Annual Tech Session lessons learned...
October 5, 2014
Had I done it on purpose, it would not have been so interesting. But for those of you who read the notice of our annual tech session (August 2014). I have to ask you, did you notice the articles photograh of the V8 Northstar was not from a '93 Allante? Had our web site publisher, who was not the tech director, carefully edited the article, he would have noticed that the photograph used near the byline for the article was not an accurate depiction from an Allante. Many have mixed emotions about the Northstar. It's not uncommon to see someone ask on Cadillac forums, which year Allante should I purchase/own? Followed by the debates over the model year itself, the engine, oil type used (conventional vs. synthetic) the breaking systems and more.
My first Allante was an '89 with the 450L V8 200 HP and then I bought my current '93 with a Northstar 4.6L Northstar DOHC V8 290 HP. I can tell you with all honesty I enoyed them both. But I'd be only telling a half truth if I didn't mention, the Northstar has been my personal favorite. Knock on wood, it's been both reliable and maintenance free. Treated to proper care and feeding including; regular oil changes (conventional), replacement of fluids, solvents, the air cleaner etc. - and Oh! a little grease in all the right places.
But let's go back to the photograph of the Northstar itself from the original article and see how it differs from the photograph of my '93 Northstar and the story that we are about to tell. Honestly while I no longer own one of these (I know not how to cook), think of a pressure cooker you might use in your kitchen. A modern pressure cooker allows for the release of pressure in the pot in any number of different ways. Now imagine if there were no release mechanism? A pressure cooker without the release valve for the pressure itself? That is an ingredient for a bomb.
Now imagine if the engine cover/plenum on your Northstar V8 has no "alternative means" for releasing pressure. And so I've attached two additional photo's to this article (above) to share what I'd learned in a recent technical session with a bunch of old guys and gals who have a great deal of experience with the car.
The first photograph in the series is the glamour shot used for the original article. The second photograph is of a club members '93 V8 Northstar and the third photograph is of the Engine in my '93 Allante. They all look like great engines to me; a clear demonstration of good old American inginuity with plenty of Horsepower to spare. Originally designed and engineered for this unique Front Wheel drive convertible slash hardtop coupe we call the Allante'. But I digress.
What's important about the first photo is; it's a great photo of the GM Northstar V8 DOHC. What's interesting about the second photograph is the hold-down screws themselves (look closely) and as importantly what's not seen is a polypropene gasket. The cover/plenum itself is attached in a way that allows pressure to escape (which should never happen in a properly tuned engine) and includes torque based cover screws with a flexible rubber o-rings that will give under pressure. The polypropene cover gasket is also designed to compromise itself under pressure and allow for enough expansion should the dire circumstance require it.
The third is a photograph of the Northstar V8 DOHC and the engine cover on my Allante. Note the difference in hold down bolts? What's not visible is a cork gasket that some would argue cannot be compromised as easily as polypropene gaskets under extreme pressure (think flammable vapor and a spark) and the visible lack of any pressure release system overall. KABOOM! "Hello Tow Truck man".
In a nutshell, that's just one of the things that I learned at the Allante Atlanta Car Club annual tech session last month. There's more to come so stay tuned.
On a final note, there are two important things to take away from this article. The first is, combustible materials combust. In a well maintained Cadillac this engine should give years of service through the theory of controlled combustion and the combustion engine. The second is, uncontrolled combustion -- is just not good when and if it happens.
So, what is the replacement modified engine cover for the '93 Northstar V8 DOHC to make this small change? I'm told, but have yet to find; 1993 and 1994 Northstars had this modifed plenum and will fit the Allante Northstar
And what's the skill set needed to perform the update? The good news is, if you have a torque wrench and know how to use it your more than halfway there. And remember, don't use any solvent or grease on the engine cover gasket. It should be clean and debree free.
Enjoy your Allante!!!
Thomas B