Spark plug hole exploded. New head or new engine?

[VWYogi]

So I recently had a fun breakdown involving the infamous "white smoke" and my 1984 1.9L Vanagon

I noticed my RPMs dropping and almost immediately I heard a backfire sound come from the engine and had no power. I coasted in about 300 yds to a truck stop looking life Cheech and Chong had just burned one down. My first thought was, head gasket was blown, but I had no milky oil.

After getting it towed and finishing my work week I started looking around the engine. First thing I noticed on the passenger side cylinder head was that my #2 spark plug wire had been blown off and with my next move, was horrified. I went to unscrew that spark plug and with only about 10-20% of the threads left (seen in photo), pulled my spark plug out. That backfire sounds was my spark plug hole exploding. While sinking into a point of depression and confusion I also realized that I had coolant leaking from the 2 cap nuts located on the cylinder head (seen in photo). Filling up my bone dry coolant reservoir no more that 5-10% would result in a steady flow from those cap nuts.

So with my situation painted out for you and what basic WBX engine knowledge I have, and have yet to gain, along with the unknown damage that has yet to be found once I open the Cylinder head, I ask The Samba this.

Could replacing the Cylinder Head be all that this job entails, and can I make that judgment call on my own by taking the head off?

Is rebuilding the entire engine necessary if the damage is minimal?

I was quoted $5,000 from a shop in Corvallis OR with giving them the info I just gave you (seems steep). Does anyone know a reputable shop in the Willamette valley?

My head is swimming with thoughts, ideas, routes, and what ifs on how to go about this bullet hole in my cylinder head. Any and all conversations are welcome in hopes that I can get a good game plan for moving forward.

Thank y'all
Yogi the bear

[4Gears4Tires]

Just drill it out larger and helicoil it, it'll be fine.



Definitely pull the head since it's 100% trash and needs replacing and then make an assessment on the motor. There's a high chance with a replaced head you'll be just fine.
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'87 Syncro Ferric Oxyhydroxide Superleggera Edition
'85 Westy Sciuridae Domus Edition

[djkeev]

The spark plug hole was most likely stripped out during a service.
Rather than replace the head, the hole was drilled larger and a thread repair insert was installed.

Being careless a short thread insert was probably installed instead of the proper long threaded repair insert.

After a period of time the short threaded insert simply lost its ability to grip and blew out.
Not unheard of, but not an every day occurrence either.

Source a new AMC head. Educate your self about the short comings of the AMC valves and keepers beforehand.
Shop wisely..........


Dave
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Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

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http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert

[GoEverywhere]

It'll all come down to what you find when you pull that head.

MOST LIKELY, you'll find that it blew out on the combustion stroke, everything went out and nothing remained inside the engine to foul your piston. If thats the case you'll just need a new head and you'll be fine. If you're super unlucky some part of that head chunk fell down inside the motor and scored up the piston or cylinder and then you'll have to repair that too.

Since you mentioned Corvallis, I'd go check out No Name Garage in Eugene, OR.
They have a good reputation for VW repair in Oregon, Especially Vanagons.

[Red Ryder]

Wow, $5k repair estimate? Somebody really did not want that job…
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“Most everyone’s mad here. You may have noticed I am not quite all there myself.” — Cheshire Cat, Adventures of Alice in Wonderland

“Scarlett” — 1990 Vanagon Carat Wolfsburg Edition (Tornado Red)
“Nigel” — 1999 Jaguar XK8 convertible (Alpine Green Metallic)

[Abscate]

A proper repair could easily cost 5k all in
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[Red Ryder]

[djkeev]

[VWYogi]

[MarkWard]

Exhaust valve seat came loose and held the valve open and the piston hit the valve and bent the pushrod enough that it bent the tube. That cylinder did not explode the spark plug. It got hot enough the aluminum started to melt. You’ll need a head, piston, pushrod minimum. I wouldn’t waste $$$ on it honestly. You need to figure out why it was melting. Aluminum melts at roughly 1500f degrees.

[Abscate]

You can’t just “ look at stuff” and tell its condition. The tear down it’s as much diagnostic as repair.
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[outcaststudios]

[Howesight]

Those previous pics and the recent ones are real horrorshow!

That engine might be saveable with enough replacement parts, but an upgrade to a "take-out" 2.1 engine from an engine converter might also be a good idea. As Mark Ward noted above, a complete rebuild will be in order.

As a gearhead/nerd, I am curious how the failure occurred. At first blush, it looks as though the aluminum erosion between the valves, near the spark plug, and on the one side of the affected piston looks like classic knock damage. However, the WBX engine and the "Heron" cylinder hear/piston design is very resistant to knocking, normally. It remains possible that there was knock. If a cylinder has oil control problems, the oil in the combustion chamber can increase the probability of knock. The affected piston has missing metal, but it's not possible from the photos to determine if that caused or resulted from a knocking event.

If there had been a metal failure near the spark plug threads (due to, perhaps, a poor spark plug thread repair), then a chunk of aluminum, or a spark plug electrode, might have become wedged in between the exhaust valve and seat. That would cause all kinds of havoc, since the exhaust valve needs to seat properly to cool it. But the aluminum erosion would not be explained, unless the exhaust valve remained wedged just slightly open, by debris or a bent valve stem, and the exhaust gases would then travel in the valve-face-to-valve seat space and act like an oxy-acetylene torch, heating the adjacent aluminum to melting and the exhaust valve seat to the oval shape which it clearly ended with.

Finally, it's not possible to tell if the cylinder head failure caused the coolant leak or whether low or no coolant caused the head failure.

Yuck! Hope you find a solution within your budget!!
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'86 Syncro Westy SVX

[RolandD]

Was the bent push rod tube on the same cylinder as the burned piston/head? If so, what does the pushrod look like? The damage to the pushrod tube looks more external than internal.

Roland

[Wildthings]

Loose/broken head bolts would cause a loss of coolant, so once coolant got low aluminium started melting and things kept going south from there. That is one scenario, there are surely others.

I have a 2.1L takeout engine in my 83 1/2 have maybe six or seven years on it by now, but not a super amount of miles. Went with the full 2.1L exhaust and cooling system. Want to swap to the Digifant someday but keep the AAR instead of going to the ICV system as I have neither AC or power steering.

[VWYogi]

[VWYogi]

[GoEverywhere]

[Abscate]

That looks like a ready to ship GEX. Pull that piston, be ready for a surprise
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[DanHoug]

the left side of the piston is melted and it looks like you have about 0.020" piston to cylinder clearance now. the top of the piston is splattered and there's molten aluminum in your exhaust header.

iff'n you're really cheap and don't mind labor, put a new cylinder head on and see how she chooches. be aware that the proper fix is to pull the engine and put a new piston and cylinder in that hole, or all of them. can it be done without pulling the engine? yes because you can pull the cylinder out, take off the rod bolts and remove the piston and rod, but if the back end of the rod cap drops into the crankcase, you ain't getting it back without some serious good karma.

so, in the immortal words of Dirty Harry.... "Do you feel lucky? Well, do ya?"
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-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
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