QuestionThank you for Your response John,it was very helpful.I'm sorry I have not responded sooner but I have been busy checking the items You mentioned. I checked the deck with a steel straight edge and a feeler gauge, down to .010,and there was no place where the gauge would pass below the straight edge.It appears to Me that this should be alright,but please correct Me if I am mistaken.All the cam lobes are the same however I found one hydraulic lifter which seems to have an unusual wear pattern on the bottom so I am going to replace it. I have also checked the pistons and the cylinder bores and all are within tolerances, which I consider strange due to the fact that the engine has 140,000 miles on the clock.I have honed the cylinders,the other parts were dropped of at the machine shop to be tank cleaned. I do not know how to pressure test the block as it is still in the vehicle. The machine shop says the heads are fine,no cracks and only a very slight milling was needed.I will check the end gap on the rings when they arrive.I'm beginning to think this engine is not the original.Is this lack of wear possible? Could this be a replacement short block with original heads?
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The text above is a follow-up to ...
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i purchased my 1997 disco last year,it has 135,000 on the clock it was in nice shape,no dents,dings or rust and everything worked.it did needed some work though,i replaced the alternator, repaired some coolant and oil leaks and gave it a good cleaning inside and out.it was previously owned by a woman so i felt it probably had not been beat upon.after driving it for about 4 months i decided to do a compression test, all cylinders were textbook except for #3 which was extremely low.after reading up some on the rover 4.0 i felt i most likely had either a dropped liner,a burned valve, a cracked head or a blown head gasget.i removed the head and to my surprise the valves appeared fine,the head gasket showed some wear but nowhere near what i would expect to find with such low compression.the liner also appeared to be fine as it was flush with the top of the engine block and had a carbon ridge the same as the other cylinders.i then brought the head to the machine shop to have it checked for warping , cracks, and valve leakage.at this point i must say that the top end of the head,the valve cover,rocker arms,and push rods were extremely dirty,in fact i have never seen a head this dirty before,all caked with oil sludge and residue.the machinist put the head in the tank for a few days,he commented that he had seen a good share of bad land rover heads before and this one,although dirty appeared to be in good shape.returning home i decided to remove the other head,it was just as dirty as the other,however when i removed the valley gasket the valley was remarkably clean.when i brought the second head to the machine shop to have it cleaned and checked the machinist told me the first head checked out ok no cracks,no valve leakage and it needed to be milled ever so slightly,he then suggested that i check the piston rings.i went home and dropped the pan,which was also fairly clean considering the state of the top of the engine.i popped out pistons #1,3,5,7,all compression rings appeared fine,none were cracked the oil rings however were dirty and appeared to be stuck in.the cylinders have no ridge or scoring.i am about to hone the cylinders and install new rings and rod bearings. i am concerned i am overlooking something,i intend to clean the whole top end,intake,throttle body,
etc,and reinstall the heads with the updated gasgets.i don't want to go through all this work and still ave the same problem, is there something else i should look for or check before proceeding.
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It sounds to me like you have mostly covered the bases between the valve job and the stuck rings. Here is what I would be doing:
1) tank clean everything
2) check the cam - worn lobes = low compression
3) check heads for cracks
4) perform complete valve job
5) lightly surface the heads so they are perfectly flat and even
6) check the deck surface of the block
7) pressure check the block
8) hone the cylinders and fit new rings, and make sure the diameters are OK (oversize pistons could be needed)
The tasks I have added (that you did not mention) are the decking, the head surfacing, and the cam. All could cause your problem.
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John
AnswerI've a few thoughts to offer:
1) 140k miles - we often can still see the hone marks in parts of the cylinder. Your story about 'lack of wear' is consistent with my own experience.
2) As to the possibility that the block was changed - it certainly could have been changed. Hard to tell. There's a casting date stamped near the seriel number - look there.
3) Your statement that you checked the block with a .010 feeler . . . Did you make a mistake in decimal place? A flat block is flat within .001, not .010.
4) If the lifter has funny wear, you need a cam also
good luck, John
