Engine experts! – Chevy V8 engine damage, cause??

[pnut]

This engine was rebuilt using Holley Systemax components about 3000 miles ago. I removed the engine, externally refreshed it, and installed it in my Jeep. So there is a history of it running good with no problems.

Initial startup had misconnected vacuum lines, and timing was off. Ever since then (10 minutes total run time until now), the engine runs very poor with excessive valvetrain noise, and coolant leaking excessively into cylinder number 8. Upon disassembly, I found a head gasket failure in the 4 corner cylinder outer walls (see picture closeup). I also found 3 rocker arms with flattened roller tips. No other damage was found to the pushrods, hydraulic lifters, valves, springs, heads, or piston heads.

Felpro says this kind of failure is caused by excessively high combustion chamber temps (detonation, lean, etc).

My best guess is that at one point when first starting the engine, I had one massive detonation which caused the head gasket failure, and causing the valves to push back on the rockers, causing the damage (valve 1Exhaust, 5Exhaust, and 7Intake).

I have replaced head gaskets and rocker arms. I want opinions from anyone who has ideas of what might have caused this so I don’t just put it together and have the problem occur again. Has anyone seen this kind of failure before? Any ideas of other damage I may not have found that exists? Guesses, questions, and ideas are welcome. Thanks.

[LEVE]

Nah... I don't buy it. That would have to be one heck of a pre-detonation. If it were that bad, I'd think you'd see ruined lifters and bent push rods. The sleeve collapse concerns me, and I wonder what caused that? To me it's a clue to the failure, however is it the cause or a result?

[pnut]

LEVE, what sleeve collapse are you speaking of? The head gasket sleeve? If so: that could have been a faulty gasket, or faulty torquing of the head when it was originally installed. Also remember this was in 4 cylinders all in the same place (outboard corner cylinders, on the outer edge of all 4).

My guess is that the failed head gasket already existed, it's just that whatever "event" took place caused it to fail quickly. Is it even possible that this engine was running for some time with the rocker arm that way (failed)? It just seem too coincidental that they happened at the same time (coolant leak bad, poor running, and rocker arm discovery). I cannot say for sure whether or not the rockers were damaged before I did the install and outside rebuild.

what would cause that "flat spotting" of the rocker rollers? I can only think that one singular impact caused that, and not multiple???

[LEVE]

OH...my, that picture is with the head gasket still on? It looked like a sleeved cylinder that had collapsed inward. Goodness, I'm stupid.

[pnut]

Yep, that metal ring is a part of the head gasket. That's why I was able to simply put a new head gasket on and re-assemble.

[LEVE]

[ QUOTE ]
Yep, that metal ring is a part of the head gasket. That's why I was able to simply put a new head gasket on and re-assemble.

[/ QUOTE ]I wondered about that, but heck <ul type="square">[*]A little ridge reaming... and[*]The piston would clear it anyway...[*]The rings wouldn't hit it...[/list]I may be stupid.. but I'm also logical about it!

[RRich]

A shot in the dark ---

Are the cylinder walls scratched or galled?
I think if it was from detonation you'd see more of a burned condition of the carbon on the piston. Kinda like it would look if you'd used a torch to try to melt it. The puicture looks like it was hot, but not overly so.

Too lean it would look "cleaner" than it does. The carbon tends to melt and form little rounded droplets more that the oily/crusty deposits.

The rockers look worn, not impacted, like the roller got stuck and wouldn't roll, wearing the notch and mushrooming the valve stem.
Those very hard rollers shatter with an impact rather than dent. I doubt it was an impact. Try smacking that one with a sledge - you'll see.

Looks like a severe lack of lubrication.

Hmmm, rear cylinder, was running fine, engine was pulled and installed - something happened in the installation process?

Hmmm, the distributor base cuts through the oil galley - could it be the distributor wasn't seated down all the way, allowing the oil to bypass the galley? Isn't oil pressure line at the back, before the oil galley and right over the pump? Where the pressure would still read high?

I'd have a close look at the timing chain and gears too for wear and signs of low lubrication. And the cam itself.

[pnut]

Interesting thoughts, especially about lubrication. If I had a lubrication problem, wouldn't oil pressure gauge read odd pressures? Same thing about engine temps, wouldn't they spike with poor lubrication?

It IS possible the dist was not properly seated, but only for a very short time (less than 1 min) and after the poor running began.

No scratching or galling of cylinder walls, they look new.

Before I installed the engine, I did give it a complete cleanup, repaint, new valve covers, etc. I did have to re-set the distributor, but no internal engine work was done. Same carb, fuel pump, oil pickup, etc.

This link will show you the engine on the stand and you can see generally what I did to it:
http://rubicon.off-road.com/jeep/fea...wap/index.html

[Pete88YJ]

Are you saying that the front and rear cylinders of each bank are showing this head gasket problem, and it's in the same spot as this?

That's right next to the alignmnet pin, as shown in your photo. IIRC, there's an aligment pin front and rear.

When cylinder head gaskets blow, isn't it common for them to blow between bores, where the gasket is the thinnest? Why would it blow where it did, and wouldn't it also blow OUT, rather than IN?

I would think that woudl point to an installation problem - not properly seated on the pin????

The only valvetrain problem I've ever had was having my 400M ford physically push a pushrod THROUGH a rocker arm. I thought "Must have been a stuck valve?" I replaced it and went happily onwards. Did it to me twice, on 2 different valves.

Perhaps you've got the same problem? Stuck valve?

Just my guesses.
Pete

[RRich]

I think the port for the gauge is enough toward the pump - upstream - of the leak - if the distributor was bypassing the oil the pressure might read close to what it should, not low enough to really notice.

The roller - if it was seized or impacted by something, I'd think the roller would shatter, rather than dent. Try whacking it - it's bad anyway. And the valve stem would look a little different - that one looks like it mushroomed from wear. If it was impacted the edges of the mushroom would look more cracked and splintered - like the end of your cold chisel. That one looks more formed, like it was slowly worked into the mushroom.

If it was a stuck valve I'd think the pushrod would bend long before the roller could dent like that. Use a strong magnifying glass on the dent - you should be able to tell if it's wear or impacted.

Are the valves still free?

Look at the distributor base carefully, and at the two lower holes down in the block where it fits really close - where it cuts through the galley.

Good catch - The alignment pin may have had a role in it too. It may have kept you from initially torqueing it down properly - if the dowel pin was too long or had dirt at the base of it - or in the hole. Then slinging it on a crane stretched it up just enough. How was the sling attached?

Could be a combination of unrelated things, pin, pressure etc.

Not exactly like this problem - but I had a massive oil pressure loss on a '56 265 block one time. I did a tune-up, lost most of the oil pressure. Turned out the 265 distributor had a flat spot milled on the base - stock - I'd turned it wrong, the oil bypassed back into the pan.

But - if the distributor is even only 1/8" too high, not totally seated, it can allow the oil pressure to bypass. 1/8" is seated enough that everything works, pump spins etc, but it bypasses down below.

Hard to tell from pictures!