Compression ratios?
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HT4100 4.1, 4.5, 4.9 Discussion, Compression ratios? in Cadillac Engine Technical Discussion; I know that the 4.9 liter has the 9.5:1 compression ratio, and to my understanding the MPFI 4.5 liter does ...
  1. #1
    illumina's Avatar
    illumina is offline Cadillac Owners Connoisseur
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    Question Compression ratios?

    I know that the 4.9 liter has the 9.5:1 compression ratio, and to my understanding the MPFI 4.5 liter does too, but I would like to know what the compression ratio for the TBI 4.5 liter from an '89 Deville is. I heard somewhere it is 8.5:1 or so, but I am not real sure.

    The reason I ask is because I'm about to buy a 4.5 liter block for a replacement of the engine that's in my '89 Deville right now, and I wanted to have some extra work done to the engine for better fuel economy and performance. I plan on dumping the current engine that's in there now into my '86 Fleetwood so I'll have it running.

    If anyone knows for sure, please post it!

    Thanks

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    Tailfin's Avatar
    Tailfin is offline Cadillac Owners Enthusiast
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    Re: Compression ratios?

    http://www.carfolio.com/specificatio...22561&Cadillac

    That page says 9.00/1...but I haven't found a cross reference yet...

  4. #3
    illumina's Avatar
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    Re: Compression ratios?

    Thanks! Hopefully I'll get some more information on this, but the plan is to deck the heads for about a 10.0:1 ratio. Mayber a little higher...

  5. #4
    ehall's Avatar
    ehall is offline Cadillac Owners Connoisseur
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    Re: Compression ratios?

    This thread is ancient but I was thumbing through the owners manual for my 1985 4.1 earlier today and it said 9:1 in a little spec chart table

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