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Thread: 3.5 low compression on cyls 7-8

  1. 22nd April 2012, 04:37 PM #1
    theg
    theg is offline Master Supporter
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    3.5 low compression on cyls 7-8

    Got a hotwire 3.5 disco motor 220,000 klms and today I ran compression tests out of curiosity .
    I bought this disco for parts as a non runner .
    Apart from a major exhaust leak out of the y pipe flange gasket where it meets the header the engine seems to run fine . ( havnt driven it though only ran it in the driveway)
    Results of the compression test are alarming though . Got 140 on all but 7 and 8 only got 100 .
    Anyone know if these 3.5s have a habit of wearing the bores or rings on the rear cylinders . Ive seen this in small block chevs before .
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  2. 22nd April 2012, 05:09 PM #2
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    bee utey
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    I haven't seeen too many worn bores on Rover V8's, it seems the sleeves are much tougher than neat grey cast iron. You could have dirty/rusty valve seats, a worn camshaft, or broken compression rings. All of which I have observed on these engines.
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  3. 22nd April 2012, 06:22 PM #3
    DeanoH
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    Try squirting some oil into the sparkplug holes and see what difference it makes to the compression. If it goes up heaps then rings are probably the culprit.

    Deano
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