So I just want to say that a budget L31 is probably still the best HP per $$$ you can swap into one of these vehicles. I just built one on a small budget using a LT1 rotating assembly and upgraded the cam, valvetrain and to a ProFlow4 EFI. It did not go into a 3rd gen but did replace the 6.0L I had swapped in place of the OE 305 TBI. I have all of 2K into the engine from air cleaner to pan and water pump to flexplate. Shopping around, re-using good used parts and the Summit Bargain cave at the Arlington, TX store 20 minutes from the shop all helped the budget. This one is 10.2:1, has aftermarket Vortec castings cleaned up a bit with intake bowl, exhaust porting, chamber cleanup and valve work. LS6 springs and Comp 787 retainers. Jegs 1.6 rockers re-used from another engine I had. GM single roller timing set, Melling M99HVS oil pump and Milodon windage tray cleaned and re-used from the same engine. The cam is a GM 6492 and the LS lifters were torn apart, cleaned, inspected and re-assembled. Should be good for ~380 HP and 430 TQ at the crankshaft with the HP peak under 5,500 rpm. Just a good torquey, fuel efficient daily driver that has a little power. The 6.0L LS was a gutless pig unless you rung its neck with RPM. That was even using Lloyd Elliot ported 862s for more compression and a very mild truck cam with emphasis on low-speed torque.

 

Here is the budget L31 in its new home. Even re-used the L31 accessory setup in this application to get a better, cleaner, more compact layout. The garbage R4 compressor also hit the scrap pile. The Vortec style Sanden or Valeo compressors are smooth, quiet and efficient compared to a R4. I am going to use the later style 105A alternator for now, but I have an AD244 that has a bad rectifier diode and the upgrade kit to make it 200a later down the road. I like the fact that very little has to be re-engineered for this swap as well, which makes it an easier swap for a beginner than a full blown LS swap where nothing fits correctly. I have played with a ProFlow4 on a C10 with a freshly built big block 496, hooked it up, ran through the setup menu, let the fuel pump prime, turned the key and it roared to life. Set the timing, then adjusted the screw on the throttle body to correct the IAC counts. Topped off the fluids, then took it around the block. After a couple of days of self learning off its wideband it ran as well as anything with OEM injection. At that point I played with the pump shot a bit to get a slight hesitation out of a WOT stomp and it was near perfect. On the chassis dyno we played with the timing curve and WOT total advance a bit, made a bit more power and played with the vacuum advance a bit to get the best cruise timing. I have ZERO doubts this 350 will be the same way. The 29 lb/hr injectors are good for way more power than I am making even with the 43.5 psi regulator opposed to the 58 psi regulator they offer for the same unit. The setup menu has configurations for both as well as for boost, if you can read between the lines on what this engine may get someday down the road. A small single turbo at 7-10 psi. I am doing away with the vacuum cruise control setup and have one of the OBS style Vortec electronic cruise control actuators to install.

 

Nice project. Keep pictures and info coming. Edward.

 

Worked on it some more this evening. Just like the C10, Edelbrock needed to make their harness 18-24" longer overall from the distributor to the ECM for the harness to work in any OE hole in the body. I wonder if their engineering department is just that dumb or did not get the memo that not everyone installs these EFIs on a ground up built purpose built race car or fiberglass bodied show car. The average Joe is installing this on an OE bodied vehicle and not wanting to drill extra holes in the floorboard or firewall, when suitable ones already exist on many cars, if they would only make the harness actually useable length. Atleast Painless got the memo on their TBI and TPI harnesses and offered them in 2ft longer versions. Edelbrocks harness would probably be 4 feet too short to go into the OE opening in the kick panel behind the fender of a third gen, just for everyones information.

 

Whose brand?
There's a fellow at work whose had me check out his 81 Z28. It's a 2nd owner car, nice shape with a 4 speed and has a hot rodded 350. I was surprised to see camel hump heads! It's a mismatch of parts with huge headers (look to be 1 7/8") and a dual plane intake and a 600 CFM Carter carb. Once we sort through it and try and dial it in (he claims it's a real dog) I'll try and talk him into a different set of heads. The Vortecs always come to mind as they really are the best bang for the buck in a modest build. Just like your L31. There's a solid market for the camel hump heads and finding them in decent shape is getting more and more difficult.
Thanks for the tech as always.

 

I think they are Speedmaster. The only identifying numbers or letters anywhere on them is DD cast in raised numbers where the GM casting number usually resides.

 

As I've posted many times, I've the RHS version of the Vortec with 2.02/1.60 valves. After some bowl blending and an entry level 3-angle valve job they're up to 255+ on the intake. Plenty enough to make a 500 HP target. As it is I imagine on an engine dyno (a possibility this fall) I should be 450 HP/450 TQ. 6200 RPM.
They were discontinued shortly after I bought them in 2010 which in my opinion is unfortunate. Could very well be they re-emerged in another guise by another brand although I doubt that.

Again, well done on that L31. I like the tech.

 

Should make for a fun combination.

Like I said this one is for a heavy cruiser though. It is even getting a clutch fan on it. In addition to cast iron manifolds and cats.

 

So I got a good kick out of the message Edelbrock's tech guy left me in regard to some feedback I left on their website. They claim their harness is universal length and that the little plastic enclosure is heat and water resistant enough to mount under the hood. They also mentioned that their EFI system is not designed to be compatible with AC although I could raise the base idle. That means that anyone using a cycling style AC system will be living with idle that surges up and down everytime the AC cycles. I will probably end up getting this thing running with the Edelbrock controller mounted under the hood and their short harness, then ditching it for a P59 setup after I build the harness to use the GM PCM. I will do the coil per cylinder 24x swap when I do the P59 as well as add a Fuel Composition sensor to run E85. I have a spare 24x reluctor.

 

i have the converter bolted up, changed the transmission fluid and filter and slid on my $60 Summit bargain cave TH400 pan. New adjustable red-stripe modulator. Then fitted my temporary exhaust to it. 2.5" pypes downpipes into turn downs, added a hanger on each to hold them in place. I had an 02 fitting added on the LH exhaust pipe to add the ProFlows wideband sensor. I added the sensor well upstream of the exhaust exit so that the Edelbrock ECU can start learning and remapping the base fuel map immediately after startup. I am sure this is going to be obnoxiously loud but it gets me to a point that exhaust is diverted away from the body for inital startup and break-in. Only have a fuel tank and radiator left to install, then wire and plumb the fuel, cooling and p/s systems up. I need to go through the brakes, new master cylinder, new hoses, new calipers and wheel cylinders. Turn the rotors and drums, fit new pads and shoes. Then add fluids and let it rip. I found my timing light and will have to set the base timing and adjust the idle screw for the correct IAC counts after it starts the first time. Then after I seat the rings (I have a nice empty 55 mph service road 1/2 mile from the shop that I use to seat the rings and bead in the brakes) it will take a trip to the A/C hose builder 1 block over to have the ac hoses built then a few miles down the road to the muffler shop.

 

I set up the base map for this last night. I picked the engine size, cam size from the various ranges, as well as the 43.5 psi fuel pressure option to match the regulator. I let it build the base map, then I adjusted the timing settings. For now I set the Idle timing at 12° (which is the starting point of the " mechanical advance similar to initial advance of a regular distributor). I set the WOT timing to give 26° total at 3,600 rpm. I added to that 8° of vacuum advance, set the starting point at 4 in/hg and the end point at 16 in/hg. Edelbrocks vacuum advance function works like ported vacuum per the instruction sheet, kind of annoying but is what it is. I set the commanded idle for 650 rpm. The idle AFR is set for 14.1:1, the cruising afr to 15:1 (slightly leaner than the 14.1:1 stoich value of the common E10 fuel here) and the WOT is set for 12.5:1. I will see how that works, then creep up on more timing after it breaks in and I read the plugs. After this pig gets new tires, new U-joints and a new carrier bearing it may find its way on to a chassis dyno to optimize the fueling and timing as well as to find out what it makes. It should be able to make ~300 hp at the tires. I know it will definitely give some of the cammed 5.3Ls I have tuned in the area a good run with all the added low-midrange torque a Vortec 350 naturally makes. I kept the stock TH400 converter (2,000-2,200 rpm stall speed) and 3.08 gears. TH400 at ~120K miles on the unit was driving and shifting solidly behind the ~450 hp 6.0L that came out of this.

 

Pat's budget L31 with a GM LT4 Hotcam just hit the dyno as well. Basic budget combination very similar to what I ran close to 20 years ago. I believe five7Kid had one of these setups in a former LG4 car and ran mid 12s at altitude in Colorado with it. IIRC his car even had LG4 manifolds on it. Mine had a GM Q-Jet Vortec manifold off the 330 hp 350 crate engine, a 1" Hamburger tapered cone spacer and an 850 cfm Q-Jet on it with Thorley Tri-Ys. Hotcam 4° advanced, 1.6 full roller rockers and a little headwork on the Canadian 906s. Mine made 407 hp @ 5,600 and 438 tq @ 3,600 at 12° initial timing and 34° total advance at 3,100 rpm. With the 10° @ 10 in/hg vacuum advance on manifold vacuum, mine pulled 17 in/hg vacuum at 700 rpm. I feel Pat has a bit more left in his setup. I believe he has another video coming up with some additional tweaks to the combination, including a carb spacer.