Oil Cooler Install

Updated 6/12/99

With the installation of an oil temperature gauge, I saw that the car was seeing 300 degree oil temperatures. These temperatures were well above what I was comfortable seeing, despite using Mobil1 oil. Unlike a conventional SBC block, its not possible to fit a sandwich adapter on an LS1 block due to A) the close proximity of the catalytic converter would make it impossible to route hoses out via a sandwich adapter. B) With a sandwich adapter, the filter would project below the bottom of the pan, which would leave it susceptible to rock hits, and other road hazards.

After doing some research, it turns out that the iron block LS1 based GM trucks have an oil cooler option. Oil is extracted via an adapter that fits on the block above the filter. This adapter utilizes two holes that are normally blocked off on the F-body motor via a blockoff plate.

So far, it seems to be working fine. I've taken a few test drives with it. I have noticed that the engine's a bit slower to develop oil pressure on cold starts, and that my overall WOT, high RPM pressure is down a couple of PSI (I've been told that is normal).

Temperature wise - at a steady cruise on the freeway, I would previously see about 210 indicated. If I were to jump on it for a few seconds, it would climb to 225, and would take a good 20 min to come back down to 210. Now with the cooler, I cruise at about 185. If I jump on it, it goes to 195 - 200, but comes right back down to 185. In city driving, It seems to hover at about 195 or so.

Parts needed:

Oil Cooler - I used a 24 pass TruCool cooler from RacerParts Wholesale -$45

Approx 11' of -8AN braided line - $80

8 -8AN ends - $4 ea

6 1/2" NPT to -8AN adapters $4 ea

3 -8AN 90 degree fittings - $10 ea

2 weld on -8 AN male fittings - $3 ea

-8 AN T fitting with 1/2" NPT on the top $9 ea

Autometer temperature sender, with 1/4" NPT to 1/8" NPT adapter - $45

GM Truck Oil Cooler Adapter and gasket (PN: 15725587) - $40

Installation instructions:

A mock up of the oil cooler adapter is shown in figure 1. This picture was taken after the modification, but I laid the rubber hoses next to it to give you an idea what it looks like.

The finished product with the adapter is in figure 2. In essence, what I had done was cut off the lines approx 3" after the block, and had the male -8 AN fittings tig welded on by a local welder for $25.

Modify the T above by drilling out the NPT fitting for 1/4" NPT, and then slipping the collar and sender in. The finished product can be seen in figure 3.

The rest is pretty straight forward:

Remove the driver's side cat (remember to use lots of breakfree)

Pull the original oil pan cover off,(figure 4) - Note: I had already modified the cover to accept a temperature sender. Install the modified truck cooler adapter (figure 5). Torque to 106 lbs / in. That's very important, as you are dealing with an aluminum block! The new temp sender will mount up as shown in figure 6.

Pull the black cover out from below the airpump - this is where the oil thermostat will go (figure 7). The part above it is the power steering cooler which was relocated to make room for the oil cooler.

The cooler mounts against the AC condenser as show in figure 8.

You will need to make a total of 4 braided lines:

1. Feed line from motor to thermo
2. Feedline from thermo to cooler
3. Return line from cooler to thermo
4. Return line from thermo to cooler.

When running the lines, the bottom line from the truck cooler is the outlet from the engine. It needs to run to the inlet side of the thermostat.

Nick: snicko@noid.org