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What did I break? Engine cranked with an extension in the spark plug hole

What broke

  • Bent Valve

    Votes: 4 25.0%
  • Damaged Piston

    Votes: 10 62.5%
  • Other

    Votes: 0 0.0%
  • Knipex Pliers

    Votes: 2 12.5%

  • Total voters
    16

AnthonyHardy2

Active member
Joined
Aug 31, 2010
Location
Oakland, CA
So my friend changed his timing belt on his B230FT and after lining up the timing marks the car refused to start. I suspected the harmonic balancer slipped so I pulled the #1 spark plug and stuck a socket extension in the hole to verify if the engine was at TDC. The timing mark was off by about 90* so we changed the balancer and retimed the engine. We then managed to completely forget that the extension was still in the #1 hole and attempted to start the engine. This was obviously a really stupid mistake and the engine seized against the extension. Now a compression test on that cylinder shows no compression at all so I'm thinking we either bent a valve or managed to punch a hole in the top of the piston. Either way it looks like it's time for a new engine but I'm just curious what actually broke

TLDR: The engine was cranked with a socket extension in the #1 spark plug hole and now has no compression on that cylinder. How dead is this engine?
 
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If you actually want to evaluate the damage, take the head off and try to spray some brake cleaner down the valves on the affected cylinder. If it leaks through to the floor, you'll know the valve was damaged. Sadly, it's more likely that a ratchet drive hole was stamped into the aluminum piston.
 
My money is on holy piston :urgod:
Next time use a straw, pencil, something with a little more give?
Save the celebration for after the work is done?
 
Yep - neatly punched hole int he piston. And probably buggered spark plug hole threads, but that's the least of your issues.

Whip the head off, then see if you need to pull the motor too.
 
I vote for a serious dent in the piston crown, badly damaged spark plug hole threads and likely a bent intake valve and maybe exhaust valve. Given the thickness of the piston crown it would seem unlikely that you could punch a hole in the crown although if you had a good battery and a strong starter motor you might create an interesting crack.

I would typically suggest a leak down test; but, in this case don't bother. Take the head off and inspect. Valve damage is fairly easy to repair even if it requires new guides. The plug hole can likely be repaired with an insert. If the piston is seriously damaged then the piston is coming out and you can examine the bearings and rod for damage. If the piston only has a small dent you can spin the roulette wheel and make a decision as to whether you want to go any further.
 
Pull the head no questions asked. I'm in for pics. :ninja:


One time I had a little clip from the stupid factory intercooler clamps wedge my throttle plate open and peg limiter. Then it went down intake runner #4 and held the valve open. 0 compression. That was the first time I pulled a head.

Just be happy that redblocks are $0-$250.
 
Given the thickness of the piston crown it would seem unlikely that you could punch a hole in the crown although if you had a good battery and a strong starter motor you might create an interesting crack.
As the piston approaches TDC, the ratio between crank rotation and piston movement gets higher and higher, up to the point it stops moving at all. So the higher up the piston is when it hits the extension, the more the force the starter can apply.

But like you said, not even worth wasting the time to do a leakdown test. Something is obviously ****ed up, regardless of what it is you're going to need the head off to see it. Bust out the impact and pop that sucker off there ASAP. We want pics!
 
You could use a bore scope to look inside the cylinder. But with zero compression it's bad in there.

0 compression issues are way more fun to look at than partial compression losses. Here's my buddy's 1ZZ-FE car that burnt an exhaust valve from "excessive RPM" for 6+ hours. It broke 30 minutes from home and was driven back on 3 cyl.

BOwhxiO_d.jpg
 
That is a great picture.
Be interesting to see what happened after they get the head off. I did the starter motor cranking into something solid on an early 911 long ago. That bent valves and was an expensive lesson. I let the cam timing get out of time when I changed the cam chain tensioners. I didn't know I did that mistake and bam when I cranked it. I should have just reset the cam timing and it would have been fine. I learned to double check things better with that one.
 
This was definitely a learning experience and I won't be making that mistake again (hopefully). The piston looks fine through the spark plug hole and I couldn't feel any damage when sliding the extension around the piston top but who knows. This leads me to believe there's a bent valve but looking through the oil cap hole both lifters appear to sit flush against the cam lobes. I'd pull the head now but the car is parked on the street and it needs to stay movable until we're ready to pull the engine. It also runs weirdly well considering the compression test showed absolutely zero compression. At idle the car runs on 3 cylinders as expected but when you rev it the engine smooths out and almost sounds normal. The spark plug threads also aren't any worse than they were before. The plan at this point is to just replace the engine with a B21FT we have sitting around since the current engine needed a rear main seal and the spark plug threads were questionable to begin with. There will definitely be an autopsy once the engine is out and I'll make sure to post pictures but for now this is what I can see through the spark plug hole.

PUZ-jg5x9BM0q6reSZMtTv120ip9Lja-n2VNa9GAda_BQYXj04oyObavVF8q3gUGRbGphpNCePA-bZ5L0CYq33EAjE4cq0tOCZgnfS4x1ANNi_8qL04DgGpYc_cBevxn8aihGn_cfuXHv6cn4G5_QzFLD49Rdk1QYF4DyqGAYl3c0_xmzEnda9eJjg6CgznBEI09ypWhj-ZA39YZKuuqE4sOpXCjcnTvuelkxmLfQDtGXvvckDzsDssVqA3JaVrp6Iu14nRBPdTsxtpTEDzFWwpM3av__n8DeEBMHxJLmiCg3_JfRthGG3-Kc7bpsDQkqemTuAdx3nB4yNlAdKG5KHOf4-Exfl7ISlesw_A2NdtPgbJDeb0UgLwgUAYLsHdZFa-P3JTJEwxTkRbLTVBFKF0v2J_kYI49x3Egt7rvT_kzg_gctjeHEzrYJ8q5loFymzncBg1Xw_056HatTZAkK_XLwlyp7oWBzuIHfPccLK_tqIf2-NMrERTN6E93Gn5IrFE_8cFggNhuOnmWfTLGSKLgrAa3V5Iyqzi3Pyrakm5Ekog-Yn6wOu0JsfpG2RWHfjTP8-RbFmOfZjPrTu-jlP3xoU-YXURccyyfCJ3AzQ8vbHRN6139TzYLDALNMWWLJ39TZgYX-JNt2-TVNFpS30ABzmIo5isobTVJ4v7w_N-lF_B6FUMv1O_aU6sfRL6DKRaUtjRAGai1jN3673Ei1lxc_ZirlVawl7sr0BjLeNU0bpL-8B0dXNE=w681-h907-no
 
how did that sound?

There weren't any weird noises actually it just cranked a bit and stopped and you could hear the starter solenoid click. The engine does have a slight rattle but it sounds like it could just be normal piston slap.

You could use a bore scope to look inside the cylinder. But with zero compression it's bad in there.

Yeah we considered getting a borescope but at this point the engine is coming out no matter what. It's dead or it's dead the only question is if the head or block will be usable later. Even if it's just the valves the cost/ time of buying a new head + headgasket is pretty close to the time and effort of putting in a new longblock when the old one still needs a rear main seal at some point.
 
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If the engine doesn't breathe heavily then the piston could be "ok" and it's just a slightly bent valve.
 
Misfire

@h8volvopeeple---. Don't be surprised if that car that drove 30 miles with a misfire has a bad cat now
 
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