When Owning a Beretta Just Isn't Challenging Enough... NORTHSTAR!

[Rettax3]

Okay, I have a a rather varied career-path behind me, even just in the technical fields I've worked in, from rebuilding motorcycles and tinkering with (now classic) hot-rods in my youth, to jet engines and aircraft (I absolutely loved working on the old Huey UH-1 that was slid-in behind the hangar I was working in) some, ahem, decades ago, and unlearning and re-learning what I thought I knew so I could play with custom-Built cars, bikes, and even newly designed, engineered, and fabricated/machined components. But, even with the years I spent working as a professional Tech and later as a Service Writer, the one thing I never got to dig into was a head-gasket failure on a Cadillac Northstar. Now, my Teal Indy Beretta does indeed have a 4.0 Aurora L47 under the hood, but the L47 is a particularly stout variation of Cadillac's 32-Valve beast, with thicker cylinder walls and a reduced combustion-chamber size, resulting in far fewer head-gasket failures over the engine's history (I've never actually heard of one failing in a 4.0, though as with anything, it is possible...). But for several years, the Northstar's reputation seemed to be tanking altogether with reports and rumors of failed head-gaskets, resulting in repair bills well into the thousands, only to resurface again within a few years...
The problem usually wasn't the gaskets themselves, but rather GM's notion of using fine-thread bolts in aluminum blocks.
After some time, intergranular corrosion would sometimes set in, and begin eating away at the aluminum where the threaded holes met the steel head-bolts, in some cases the failures may have been caused by thermal weakening of the cast-aluminum blocks as well, and repeated stresses of the base-metal would eventually cause the threads to deform, and in more severe cases, separate (sheer off). In either event, some degree of loss of clamping-force between the heads and the block would occur, and the gasket(s) would finally lose their seal integrity.
Diagnosing a head gasket failure on a Northstar is usually very difficult. I've seen exactly two that I have been able to positively determine where failures, resulting in A) coolant loss over time and B) an overheating condition. In both cases, using a block-tester to detect exhaust-gasses escaping into the coolant system was nearly impossible to prove the gasket failure. Something about the Northstar's cooling system seems to prevent the escaping gasses from working their way up and into the coolant Expansion Tank, and part of that is simply that until the engine is put under heavy load, the gaskets aren't leaking in many cases. Thus, a fairly undefinitive yet revealing symptom is what appears to be an otherwise properly functioning cooling system, with temperatures that climb very rapidly under high engine-load. For a Northstar, this is usually as definitive as a head-gasket failure gets, which somewhat sucks for the technician who has been pumping at the damn block-tester for ten minutes, and STILL has a tester of crystal-blue fluid!

The solution is perhaps more or less profound. Re-machine the head-bolt holes in the block, using solid-body threaded inserts -enter the Timesert product line. These are fantastic, and early incarnations offered a fully synchronized insert, allowing the same thread-pitch as the bolts to be used also on the larger outer-diameter of the solid insert (as opposed to a Helicoil, which is also a great product, and is fully synchronized by necessity of design, but is in actuality a coiled wire instead of a solid sleeve and is simply no where near as strong). This repaired the damaged threads in the block, but did nothing to address the fact that the threads themselves were simply too small and too tight to hold the pressures inside the 300 HP N-Star. So, new inserts were designed that used a larger, coarser thread on the outside, where it threaded into the block, and OEM fine-pitch threads on the inside where the head-bolt threads met it. This was fine, since the inserts were typically made of steel, rather than softer aluminum. Over-drilling the holes perfectly straight, then tapping them for the larger threads is tricky, nearly impossible without a proper jig in fact. This specialized tooling is available, though IMO could use some updating in its' own design, and the pricing is very reasonable. But does it work? YES. Sigh. Well, I suppose, I mean, I guess so, from what, you know, others have said...
In all my "mechanicing", I have yet to be paid to repair the head-bolt threads on a Northstar engine... I feel so incomplete. Finally this year, I began seeking out such an animal, a head-gasket-failed Northstar, to test my wrenching patience on. And found one! A beautiful relatively low-mile STS Seville, well equipped, that needed a new home. I've wanted one of these cars since before the late-nineties remodel, and have finally determined that I now (surprisingly) like the newer ones better. Which this one is...

To me, this is a beautiful car. But hey, I also like Berettas, so what the heck do I know about style??

Unfortunately, my Summer has gotten completely away from me, and I'm still finishing up the 2nd Audi TT we adopted into the family (yes, ON PURPOSE! BE NICE!). So I have yet to pull the engine from this car to repair it. But it runs great, drives great, and sounds great (the exhaust was damaged by the previous owner, a hole punched into the resonator, and it sounds like an old-school hotrod -no mistaking that this is a high-compression V-8!). I just can't drive it very far without finding a hill, and just watch the temperature gauge climb then! Yikes! But, part of the positive offset of having to wait for this car to line-up as an active project, is I've been able to open my eyes to the fact that I will never be truly happy with this car, so long as it remains an automatic... So, I've had my eyes open for another F40 Six-Speed transaxle, but so far I'm unable to find one near me for a price I am willing to pay (I SHOULD HAVE bought more from Schram back when they imported the last of the N.O.S. from Germany 10+ years ago, instead of just the ONE I put in my GTU! They were $400 plus freight...). Most likely, this car will get a Muncie/Getrag 282, one of the spares I have in storage from a Beretta. Possibly, it may get the rebuilt 284 I have instead, but being essentially irreplaceable and the pull-type clutch also being utterly unavailable absolutely everywhere, that transmission scares me just a little. Is it stronger than a 282? Yes. Is the 282 strong enough for a more or less stock H.O. Northstar, in a heavy-as-hell Seville? Hmm, YES. Sigh. Well, I suppose, I mean, I guess so, from what, you know, NO ONE ELSE has EVER said... I guess, again, I will be happy to be the first one... But so far, the 282 in my Quad-Cam Z-26 Turbo is doing fine, and I'm willing to bet that car's LQ1 3.4 Twin Dual Cam has more power, and more importantly comparable torque. So, ONE DAY, we will see. Hopefully...