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This Q/A was in Kit Car Builder Feb 06
Q. Doc, what's your opinion on the Cadillac Northstar as far as its suitability for use in a kit car? Some time ago. I saw some show cars with such engines installed, but I haven't seen many lately. Are there some major problems with these engines, or are they undiscovered gems, instead?
Jeff Wheatley
Boise, ID
A. Thanks for the question, Jeff. We've been meaning to talk about the Northstar, so now we will take the opportunity. The first Northstars to see action were the L37 4.6L units that powered the Eldorado, Seville STS and (c'mon, you remember) the Allante. By present standards, this engine would be considered pretty technically advanced. Back in '93, when it was introduced. it was hailed as a breakthrough powerplant that would be the basis for the resurgence of the Cadillac nameplate. It was even considered to be one of the best engines extant at that time.
Made of a die cast aluminum alloy, sporting four cams and 32 valves, producing close to 300 horsepower using GM's latest powertrain management system, and boastint! of minimal maintenance needs, it appeared. that Cadillac had the dream engine at their disposal. It was promoted as such, which is why it appeared in many shows and custom cars on or around the time of introduction.
Since that time, many of the refinements to this powerplant have been in the name of durability and reliability, although horsepower has increased slightly. For instance, although Cadillac was touting coolant change intervals of up to 150,000 miles, the truth was that the coolant got changed much more frequently than that and in an impromptu fashion due to chronic leakage developing in a couple of different places. Makes you wonder if Cadillac knew something when they included a feature in the engine management that sequenced the cylinder firing in a way that reportedly would allow the vehicle to be driven up to 50 miles without coolant or the subsequent engine damage resulting from its loss! Cadillac also boasted of potentially longer oil service intervals, due to an increased crankcase oil capacity (close to 8 quarts). Of course, this was all moot if the the aforementioned coolant loss occured. Then, all of that extra oil in the crankcase would be called on to perform double duty as lubricant AND coolant! Did I mention that those chronic coolant leaks rarely occurred at the same time? Too frequently, after a few of these coolant loss episodes, another chronic weakness this in the cylinder head bolt/block thread area would manifest itself! It wasn't unusual that around the time of the first tune interval (an otherwise commendable 100,000 miles), the owner would now also be faced with a major mechanical failure.
Experience has shown that the only way to affect a warrantable repair for such a condition is to replace the engine with a new unit. There are a few reasons for this.
The first is that, with the exception of the rare super-low-mileage used engine, any wrecking-yard Northstar engine will probably have a similar history as the one needing replacement. What would be the point of going to all of the work to change engines, only to, in short order, have another of these pattern failures involving the replacement engine?
Got Rebuilt units? I'll have to answer that one with "The Universal Congress of NO!" That's right. Not even the manufacturer offers a remanufactured replacement Northstar engine! You know that if they thought it was a good idea, they would make them available.
Other rebuilders have looked into the prospects, but certain design hurdles (non-machineable, cast-in cylinder sleeves), design flaws like casting porosit in the engine block (see other question in this column), lack of replacement rebuilding parts (oversized bearings, etc.), and the general labor-intensive nature of the task vs. the actual cost of a new engine-have fairly obviated the rebuilding issue.
The third reason for going with a new unit is the fact that you do get quite a lot for your money. It's not just a bare "longblock", as in engine block and cylinder heads only. It's complete with oil pan, timing cover, crank pulley, valve covers, coolant crossover, water pump and thermostat, and many of the needed sensors. Plus, you get all of the available design updates and a decent warranty. Unless of course, use in a kit car voids that warranty (unthinkable)!
The fact that the Northstar powertrain has been used in transverse mounted applications makes it attractive to the kit car community especially those involved in Fiero/Lambo projects.
As you no doubt have already deduced, use of the Northstar engine, while being totally viable in many respects, will be fairly costly in the greenback department.
Additional costs to consider would be the fact that, what with the engine and transmission management systems being fairly well integrated with each other to begin with, you'll do best to use the correct O.E. transmission, powertrain management system and wiring harness.
Rebuilding the transmission is possible, and cheaper than a new one, but still pricey. Good-used electronic control units (ECU's) and wiring harnesses are available for fairly low-bucks and there are some companies out there that know how to handle some of the programming.
I think that for all of that, these Northstar powertrains are not in the "undiscovered gem" category, but they do offer advantages if you are willing to ante up.
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