Cadillac 4100,

[BodybyFisher]

I missed the 4100 and 4500 engines both owning one or working on one. I have heard good things and bad things about them.

In my mind, I have them marked as somewhat inferior, but I know that KHE has said good things about them. I became curious when I saw a 4100 in an Allante on Bruce's post.

Post your experience with this engine both good and bad, I would like to know more about these engines.

[Bruce Nunnally]

I read your question to be, what personal experience do people have with it? and I missed it also.

I do want to chime in that it is important to understand the context of when this engine arrived. It was due to premiere in 1983, but the down-sized cars it went with were delayed until 1985, which would have provided more time for development. Unfortunately, two of the across-the-line Cadillac engines were both flaming out -- the 8/6/4 368 catastrophe, and the diesel engine catastrophe.

In the case of the 8/6/4 problem, Cadillac had taken the otherwise reliable 368 and added a mechanical system for multi-displacement, running either as a V8, a rough V6, or a V4. Even in V8 mode it only made 140hp, so one can imagine how it did in V4 mode. It was a disaster.

In the case of the diesel, GM had made a diesel engine out of a gasoline engine is the way it was explained to me, and it had a tendency to self-destruct. Many lawsuits over this engine.

Cadillac also offerred a 4.1L buick V6, in an attempt to get something the buyers wanted.

So, the best choice seemed to pull forward the 4.1L HT-4100 V8. It had over 1,000,000 miles of development on it already, so it arrived a year early than planned, in 1982, to save the day. Unfortunately, it was used across the line, in the larger cars instead of the down-sized cars it was designed for. Also, it had iron heads, and an aluminum block. This seems backwards from what you might expect, but there you are.

It was also considered by other parts of GM as a new, light weight V8 for use in other GM brands. It looked very promising in 1982.

Initially, there were some infant problems. Head gaskets would adhere to the block, and then with the different expansion rate of the iron head, get ripped apart. New head gasket designs helped. The cam shafts were too soft, and would experience lobe rounding. The engine was VERY sensitive to intake leaks, and to overheating. Some issues were fixable, some were inherant vulnerabilities in the design.

Eventually, Cadillac engineered improvements, and the 4.5L and following 4.9L engines were very reliable.

[coolnesss]

I had an 84 Eldo Touring with the 4.1 and drove it something like 70k miles.

At one point it lost power - as if the catalytic converter were bad - but it wasn't that. After spending alot of diagnostic dollars on it with no result, someone said: run some Marvel Mystery Oil through it. Well, I did, and it cleared up the problem fast.

Other than that, it was a fine engine, if somewhat underpowered. Everything else went wrong on the car, but I loved it anyway. I still think that's one of the most elegant body styles the Eldo came in - it was relatively small, but completely comfortable and handled real well. I loved the car.

[KHE]

The HT-4100 engines had some problems initially but improved gasketing technologies made the engine very reliable by 1983 or 1984. If I were looking to buy a vintage Cadillac, I'd want an '81 with the V-8-6-4 (because of the big block engine and 12 bolt rear end) or an '83-'84 with the HT-4100. I have had positive experiences with the HT-4100 in two cars. Granted my expierence is not a statistical significance but then again, I am not lucky by any means....

Regarding the diesel engine... the diesel was NOT made from a gasoline engine. The displacement was the same but it was not a matter of making a 350 burn diesel fuel. The notion that the GM diesel was a gas engine conversion was an urban legend... The largest failure mode was loss of compression due to the wrong oil used. That engine specified straight 30W diesel oil available at truckstops but not at the local store. Many just used 10W40 oil wich was TERRIBLE for that engine as the viscosity improvers caused deposits that caused the rings to stick resulting in loss of compression. The diesel engine got blamed when in most cases, it was the vehicle OWNER who was at fault by using the wrong oil... Then there were the owners that did not use the block heater and when the engine would not start, they'd get out the either or WD-40.... both were death to that engine. There was an issue with the injection pump on the GM diesel but that was resolved by the early 1980s. Actually, by the mid 1980s, with all the improvements, the diesel was for the most part bulletproof but its reputation suffered and was discontinued.

[The Fred]

I missed the 4100 and 4500 engines both owning one or working on one. I have heard good things and bad things about them.

In my mind, I have them marked as somewhat inferior, but I know that KHE has said good things about them. I became curious when I saw a 4100 in an Allante on Bruce's post.

Post your experience with this engine both good and bad, I would like to know more about these engines.

I've had my share of 4.5 motors and I would say they're solid and reliable.

I've never heard of an Allante with the 4100- wha year was it?

[BodybyFisher]

This history shows that when it was introduced, the 4100 was used:

http://100megsfree4.com/cadillac/cad1980/cad87a.htm

[The Fred]

This history shows that when it was introduced, the 4100 was used:

http://100megsfree4.com/cadillac/cad1980/cad87a.htm

They got 170 horses out of the 4.1?!

Even the early 4.5 didn't make that much !

I'll be darned.

[Cadillac Jim]

The higher horsepower of the 4100 as built for the Allante is, in part, due to the resonant intake that is prominently displayed in the picture on eBay. Anyone want to try that intake on a 4.5 or 4.9? The price is only $150, but they won't ship -- it's for pickup in the DFW area. You can arrange for your shipper to pick it up, I would imagine.

[clarkz71]

Regarding the diesel engine... the diesel was NOT made from a gasoline engine. The displacement was the same but it was not a matter of making a 350 burn diesel fuel. The notion that the GM diesel was a gas engine conversion was an urban legend

Your correct, it wasn't made "from" a gasoline engine. It was made from a "beefed up" gasoline engine. The block was much stronger and had the larger crank journals of the big block olds. As a matter of fact, the Olds racers use the 350 diesel block with a 425 crank to make a great 411 ci nitrous motor.

[Ranger]

Well I had 2 HT4100's and 1 diesel. Never cared for either one. The HT4100's where terribly under powered. Lost a head gasket on one of them. It actually had coolant squirting out the side of the block/head joint. Not Cadillacs finest hour.

On the other hand, my father bought an '89 with a 4.5 and drove it til he had to stop driving. Sold it to my neighbor and he drove it til he hit a deer a year or two ago and had to junk it at about 160K I believe.

As for the diesel, it too was terribly under powered. Never leaked a drop of oil as they were noted for. Only failed to start in the cold one time and that was after it was already warmed up, go figure. I did replace the injector pump as Kevin mentioned, but when the head gasket went, I dumped it.

[WarrenJ]

I had one in my '83 Coupe d'Elegance. Well, actually two.

It simply refused to run smoothly on regular; had to use premium fuel. Then one day accelerating onto the Southern State Parkway I was a little too heavy on the pedal and half way through second gear the car suddenly and unexpectedly downshifted to first. I didn't get off the throttle fast enough.

Those of you who have ever busted a timing chain at high rpms know what I experienced next! Oh, that UGLY noise. I had it towed, thinking I'd be driving with a new chain in a day or three.

Well, not so. The block had cracked up front at the camshaft. Woe was me.

I had a recycler swing a used engine into it and he did a superb job. There was no indication the engine had been changed (except that it was now immaculately clean under the hood). It ran like silk and at every stoplight I thought the engine had stalled; it was that smooth/quiet.

A few years after I sold it I ran into the fellow who'd bought it. He had 240,000 miles on it, made regular trips to Canada, and proclaimed it the best car he'd ever owned. He also hadn't washed it since the day I gave him the Title. I didn't know whether to congratulate him or hit him. What a beautiful automobile that had once been.

So mixed emotions for me: it was the worst of cars; it was the best of cars.

Next came my Mark VI, another underpowered 125hp land yacht.

These days I thank the gods every day for the Northstar.

Regards,

Warren

[OynxSTS]

The notion that the GM diesel was a gas engine conversion was an urban legend

Your correct, it wasn't made "from" a gasoline engine. It was made from a "beefed up" gasoline engine. The block was much stronger and had the larger crank journals of the big block olds. As a matter of fact, the Olds racers use the 350 diesel block with a 425 crank to make a great 411 ci nitrous motor.

The second point is closer to the truth then the first... The Olds 350 D and DX blocks are definitely unique engines... BUT the truth is that they are very closely based on some of the very best gas engines GM ever made, and share a ton of parts. The top of this block is basically a 68-70 Olds 350 with ever so slightly thicker sleeves and the bottom of the block is bone stock tooling from an mid 70's Olds 455. With head bolts from a '77 Olds gas engine.. Can you say "a dog's breakfast" These motors even retained the hole and linkage for a distributor! Olds cleverly used this hole to drive a vacuum pump to run the power brakes...

This yielded the engine's infamous problems... The main bearings and supporting oiling system were designed for a gas motor as were the head bolts... Both proved problematic. With proper and perfect maintenance these motors could last... but one mistake and the motor was dead... Most of GMs offerings (both now and then) were somewhat more forgiving.

[clarkz71]

These motors even retained the hole and linkage for a distributor! Olds cleverly used this hole to drive a vacuum pump to run the power brakes...

And the oil pump.

[mmarinov]

Next came my Mark VI, another underpowered 125hp land yacht.

These days I thank the gods every day for the Northstar.

Regards,

Warren

Amen, Warren - I had a '79 Mark V that even with the Windsor was exceptionally underpowered. Beautiful car, though. Like you, it was the best of cars, yet somehow not so much.

[stsjoe]

Mike, my 85 Eldo was a 4.1 and as its been said it was under powered but never gave me a problem. The Deville was a 89 with a 4.5 and it was surprisingly quick and like the 4.1 never gave me any trouble. Still think the eldo was the best looking of 'em all Triple blood red the only photo of it is on the frapper map

Take it easy, Joe

[WarrenJ]

Amen, Warren - I had a '79 Mark V that even with the Windsor was exceptionally underpowered. Beautiful car, though. Like you, it was the best of cars, yet somehow not so much.

I had a '71 Mark III with the 365 hp 460 c.i. engine. I rejetted the carb, recurved the distributer, and added oversized pipes.

That 5,000 lb. torque monster would have been a race car if it weighed half a ton less. Even so, it passed most of what was on the road in those days.

I'm grateful things have come full circle and I've got horsepower again.

Regards,

Warren

[PAUL T]

I have not had any issues with the 4100. As far as the diesel, my father-in-law had a 81 Olds 98 with the diesel. I always thought it was great, it would get 32 MPG, that was the same mileage my Pinto was getting. The most problems we had was not with the engine it was the torque converter. I know we had to replace at least 2 before it was retired. He still has it.