HT 4100 rod knock

[feuer-zauber]

Hi-My sister bought a 86 Sedan Deville that supposedly had a new longblock 2 years ago and the piece of crap is already dead. The past year it was nothing but trouble: alternator died, tensioner died soon after (prob. thanks to her mechanic), oil filter adapter developed a leak/crack and had to be replaced. And then about a month ago the rod knock began. So, she gave the car to me and I'm deciding what to do with the thing. I haven't did an oil pressure test on it and the knock isn't too bad just yet. I don't know anything about this engine but I looked on the net and I found a lot of unfavorable stuff about it. What was the deal with the HT 4100 (re. engineering flaws)? How much work would it be to fix it? I know this would depend on the damage but maybe just a re-main kit or new crank? I've rebuilt a GM 305 and Ford 390 before and I got the time. Thanks for any info

[TheBigOne]

Are you sure its a rod knock?? You know the cams go flat on these kinda cars and it kinda sounds like a rod knock.

[LoneEagle]

I am mostly speaking of the Ht4100 in the rear wheel drive Coupe and Sedan Devilles and the Fleetwood Brougham. 1982-1985. The Ht4100 Engine has 2 major enemies. Heat and the use of the recommended visconsity oil. Most people just look at the instructions on the filler cap. I suggest the following. If the Ht4100 is driven in temperatures above 80 degrees farenheit use 20w50. Some may say use straight 40 weight but when you have a sudden cool morning dependent on where you are I think you will appreciate more the 20w50.
Change the fan clutch to the type that does not have the temperature sensitive clutch. The auto parts stores will usually have this if you ask. You will know the difference at idle and during excelleration, or just sit and rev the motor in the drive way and you will hear the difference and the amount of air being pushed through. This gives you more air flow over a wider variety of temperatures and the 4100 needs all the help it can get.
The Ht4100 can run, heat up and knock and if you have good oil and keep from giving it to much throttle in the severest conditions. It will cool down and start up again and run fine. But if it's hot and your oil isn't up to par etc. You just fried. This aluminum block engine can expand and contract with temperature. Knock then run like new again when cold. But once it goes bad and when you first start it cold and hear kunk,kunk,kunk it's done for. Unless some time if it has not been started in a long time and the oil has to circulate at first cold start, It may make a similar sound but not as harsh.
If your Ht4100 is done for there are a variety of engines that will fit. That body style ran without major redesign from 1980 through 1992.
Engines ranged from the 368cu., 368 modulated displacement, The 4.1Litre=4100, 5.0, and 5.7=350cu.. One could find a wrecked 1992 with a 5.7 and pull the engine and have all the hardware and if needed rebuild that instead of the poor Ht4100. What I would like to see is someone who really is in the know and wants to spend the money put a 6.0 Escalade engine in there.
This 6.0 application with me is only speculation but I would not be surprised if it's soundly possible. If getting parts off that 92 remember the springs for the suspension for the engine should be heavier.
I say in defense of Cadillac that the Ht4100 did acheive a desired objective. After the bad publicity that was put out there on the 368
v8-6-4, Cadillac had to come the next year with somthing that would give the desired gas milage. Cruising at 70 mph. after feeling what may have felt like a fifth gear shift which was actually the lock up torque converter engaging and checking the mile per gallon sentinel and it is reading 27 mpg, and the engine feels like the rpm's are just barely rotating, It's good highway cruising brother. The Ht4100 Has digital electronic fuel injection, key word digital not just electronic, It "was" 1982 when it made it's debut, plus self diagnostics. Self diagnostics already introduced by Cadillac on the 1980 Seville and Eldorado. The 4100's computer systems and such were very reliable but they just did'nt count on that finicky first for Cadillac, aluminum block.
This engine continued to be the main engine for 4 years and a generation came to think of Cadillacs as slow when they had since conception been some of the fastest cars on the road. the Ht4100 was so underpowered that they did not put it in the factory limousine that year and continued with the cast iron block 368 modualated in the Limo.
When it's all done I would still rather a 70 Eldorado 500cu with 400 horses or the first 472in 1968 with 375hp., where in with fresh full tune up would cause you to have to no more than tap the accelerator or the right rear tire would chirp, or the old 390 with that mini high rise intake 325 hp. and the 4 speed jetaway transmission wherein if you had it floored would go into fouth at about 75 mph and give you more push you to the seat as you jetted away from already cruising or from stand still with it's quick first, second shift to get you started rolling.
Well goodbye happy motoring, and a nice blessed day.
Demetrius "LoneEagle"

[kaskillah]

Yeah, I agree with Lone Eagle. There are lots of better engines for your SDV. The 4100 is too difficult to rebuild, you'll need a lot of special tools for the rebuild. I would imagine a good engine for your car would be the old tried and true Chevy 350. A Chevy engine in a Caddy? Why not, it's not a collectors car, go for what's cheap and easy.