Combustion questions

[Baz]

Had a good look at the cyl head, valves and pistons today.
I'm not happy. /ubbthreads/images/graemlins/mad.gif
Problem 1, A phenomenal amount of carbon in all 4.
Problem 2. #3 exhaust valve was distinct, as it was tan in colour, not black and thick like the others.
Problem 3. Inside #3 cylinder resting on the crown was a shard of metal, about 1/4 long, very thin and curved. No damage or scratches to the cylinder walls or cyl head though.
Problem 4. I can assume that mixture will cause all the carbon, I can sort that out, but what about cyl #3? What happened in there and how can I stop it happening again.
Compression test was nothing abnormal prior to invasive surgery, 180 all round +/- 5 wet.
Grrrr.

 

[tony barnhill]

Is the valve still intact? spring? anything else in system broken? What about carb? anything broken there that could be sucked into gas chamber?

 

[Baz]

Valves, springs, and carbs look (to my untrained eye) to be OK. Nothing missing and performing correctly. Plugs now removed are all intact, just sooty, though I can't speak for any past plugs.
The Ex valve is really bugging me, the rest of the head is sooty, but just the valve is tan, wierdest thing.
This is the cyl right next to that stud I had problems with, detonation problem due to that valve?

 

[jlaird]

Sounds like a head rebuild just might put it on the mend.

 

[Baz]

I agree Jack, but what bothers me is what caused it (loose debris) and will want to avoid it in future if I can, if its avoidable. Hate to think that something more sinister is going on, but you're right, an oil bath and new stuff in there will have a big + effect.

 

[jlaird]

Could be most anything. Could have even been in there since the head was last off. I know should have gone out the valve port but....... If nothing is found when head is rebuilt, press on and don't worry about it. Glad to hear the compression test was excellent. And yep a bit rich.

 

[Biff]

Anything missing from the top edge of piston #3?
From your description sounds like it could be a piece from the top ring groove from the piston.

 

[jlaird]

Point, what kind of metal is it, clean it up and taste it, your teeth will tell you mostly. And I don't want to hear piston, although it might not be a problem if it is not as deep as the ring.

 

[leecreek]

If #3 exhaust was tan, I would suspect it wasant seating very well and was hot enough to keep the build up off the valve. If the whole #3 cylinder was clean then I would suspect cooling fluid from somewhere.

 

[Westfield_XI]

Check to see if # 3 valve seat is intact.....

 

[aeronca65t]

That piece of metal sounds like the end of a thread from a bolt or spark plug. Maybe when you re-did the stud, the very end of a stud had a loose burr that broke off. Could also be a loose burr from a threaded hole in the block (but less likely).
Might also be the edge of a newly installed valve seat (has it had valve seats installed lately?)
I thought about upper piston ring too, but I think you'd see some evidence on that piston or cylinder wall.

Sooty plugs can be rich mix, wrong timing or weak ignition.

Get an old spark plug and adjust it for a very large gap (1/4" if possible). Then be sure it is touching against the block while hooked to one of the plug wires. Crank the engine over and see if you have a nice, strong spark jumping the gap. (don't touch the wire while cranking!...you'll get a shock!)

Be sure that carb floats are not stuck.

You're not running an aftermarket fuel pump, are you? (a lot of times an all-purpose pump has too much pressure for these cars....they force too much fuel through unless you use a pressure regulator).

To get things approximately correct with carb fuel mix, be sure that the shoulder on the piston damper needle is "even" with the piston and that it is not sticking as the piston slides up and down. Rev the engine and observe that both pistons in the carbs move up and down together (remove air filters to do this).

Basic mixture setting is: turn the jet nuts (under the carb...the piston needles go through them) all the way "up" and then unscrew them two full turns (the repair books say "12 flats" because these are like hex nuts, with 6 sides).

 

[Baz]

[ QUOTE ]
That piece of metal sounds like the end of a thread from a bolt or spark plug. Maybe when you re-did the stud, the very end of a stud had a loose burr that broke off.

[/ QUOTE ]

Thanks Nial for leading my investigation in that direction.
99% sure that's what it is without tasting it. It's consistent with the location of the stud, and the amount of grunt required to budge and a couple of new threads I cut into it, but I'm upset as I thought I had a cleaner area than that to allow something so damaging to get in the cylinder.
Fuel pump is OE and the carbs, heh, I thought I did a great job tuning them (apparently not), are in a box for rebuild. I didn't notice the floats stuck or anything sinister with the needles, but I wasn't investigating.

Would a compression test reveal anything about the valve seat? Again, not a major concern now as the machine shop will be 3-angle grinding in the very near future.

Thanks all, some Easy Off oven cleaner should cure the rest.

 

[Hap Waldrop]

That tan colored burned that scares you is exactly what you should see everywhere else. The black sooty could either be too rich on fuel or oil getting past the rings or getting past the guides, that should result in some smoke from the tailpipe. The piece of debris sounds to me like something that made it way into the cylinder from the induction end, a simple magnet test will tell you if it steel or not. This is where a leak down test done before teardown could have told you a ton of info.

A leak down tester is $100 or less and for me has basiclly replaced the compression gauge, I hardly ever use one anymore, all they can really tell you is if there is a bad problem, not much else.

 

[Roger]

I'd expect an exhaust valve to be tan, and worried about a sooty one!
If there's no obvious damage, I'd shrug about the mystery object, and investigate what's wrong with 1,2 and 4.
Bad rings, maybe?

 

[Baz]

Tan colour is one thing, but it was very crusty atop the soot. All were sooty and I really believe that mixture is the primary culprit. I couldn't actually see the valve (s) at all beneath all the that crud.
The mystery object is outtathere and the lumps are in the charge of the machine shop.
Learned a LOT about internal combustion engines this week, and the intricacies of valve grinding.

Not the best picture as I had tried to 'scrape' some of that crust away, getting new valves anyway, not a big deal, but you can see #3 EX is disgusting, whereas the others are just dirty.