Rusted Out 1970 850 Spider Fix-Up

I don't believe it- you've done so much for your car and will give it up for an engine problem?
It got you home, so it's probably minor.
Parts are much more available now (thanks to the internet!) than when I had my 850 in ~1986; it had hardly any compression, I had to preheat the spark plugs with a propane torch to get it to start.

To start with, I'd look at the top of the carb (the air cleaner nuts on my 124 vibrated loose!) and under the distributor cap.
 
Y’know those three studs and bolts that hold down the air cleaner base? Well, one of mine was missing. Oh, the nut and washer were still in the aircleaner, but no stud. Uh oh. Carb off, nope, not in there. Let’s look at the plugs

First three look good.
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Cylinder 4….uhhh…
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Guess the head is coming off. No bolts snap off, so it goes quickly. Here is what I found.
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One of these things is NOT like the other! Mashed stud potatoes. Amazingly, the valves still look ok. How did that stud get past them? Intial overview of the piston doesn’t look too bad either, but I have more digging to do after I cool off.

What a mess!
 
Serious bummer. Loktite is your friend. I have always had paranoia about those studs
 
I don't want to say this is about what I expected, but...
I moto-tooled mine, and put the head back on successfully. Do you have impressions in the top of the piston, too?
And there may be some damage above the valves, as the stud may have also bounced around up there.
 
kmead said:
Serious bummer. Loktite is your friend. I have always had paranoia about those studs
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Maybe time for a sticky of “hey other owners…watch out for these things” or something like that. Foresight better than hindsight. I will never trust them again!
 
Well, here is the piston. Kinda chewed on a bit. I am leaning towards a washer getting in there. As I suppose it is possible that one could slip past a valve, and wedge in away from the valves. No sign of the stud yet. Maybe it fell out the air cleaner? Who knows? The cylinder walls are fine, so I am leaning towards smoothing out the head a bit and putting it all back together when my gasket set arrives. No signs of valve bending or edge damage. Obviously this cylinder will not combust quite as efficiently, but I think it should still run ok. Thoughts?
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You can spray some WD-40 into the ports to see if it gets past the valve(s), this will tell you if they still seal (not bent or seat damaged).
I smoothed out the rough areas on my head and piston top and went with it, you probably can too.
Shake the exhaust to see if anything went on out the exhaust valve (mine did).
All 4 nuts and two studs went missing on my engine at freeway speeds; they make quite a clatter, eh?
 
Daniel Gibson said:
Maybe time for a sticky of “hey other owners…watch out for these things” or something like that. Foresight better than hindsight. I will never trust them again!
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Yes, have to admit as a newbie, I have no idea what I’m looking at or what you’re all discussing. :)
 
Jefco said:
You can spray some WD-40 into the ports to see if it gets past the valve(s), this will tell you if they still seal (not bent or seat damaged).
I smoothed out the rough areas on my head and piston top and went with it, you probably can too.
Shake the exhaust to see if anything went on out the exhaust valve (mine did).
All 4 nuts and two studs went missing on my engine at freeway speeds; they make quite a clatter, eh?
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Oh boy, did they ever. How did yours make it to the exhaust? Must have been nothing left but metal crumbs.
 
Apparently, some of the nuts went thru with little fuss; I found none of them, and slight hexagonal marking. The stud left threaded impressions in the piston top and the squish area on the head, but also found its way out thru the exhaust valve too.
I smoothed out the damage, expecting any leftover sharp edge to create a hot spot, and put it back together successfully.
This was on an 1800 twincam, not an 850 (that came next, after the 124 coupe took out a deer); your squish area looks pretty bad, worse than mine was, but there's a lot of material in that area; just don't damage the fire ring space around the edge.
 
Daniel Gibson said:
Well, here is the piston. Kinda chewed on a bit. I am leaning towards a washer getting in there. As I suppose it is possible that one could slip past a valve, and wedge in away from the valves. No sign of the stud yet. Maybe it fell out the air cleaner? Who knows? The cylinder walls are fine, so I am leaning towards smoothing out the head a bit and putting it all back together when my gasket set arrives. No signs of valve bending or edge damage. Obviously this cylinder will not combust quite as efficiently, but I think it should still run ok. Thoughts?
View attachment 50274
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:( :eek::(:eek::(:eek::mad::mad::mad:
 
Daniel Gibson said:
Well, here is the piston. Kinda chewed on a bit. I am leaning towards a washer getting in there. As I suppose it is possible that one could slip past a valve, and wedge in away from the valves. No sign of the stud yet. Maybe it fell out the air cleaner? Who knows? The cylinder walls are fine, so I am leaning towards smoothing out the head a bit and putting it all back together when my gasket set arrives. No signs of valve bending or edge damage. Obviously this cylinder will not combust quite as efficiently, but I think it should still run ok. Thoughts?
View attachment 50274
Click to expand...
I agree with your analysis. I had a similar issue with a M6 nut that went missing. Clean up, new headgasket and give it a shot. I agree use locktite on the studs as well as nylock nuts. Don't forget to shove a rag down the intake while you're doing the work on the air cleaner. I like anti-seize on the head bolts. Of course, follow the correct head bolt tightening sequence and pattern.
 
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