1984 Eldo Biarritz 4.1 V8 Engine

[D.Yaros]

Are the 4.1L V8 aluminum block, cast iron cylinder insert engines (HT4100) a disaster waiting to happen which shouid be avoided under all circumstances?  Would it serve one well in use only as an occasional driver?

- The HT4100 was prone to failure of the intake manifold gasket due to scrubbing of the bi-metal interface, aluminum oil pump failure, cam bearing displacement, weak aluminum block castings and bolts pulling the aluminum threads from the block.  https://en.wikipedia.org/wiki/Cadillac_High_Technology_engine

[Eric DeVirgilis CLC# 8621]

Plus soft camshafts/lifter wear and weak undersized main bearings. Only one HT4100 gave me an oil pump issue - an '85 Sedan deVille (FWD).

Head & intake manifold gasket required the use of GM Engine Coolant Supplement to help prevent leaks.

Just a terrible engine all around although a few gave reliable service well into six-figure mileages. One I saw with over 400K according to the original owner - almost exclusively highway driven - on an '84 Fleetwood Brougham.

Absolute nightmare to work on especially with age because of the galvanization from dissimilar metals used in engine parts and hardware.

Personally I avoid them.

[James Landi]

Hi David,  much has been written about the 4100 HT--- I have owned four Cadillacs powered with these engines, bought them during the late 80's and early 90's when one could find a lovely car selling for cheap.  Yes, the first issue that brings these engines "to grief" is the failure of that surface between the iron heads and intake manifold that also joins with the block.  If you catch the problem right away, before the engine oil is diluted with coolant, new gaskets and a revised bolt system will take care of this problem.  Alas, though, there are others. You;ve a heavy, less than aerodynamic car being pushed (or pulled), with an anemic engine, so if one drives these engines aggressively and attempts to "floor" the pedal in frustration, you'll literally destroy the engine.  You;ll find that driving the 4100 in aggressive traffic conditions a white knuckle experience, as there is nearly ZERO reserve power.  And keeping up with traffic on hilly grades is impossible over 60 mph.  So, of the four 4100's, one lasted for 315,000 miles --- I NEVER kicked it down and revved the engine, always changed the coolant, every 2 years, and NEVER EVER used STOP LEAK--- one GM coolant pellets--- my 85 Eldorado convertible went through 2 4100's-- both developed "death rattles" that were sufficiently grinding and horrible that no mechanic would even attempt to diagnose the issues.  I replaced the engines with used 4100's, and they ran another 50 or 60 thousand more miles.   Finally, I had an Oldsmobile small block installed-- bullet proof, and it ran just fine. Yes, it's possible to baby these engines, and if you're fortunate, you get one that runs and runs, but you'll need to be very careful, and really "baby it."   Hope this helps,  James

[Matt CLC#18621]

Quote from Topic “1979-1985 Cadillac Eldorado-By Matt Litwin from January 2009 issue of Hemmings Classic Car”

“In 1985, there was a change in the casting of the blocks for these engines--reinforcements were added. Eldorados with serial numbers after FE623772 had this new block and are sought after by knowing buyers.”

https://www.hemmings.com/stories/article/1979-1985-cadillac-eldorado

Regards,
matt CLC# 18621
i am 2nd
 

[TJ Hopland]

Its a tough call.  If its priced right and really seems to be in good shape then maybe.  Other than the engine those are pretty nice cars and partly due to the engines and their era they don't tend to be that valuable so if you can get one for a couple thousand and not have to put much into it you may get some hours of enjoyment out of it but it all ends if there is an engine issue.   No quick fixes or patches and they just are not good used ones out there and those offering rebuilds would be questionable.  You really can't correct its flaws with a rebuild plus there are some unique aspects of this engine that not all would have the experience to deal with properly.

[cadillactim]

I actually rebuilt one of these engines. I was shocked when I saw how skinny the O rings were that seal the cylinder inserts from the block. That being said! You have O rings that are now 36 years old. Sooner than later They will fail and you will have antifreeze leaking into the cylinders, thus engine failure.

Run Forrest, run!

Tim

[76eldo]

I have owned enough of these to tell you that these cars bring little money because of the engine. Never spend more than you are willing to walk away from.
They are not a good car to get involved with.

[chrisntam]

snip....
- The HT4100 was prone to failure of the intake manifold gasket due to scrubbing of the bi-metal interface, aluminum oil pump failure, cam bearing displacement, weak aluminum block castings and bolts pulling the aluminum threads from the block.  https://en.wikipedia.org/wiki/Cadillac_High_Technology_engine

I think you answered your own question.  Here's where I ask, but other than the items listed above (and in the multiple responses) these engines are ok?

 

[Alan Harris CLC#1513]

Years ago, when these were late model used cars, I asked the service manager at the Cadillac dealer if they were really that bad or if people just didn't maintain them well enough.

He answered without hesitation, "No they really are that bad."

[Eric DeVirgilis CLC# 8621]

Quote from Topic “1979-1985 Cadillac Eldorado-By Matt Litwin from January 2009 issue of Hemmings Classic Car”

“In 1985, there was a change in the casting of the blocks for these engines--reinforcements were added. Eldorados with serial numbers after FE623772 had this new block and are sought after by knowing buyers.”

https://www.hemmings.com/stories/article/1979-1985-cadillac-eldorado

Regards,
matt CLC# 18621
i am 2nd

Just Eldorados? Why not 1985 Sevilles and Fleetwood Broughams?

Even the new transverse mounted 4100 that first appeared in the downsized C body DeVille/Fleetwood of 1985 that lasted until 1987 still hadn't managed to shrug off all HT4100 weaknesses although they did receive some improvement - albeit marginally.

The bottom line is that any 4100 is a crapshoot, even the Supposed best of them. And yet one 1982 I knew from new never gave a lick of trouble after having accumulated over 100,000 miles. Go figure...

[TJ Hopland]

Like Johnny Cash said you want one that was built on a Wednesday.  If you want to know what was wrong with all the other days listen to the song.

I think by the time they got into the smaller transverse cars they tended to have a little better survivability rate but it was for sure never as good as their all cast iron ancestors.  Cadillac / GM wasn't the only one with issues in that era.  There were several engines that went into popular cars that just were not reliable.       

[Scot Minesinger]

This is the worst engine Cadillac ever made.  I drove them new in the early 1980's and recently...people were tailgating me leaving the stop light...they are as bad as I remember them to be, maybe worse.  Their performance is the worst thing Cadillac ever made since maybe the 1910's reliability which is also the worst ever aside.  I hate this engine.  Did I mention that this is a bad engine?  I would not accept a Cadillac with this engine even if it was given to me free.

[D.Yaros]

Boy, I am surprised at and grateful, for the condemning responses!  They certainly tell me what I wanted/need to know.  Thanks!  Too bad, as I was falling for what I think, style wise, was a really nice looking car.

[Eric DeVirgilis CLC# 8621]

Boy, I am surprised at and grateful, for the condemning responses!  They certainly tell me what I wanted/need to know.  Thanks!  Too bad, as I was falling for what I think, style wise, was a really nice looking car.

Buy a 79-81 - if you can live with a coupe.

[79 Eldorado]

Dave,
If you really like the car you could convert it to an Oldsmobile power plant. Copy the Olds 350 set-up in the 1979 or even use an Olds 403 as Bruce Roe did. My point is if that car is perfect for you except for the 4100 that's something which can be corrected.

I wish I still had the 4100 Eldorado I had with the factory sport (blackout?) package, console and bucket seats. Finding something exactly optioned the way you want it in the correct color and in great condition will be a challenge. I've only ever seen 1 other like sport edition I had. Swapping out the 4100 for the Olds motor will require specific brackets and different AC hoses etc but it can be done and when you're done it will be a "cleaner" under hood than anything made in that time frame with what looks like a wheelbarrow full of vacuum hoses poured over the motor.

I don't know where you are from but if you're close and you need to see an Olds in an E-Body for reference you can even stop by. I have the original 1979 EFI 5.7L Olds and a 1979 Toronado also with an Olds motor.... obviously

I hate to see a nice Riv or Toronado sacrificed but anything with even the Olds 307 would be fine for the majority of the parts. You could find an Olds 350 or a 403 separately. If you did end-up finding a donor car which was not a Cadillac please let us know because parts are scare and nothing should go to the junkyard until everything worth saving is saved.

Scott

[Scot Minesinger]

Agree, if the engine was different it would be nice car.  Working on a 1980 Eldorado with 368 and it nice.

[James Landi]

Not certain you should throw in the towel.  I mentioned that I had my '85 converted to a small block Olds.  While the earlier Eldo conversions (79-80) have the bullet proof engine, the 84-85 convertibles have a much nicer ride (improved) with a better suspension and, I believe exclusive to these models, around 250 pounds more weight.  With the proper tires (I used Vogues), it proved to be a great riding car. I sold mine to our wonderful leader, Glenn, who expressed interested because of the conversion.  You might wish to discuss this with him..  What was of great interest is that the small block Oldsmobile 2 barrel carburetor engine was able to accept the distributor from the mortally wounded 4100---dropped right in, so the management system in the car continued to work. If you get the car at the right price, and it's in good shape, you might run the 4100 until it dies (if it dies), and have a reserve for the conversion. I think the bottom line on this is that these convertibles are strikingly beautiful, especially with the top down, and they have a great ride--- so something to consider.  Happy day, James

[Eric DeVirgilis CLC# 8621]

I think the fuel data panel readout will be lost when a carburetor engine is installed where a HT4100 had once been.

[TJ Hopland]

A good running but a little rusty E body will still go for $2k in my area so a donor car will cost you and at least in my area there are times you can search all the local online stuff and not find any E's for sale.   Likely cost you a lot more if you don't live in a rust area.  If its not a good runner then you have to fix or find a good Olds motor which is easier said than done these days.  Its been 30 years since any Olds motor was made and 40 since they were made in any real quantity.

I do kind of wonder if you found a Olds 260 if you could but all the 4100 electronics on it and if it would run decent?  Displacement I would think would be close enough.  GM and Holley used the same throttle body mount so I don't think getting the adapter would be difficult but I have not looked for a while so it could be discontinued.   I can't imagine finding a 260 these days would be easy.   That was never a super common engine and only went into some pretty crappy cars that no one really saved on purpose.   The cars where that was a reasonable option generally had the Buick V6 as a less expensive option so since they were cheap cars many seemed to go with the cheaper option.

[76eldo]

Dave

If it’s cheap enough it may be worth it.