Uphill Battle To A 4-Digit LB7

Getting to 1,000 rwhp is harder than you think

Published in the August 2009 Issue August 2009 Build, Duramax, Feature

engineOver the last year, we covered basic horsepower recipes to achieve landmark horsepower levels in our series called Horsepower Road Blocks. That series has ended as we have outlined recipes for most of the light-duty diesel engines in the truck market.

The next step for us is to take you, our readers, through the experience of building a high horsepower engine. There is really no better way than to jump in and start. What we didn't realize is that this wasn't going to be a normal buildup article and it actually ended up being something a whole more like what most people end up going through. One thousand horsepower is a big number that very few have achieved. Knowing that the road less traveled is often a difficult one with lots of unforeseen challenges and obstacles that must be faced head-on to achieve the results desired, we headed off to meet Jim Jones.

We are following the buildup of Jim Jones' LB7 Duramax engine for this story. (The LB7 Duramax is the original Duramax that was produced and introduced in 2001 and was in production until mid 2004.) As with most people who are building a high horsepower engine, he started out with a good core motor that he purchased through a salvage yard. By using a core motor and not his own he wasn't left without a vehicle (until he started playing with different tunes getting ready for the new motor and bent a rod in his daily driver).


Buying a core motor can be somewhat of a difficult challenge. Unless you know the person who is selling the engine and perhaps the truck it was in, it is hard to tell what condition the motor is in when it arrives on a pallet. Asking for a warranty isn't unheard of when buying an engine through a salvage yard, but make sure you know exactly how long that warranty is and what all it covers. In our case, the engine sat on the floor past the warranty period as parts were collected to build the engine. So, in essence, there wasn't a warranty, which was too bad.


Once the engine was fully torn down, it was sent to Guy Tripp at SoCal Diesel. Tripp inspected each component to see what was good and bad. He determined that the "Good Running Core" got extremely hot (probably caused by the aggressive programmer with no EGT gauge). The head gaskets had actually indented into the cylinder heads, the crank was overheated and discolored but the block appeared useable.

Next, the block was machined. It was going to be cleaned, bored 20 over and then honed. Upon boring the first cylinder, the walls started flaking apart due to the rust that had accumulated in the cylinders from stagnant water. While the magnaflux showed there were no signs of cracks, it unfortunately doesn't show the condition of the actual metal.

So Tripp called Jones and discussed the options with him. After a rather short discussion, they opted to pick up another core motor. Tripp searched around to find a good core motor that wasn't outrageously priced. After a month or so, he came across another core. So, core motor No. 2 was purchased.

When the core finally showed up, Tripp disassembled that engine and began the inspection process. The crank was good and would work for Jones' motor but the block was cracked in the main webbing, beginning at the oil hole and extending into the cam bearing bore.

So Tripp went back and started looking for another core. Again, after a month or so, core motor No. 3 was purchased. Tripp again disassembled it and began the inspection process. As luck would have it, this time the block was good and useable for the engine build.

The main journals were honed to spec and then the block was set up in the CNC machine to have the decks cut square to the mains (Duramax blocks have a tendency to be slightly off, so the pistons to cylinder head clearance will vary from cylinder to cylinder, which is bad). So the block was bored and honed using torque plates that simulate the distortion that occurs in the block when a cylinder head is torqued down, oil passages were debured and the block was chamfered (basically the sharp edges were knocked down and rounded). Then new cam bearings were installed.

With the bottom end ready to be assembled, the final piece of the puzzle was the cam. Tripp flowed the heads, talked to Jones to determine what he is using the engine for and opted for a mild cam that is a cross between a daily driving cam and a full competition cam. It is designed to spool the high pressure turbo (the little one in a compound setup) quickly and leave the valve open long enough to fill the cylinders for higher horsepower.

Check out next issue to see the final reassembly, tuning and the final dyno number.


Carillo Rods

Dynomite Diesel Performance

Floor It Diesel

Ross Racing Pistons

SoCal Diesel

Texas Performance Diesel

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