Hey, that sounds like a good idea, I was thinking of balancing an egg on the camshaft to see if the lobes were worn.

Ok, in seriousness, I think I'm done with the improvised diagnostic testing.

The last thing I did before I cleaned up for the week was fill up #5 with some 15W-40 and see how long it takes to drain. It doesn't. I interpret that as an intact piston.

Injectors are going back in for now, and I'm going to keep driving it till I can order parts for a head job and plan out a weekend to pull the head.

Thanks everyone for the help, I'll post pictures of the insides when I get the head off.


..one other thing.. what the heck does "let the dog see the rabbit" mean? I mean.. I had a Labrador, I trained him for birds, and every time he saw a rabbit he'd watch it run away before he got the notion in his head to chase it. Then he'd look at me askance as if to say "I don't think that was a bird, but whatever it was, weren't you supposed to shoot it so I could bring it back?"

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'82 300SD 351k

If you go rabbiting with dogs... etc...

Esp a lurcher, so named because while most dogs will follow the rabbit track when chasing it down, a lurcher will always aim straight at the rabbit, "lurching" the corners.

I, for one, am looking forward to seeing what you find when you remove the head. BTW, did you study the valve action on number 5 while you were adjusting the valves?

Valve action?
I spend a little time seeing if parts (rockers, valves, etc) have any abnormal play, is there anything else I should do?

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'82 300SD 351k

I was thinking about the possibility that a worn cam lobe might not be making the #5 intake valve open fully.

At cranking speed almost any inlet valve lift is sufficient to full charge the cylinder. Plus of course inlet valves are always larger so the same amount of lift = greater opening WRT an exhaust valve.

With just short manifolds you can easily hear blowing valves on tickover.

Actually this is not necessarily true. If the lobe is worn in a way that changes the duration of it's open position the cylinder will not fill properly and hence will give a low compression. This would show in a leak down test as a cylinder with sound rings and sound valves.

Your advice is good to a point but not necessarily for a do it yourselfer.

And a repalcement cam is a lot less work than pulling a head and a good used cam can be had for probably less than a head gasket set.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

In this scenario, low compression would only be possible if the valve restricts airflow to such a degree that there is a slight vacuum in the cylinder prior to the compression stroke.

I cannot fathom any scenario where this would occur at cranking speed unless the cam lobe is basically non-existent.