Tech Info - LT5 Eliminated Systems
The LT5 runs perfectly with all that is eliminated described here.
Marc Haibeck has addressed all items in a modified Low 87 Octane and a High 91 Octane Chip.
1. Eliminating Secondary Throttles/shafts
Install Dorman freeze plugs 555-108 with Loctite 262 to plug the secondary shaft ports for a complete elimination of Secondary throttle shafts and associated vacuum canisters (90 Heads on Left and 91 Heads on right) .
2. Eliminating Secondary Throttle Vacuum system
There are two vacuum sources (Electric Vacuum pump and Plenum)
Remove everything except the diagnostic vacuum sensor
that is located under the ECM
. The sensor is connected electrically and the hose nipple open to the atmosphere. Remove all of the vacuum lines, the Secondary Vacuum Reservoir, the solenoid valve and the electric vacuum pump
. Use Marc Haibeck
CHIP's Marc Haibeck
Secondary Vacuum System
Diagnostic Vacuum Sensor
There are two vacuum check valves
under the plenum (one connected to HVAC tank
and one connected to Secondary vacuum reservoir
). The check valve connected to HVAC tank
(via the "Y"
cited below for Eliminating Air Induction System
) remains in position connected to passenger side source of plenum vacuum and connected to the HVAC
vacuum line in the harness to rear of plenum.
The check valve connected to the Secondary Vacuum Reservoir
and drivers side source of plenum vacuum can be capped off since the Secondary Vacuum Reservoir is eliminated. This is shown in the Eliminating TB coolant system
3. Cruise Control/HVAC and EVAP Purge System.
The Cruize Control/HVAC Vacuum is taken from the passenger side of plenum. From there one vacuum line goes to the Cruize Control under ECM/Brake Cruize Vacuum Release (one line) and the second line goes to the HVAC System through the passenger side Fuel Injector Wire Harness (second line). The Vacuum line to the Cruize Control includes the Cruize Control Vacuum Reservoir under Drivers side Headlight which is left in place
. The other vacuum hose connected to the Cruize Control is for the brake pedal cruise cancel function.
The EVAP Purge system (1991 ZR1) draws vacuum from under front of Plenum and through the Solenoid valve. When the Solenoid valve is activated, vacuum is directed out the right side under Plenum back along the passenger side frame rail to the Charcoal Canister directly behind the Passenger Side rear wheel. The 1990 ZR1 Charcoal Canister is located under the Drivers Side Headlight. (Vacuum for the 1990 Charcoal Canister is taken from the drivers side front of Plenum as well as a vacuum line from beneath the front of the Plenum. See Vacuum Systems 90' and 91' (Secondary and Cruize/HVAC)
Cruize Control and HVAC Vacuum System .....................EVAP Purge Vacuum System (1991) with Solenoid
Marc and Pete suggested to eliminate the EVAP Purge circuit completely and capping off that vacuum source under front of plenum. I just replaced my charcoal canister and Marc says he does not address that removal in the chip as it has no effect. I left that associated vacuum and electrical connection including the Evap Purge solenoid in place under the plenum.
This discussion and photo is for a 1991 which has the Charcoal Canister just to the rear of the passenger side rear wheel. The 1990 has the charcoal canister under the drivers side head light so the Vacuum Connections for Charcoal Canister are different as well as the vacuum lines which for the 1990 you will not find the large loop for charcoal canister under the Plenum. You will find the Plenum Nipple (Purge Vacuum Connection) on the 1990 is straight out of the plenum rather than angling back under the Plenum. On a 1990 you will also find a vacuum nipple angling back under the plenum from the Air Horn which provides vacuum depending on throttle position to the Purge Canister Control valve under the Drivers Side Head Light (1990 only).
4. Eliminating Throttle Body (TB) Coolant system
See this link for TB Coolant Blocking drilling and threading details Injector Housing TB Coolant Blocking
Install 1/8 inch NPT allen head pipe plugs (21/64 or 11/32 drill) two each side of Plenum
(Two each TB Coolant and Injector Housing (IH) Coolant) as shown (The associated two IH coolant ports in the IH should also be plugged on each side
). Total six coolant ports plugged One each side TB, One each side Plenum, One each side Injector Housing.
Or as you like....just install the two 1/8 NPT Aluminum pipe plugs in the Injector Housings as shown.
Photo by Ccmano
Remove Plenum and Block TB Coolant at Injector Housing (LT5 will have TB Coolant Blocked but Undetected and engine appears stock). This will require you insert a plug in the Coolant Return Line on the Passenger side of the Plenum (the only TB Coolant Hose that requires a hose clamp).
See Summit Racing 1/8 inch Aluminum Pipe Plugs for Aluminum Pipe Plugs. When you install the plugs.....keep trying the plugs as you tap to make sure the final installation is about flush or out 1/16 inch and use Permatex on the plugs.
. The Injector Housing Plug must be FLUSH however.
Remove TB Coolant hose and tubing left and right side of plenum and plug hose return to coolant tank passenger side See Brass Cap just above the "T" on Passenger Side. Initial Coolant Fill
may be somewhat affected by the TB Coolant Elimination (see item #4 Initial Coolant Fill
). The "T" connects the top of the radiator Air Vent, TB Coolant Return, and Coolant Reservoir in front of Passenger side. With the TB Coolant Return Blocked, what is left is a coolant line from the Radiator Air Vent to the Passenger Side Coolant Reservoir. See (Filling With Coolant and the Air Locked Water Pump) for Detailed New Coolant Filling Trick.
A brass nipple that fits tight inside the rubber hose with a male 1/4 inch pipe thread and a 1/4 inch Brass pipe thread cap (female thread)
I left about 2 or 3 inches of rubber hose above the "T" that connects (did connect) the TB vent, Radiator top vent, and Coolant surge container in front of passenger side (the highest point in the LT5 Coolant System).
Note 1: The TB coolant path back to the passenger side overflow tank does provide a path for air and potential air lock to return to that passenger side tank during initial coolant fill. However, the Plenum to TB coolant hose sits only an inch or so above the IH coolant manifolds on the passenger side so the benefit of using that path to bleed air vice the top of the coolant manifolds to the radiator is very small. Marc has decided to bypass the TB coolant (vice eliminate all TB coolant hoses) leaving that coolant path back to the passenger side overflow tank in place to assure issues would not arrise on rebuilds for those unaware of coolant initial filling and water pump potential air locks.
Note 2: Air Pockets as a result of TB Coolant Elimination Tricks. See (Filling With Coolant and the Air Locked Water Pump) for Detailed New Coolant Filling Trick.
The 5th plug (Plenum Vacuum) is for Plenum Vacuum drivers side only which was connected to the vacuum reservoir. The tubing can be removed and a 1/8 inch NPT allen head pipe plug inserted exactly like the plenum coolant plugs.
a. When you run the tap....keep checking the pipe plug for depth so you end up tight and flush
b. When you run the Drill.......remember you are in ALUMINUM so go very easy and slow!!!
(you can do it without a drill press
Use a bit of Permatex gasket sealer or Teflon tape on the pipe plugs.
5. Eliminating Air Injection system
The Air Injection System including the Air Pump
has been eliminated (especially for those who are installing Headers). Associated with the Air Injection system is one vacuum line on the drivers side fender skirt above the shock tower. I eliminated the "T" and just moved the "Y" in front of "T" about 3 inches and plugged the "Y" back in where the "T" was. This modification maintains the Cruise Control Vacuum and the associated Vacuum to the Cruise Control Vacuum Reservoir under the Drivers Side Headlight.
6. Eliminating Positive Crankcase Ventilation (PCV) Pipe and added Oil Catch Can.
See Details for Oil Catch Can Installation
The PCV pipe along the plenum drivers side from PCV valve at rear of Plenum to Plenum Vacuum at front of Plenum eliminated. Stainless steel braided hose is used from the PCV valve at rear of plenum to Oil Catch Can (LT5 Added Systems)
and then on to the Plenum Vacuum.
The PCV hose
connected under front of plenum (Vacuum source) is connected using SS braided hose to an Oil Catch Can
external to the engine which Oil Catch Can
is connected to the dual PVC valves
hard line located at the rear of the plenum. The MAP sensor
(located at rear of plenum) is connected to the rear of plenum (Vacuum source).
7. Eliminating Stock Exhaust (installing SW Headers).
SW Offroad Headers
. As you know it is difficult to install headers with LT5 in the ZR1. With engine out I was able to install 14 of the 16 header bolts with locks (on each Header) in just a few minutes.
Installing the the LT5 with Headers Installed is easy if the LT5 is tilted to the rear considerably. The LT5 has to be prevented from rolling from side to side
. Leave the Fuel Rails, Plenum, and Bell Housing OFF untill after the LT5 is installed in the ZR1
1. You definitely need a load leveler (to UNLEVEL or tilt the LT5 to the rear).
2. You CANNOT use the standard lift eyes
for the LT5 because as you load UNLEVEL (Tilt engine to the rear) the engine rotates if you lift LT5 on diagonals
3. You have to lift with nylon straps around Flywheel (rear) and around Harmonic Balancer (front). Actually around more stuff on front.
4. You have to remove the A/C Temperature sensor cover (passenger side firewall) and Wiper Motor (Drivers side firewall).
See How to Replace the Wiper Motor
5. You DO NOT have to remove the hood and the ZR1 can sit on the level.
A/C Temp Sensor........................Wiper Motor.............Do NOT use standard Lift Eyes installing LT5 with Headers
Installing Engine In ZR1
Lifting The LT5
Last UPDATE of post 1 Dec, 2014