” The LT1/LT4 instructions states the VSS input is optional unless running a Connect and Cruise transmission, this is incorrect. The LT1/LT4 control system MUST see VSS, if it does not see VSS the ECU will limit throttle to 30%. It does this to protect the engine from over speed.” The above information comes directly from GM Performance and Powertrain dated October 2016.
There needs to be an updated and improved I-sheet for the T56 install kit because nowhere in the I-sheet is there anything about the electrical connections that are needed or where they are located. Now that we know that the VSS is needed, it’s critically important that installers get the right info or deal with an engine running in “limp mode”. The VSS signal connector on the end of the LT1/LT4 harness looks like this:
It’s a 2 pin clip-on connector that will only work in the Solenoid lock-out connection, not the VSS connection. The T56 magnum VSS connection is on the passenger side, opposite the lock-out connection as shown below:
The connector shown below is generally referred to as a Ford T56 VSS connector, this should be part of the T56 install kit, but it isn’t. To use this connector you’ll have to cut off the connector that’s there and wire in the new one. Since this is a reluctor (magnetic) generated signal, either side of the connector will work.
In my previous LS installs, I did not connect the VSS signal into the ECM because I ran the signal directly into the electronic speedo. The LS3 engines, from what I can tell are all set up for automatics rather than manual transmissions (even though I thought I ordered the manual version), so the signal the ECM is looking for is double what you get from the T56, so it didn’t work. On the LT4 ECM, it’s looking for 40 pulses which is what the T56 produces, so for this installation it will work correctly. Some T56 transmissions produce a 17 pulse signal.
To drive both the ECM and a digital speedometer from the same signal follow this schematic from Autometer. Circuit 821 is the positive wire for the VSS in the GM controller wiring harness and it’s purple/white, use this wire to drive the sender signal on the speedo if you have problems with the VSS out signal from the bulkhead connector.
The other issue in the LT1/LT4 I-sheet is that signals from the bulkhead connector will drive a speedo and tach, but the oil pressure will require it’s own sender. The only way you can use the oil pressure signal from the bulkhead connector is to use a factory style gauge. There is no provision to add a water temperature sender on the LT1/LT4 engines, but you can add one in the radiator hose or the radiator itself, or you can modify your water pump as shown here. For detailed installation instructions for Autometer gauges click here.
Dakota Digital VHX gauges offer an BIM -01-02 module that takes the signals from the OBD-2 connection, rather than the bulkhead connection and converts the signals correctly to run their gauge packages. For more information see my Dakota Digital post.
Still double checking everything. Dip stick doesn’t register until 7 quarts, capacity is 12 quarts including oil cooler. Engine is in “limp mode” and won’t rev beyond 3,000 rpm because of the VSS signal (see next post).
After 8 months of constant custom fabrication, endless phone calls to the GM Performance Power train division, the Z06 Camaro is just about there.
You never know until you close the hood for the first time whether everything’s going to fit. This time it worked, the Z06 Gen 5 LT4 crate engine fits into the stock engine bay of a 1968 Camaro.
This view shows the new style PCV system with the intake plumbed with the stock lines from the Cadillac CTSV. These are metric fitting and aren’t easy to adapt to, so I used a aftermarket Spectre vacuum accessory kit to plumb into the intake. You can see the line with the extra foam rubber wrapping around the line that goes into the intake.
On the right side is one of the Intercooler lines hooked up and connecting to the expansion tank (far left square alloy tank.) Right below to the right is the MAF (Mass Air Flow) connection that has to be a minimum of 10″ from the engine.
The engine wiring fuse panel is the same item that’s used on the LS series of engines. I’d hoped to install it on the firewall, but there just wasn’t enough space available, so it ended up on the passenger side inner fender well.
One of the great features with both the LS and LT engine management systems is that they take control of all electrical requirements including both the fuel pump system and the fan(s). On the LT engine there are two fan controllers whereas on the LS there is only one with the stock harness. After the main battery/alternator/starter feed is connected any additional electrical demand is feed into the body wiring fuse panel.
Hold on to your hat boys, this thing is huge. Compared to the ECM (E38/67) on the LS3, the new generation ECM is more than double in size. To get this thing to fit, I cut off the back side of the heater and boxed it in. You have to use a big block heater system because the small block core coolant pipes exit in front of the back of the block.If you don’t want to mess with that approach, it’s best to install a Vintage Air system, throw away the old school heater core and install a blanking plate. This is what the factory did on the 1970 SEMA Camaro.After much deliberation I decided to drill mounting holes through the thin sides and use the existing heater box mounting bolts. Add a nut union and you’re good to go.
The LT1 and LT4 crate engines have no provision to add a coolant temperature sensor like the LS series does. GM uses a CAN bus called GMLAN that communicates information from each of the various engine components using packet data similar to IP packets in a computer network. Similar to a train pulling a number of cars around in a circle, the packet data for each sensor rides in it’s own car delivering the data at the appropriate moment needed.
Unlike previous generations, the LT is the first engine in which the water pump is no longer in the center of the engine as shown above. There is a coolant temperature sensor, as seen above on the top right, but I have been advised by GM Performance and Powertrain not to tap into the signal for fear of reliability issues within the packet data stream used by GMLAN (CAN BUS). Since I am not using the radiator coolant to cool the oil cooler, I chose to cut off the end of the stub and plumb in a conventional coolant temperature sender.
Using a 1/4″-18 NPT tap, I threaded in a coupler and then added the sensor. This serves two purposes, one it plugs the fluid passage and adds the sensor in a convenient location without having to weld in an additional bung. Make sure you get the appropriate sender for the gauge manufacturer that you using because there are many different types. Also make sure you bench test the sender before installing.
Here’s the water pump reinstalled with the coolant temperature sensor pointing straight down.