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Cadillac & LaSalle Club Forums => General Discussion => Topic started by: D.Yaros on May 18, 2020, 05:15:36 PM

Title: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: D.Yaros on May 18, 2020, 05:15:36 PM
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
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: Eric DeVirgilis CLC# 8621 on May 18, 2020, 05:32:38 PM
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.
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: James Landi on May 18, 2020, 05:44:12 PM
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
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: Matt CLC#18621 on May 18, 2020, 06:11:46 PM
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

Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: TJ Hopland on May 18, 2020, 06:12:31 PM
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.
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: cadillactim on May 18, 2020, 08:07:42 PM
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
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: 76eldo on May 18, 2020, 09:50:20 PM
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.
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: chrisntam on May 18, 2020, 10:16:39 PM
Quote from: D.Yaros on May 18, 2020, 05:15:36 PM
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?

:o
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: Alan Harris CLC#1513 on May 19, 2020, 12:16:46 AM
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."
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: Eric DeVirgilis CLC# 8621 on May 19, 2020, 11:23:35 AM
Quote from: Matt CLC#18621 on May 18, 2020, 06:11:46 PM
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... ???

Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: TJ Hopland on May 19, 2020, 11:37:17 AM
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.       
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: Scot Minesinger on May 19, 2020, 02:35:27 PM
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.
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: D.Yaros on May 19, 2020, 03:20:55 PM
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.

Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: Eric DeVirgilis CLC# 8621 on May 19, 2020, 04:22:36 PM
Quote from: D.Yaros on May 19, 2020, 03:20:55 PM
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.
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: 79 Eldorado on May 19, 2020, 04:52:07 PM
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
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: Scot Minesinger on May 19, 2020, 05:50:02 PM
Agree, if the engine was different it would be nice car.  Working on a 1980 Eldorado with 368 and it nice.
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: James Landi on May 20, 2020, 08:19:44 AM
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
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: Eric DeVirgilis CLC# 8621 on May 20, 2020, 08:55:20 AM
I think the fuel data panel readout will be lost when a carburetor engine is installed where a HT4100 had once been.
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: TJ Hopland on May 20, 2020, 09:20:27 AM
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.
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: 76eldo on May 20, 2020, 09:46:07 AM
Dave

If it’s cheap enough it may be worth it.
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: James Landi on May 21, 2020, 04:04:23 AM
Eric...TJ... electronics do run with the 260 Olds ...fuel mileage included. I've been there (260 Olds conversion) and done that .,6 years ago, I.know it works  just fine  James.
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: 79 Eldorado on May 21, 2020, 09:09:21 AM
I'm just curious why nobody has mentioned the Olds 307. It seems like the 307 was used in basically everything Olds powered from ~1981 through whenever they stopped using it in the Cadillac Brougham (Including the Riv and the Toronado from 1980-1985). As I recall the 260 was not highly regarded but I don't remember what the concern was and how easily it could be overcome.

Regarding donor vehicles an E-Body is ideal but it seems like any vehicle with Oldsmobile compatible brackets will work. Using something other than an E-Body would require motor mounts and the shallow front oil pan used on the E-Body. The AC line could be re-made because those would likely be unique. Bruce pointed out exhaust manifolds. There is a place manufacturing Olds exhaust manifolds. They have one for the passenger side with a single outlet. The E-Body is pretty unique on that side but I don't remember what it's trying to clear HVAC module? I can go look. What became a crossover on later Olds with single exhaust was more of a Y on the E-Body at least in 1979.

Am I missing any other hard to source parts? Again E-Body ideal but opening up the search would make it easier to find at least a donor motor. I recently looked to see if motor mounts were available new... I did see at least one seemingly incorrect listing. I didn't check for an oil pan.

Scott
PS: My preference would be either the 403 or the 350 but just following on the lines of those might be harder to find.
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: Eric DeVirgilis CLC# 8621 on May 21, 2020, 09:22:15 AM
Quote from: James Landi on May 21, 2020, 04:04:23 AM
Eric...TJ... electronics do run with the 260 Olds ...fuel mileage included. I've been there (260 Olds conversion) and done that .,6 years ago, I.know it works  just fine  James.

You were able to keep Fuel Data panel in operation with a carb engine?  :o :o :o 

Out of curiosity, do all the self diagnostic functions through Climate Control panel still work, ie: when depressing the OFF & WARMER buttons?
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: TJ Hopland on May 21, 2020, 09:58:07 PM
I do recall James' story about the 260 with a carb and the 4100 dizzy still working.   What I was wondering is if you could go a step further and also put the throttle body injection on. 

I would think in his case the diagnostics would work the same.  All he would have had to be missing was the injectors and possibly what ever the idle control method was.  It is a little odd that the computer wasn't angry that the injectors were missing but I guess I never tried running an engine with them disconnected so maybe in the design meeting when the computer nerd said we need a trouble code for that everyone else in the room sad why?  You will know if they are not connected because it won't run.   With multiport there are codes for injectors but maybe when there was 2 it just wasn't needed.

Thinking more about it I also wonder how it would not be angry that a lot of the emissions stuff was missing too.  I'm assuming he didn't re install things like the EGR control solenoid to the Olds motor and the diverter valve on the smog pump.  Those things would for sure have codes because they were required to for emissions.   Hopefully he can fill us in on those details. 

I didn't recall in James' story that the trip computer still worked and seemed to be useful.  That is interesting but I guess shows how not especially smart it must have been.  I guess I never really thought about what data it was using to calculate economy.   Apparently its just using manifold pressure and rpm which I guess makes sense.  It takes those readings and then some sort of calibration number burned into the prom chip and does its calculation.  RPM is RPM and the manifold pressure would give you an idea of the load so that would be all you really need to make a good guess.  Manifold pressure would have had to been still hooked up and working because that signal is used to adjust the timing just like it did with the vacuum can on the old dizzy.

A 307 would be an option I was just saying 260 because I wondered if the displacement being close to the 4100 would let the EFI system work reasonably well.   I don't think you would have a good a chance with a 307 and I suspect a 350 would be a disaster without the ability to create a completely new tune in the computer as well as change injectors and other things like maybe even the size of the throttle body.   All possible since the trucks used the same basic system on 260-454 motors but just 10 more things you would have to source and figure out on top of the 100 you already had on the list.

I don't think there was really anything wrong with the 260.  I think it was actually the best of the bunch, the Chev and Pontiac versions seemed to be a lot worse.   I think the big reason it just never got anywhere is it for sure wasn't any smaller physically than the 350 or 403 (307 came later) and I don't think it was any lighter so it really didn't gain you anything.  IF you could keep your foot out of it you could likely get the same MPG with the 350 or even 403 thanks to the Quadrajet but when and if you needed more power you had it with those engines.   

All those downsized engines including the Cad 368 were really not efficient for their size and weight.  They all had pretty tiny valves to accommodate the small bores because they all kept the 305/5.0 ish or even 350/5.7 strokes (or 472/425 in the case of the Cad).  That just isn't a combo for a good breathing engine which was an extra problem trying to control emissions.       
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: JerRita on May 21, 2020, 10:28:06 PM
Despite the negative comments I'll give you a positive one I have 3 of these a 84 Brougham D'elegance, 84 Eldorado H and E convertible and an 85  Seville D'elegance roadster. The brougham has over 100K on the original motor, the Seville is the upgraded motor and the convertible I got for a song and rebuilt the motor to the new specs. Great cars to cruise around town. I don't drive aggressively and haven't had any major issues, fingers crossed. JeRita   
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: TJ Hopland on May 23, 2020, 09:42:44 AM
I don't know what it is about the above photo of the Seville but that specific photo really captures the love it or hate it aspect of those cars.    Maybe its the angle?  You don't often see a shot fairly square from the side like that.  Maybe its the colors and the background?   

I was hoping James would be back with more details about the electronics part of his swap.  I was working on a TBI system yesterday thinking what if and noticed that I forgot about the Throttle Position Sensor which he would have been missing unless he was using an 80's carb not native to a 260.  You need the TPS for the fuel part but I suppose maybe its not needed for timing.  I would guess that the timing signal would primarily come from MAP and TACH but a missing TPS signal like the rest I mentioned you would really think would throw a check engine light and throw the computer into a fault mode where its going to do things like run fixed timing.   
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: 79 Eldorado on May 23, 2020, 02:55:14 PM
TJ,
The Cadillac may have used a more sophisticated fuel economy algorithm but I still remember the first fuel economy gauge I ever saw. It was a mechanical needle and I think it was in an 80's B-Body. I asked a colleague and they told me it worked on vacuum only. It was an instant-only with no averaging. It's been a very long time since I saw it.

If you are looking for a vote on the polarizing Seville design I would just say IMO it would be a PERFECT donor car for the engine/brackets/AC..... I've seen other threads on that specific topic so no sense getting off the track.

Scott
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: Eric DeVirgilis CLC# 8621 on May 23, 2020, 04:26:50 PM
Fuel economy gauge is completely different than the mileage display used in Cadillac which used engine data input to make mileage calculations.

I would love to see a working MPG display on a car whose engine was replaced with a carburetor engine. HT4100 MPG display had readouts for instant/average economy (the latter figure displayed as a decimal), fuel used and range. I can't see how this could work without the fuel consumption being metered in some way.

Although not mentioned in the owner's manual, I discovered that depressing the RESET button with the RANGE displayed, the display would read the number of gallons in the tank (displayed as a decimal). 
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: TJ Hopland on May 23, 2020, 11:10:26 PM
If GM didn't change their TBI systems in later years disconnecting an injector doesn't seem to bother them, no check engine light or anything.  I found that out today trying to keep a truck alive.  Its a long story as to why I'm running on a single injector now but it looks like the truck will live to haul garbage around the property for a while longer.   I do really like the TBI systems and some GM engines.  This truck kinda like the knight in Monty Python,  its pretty much just a torso but it keeps screaming 'come back and fight'.   
Title: Re: 1984 Eldo Biarritz 4.1 V8 Engine
Post by: James Landi on May 24, 2020, 08:12:03 AM
The 4100's ECM has a "soft fail" mode, so that when we substituted the Olds 260 and dropped in the 4100 distributor, all systems were "go" - we reconnected the temperature ecm plug ( and, of course the distributor plug), but as mentioned above, nothing having to do with anti pollution devices-- if you're wondering how the ecm handled fuel economy with some of its functioning disconnected, I calculated that with the 260, I lost an average of 1 mpg but had the peace- of- mind that Mrs. Landi and I would not have to ride home in a rental, while the 4100 ignominiously dropped dead somewhere on interstate 95. And you're correct about the mileage/fuel economy digital display-- it is, in fact, connected to the engine through a vacuum hose-- I was both very happy it still worked, and disappointed to learn that I had assumed a much more sophisticated and accurate engineering design stunt. ALL of the automatic air conditioning controls fully functioned after the change. The 260 pulls the Biarritz convertible (250 lbs heavier than the Eldo coupe) just fine... and as far as the ride quality with the heavier iron lady in the front end, the suspension did just fine.  I always add, at this point, that having owned four of these misbegotten 4100's, I had an Eldorado coupe that I purchased in the early 90's with 58k miles, and it ran until it reached 315,000 miles-and died in 2013.  I have absolutely no idea why this happened and the other 3 4100's developed "death" rattles after 100K.   I feel that you can get some decent service out of the 4100's if you don't use them for extensive highway travel... that's when they fail, I could go into detail about getting the panicky, sinking feeling, but I won't ruin your weekend.-- Happy day, and be of good cheer,  James