Thread: 3.9 V8 Low Compression One Cyl

If you are clued up mechanically, source the bits you think you will need, and repair it.
If you think it's worth keeping that is.........
You don't sound convinced......

Heads and sump come off in the vehicle, probably just needs a broken ring replaced. As set of rings and gaskets won't break the bank. Possibly a good time to replace the cam and timing chain too, if it's aged.

Do a cylinder leak down test, spark plug out of low comp cylinder, that cylinder on TDC on compression stroke, make up a fitting to introduce compressed air into the cylinder, (old spark plug base and attach the compressor air hose to it), while the air is on the cylinder, listen in tappet cover filler or crankcase breather, exhaust pipe, and inlet manifold/inlet tract for air hissing through, this may indicate the leak path i.e crankcase, worn or broken rings, exhaust pipe, burned or riding exhaust valve, inlet manifold, burned or riding inlet valve.
This method will save some unnecessary "undressing" of the engine it may only need a valve repaired/replaced, and only one head off.
Full engine overhauls can run into lots of money and these V8's have usually lots of life (Klm's) in them, no need looking for trouble all over the place 'cos you will usually most certainly find it, and remember it is still only a $3,500 vehicle.
Just thinking, years ago our old 3.5 V8 Rangie had a weak cylinder at about 500,000 Klm and the cause of that was a cam lobe nearly completely worn off the exhaust lobe of, I think, cylinder number 8, so that cylinder was low on compression and not contributing much to the game, not sure if camshaft issues were still featured in the Disco V8's of later years and bigger capacity, but check/measure the valve opening/closing on the weak cylinder to see how it compares with the others.

Thanks guys. I think I may have a go at fixing it myself. 25 to 30 years ago I used to rip heads off my cars to replace head gaskets or get machine work done on heads as I had no money and it was the only way I could get my cars back on the road.. I have grown old and have not been so mechanically adventurous in recent years. No reason why I shouldn't attempt this work.

Got some work to finish off on my 70 year old wooden river boat first. So if the D1 has not been sold within a few weeks then I am going to have a go. Kinda looking forward to that happening.



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First issue I have come up against is the ram housing doesn't seem to want to budge from the intake manifold after removing the 6 bolts.

Any suggestions on how to tackle this? I don't really want to start wedging something in between the housing and the manifold to pry them apart.

Originally Posted by CV888

First issue I have come up against is the ram housing doesn't seem to want to budge from the intake manifold after removing the 6 bolts.

Any suggestions on how to tackle this? I don't really want to start wedging something in between the housing and the manifold to pry them apart.

Apply downwards or upwards force at the throttle body side, a fist bump or rubber hammer blow or a lever between the TB and the rocker cover.

Slowly getting there. Intake is off, hope to get head/s off today. Hoping it's only replace head gasket. Maybe a valve, which would mean machine shop. Anyone recommend a land rover knowledgeable head shop in adelaide?

Very slow progress as I have other projects (old boat) and I really don't need the D1 on the road until September, so I am taking my time with her.

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I have the head off and had it checked at Triumph Rover Spares. Passed the hardness test fine, and the test of the valves shows they are sealing ok. And appears not to be warped using a straight edge.

It must be something else.

I noticed when taking the head bolts out, working from outside to in, that the last bolt, the middle long one, was not torqued up and came out very easy. Then I checked the block and sure enough the thread is stripped in the block. And there a black marks on the block going from the barrels to the out side of the block adjacent to the loose bolt. The gasket is the same. I am assuming that this is the problem. but would this be true if the head and the block are straight?

I don't really want to get underneath, take the sump off and remove the piston if I don't have to.

I will try to post some pics of block and gasket.

Any comments? please?