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...

[woody90gtz]

The 282s are pretty good, lots of guys use them in v8 Fieros.

[Rettax3]

The 282s are pretty good, lots of guys use them in v8 Fieros.

I appreciate the reassurance, you have some very solid experience with those guys too. It helps alleviate some worries, because I do have concerns...

Yes, some Fiero-Builders have used adapter-plates to mount 350 SBCs next to their 282s, those engines definitely offer a healthy torque-curve if built at all. BUT, Fieros don't weigh very much, and even utilizing them as RWD platforms that squat into their launches, breaking traction is more likely than breaking drivetrain parts. On a 4,000-pound Seville? I am.. Pretty sure.. a 282 will be fine... My GTU's 3800 S/C produces enough torque to match a N-Star, in fact I'm pretty sure mine actually exceeds the stock H.O. L37 Northstar's torque. But heavier cars offer more down-force, equals more traction, and more mass to move. So, I have concerns. I also have spares.

It is a very nice car to drive, and ride-in. I am looking forward to making it 'mine', with a little re-working.

I had to drive out for a couple-day trip to pick the car up and tow it home, but even though it wasn't quite as clean as I had been led to expect, I think it is a good car that I got a good deal on.

Most of the project will be bolt-in, I've already made a Northstar-capable flywheel that fits a 282 (when I started reworking the L47 setup in the Teal Indy oh so many years ago...) but have since figured out an easier way to do it, and know that the stock shift-cable routing doesn't work because of the N-Star's coolant cross-over housing (which also houses the water-pump), but have experience making new -everything- for the cables to control the shifts, thanks to the F40 Six-Speed in the GTU. I will need another five-speed shifter assembly, and will make a bracket for it, but the clutch-pedal setup will be straight-out frustration for me, building from the ground-up. I still have everything needed for custom steel hydraulic-line for the clutch, thanks to the Z-26 Quad-Cam Build, and 282 transmission-mounts have become one of my specialties... I'm not concerned over the PCM's necessary modifications, those are minor, aside from an occasional low-idle issue I expect to encounter after longer decelerations. CV axles should be direct-fit from five-speed Grand Prixs, either 282 or 284, which ever transmission I end up using. Outer hubs are splined the same, and track-width is, I believe, close enough. I can cut my own half-shaft splines if needed though, so that is good to go. Shift-cables, I still have some spares, and that isn't any worse than what we all face here as Beretta owners, so I can cope. The rest is just wrench-time. I hope to have my plate cleared before the end of the month, but Life is what happens while we are busy making Other Plans... So... I expected this done before the end of Summer. Oops.

[Rettax3]

So... Yeah. It may be becoming apparent that my proverbial 'eyes' are bigger than my metaphorical 'stomach'... I didn't get very far with this STS yet, aside from getting a parts-car (with I believe a good H.O. engine with even lower miles than mine). HOWEVER, I do believe that has sorted me out very well in this case...

I have been fortunate enough recently to obtain what may be one of the few remaining '06 F40 Six-Speed transaxles still left untouched... A fellow Fiero-modder was looking to move on with life, and I was able to purchase my second zero-mile F40 for about the same cost as it would have been back when I bought my first one around 14 years ago for the GTU. A few periphery components have increased in price along the march of time, but the main obstacle I am having is needing to re-engineer this conversion all over again -the parts and processes that went into my GTU Build with the 3800SC won't help me very much with this Caddy...

For one, the hub-splines at the Cadillac's outer ends of the CV axles do not match either the Beretta's hubs, nor the transmission's own Pontiac G6 axles. For another, the Seville is a bit wider than the GTU, so even though I had to cut-down one of the Cobalt SS CV axles I used in my Beretta by one inch, that extra inch of length might not be enough now, even if I could use the Cobalt axles in the Caddy (again, due to hub differences, I cannot). The jackshaft options appear to be the same (and limited -I have yet to find a G6 jackshaft, ever, which used a male spline on each end rather than male/female configuration like most others use), though price has crept up a bit. The hydraulic-line and Master Cylinder assemblies will be the same -2001 Grand Am 2.4/5-speed- and these are cheap and plentiful, and they plug right in. However, with the clutch/flywheel configuration I used in the GTU, the transmission rattles like a Detroit Diesel with no oil, and while terribly annoying on my hard-edged performance-centered GTU, it would be intolerable in the 'performance/luxury focused Seville. So, Dual-Mass flywheel time. With, err, a Northstar crankshaft bolt-pattern... Right. I think I found a viable flywheel to adapt however, which will likely require minor work, such as a centering ring adapter from the crank hub to the flywheel, but it might actually bolt onto the N*'s crankshaft (it is being shipped as I type, supposedly). Ring-gear tooth-count matches the N* V-8, and the F40's deep bellhousing should allow for any variation of flywheel thickness I may encounter -I can still extend/shim the concentric Throw-Out Bearing as I did for the Beretta if need be, and far from having to MILL 5/16" off the bellhousing as I had to for the GTU, I should have plenty of room to work in the N*'s huge bay if I need to shim the transmission out, as I had originally done when I first Built the GTU with a Muncie 282 and had to clear the 3800's thicker flywheel (thicker than a Beretta's flywheel, just to be clear)...

Currently, I am looking at 'updating' my Caddy from 33-spline hubs to 30-spline, as GM has an otherwise mostly-identical wheel-hub that will bolt-in for me... Which snow-balls to modifying the brake rotors and swapping wheels, as one of the few differences is a change in wheel-lug bolt-pattern from 5-on-115mm to 5-on-120mm... And what about the rear wheel bearings and brake rotors? Multiple options there too, as it turns out, but nothing I have found yet is 'bolt-on'. I have a nice set (five) of BMW rims that look to fit to car's offset and the 5-on-120mm lugs, and I was unhappy with the stock chrome STS rims on the car anyway. CV axle options are plentiful, once I get my ideal length measured I should have no problem just buying what I need -Buick, Saab, and other GM lines have made this easy for me, with the same inboard AND outboard spline-count, once I swap those front hubs!

Keeping the clutch from costing $300-$600 for a stock-level unit will be challenging, and may result in some parts modification, but once I get the test flywheel in, I will know more...

This weekend, I am pulling the N* from the parts-car, everything is unbolted, unplugged, or already cut-off (thieves had butchered the upper radiator core-support and A/C system to steal the radiator and condenser, and the exhaust was cut too -you can all guess why...) to drop the engine, transmission, and front suspension out the bottom with the subframe, so now I just have to lift the car's body up off of the assembly and drag that out from under. I still plan on repairing the original engine, even if this one proves to be good, but might wait until I am ready to twin-turbo the engine too. And who knows how long from now that may be??