Engine compression..or lack thereof

What other than no compression would be an indicator of a broken valve spring? I have strong compression on outside 4 cylinders and no compression on center two. I checked it with a gauge. The 230 engine that I bought thinking I would rebuild had two broken valve springs in it. Is this something prone to these engines? The springs are half a decade old and I know corrosion can play havoc on them. Maybe just carbon under the valves? What is the best way to determine the problem other than pulling the head? I am a wrencher's wrencher so I have no fears of doing so but I just wondered if any one else has had this problem.

I think it's more fatigue than corrosion, but assuming the cam is good and a valve isn't hung open, a spring is a likelyt candidate. I assume you are familiar with pressurizing a cylinder through the spark plug hold in order to remove a valve spring while the head is still on?

You can use the pressure recomended above to see if it's a leaking valve too. If it's the center two, 3 & 4 cyls., it could be a blown head gasket. If you use the pressure method and the gasket is blown, you'll hear the air comming out the other cylinder. Good luck, keep us posted.

WillWagner, Now that is an idea, blown head gasket. I will put some pressure on it and see where the air is leaking to. If the leak is to the exhaust or carb, valve problem, to the to the other cylinder, head gasket. Thanks Clinto, fyi it is a flat head so the valves are beside the cylinders. I knew you guys would come thru! If it is only a blown head gasket I will be very happy! Wish it wasn't 10:30 at night, I would do it right now!

Thanks Clinto, fyi it is a flat head so the valves are beside the cylinders.

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oops

Head gasket it was. Now I understand everything. At first the engine seemed to be over heating by loosing coolant thru the overflow tube. But the gauge wasn't showing over heating. Well, now I know the pressure was coming from the cylinder to the coolant passages in the head via the leaking gasket. This failure was avoidable. Two owner's back (Pre Big B) had re-built the engine. Well, the TM9-1840A recommendations of the tightening sequence and re-check after reaching operating temp could not have been followed. There may have been 2 or 3 head bolts that I feel were tight, the rest could easily be loosened with my 1/2" drive ratchet. I am surprised the head gasket didn't go sooner.

Ahhhhhhhhh. All the world loves an easy fix !

The springs are half a decade old and I know corrosion can play havoc on them.

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We assume you meant half a century old? I wouldn't think 5-year-old valve springs should be crumbling away due to corrosion...

Glad it was en easy fix...

Jon

Glad it turned out to be relaitvely minor. You had me concerned when i first saw the post. That truck doesn't rrealize how lucky it is that you bought it.

just o another note before putting it back together. That head may be warped? Have it checked and shaved if needed. Also check the block deck? This could be a reason for loose bolts and or the head gasket blowing,if so you will just have it do the same thing again.. Bummer this happened..

Got the new head gasket ordered to replace the blown one in the nearly 54 year old engine and new thermostat. Wonder if the truck could get a senior discount at the gas pump in a couple of years? The old thermostat fell apart and was clogged with all kinds of stringy junk. Head bolts all looked great, maybe NOS from the rebuild? They had some kind of black anti corrosion coating above the threads. I will get the head flatness checked.

Got the new head gasket installed and new thermostat. Only snapped one head bolt, of course it was the 4th to the last to tighten, couldn't have been the 4th one. Luckily it left a bit above the engine block to get a hold of and it came right out. BigBee, I applied a bit of OD to the red barn painted parts after stripping. It looks a bit better now. (I know, I know a photo is coming) I checked the head flatness with a straight edge and shim gauge. The manual says .004 per foot of length is ok, I only had about .001 per foot so I was satisfied with the head not being warped. Fired right up after getting it all together, gave the wife and kids and some friends a ride around the block and all was well.