1980s Allante engines

[TJ Hopland]

What was different about the 87-92 Allante engines?

They all had their own aluminum heads?  Because they all had that tuned port intake?  And were multiport injection?  Were they all sequential injection?  Was the compression higher than the standard engines?  Did they require premium fuel?

Did they turn out to be pretty reliable?  Did the aluminum heads lessen some of the sealing issues the others had presumably because of the differential expansion rates? 

And the block and head changed a bit for the 4.9 so that is why it never got the 4.9?

Why didn't that engine ever make it into other cars like a Eldo or Seville touring edition?     

[Dave Shepherd]

Good questions I was a Cadillac employee during that period. Overall they were troublesome and  created a lot of customer dissatisfaction. The 4.5 was the least troublesome engine overall. Internal engine specifics/differences  are probably  published in some Allante publication, but you knew that. Seem to remember 89 minimum fuel recommendation.

[TJ Hopland]

Hopefully someone knows the story.  I would assume it was either stupidly more expensive or really didn't help anything otherwise say when they went to the 4.5 all the cars would have got the fancy intake.   Even if it was more cost which I'm sure it was if it was better I would think they could have justified and people would have paid the higher cost. 

I know 90 the other cars went from TBI to sequential multiport and that was also when they went to premium fuel requirement.  I suppose one issue is that tuned port manifold looked pretty tall so maybe it would not fit in the regular cars?

Lots of other Cadillac oddities from this time frame too like why didn't they go distributorless at some point like when they went to multiport or the 4.9.  If they were hoping the Northstar would be online sooner why did they bother with the 4.9?  Or was it the Northstar was so much more expensive they thought they needed the 4.9 as a lower cost alternative?       

[Dave Shepherd]

All good points, but I think the answers would only come from Cadillac hierarchy, way above my pay grade.

[Alan Harris CLC#1513]

I was the owner of a 1987 Allante as of 1992 or thereabouts. The rest of the car was sufficiently troublesome that the legendary HT4100 engine was barely noticeable. Dave Shepherd (above) is right. The created a ton of ill will for Cadillac. It was a beautiful car and a great idea, but the execution of the concept was totally poor.

The eighties automobiles generally were the cars that drove American customers away from Detroit and into foreign cars. 

[V63]

It's important to point out that the feds getting into the automobile business shares a lot of fault here. CAFE
 
And the current administration and its electric agenda will likely prove disastrous to domestic manufacturers.

[TJ Hopland]

The rest of the car was sufficiently troublesome that the legendary HT4100 engine was barely noticeable

Its seeming like this may be why even Allante owners didn't or don't seem to know much about the engines.  There has to be someone that knows about these engines.  Hopefully they will see this or someone that knows them will see this and be able to get us some details. 

The only reason I even knew the Allante was different is I always wondered what the extra odd looking gaskets in the 4100 gasket sets fit.  The intake gasket kinda looked like the Olympic logo and in the few photos of the engine that are around you can see the long runner tubes on the intake that must have terminated into a more traditional looking lower intake with that mystery gasket I always wondered about. Maybe that is a clue?  The benefits of the long runners were maybe null because they then had to bend into a more typical lower intake? 

[James Landi]

''I was the owner of a 1987 Allante as of 1992 or thereabouts. The rest of the car was sufficiently troublesome that the legendary HT4100 engine was barely noticeable. Dave Shepherd (above) is right. The created a ton of ill will for Cadillac. It was a beautiful car and a great idea, but the execution of the concept was totally poor.''

Having owned several 4100's, and now owning a 88 Allante with the 4100, the design upgrades that were whispers and insider information about these deeply flawed engines appear to, over time, be remedied.  There was so much bad press about the 4100's and it was all so deserving... but over a half decade, GM fixed them so they became dependable-- all insider information.

[smokuspollutus]

Heads were still cast iron. There was never an aluminum head for the 4.x engine.

The 4.1 Allante shares the same shaped water crossover with the 4100, and it was updated to the 4.5 style when the Allante got that displacement in '89.

1987 Allante 4.1 had the roller cam the 88-95 "base" 4.5-4.9 engines had.

Of course the intake was 2-piece tuned port setup in all years that the other cars never got.

Allante oil pans were cast aluminum as opposed to stamped steel.

89-92 4.5 Allantes got stronger rocker bars.

No Allante 4.x had AIR injection holes in the heads and I believe 89+ did not have EGR either.

Allante never got the 4.9 liter stroker crank and stuck with the 4.5 PFI lightweight piston/rod/crank/liner setup 90-92. The 89 curiously made the power with the 4.5 skirted piston & TBI rod assembly. Allante never got the 4.9 gerotor oil pump either.

It sounds like a lot of changes but there's really no structural difference between a 130 horsepower 87 4.1 in a Fleetwood d'Elderly and a 200hp 4.5 red and black Allante roadster.

[TJ Hopland]

Interesting bit about the AIR and EGR differences.  Was the tuned port enough to not need that stuff or did this car make it into a different class then the rest of the cars so it didn't have to meet the same standard?

The rest of the details sorta just raise more questions.  I was hoping stuff like that would just answer questions but even more head scratching trying to figure out what the heck they were thinking.

Things like the aluminum pan...  Probably about the same weight as the steel one so not a weight savings thing. Cast would cost more so it wasn't a money savings.  Maybe improved cooling without adding an external cooler?  Most likely was a fit issue?  Something different about the Allante body or suspension got in the way and it wasn't possible to make a stamped pan the required shape so had to be cast.

[James Landi]

''...things like the aluminum oil pan...''   Hardly an improvement--- the steel drain plugs often destroyed the threads as folks wrenched on them to ensure a tight fit... the cost for a proper replacement was (is) over $600. I ''heard''that the cam shafts were changed (as the early 4100 shafts wore lobes out) and that the engine block castings were re-enforced  as the ''under warranty '' 4100s started to pile up like cord wood next to Cadillac service areas...again, nothing official from GM , I'm reporting hearsay.

[smokuspollutus]

Not sure what the rational was with the pollution control bits. The regular 4.1/4.5/4.9 all had EGR from beginning to end. The AIR holes in the heads disappeared in '88 with the regular 4.5 across the line and didn't come back.

I would say the aluminum pan was some combination of advertising material/leak tightness. Possibly cooling but all 4.x cars had an oil cooler in the rad tank. Underneath the front of the Allante is basically identical to the same year Eldorado so I don't think packaging was an issue. All speculation though.

The blocks were the same 87-89 across the line with both the triangular reinforcements that started on the first transverse engines and the new for 87 vertical reinforcements around the head bolts as they prepared to increase displacement. The blocks changed slightly in 90 to accommodate the future stroker crank but are almost identical besides some casting clean up near the crankshaft.

The cams were the same unfortunately for all roller 4.x engines. The specs are almost exactly the same as the 4100 flat tappet.

Really besides the intake there wasn't any high-dollar difference with the Allante motor. Seems like they did what they felt they needed to/could do to increase the power for the least amount of money. Then they burned up whatever parts they had and didn't change the displacement once it became clear the car was destined to be a dud. Kind of a shame, a tuned port 4.9 with a 10-20% horsepower and torque premium over the "regular" 4.9 would have made the Northstar a lot more difficult to justify if it could have gotten filtered into the rest of the lineup.

[TJ Hopland]

On the smog system I missed the detail about in the heads vs other locations like the manifolds and cat so I guess not as big a difference as I was thinking. Probably a cost savings doing it external vs internal.  Could have been something like the head machining machine only had 4 tool holders and they needed that 4th tool for something more important.  Changing to machines that could hold more tools or running through another process would have just cost too much.   

Was the upper intake plastic on these?  If it was it would have had to have been among the first and maybe they thought melting the intake with EGR would be annoying.  Obviously they got over that and just let em melt a few years later.

Does anyone know anything about the overall design team for this car?   Was it old people that just didn't get it.  Was it young people that didn't have the experience and wanted to try everything new?   

[Dave CLC#16900]

I came in Cadillac as a contract emissions engineer to work on the Northstar Allante and eventually the Aurora 4.0L.  All of the emissions folks were young and many were contract.  The '87 Allante emissions people were all contract.  The engineers working on the Northstar engine itself were young, in-experienced and some dumb as a bag of hammers. 

GM told Oldsmobile to share the 2.3L Quad 4 design with these clowns.  They originally had a PCV port on the left side of the cylinder head that oil would load up in on a highway ramp and then shoot down the throttle body.  Impressive smoke show.  The engine engineers thought as the engine was twice as big as a Quad 4, using twice the oil was ok....  Clowns.  I left the company because I had a better offer and they were prioritizing hiring the engine engineers over the emissions engineers.

About the car itself, I liked the styling.  Handling wasn't great.  Going down Pikes Peak on a test trip with overheated brakes due to a miswired shifter (could only command 3rd) is forever etched in my memory.  I managed to change the software while driving to eventually get 2nd gear.  Glad it was the weekend before the race up the hill and all of the dirt corners were graded.

I drove 3 brand new test cars and every one leaked water with the optional hardtop in the company car wash.  Most got my left knee wet, one got the right side instead.  We did a lot of work with upgraded brakes, interior, powertrain to make the Northstar Allante' for only half a year.

[Dave Shepherd]

Northstar, 2 quadfours "glued" together. Lol I drove one of the first Sevilles on LI back in the day. Lottsa issues with them going forward.

[James Landi]

''I came in Cadillac as a contract emissions engineer to work on the Northstar Allante and eventually the Aurora 4.0L.  All of the emissions folks were young and many were contract.  The '87 Allante emissions people were all contract.  The engineers working on the Northstar engine itself were young, in-experienced and some dumb as a bag of hammers.''

Dave's narrative puts to rest any ''benefit of the doubt'' that I still had regarding GM's rush to market with innovative, yet flawed products.  Apparently, the corporate ethos encouraged flash over durability and product reliability, and the purchasers and dealers be damned.  We're still enjoying our low mileage and much loved '88 Allante, but we're realistic about all of the major flaws and frustrations, so we drive it ''on occasion'' and on perfect top down weather days.   James