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1983 Coupe Deville
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51 Posts
Discussion Starter #1
All right after owning my cadillac now for over a year I have a question about increasing the power of the HT4100. Is it even possible to get more horsepower out of her or not. if there is post any suggestions on the thread. I'm hoping this thread will help any one else that owns the same cadillac as me. Thank you!
 

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93 Eldorado 4.9, 95 Fleetwood 5.7 LT1.
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447 Posts
The easiest way to get more power out of the HT4100 is to replace it with a 350. Just to be clear I'm not trying to be funny, just stating fact!
 

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93 Eldorado 4.9, 95 Fleetwood 5.7 LT1.
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447 Posts
Than I'd say your wasting your time & money. Before you answer do a Google search on your engine & you'll see where I'm coming from on this issue, as meany more on this site will tell you. Short of running synthetic oil & maybe a set of custom made of header's there's not much more you can do! Let me rephrase that, there's not much more you can do without that engine blowing apart after mod's!
 

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1979 Sedan deVille d'Elegance
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4,153 Posts
I agree with BigCad, stressing the HT4100 with higher performance is probably the best way to accelerate the probable melt down the engine will inevitably have, at which time, if you like the car, you will be asking yourself (and, has history suggests, you'll be asking for advice on this forum) if you should find a replacement HT4100 or upgrade to a more durable engine as BigCad suggests. Maybe aim for LOW performance by driving the car nice and easy and hopefully you can milk as much remaining life as possible from your current engine. Good luck! :)
 

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1983 Coupe Deville
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51 Posts
Discussion Starter #6
What engines would fit in that big old car anyway? Besides the 350. Is there a better ht4100 out there that would last?
 

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chevy 350 powered 86 FWB, 00 safari h.t. 66 toro, 83 lesabre
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Evo38 said:
What engines would fit in that big old car anyway? Besides the 350. Is there a better ht4100 out there that would last?
Is there a better HT4100? -NO
What engines would fit?
Pretty much any RWD GM engine given you can make custom mounts.
The easier ones (given you want good power for fairly cheap), I'd say olds 350 or 455, chevy 350 or 454, cadillac 425,472,500.
Cheapest would be the chevy 350 or 454 (buy an old ratty looking/ wrecked truck for 1k or under, pull the engine and trans, install in your car) or olds 350/455 (buy a rusty large olds sedan for 1k or under and pull the engine and trans for your car)...running caddy big block donor cars seem to be getting expensive (at least around here)
 

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'80 Fleetwood Coupe, 1994 and 1995 Mercedes 140 Coupe
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Some have retrofitted later 4.9 engines but it takes a whole lot of work.

The HT-4100 runs like a finely tuned watch or it doesn't run at all.

IMO, no way can you ask for more power without risking problems.

Last '83 CDV I had landed up with 507 C.I./TH-400 2.28 posi. Still got 17 MPG on a steady highway roll. Not so good around town.
 

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84 Coupe w/500
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5,665 Posts
Unfortunately, there isnt much you can do to the 4100 to make it faster. Actually, I dont think there is one performance part made for the engine and the rear end already has something like 3.42 gears. Opening the exhaust would make you slower in the streets and a little faster in the highway. If you are looking for power at the green light, you want exhaust with back pressure(quiet). Can anyone think of a beneficial performance mod for the 4100 cars?
 

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1983 Coupe Deville
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51 Posts
Discussion Starter #13
I don't so much want it faster but a little more power would be perfect for the HT4100.
 

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2014 ELR
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9,728 Posts
Everything you do to a 4100 to add power will make it one day sooner to spinning a main bearing. Trust the advice you are getting. Leave the 4100 alone. If you have extra money, and want more performance from your car, start collecting a new engine/trans/rear end (because you will need them all with higher HP). Chevy 350s, big block Chevy, Olds small or big blocks, Cadillac big blocks... they all bolt in with the correct mounts.
 

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85 FW Brougham, 68 Wildcat 'vert, 92 & 96 Roadmaster Wagons
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934 Posts
Only if it also had the matching chrome air intake cover, otherwise you'll just crush the valves.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,737 Posts
You can install an 81 Cadillac 368 throttle body off of the infamous 8/6/4 motor. Swap over your injectors and TPS. Bump the timing to 12 degrees. It requires a thick throttle body base gasket off a 4.5 engine. Throttle blades are larger in diameter which will increase torque. Around town below 50 MPH it feels like a 350 engine.
 

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1983 Coupe Deville
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51 Posts
Discussion Starter #20
What made/makes the HT4100 so bad? Very detailed description would be much appreciated. Thanks!
 
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