How Can I Add More Horsepower To A 1985 Eldorado?
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The Classic Cadillac Forum Discussion, How Can I Add More Horsepower To A 1985 Eldorado? in Past Cadillac Vehicle Discussion; I'm tired of such sluggish performance, is their anyway I can increase the horsepower and pick-up relatively cheap? This Eldorado ...
  1. #1
    TheChicagoan is offline Cadillac Owners Member
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    How Can I Add More Horsepower To A 1985 Eldorado?

    I'm tired of such sluggish performance, is their anyway I can increase the horsepower and pick-up relatively cheap? This Eldorado has no rust whatsoever and is in excellent shape, it has a 4.1 V8 with TBI and a 4-speed transmission, its the base coupe model with FWD. I'm not looking to swap motors or anything major like that, just simple add-ons or replacements. Maybe increase fuel pressure and add a computer performance chip? I was thinking of adding a CB Radio as well, I know this car had the option for one, is there any predrilled holes in this Eldorado to set up one that any of you enthusiasts know about? Also would an addition of a Hooker Aerochamber Muffler be a good combination with also a straight exhaust? Thanks in advance.

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    Faded Crest's Avatar
    Faded Crest is offline Cadillac Owners Connoisseur
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    Honestly, I don't think there is much of anything you can do to a 4.1. In fact, when I saw your thread title the first thing I was going to suggest was to install an Olds or Chevy 350. Sorry. It is what it is on a 4100. Those Eldos were beautiful cars. What a sin of Cadillac to put such a crappy little engine in them when Olds Tornados and Buick Rivieras got 307's and 350's.

    By the way,

  4. #3
    TheChicagoan is offline Cadillac Owners Member
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    Thanks for the advice and welcome! Honestly, if I ever was going to spend money on an engine swap it would with a 1970 500 engine drop. I can just imagine having 400 horses in a much trimmer Cadillac. haha! I wonder if anyone has done that with an 85?

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    Faded Crest's Avatar
    Faded Crest is offline Cadillac Owners Connoisseur
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    Have not heard of anyone doing it to an Eldo. Some have done it with Broughams though. Finding a '70 500 might be a challenge. I wish there was something you could do to juice up your 4100, but I can't think of much. I have owned a lot of 4100 cars myself and they were always all show and no go! LOL.

    Now there is one guy somewhere on the forum who is into 4100's. He doesn't post very often, but maybe I can dig up his user name for you.

  6. #5
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    talismandave is offline Cadillac Owners Master
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    Hi, welcome to the forum. I have always had a huge soft spot in my heart for those Eldos. A friend of mine had one and when I would go visit him in Florida I always enjoyed cruising in it. There was a radio unit with CB for that on EBAY a while ago. $99. Might check if it is still listed. Also might check to see if K&N makes an induction kit.
    Enjoy the Caddy and the forum!Attachment 90394
    This was in 1980. He was showing off damage on rear quarter after we had a small confrontation at the club the night before!

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    carnut is offline Cadillac Owners Master
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    Years ago I put the throttle body from an 81 368 cu in (8 6 4) engine on my 84 Eldo because that throttle body had bigger throttle blades. It required the thick base plate gasket so the blades would not hit the manifold and the longer bolts that secure it to the manifold. You must also swap your 2 injectors onto this throttle body as well as your TPS. I set the base timing to 12 degrees BTDC as well. Made a big difference on take off from a stop. Actually would chirp a tire at full throttle from a stop! The car was much more responsive and it did not change the fuel mileage. I also changed the cruise control servo to one that used a bead chain connection to the throttle body instead of the rod because there was no way to attach the rod. All the external hoses and fittings plug back in the same places and the air filter fits as well. DONT use the injectors from the 368. They pass more fuel and will super heat the Cat. Converter! The factory CB radio requires a specific "dual band" power antenna to get reception and the early radio dash face (1982 ) to mount a dual shaft old school radio. There was a clip riveted to the dash beside the ash tray to hold the mike. On the exhaust I used a Chevy truck ( 1986?) single inlet dual outlet muffler and had tailpipes made up to mount on either side of the fuel tank. The tips were Z28 rectangular stainless to match the sharp angles at the rear of the car.

  8. #7
    TheChicagoan is offline Cadillac Owners Member
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    funny story haha! Yea I'll check on ebay and see if that CB is still listed.

    ----------

    Whoops might have replied to the wrong post..... Anyways thanks guys for the advice so far. Every bit helps!

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    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    A 1970 500 eldo motor is a rarity. Really, tho, the 71-76 engines are more common and produce just as much, or more horsepower on pump gas with the right tuning. The later 425 and 368 engines are architecturally similar and can be made to produce power as well. I've seen a Chev Suburban with a warmed '74 472 doing four wheel drive burnouts and pulling 12.5 in the 1/4!

    The 4.1 has its share of challenges. Structurally it is not a strong engine and because of the myriad problems it had when new, what might have had some following was effectively and thoroughly killed. General Motors bad engineering at its worst example - well, that and the Olds diesel 5.7.

    However, there have been a few people who have coaxed a few horsepower from this engine. Minor tweaks to the injection, air intake and calibrations can yield a few much needed horsepower. Remember that this thing had about 125 or so from the factory, so gaining an extra 5 or 10 hp will really help and be felt. If you want to spend some money and do some phone calling, a custom cam shaft would really help, as would cleaning up the combustion chambers which for some reason on this motor, were awfully rough. An engine oil cooler and trans cooler would be needed as well.

    Not an impossibility and certainly a hot rod triumph if you can pull it off.

  10. #9
    TheChicagoan is offline Cadillac Owners Member
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    When you were talking about cleaning the combustion chambers, are you referring to the heads? The intake and exhaust passages? Would it be smart to have these areas ported and polished, can we install larger valves? And my Dad thought to shave the heads to boost the compression ratio, as we are already buying premium gas to try to make it run right. What do you think?

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    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    Quote Originally Posted by TheChicagoan View Post
    When you were talking about cleaning the combustion chambers, are you referring to the heads? The intake and exhaust passages? Would it be smart to have these areas ported and polished, can we install larger valves? And my Dad thought to shave the heads to boost the compression ratio, as we are already buying premium gas to try to make it run right. What do you think?
    Polishing the chambers, ports and valves will do a lot. It's not a strong engine so even little things will make a difference. I wouldn't try too much compression, I don't think the engine would stand it. Larger valves may require the block being notched and the pistons "eyebrowed." Again, not recommended. BUT, tuning a little here and there should wake another 15-25 hp which would REALLY be felt.

  12. #11
    carnut is offline Cadillac Owners Master
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    We need to remember that this fuel injection system is a "speed density' system. No mass air sensor to enlarge, no real way to change the fuel delivery curve. The larger throttle body with the original injectors allows more air to enter the engine earlier giving more torque but not affecting horsepower or mileage. Torque is the power we feel every day leaving intersections, getting on the freeway, passing a car etc. Horsepower is top speed. Where does anyone use that? I find it best to concentrate on raising torque rather than horsepower on a street driven vehicle. Adjusting the base timing from 10 to 12 BTDC makes a noticeable improvement, and its free! Quality ignition parts, factory recommended spark plugs, a good quality set of plug wires routed according to the factory service manual are necc. before any major work would be recommended IMO.

  13. #12
    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    I agree. Even simple tricks will make improvements on this car.

  14. #13
    Big Pip's Avatar
    Big Pip is offline Cadillac Owners Fanatic
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    I love my 86 'El Do but it had the 4.5 in it. I put in a bigger coil and upgraded the plugs and replaced the wires cap & rotor then I installed a flowmaster on the back. Sounded great and made improvements were noticable. I think I even bought a used flowmaster off craigslist for $35. It sounded great!

  15. #14
    Fleet's Avatar
    Fleet is offline Cadillac Owners Enthusiast
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    Re: How Can I Add More Horsepower To A 1985 Eldorado?

    I don't know what the axle ratio a 1985 Eldorado has... maybe 3.15:1. Changing to a lower axle ratio would definitely help acceleration. Something like 3.36:1 or 3.50:1.

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