Lil Red - Duramax 6600/Allison 1000 Conversion & OBS/NBS Dash Conversion

[More Power]

This image shows more detail about how the intercooler end-tanks were modified. The inlet/outlets were moved outward to clear the boxed sections of the radiator core support and then modified to help provide more clearance for the head/park lamp assemblies.

I made all of the cuts/mods to the original intercooler, then took it and the various pieces to a metal shop for aluminum TIG welding. If doing this again I'd buy my own TIG welder and learn how to use it. In the end there would be no labor charges and I'd still have the TIG welder... all for about the same final cost. And incidentally, once all of the mods were completed I flushed water through the intercooler in each direction several times to remove any debris that might have collected.

Of course, there are alternatives for intercoolers. You can buy a generic intercooler core that suits your installation, then modify it as/if required. We did that very thing for a 6.5L diesel Suburban in an article here in The Diesel Page a few years ago. At the time, the total cost, which included the core, all of the hoses, clamps and piping cost about $400 total. So, you don't have to begin with a Dodge or GM intercooler. It just needs to be sized for a diesel engine approximating the displacement of the Duramax and fit into the available space.

In addition, I know of at least one Duramax conversion running without an intercooler. An owner in Canada used our mounts and Conversion Guide, but chose to avoid the installation of an intercooler because his use for the truck would be mostly light-duty. Personally, I'd still want an intercooler because of the ~20-psi boost pressures and the heat load that creates, but the installation in that Canadian truck shows that a conversion can work without an intercooler in certain situations.

How is the intercooler mounted, you might ask... The intercooler shown here is setting on 3/16" thick rubber strips that had been glued onto the radiator core support using silicone caulking - to the horizontal and vertical surfaces where the intercooler core made contact. You can see small portions of the strips I'm talking about in the above image. The modified hood latch assembly then clamps the intercooler to the radiator core support. It's been a successful and solid mounting strategy for a long time... although, if your truck will see lots of rough road or off highway use, I'd consider welding some 1/4" aluminum mounting tabs onto the intercooler core end-tanks that allow bolting it to the radiator core support using rubber-isolated hardware - along with the rubber cushioning strips mentioned here.

Jim