Engine heal thyself?

[zachmac]

I know several of you have followed Craig's (ga.spyder) recent troubles with Fiats. He finally got the 82 FI car back to running good only to have an idiot in a van try to run over him! You may also recall he was especially frustrated for a while when in addition to his 82 FI car acting up the 76 developed what sounded like a rod knock. The 76 came to me for a very fair price with the assumption of a bad lower end.

Before I bought the car from Craig I happened to get a chance to stop by his place in Ga and look at the car and hear it run. Sure enough, it sounded like someone was beating #1 on the driver's side of the block with a sledge hammer. I would have bet a fair sum it was a bad rod bearing or rod.

Fast forward a week or two and I've bought the car from Craig and he going to bring it to me in Aiken. In the meantime he needs to move it one day and has no help so he figures what the heck, it can't get much worse if I just start it briefly and move it a few feet. He starts it up and 'what the hey, no knock'! Drives it a few miles and it runs smooth with no knock, good oil pressure and no overheating. Being a man of honor (and having no idea what is going on with the engine) he calls and tells me "you MAY be getting a better deal than we knew?"

Delivery day comes and Craig drove the car on the trailer, drove over and drove it off into the garage at my place. Sure enough no knock, but still what now sounds to me like a lighter tapping in the valve train / head. Shut it off, thank Craig and commit to get into the engine soon.

Fast forward another month and I realize I haven't found any time to even look at the car let alone work on it (I did order a full engine gasket set). So, i start thinking maybe I need to just flip it someone else with more time. Last night I take a friend who might want it for his wife over to see it and we give it a go. Starts right up on second try and not only is there no knock, there's no tapping (once warm, I think it could use a valve adjustment, but nothing out of the ordinary).

So, before I pull it all apart let the speculation begin! Again, back when the knock was there Craig and I and anyone else who heard it would have SWORN it was a bad lower end. When it went from a knock to a slight tick a mechanic friend of mine said the ONLY similar case he had ever heard of or seen was a car that had a CHUNK of carbon break loose in a cylinder and sit there and burn like a wick which of course caused random ignition. I said "You don't understand, this was like someone banging on the block with a sledge hammer!" and he said, yep, exactly like that until the carbon burns up and blows out the exhaust. What I do know is the more I run the car the quieter it gets and the ticking is pretty much gone!

[manoa matt]

Two cheap and relatively easy procedures you can try to confirm your suspisions.

Take the plugs out, and turn it over by hand. Have a good flashlight and look down the plug holes at the top of the pistons. With the piston all the way down you can see the entire piston surface and the cylinder walls. If you find a chunk of carbon you can extract it with a piece of wire with a bit of duct tape on the end.

You can drop the oil pan to check the main and connecting rod bearings. No need to remove them, just wiggle them back and forth to see if one is looser than the others.

[zachmac]

Two cheap and relatively easy procedures you can try to confirm your suspisions.

Take the plugs out, and turn it over by hand. Have a good flashlight and look down the plug holes at the top of the pistons. With the piston all the way down you can see the entire piston surface and the cylinder walls. If you find a chunk of carbon you can extract it with a piece of wire with a bit of duct tape on the end.

You can drop the oil pan to check the main and connecting rod bearings. No need to remove them, just wiggle them back and forth to see if one is looser than the others.

Matt,

I doubt at this point a rod bearing is even a possibility. Oil pressure is good and they DON'T get better by themselves. Plus, I question your characterization of dropping the pan as "relatively easy". After all, with the choices of dropping the cross member or performing contortions to remove the / install the oil pump getting the pan off ain't exactly easy. Doable yes, easy no. (Unless the early cars don't have a baffled oil pan?)

As far as a look see in the cylinders, I think that along with a compression check are indeed the next logical steps.

[manoa matt]

Relative is a relative term, only relative to the person performing the "relatively" easy task. A.K.A. grammatical modifier

[zachmac]

Relative is a relative term, only relative to the person performing the "relatively" easy task. A.K.A. grammatical modifier

Well if I can get a relative to perform the relatively easy task I'll sure get them right on it!

[majicwrench]

Have seen several engines heal themselves, yes, something, carbon, a lock washer, a piece of gravel when changing plugs, something gets in cylinder. I wouldn't bother checking compression, but would be fun to look into cylinders. Among other things you are looking for pistons with dents in them from whatever.....
Keith

[pooldoctorstl]

Check aux shaft and timing marks.

[So Cal Mark]

if the oil pressure is good, you can bet the bottom end is okay

[zachmac]

if the oil pressure is good, you can bet the bottom end is okay

Exactly!

[zachmac]

Check aux shaft and timing marks.

Aux shaft jumped was one of my first thoughts when it was banging hard. In addition to checking it and the other marks (got to do one to do the other after all) I'll take a hard look at the belt and tensioner. For the shaft to go from good to bad back to good the belt would have to be slipping a lot (or the aux shaft gear is stripped / broken? The belt and tensioner are unlikely as the car ran well at all times (even with the knock) and there isn't much chance a belt is worn enough to slip the aux shaft and maintain cam timing.

Hopefully I'll get time today to turn some of this conjecture into fact or fiction. I just knew how much everyone (including me) likes to play the "what about" game prior to actually just getting out the wrenches and using boring old facts.

[BEEK]

1800 engines do not have rod clearance problems with the aux shaft, so there is no reason to check the timing of the shaft. as there is no real timing for the 1800. the 2000 uses an offset fuel pump lobe whereas the 1800 has a cam like lobe, so there is not a clearance issue. just my 2 cents worth

[ga.spyder]

I can confirm that the motor sounded awful.I was sure it was the lower end.The oil pressure is good.I was amazed to start the motor(I really hadnt done it since it started knocking) and the knock was gone.I am sure a compression check will show lower on some cylinders,as the car is smoking a good bit.It will be interesting to see what gives.

[pooldoctorstl]

Steam or oil smoke? If steam, it may be a bad head gasket or cracked head and it is getting water in a cylinder and banging. Be careful, if that's what it is a bent rod is not far away. See what the plugs look like and if you can, look at the top of the pistons. The clean one is the one with the leaking water.

Jeff

[ventura ace]

1800 engines do not have rod clearance problems with the aux shaft, so there is no reason to check the timing of the shaft. as there is no real timing for the 1800. the 2000 uses an offset fuel pump lobe whereas the 1800 has a cam like lobe, so there is not a clearance issue. just my 2 cents worth

???????????????? My 1.8L does interfere with aux shaft, so I'm sure that there are others out there like mine. Be sure to check the aux shaft timing. Better to be safe than to have a ruined block.

Alvon

[mdrburchette]

It was definitely an oil smoke that I saw on the track at Road Atlanta.