Gen V LT1/LT4 VSS signal information

” 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.

Gen V LT4 ’68 Camaro Hood closes

After 8 months of constant custom fabrication, endless phone calls to the GM Performance Power train division, the Z06 Camaro is just about there.20160829_164555_richtonehdr
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.

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Gen V LT 4 Intake, MAF and PCV Plumbing

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.

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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.

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Gen V LT 4 Engine wiring and Fuse Panel

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.
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O
ne 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.
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Gen V LT 4 Dual Fan Radiator

For this build I knew I wanted a dual fan setup, so the search was on.  Most of my buddies spend big bucks and use Ron Davis products, but his build time was too long and the price was around $1,300.  I’d used offshore all aluminum radiators before and had good results, but for this build I wanted something made in the USA. I finally decided to go with Entrophy Radiator in Illinois.entrophyrad
It’s made beautifully and it’s a fair price for the quality.  Once installed I needed to re-manufacture the shroud because there wasn’t enough room for the intake.
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I lowered the driver’s side fan mounting location 1 1/2″ which gave me just enough room for clearance for the Spectre 4″ 75 degree inlet.  If you look closely you can just see the stacked plate oil cooler that I’ve plumbed in to replace the factory cooler on the side of the pan.  I’ve also eliminated the water cooling feature and only using air to cool the oil.  I’ll also be adding the same type of cooler to use for the Intercooler.
rad2
Another advantage this radiator has is it’s already plumbed with both a steam port vent and a coolant temperature sensor.

Gen V LT 4 ECM

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.20160624_180546If 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.20160624_183133After 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.

Gen V LT 4 Coolant temperature sensor

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.
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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.
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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.
water pump with sensor
Here’s the water pump reinstalled with the coolant temperature sensor pointing straight down.

 

Gen V LT4 Pan modification

The LT4 engine is a very tall configuration, much taller than an LS or a conventional SBC, because of this I was unsuccessful installing the engine/drivetrain combination because I couldn’t get enough angle to slip it past the crossmember because the top of the engine kept hitting the firewall.
modified pan
I
 also had a problem with the stock oil cooler which is bolted on to the side of the pan, this interfered with the Morrison frame (see previous post). After several very hard and forceful knocks on the pan it came free.  The LT series of engines do not use an oil pan gasket, they are sealed using GM’s engine sealant.
1st install

We decided to remove one inch from the front of the pan and then welded in AN10 oil fittings to solve the problem.  You cannot move the oil passage location because there are built in oil galleries inside that pan that connect to the oil filter.  Once the pan was modified the engine/drivetrain just barely fit it and everything settled in, on to the next challenge.
pan install

T56 Magnum Gen V LT 4 Twin plate clutch assembly

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Ever wonder how a dual clutch set up works?
Here’s the 8 bolt flywheel included in GM part number 19329912, this kit is very expensive.  The flywheel is aluminum with a steel insert, the round ring concentric with the flywheel is the case saver for the bell housing.

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1st clutch plate, do not use a plastic alignment tool because it provides too much clearance.
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Intermediate driven plate, it’s attached to the flywheel with short flexible tangs that allow it to move and float in place.
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2nd clutch plate, not sure what the small little brown cylinder objects are used for.
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Completed clutch package bolted in place.
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Super Magnum Bell Housing.  This guy caused me a lot of alignment problems because the tolerances appeared to be too tight.  I had to bore out the alignment pin holes to get the transmission to slide in.
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Here’s your hydraulic throw-out bearing.  It’s the same one used on the LS crate motors and goes all the way back to the LS1.  Make sure you get a remote bleeder setup (Tick Performance TPSBL) because if you don’t, you’ll be cursing for days before you can get a good pedal.