Your increase was nowhere near high enough. You should only have ~10% variation in your compression. If #3 is the middle at 167, the range should be 150 minimum to 184 maximum. Number 6 and 8 are way too low. Rebuild the heads.

 

I agree, time to pull the heads and have them inspected, let us know what you find.

 

Ok....
Rave manual... check...
V-8 overhaul manual... check...
digital camera... check...
labels and markers... check...
cleared out garage... check...
fear of the unknown... hold...
respect for the unknown... check...

Certainty of Death... Small chance of success... What am I waiting for?...

I'm going in.... (I've got to do this myself. No dough for a pro. Never done this before.)

BTW: I'll take and share pictures... I'll try to do a how to write up. Doing this will slow me down, keep me focused, and make me be more methodical etc or something mumble mumble mumble.... (hopefully).

Wish me luck... if I'm not back, dial 911 and/or 999, and send in the cavalry.. (maybe if I F$%# this up, it'll be more appropriate to send in the clowns)

Oh... Do I have to take the hood/bonnet off to remove the intake manifold (or anything else)?

 

If you remove the hood it will be easier.

 

I finally got the cylinder head off last night (holidays/weather/etc)....

I had to use a 20 inch breaker bar and 50 inch steel pipe (for 60 inches of combined leverage) with a whole lot more muscle than I would have thought necessary (my first time doing this) to loosen and remove every cylinder head bolt except for one. The 8th bolt in removal sequence (per overhaul manual) was a piece of cake. I just put the impact socket on it and it loosened on the very first crank with the driver. Hmmm.....

This 8th bolt also happens to be located between the two cylinders that were giving me low compression and misfires, cylinder 8 and cylinder 6. Interesting.

So when I pull the cylinder head, I see that the gasket has blown between cylinders 6 and 8, exactly in the location of the loose head bolt. hmmm....



I think this explains why cylinders 6 and 8 had a low compression and why I wasn't loosing any oil or coolant.

I haven't taken the valves apart yet, but at first glance they appear to be ok. The head and block faces also appear flat and unwarped.

So considering this, I think this head gasket failed because of installer error (when replaced at 90K) and not properly torquing the head bolt/bolts. I don't think it failed because of overheating/warping. I don't think it failed because of excessive combustion pressure or ignition because the damage to the head gasket is localized in the one area where the loose head bolt was.

So going back to the original question of interpreting my compression test results: I don't think it was a sticking exhaust valve (still going to inspect all the valves etc). I'm pretty sure the blown gasket explains everything.

Questions:

Am I missing something here?

How would I go about ruling out combustion or ignition problems?

What should I tell the independent Land Rover shop that did the first head gasket replacement job at 70k (charging the previous owner $1700), and wanted to charge me $2500 for a valve job?

Thanks,

Thomas

 

Don't guess on the block and heads when it comes to being warped, use a straight edge and feeler gauge to make sure.

 

Actually I didn't guess. As you just said, I used a straight edge and feeler gauge to check for warpage and flatness... I plan on taking the heads to my precision grinding person to verify and confirm.

 

can anyone recommend a valve spring compressor? I picked one up from Napa but I don't like it...(could be user error or buyer mistake)

http://www.napaonline.com/Search/Det...054_0282414597

 

I would say you found your problem. The gasket pretty well tells the story. I would talk to the owner/manager of the indy Land Rover shop and show him pictures of exactly what you found. Since 60K miles have passed since the last HG, you probably won't get anything, but you never know.

While the heads are off, I would have them rebuilt or at least reseat the valves. You would hate to build her back up and run into a valve problem 20K down the road.