan with a 1/4" hole punched in the edge as a sump - it will fold small enough to fit through the sending unit flange and if necessary I can drop a couple magnets in it to hold it still. Anyone see a flaw with that plan?

http://www.walmart.com/ip/4244355?w...61770790&wl4=&wl5=pla&wl6=34438921030&veh=sem

After that it should just be wiring. Yay.

 

[benjaminearle]

OK, good progress this weekend. Got the new engine dropped in once the oil pump was replaced (cheap insurance), but once it's bolted up to the transmission, the motor mounts don't seem to be behaving. I was able to get one bolt in the passenger side mount at the rubber mount-to-crossmember interface, but on the driver's side, the holes are 3/8-1/2" off (engine needs to come forward). Would it make sense that I need to loosen transmission bracket bolts to shift the whole assembly around? Wouldn't that move the tailshaft around unacceptably? The distributor seems awful close to the firewall too. See pics and please give advice.

 

[Jims86]

OK, good progress this weekend. Got the new engine dropped in once the oil pump was replaced (cheap insurance), but once it's bolted up to the transmission, the motor mounts don't seem to be behaving. I was able to get one bolt in the passenger side mount at the rubber mount-to-crossmember interface, but on the driver's side, the holes are 3/8-1/2" off (engine needs to come forward). Would it make sense that I need to loosen transmission bracket bolts to shift the whole assembly around? Wouldn't that move the tailshaft around unacceptably? The distributor seems awful close to the firewall too. See pics and please give advice.

The trans mount is the last thing to bolt down.
Try the mounts off the other engine if you have not already, they will bolt right up to that L31 block. The GMT400 mounts wont work. Dont worry about the torque rods...some had them, some didnt. My 86k truck doesn't, my buddies 91 kBurb does. Funny thing about his motor mounts. He has to order 85 mounts. If he tries to order 91 mounts, they dont have options for R/V, so he ends up getting GMT400 mounts and has the same issue as you are having.
The 73 mounts should work just fine.

 

[benjaminearle]

The trans mount is the last thing to bolt down.

So I'm guessing by that comment that I should have loosened the trans mount bolts when i pulled the LM1? I didn't, so they're right where they were as long as I've had the truck. No worries on tailshaft alignment? I think I'll start here.

Don't worry about the torque rods...some had them, some didn't. My 86k truck doesn't, my buddies 91 kBurb does.

Should I have left off the torque rod brackets? If for some reason I wanted to run those rods are they available anywhere and what do they bolt to on the other end? I haven't had any success even looking them up.

Try the mounts off the other engine if you have not already, they will bolt right up to that L31 block. The 73 mounts should work just fine.

Do you mean the motor mount brackets (steel cup-type things) or the steel-wrapped rubber mounts? I'm using the '79 rubber mounts and it's apparent that they have the right bolt pattern, just the whole rig needs to translate. I'll be pissed if GM changed an age-old mount bracket by 3/8" from the square to the GMT400.

 

[Jims86]

So I'm guessing by that comment that I should have loosened the trans mount bolts when i pulled the LM1? I didn't, so they're right where they were as long as I've had the truck. No worries on tailshaft alignment? I think I'll start here.



Should I have left off the torque rod brackets? If for some reason I wanted to run those rods are they available anywhere and what do they bolt to on the other end? I haven't had any success even looking them up.



Do you mean the motor mount brackets (steel cup-type things) or the steel-wrapped rubber mounts? I'm using the '79 rubber mounts and it's apparent that they have the right bolt pattern, just the whole rig needs to translate. I'll be pissed if GM changed an age-old mount bracket by 3/8" from the square to the GMT400.

Mounting bolts at the trans should be loose at least while lining up the engine. I think IIRC, the torque rods just went back and bolted to the bell housing...they look useless to me, but then again, I'm not an engineer.

Take the motor mounts and brackets from the LM1, and bolt everything to the L31. GMT 400 is a complete re design from Squares, wider frame, etc.

 

[benjaminearle]

Loosened the trans mounts and hooked the engine to the hoist again. Was able to pull enough to get one bolt in the drivers side and all three in the passenger's. That will do for now until i get the rest of it buttoned up to at least me mobile under it's own power. I'm losing grace with my friend's backyard and need to be able to move it on and off the street.

Dove into the wiring this weekend. Installed the L31 harness. Found the cut wires for both oxygen sensors and soldered in those connectors and also soldered in the VSS i got from Dakota Digital. Hope I got the polarity right - I assumed the blue wire went to VSS High and the Gray wire to VSS Low. I used spade connectors on those JIC i need to reverse it. Not sure what else in the bundle that went to the transmission/C200 that I'll need. Maybe a pair to jump for transmission permissive to crank?

My plan for crank signal is to take the old chassis starter solenoid wire and run it to the purple "crank" signal in the C100 connector.

Plan for +12 to the chassis is to take the old alternator hot back to the new alternator and double up on that lug. Maybe I should do the same with the starter Hot (even though the new starter has a big lead to it from the battery) just to maintain the continuity of the old harness. SO, what to do with the alternator plug wires from the old harness. Suggestions?

Also need to install the L31 radiator, coolant pipes, trans cooler, oil cooler, power steering lines and fuel supply.

I think some water may have gotten in my fuel tank while it sat out from under the bed - anyone got a good test procedure / product to see if I've lost $100 worth of gas or not? It's E10 (no straight gas in Atlanta stations) if that makes a difference.

Wow, i look forward to doing things like installing a stereo and fiddling with the AC and windows.

 

[benjaminearle]

I might have found the unobtainable steering line:

http://shop.advanceautoparts.com/we...t_18070589-p?searchTerm=inverted+flare+o-ring

Anybody know if this is what would connect the pressure fitting of the square's steering box to the o-ring pressure outlet of the '97 L31 steering pump?

Or, does anyone know specifically what the two ends I'd be looking for are? I know the return line is a 3/8 inverted flare and I can make it up out of brake line and hose clamp it to the original soft line.

 

[Jims86]

I might have found the unobtainable steering line:

http://shop.advanceautoparts.com/we...t_18070589-p?searchTerm=inverted+flare+o-ring

Anybody know if this is what would connect the pressure fitting of the square's steering box to the o-ring pressure outlet of the '97 L31 steering pump?

Or, does anyone know specifically what the two ends I'd be looking for are? I know the return line is a 3/8 inverted flare and I can make it up out of brake line and hose clamp it to the original soft line.

Some NAPA stores do custom lines...just go that route, and be done with it.

 

[benjaminearle]

Some NAPA stores do custom lines...just go that route, and be done with it.

Happy to do so, but I need a hose that goes from what to what? Admittedly, I'm not someone who can look at hydraulic fittings and call out the size and thread pitch.

 

[foamypirate]

You should just be able to swap the entire female fitting out of your current pump and into the 97's pump. Most people do the LS swap PS this way, you just unscrew the fitting and put it into the new pump. Did the same on my brother's serpentine swap on his 1970'. This would allow you to use year appropriate power steering hoses.

 

[benjaminearle]

Thank You Foamy!

My pump had the pressure? sending unit on it also, so i just took the whole accessory bracket out of the truck and did the swap on a bench. In case anyone has found this thread looking for similar help the pressure unit has a pair of circlips holding the plastic stuff together and then a big brass fitting (1-4"?) holding the cast iron / steel fitting on that takes flow off the back of the pump and gives you an o-ring fitting facing forward. With the circlips off and plastic sensor removed just back out the giant brass fitting and the ferrous fitting comes with it (just sandwiched). Then spin in the inverted flare fitting from the old PS pump and use your old (or replacement for the square) hoses. 5/8 hex on the back of the pump, 11/16 on the pressure line to the steering box, 5/8 on the return from the steering pump.

Yay! One less system half old and half new with nothing inbetween.

Got the '97 Radiator bolted in place but can't find my lower hose and afraid the QD fitting from the manifold to the heater core is busted (i see epoxy) and will need extracting and replacing with a nipple - what a stupid design. Pot metal?

Wired the old chassis harness hots to the alternator and starter (just to complete the circuit and keep the cab/chassis wiring instact). Also figured out which engine harness wire is which (on the '79 harness) for keyed +12 (old coil switch), oil pressure gauge, temp gauge and crank signal.

On the old harness what I'm still unsure of is how to splice the old 3-wire (a plug with red and brown and a single battery +12) alternator harness into the new alternator that has a battery post and a connector with only a (tan?) wire. I'm guessing i can common all the reds and maybe my old brown goes to the new alternator's tan. Any comments?

Oh, and i sort of straightened out my hood with homemade straps. Didn't even check LMC - these cost $7

Still it sits high near the cowl on the passenger's side. A spring issue? hinges worn out? I can mash it down but it doesn't really stay.