Broke spark plug....grrr....2165cc Volkswagen

[malc]

Surely the head must be heated to expand it and the plug, if possible cooled, to shrink it.
Cooling the head will increase it's bite on the plug.
Bolts can be removed by heating around them and melting wax into the thread.

[JamesMayberryIII]

Surely the head must be heated to expand it and the plug, if possible cooled, to shrink it.
Cooling the head will increase it's bite on the plug.
Bolts can be removed by heating around them and melting wax into the thread.

Ok, I had it backwards...

[AndyB]

I thought spark plugs were supposed to be installed without antisieze on them? That's what NGK says, at least. Don't know how common that is though.

Sucks, but you may as well pull the head and minimize the damage done getting it out, and it makes a helicoil/timesert/etc that much easier to install properly if necessary.

[STINEY]

You guys won. Or the sandrail won. Or Murphy won.

Just finished pulling the head.

Had a few minutes after fixing the radio dog fence (someone missed the drive by 8' and drove over the wire on a mushy yard day, breaking the wire)
Nice day in the 50's, had a couple inches of icey snow and 2 school delays Thursday and Friday. Love Ohio's weekly seasonal changes, lol.

Everything came apart like it should, except for one head stud that the nut stuck on. Stud unthreads from block case-saver so no biggie.

Had a moment of WTF is that red fluid......then I remembered flooding that cylinder with ATF/acetone mix all winter. Duh.

The cylinder in question has some carbon build up on the piston, but that was expected too with a dead spark plug.

Also found a receipt laying on top of the opposite cylinder. Must have been sucked in by the cooling fan, amazing it went through the fan completely unscathed.

Pictures later. iPad sucks as a camera, and cutting and pasting from iPad sucks too.

[malc]

I think I'd drill out the center of what's left of the spark plug, then if a saw blade will go in there cut some grooves to relieve the pressure on the threads.
Careful not cut into the cylinder head threads.

Just a thought....this is an unknown problem for me.

[STINEY]

Pictures

Pull the 44 IDF Weber complete with intake and plug wires, pop valve cover and pull other spark plug. Soak exhaust nuts with PB Blaster. Remove rear exhaust tube from merge collector, rear tube is stuck into the collector so we'll just work around it.




Pull rocker shaft assembly and push rods, keeping track of where they go.





Here are the lower 4 head stud nuts, now accessible behind the rocker shaft.






The heads cannot be removed without pulling the upper cooling tins (chrome piece) to access the upper row of head stud nuts. And the tin cannot be removed without removing the cooling shroud, the alternator has the cooling fan on the opposite end of the shaft from the pulley, so the alternator and shroud have to come off too. The throttle cable and alternator wiring have to be disconnected along with the dual carb throttle linkage to remove the alternator.



Alternator and cooling shroud removed.



And now we can access the upper row of head stub nuts.




Head off. Had a surprise when the red fluid drained out suddenly.....its been soaking so long I momentarily forgot about the ATF/acetone mix in there.



Carbon buildup not too bad, considering I've been chasing a faulty plug for a while.



And the combustion chamber, complete with stuck spark plug threads.



Note how far out the heads are machined to fit the oversize 94 mm pistons/cylinders. Any larger and the cylinder sealing surface would disappear....the head studs are the limiting factor in how large the bore can be increased. This is the largest oversize for a stock engine case.



And today a trip through the parts cleaner at work. Be kind to your machinist, don't hand them gooey crud to work with.

[STINEY]

And success. Customer of ours is a genius at many things, and a darn fine machinist as well. He set this up and milled away at the spark plug jacket until threads started to show, and then muscled the remainder out of it.

He said it looked like carbon had locked the plug in. That what looks rust-colored on the plug threads is actually carbon, though he declined to speculate on how it got in there. He also allowed as to that it "sure was locked up tighter than a" (rest of comment ommitted due to sensitivity of any children that may be reading, lol)

He even saved the ugly bits for scrutiny.





And chased the threads.

[Barry Donovan]

Saved nicely.


big exhaust valves.
Never saw a beetle engine taken apart.

great turbo candidates.

sideways or up top..the plugs do weird things on the boxer. I have scrapped a liquid subaru head to holes non-fixable.

Subaru has tiny exhaust valves. Adds to the crazy ricer sounds for sure.

intake always remains the same, the size of exhaust only changes the speed of what it took in getting out.

I'd put that in quotes, but may be off a few words of the teacher.
The lazy sound of the beetle, it is explained by those heads. that really can be a very large little engine if you wanted it to be.

[STINEY]

Barry, if you want to see more of the innards of a stroker VW and how close things get inside, check out this short thread I made years ago while rebuilding a friends 2275cc.

http://bangshift.com/general-news/pr...oker-vw-motor/

Oops, that was the front page link, and the link on the front page is dead.....try this to get straight to the thread. http://www.bangshift.com/forum/forum...engine-carnage


Those valves aren't stock sized. Here is an image of a stock 1600 head combustion chamber.



Compared to my 044 aftermarket heads, see how much closer the valves get to each other as the valve size increases? And look at the combustion chamber size itself. I laid back the area on the sides to unshroud the valves next to the cylinder walls, and also around the spark plug. The spark plugs on these 044 heads is also a smaller diameter thread to allow more room for larger valves. More meat in them to resist cracking as well.

[Deaf Bob]

Crazy how the stud holes are cut into..

[STINEY]

Crazy how the stud holes are cut into..

Check things out on the case side of this machine work. Threaded inserts are added, THEN the bore hole in the case is opened up for the 94mm cylinders. Some of the inserts have partial threads showing after the machining.

[STINEY]

I believe I understand what happened to first cause this plug to fail intermittently, then fail permanently. The theory also fits the puzzle as to why this plug was locked in so tight with what the machinist calls carbon.

Reading about carbon "fluffing" and spark plugs. They are designed to shed these deposits as a normal event. Certain driving conditions - like hard fast acceleration with a sudden rise in spark plug temperature can cause the carbon fluff to turn to carbon "film", even to the point of shorting a plug.

Check out the description and plug with insulator glazing in the link below.

http://www.mg-cars.org.uk/imgytr/sparkplug.shtml

"Glazing appears as a yellowish, varnish-like colour. This condition indicates that spark plug temperatures have risen suddenly during a hard, fast acceleration period. As a result, normal combustion deposits do not have an opportunity to "fluff-off" as they normally do. Instead, they melt to form a conductive coating and misfire will occur."

Sure looks like my plug did something similar. And carrying that line of thought, couldn't that film also "wick" up into the threads and then solidifying, thereby locking them up? (the plug and head ARE designed to disperse heat after all)




Its just a theory, but it fits all the empirical evidence.

Bad thing is, there doesn't seem to be anything preventative to do for it, aside from staying away from terrain that requires "hard fast acceleration periods".

Repeatedly.

Like sand dunes. Nope, not gonna avoid those, no way no how.




I suppose that Lead-Fouling could be a factor as well? This engine has only ever seen 110+ race gas, Cam 2, Torco, VP. I was a 10 year old kid when lead was fazed out of fuel, but I remember the discussions around the dinner table before that about the crap fuel ruining spark plugs.
Was this what it looked like? Is the lead in the race fuel contributing to the issue?

See lead fouled plug in these links. http://www.autolite.com/media/11838/plugtips.pdf


https://www.ngksparkplugs.com/about-...d-a-spark-plug

[Deaf Bob]

The older heads we run are not seat hardened.. Idle time and WOT is all we see. No burned valves or seats on 2 motors..
Blown head gaskets, yes..

Might want to half your run time on plugs.

Amazing you get any combustion sealing at all....

[STINEY]

Lol.....they seal only on the face of the cylinder barrel. You can see the tiny witness "ring" around the combustion chamber.

That said, there is no head gasket. VW never used one in the Type I engines.

The later Type IV engines came with thin metal head gaskets there, and issued a service bulletin instructing that any vehicle in for engine work have the head gasket ommitted in order to prevent failure.

[Barry Donovan]

That is a lot of work.
I knew it was big... as germans used similar proportion as american small block.

I resorted to NGK iridium and msd ignition. Breaks up below 3k rpm into short repeated stabs.
My best setup yet. Very alive and precise.