Oil for 4100
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HT4100 4.1, 4.5, 4.9 Discussion, Oil for 4100 in Cadillac Engine Technical Discussion; Hi all, the 4100 engine in my 84 Eldo has that thumping noise which is still very minor. Which leads ...
  1. #1
    84 Eldo TC is offline Cadillac Owners Member
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    Oil for 4100

    Hi all, the 4100 engine in my 84 Eldo has that thumping noise which is still very minor. Which leads me to two questions,

    1. I am running 10w40 conventional oil, can I run something a little thicker which would hopefully get rid of the noise, or would that cause the motor to fail faster?

    2. Once these motors start making noise, are they in danger of self destructing soon, or are they still fine to drive?

    Thanks,

    Darrell

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    carnut is online now Cadillac Owners Master
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    Re: Oil for 4100

    I used 15/40 DELLO or ROTUNDA oil specified for diesel applications for years. The faint thump noise is generally the front crankshaft to bearing clearance. This noise has no effect on engine life.

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    84 Eldo TC is offline Cadillac Owners Member
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    Re: Oil for 4100

    Thanks for the reply. Good to know that it's just a noise I can ignore, unless of course it gets really loud. I will try that weight oil to see if it gets quieter. Would 20w50 be too heavy? Also, do I need to use ZDDP additive in these engines? Thanks again.

  5. #4
    Sevillian273's Avatar
    Sevillian273 is offline Cadillac Owners Connoisseur
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    Re: Oil for 4100

    Motor oil already has zddp in it, just in lower percentages than in the past. I would only use a zddp additive in an engine that has flat tappet lifters. My thunderbird has flat tappets and I use Comp Cams break-in additive in the oil. I could be wrong, but I believe the 4100 has hydraulic roller lifters like the rest of the 4.x series..

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    Re: Oil for 4100

    The 4.1 has flat tappet lifters and needs ZDDP

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    Re: Oil for 4100

    Wow I would not have thought that any engine made in the 80's would have flat tappets! What a dinosoar... This is what i use in my Thunderbird which is 15 years older and has hydraulic flat tappet lifters: http://www.summitracing.com/parts/CCA-159/

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    ehall's Avatar
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    Re: Oil for 4100

    The Jeep 4.0 was still using flat tappet lifters until production ended in 2006.

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    carnut is online now Cadillac Owners Master
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    Re: Oil for 4100

    4100's went to roller lifters in 1985. The Allante used roller lifters from the beginning.

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    ehall's Avatar
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    Re: Oil for 4100

    Everything I've read says roller lifters didn't come until the 4.5. And although I haven't my engine that far apart, nothing in the FSM for my 85 4.1 looks like a roller lifter

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    Re: Oil for 4100

    This?



    Or this?


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    ehall's Avatar
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    Re: Oil for 4100

    Sorry shouldn't have said rockers. All of the 4.x use the same interference rockers (no rollers) like these

    We're talking about the lifters (your bottom pic)

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    Re: Oil for 4100

    Which makes me wonder.... Are there any engines with factory roller rockers?

  14. #13
    84 Eldo TC is offline Cadillac Owners Member
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    Re: Oil for 4100

    Thanks for the feedback. I have ZDDP additive from Cam Shield and will add that to the oil.

  15. #14
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Oil for 4100

    I think any regular 15-40 truck oil has enough zdpp for the old flat tappet engines without having to buy an additive.

  16. #15
    joivill is offline Cadillac Owners Member
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    Re: Oil for 4100

    I Use Halvoline 10-40 and when I put this Prolong stuf in the oil 3 the noise from the lift var mutch more quiet on my Eldorado 1983

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