Successful 2182 mile rally despite exhaust valve losing clearance!

[mightyohm]

Pulled the head this weekend and discovered a few things.

1. cylinder 1 exhaust valve has very visibly recessed into the valve seat, as expected. photos attached of #1 and #2 exhaust to show bad vs. good. I am planning to take the head to a machine shop to have new seats installed.

2. I see what seems like excessive carbon buildup for 3000 miles. Pistons are coated with thick carbon. What could be causing this? What is odd is that plugs are light grey, bordering on white! (see attached) Plugs are NGK BP6ES. I might be running a tad rich but not what I would consider excessively so. Most of the 3000 miles is highway mileage and I was getting 30 mpg, which I would think also suggests not super rich.

3. A chunk of carbon is missing from pistons #2-3 (see photos). Carbon completely covers piston #1. I'm not sure why the carbon is missing from this area but there doesn't seem to be any obvious piston to head or piston to valve contact. Although given how thick the carbon is, is it plausible that the carbon is building up and making contact with the squish area of the head (or being blown away by the combustion?)

4. Hone marks still visible on all cylinders but some deep scoring on cylinder #4. Scoring is in line with the crank and not 90 degrees off as i'd expect for piston slap. I can easily catch a nail on the score which is disappointing. not sure what is causing this. I attached a photo of the scoring. Rear of the engine is upper right of the photo.

 

[mightyohm]

Spark plug photo and another shot of the head. I believe the oil on cyls 3/4 is left over from my compression test. I added too much oil which probably explains the rise in compression - it partially filled the dish of the pistons.

 

[Tom H]

Jeff, in the photo of #4 cylinder scoring I see what appears to be some numbers stamped in the cylinder wall. What on earth is that about?

Regarding the carbon build up hitting the head, look to see how much clearance (deck height) you have with the piston at TDC. There should be 18 thou clearance, plus about 25-30 thou gasket thickness, so I doubt the piston is hitting the head, or even the gasket

Tom

 

[mightyohm]

Those are droplets of oil. They do look like numbers but they are not.

 

[Bill Blue]

From the location, I would suspect the scoring is from a piston pin due to incorrect assembly. I'd pull that piston and check. If anything is wrong, I'd pull the rest just to make sure they won't start doing the same thing.

Bill

 

[RootesRooter]

How are the lifters and cam lobes?

 

[chazza]

2. I see what seems like excessive carbon buildup for 3000 miles. Pistons are coated with thick carbon. What could be causing this? What is odd is that plugs are light grey, bordering on white! (see attached) Plugs are NGK BP6ES. I might be running a tad rich but not what I would consider excessively so. Most of the 3000 miles is highway mileage and I was getting 30 mpg, which I would think also suggests not super rich.

The colour of the plug indicates to me that if anything, the plug is too hot, or the mixture too lean.

The carbon build-up is most probably due to the new engine burning a bit of oil. whilst it was running-in. How did you run it in?

Gentle revs and steady speeds are not good for bedding the rings in. Full throttle in top gear, on an upwards incline while keeping the revs moderate, is a good technique for bedding the rings,

Cheers Charlie

 

[mightyohm]

How are the lifters and cam lobes?

At first glance, fine, at least no catastrophic damage.
I'll take a closer look next weekend.

 

[mightyohm]

I took another look at cylinder #4 tonight - the scoring is also present 180 degrees from what is shown in the picture, so that does seem like a piston pin problem. I'll pull the piston and see what's going on.

chazza - I drove the car very gently for the first few miles while I solved various coolant leaks, etc. Then drove at various RPMs and medium throttle levels to break the rings in, with many cycles of acceleration and overrun. I definitely did not go easy on the rings. I avoided full throttle and high revs to prevent over-stressing the new engine. The carbs were not tuned well when I started (too lean) so I was not able to fully exercise the motor anyway. After a few hundred miles I did push the car harder, but I still try to avoid full throttle as I have more work to do in tuning the secondaries.

 

[RootesRooter]

A Sunbeamer friend suggests worn valve guides could be responsible for the excessive carbon. Another, less likely possibility, is that the ring gaps are lined up.

The oil you squirted gratuitously down the cylinders might have affected this but, how tough was it to remove the carbon from the tops of the piston(s)? With relatively few miles, I think they should have cleaned up pretty easily to almost-new condition.

 

[mightyohm]

Ok, after a few weeks away from the garage I'm finally digging back into this again.

When I pulled off the oil pan I found some very fine silver colored metal fragments in the oil.

Regarding the scoring on #4, I pulled the piston and found that the sides of the piston near the wrist pin hole have several long scratches and visible shavings near the hole. The edges of the hole are sharp and it seems like a raised edge formed and started rubbing on the cylinder wall until small bits broke off, causing the scoring.

Has anyone seen this before? I attached some pics of the scoring on the piston.

In addition, the rod bearings seem to have quite a bit of wear for only 3000 miles on the motor. I attached a photo showing the wear pattern - all 4 rod bearings look about the same.

IMG_8711 - picture of piston #4 showing scoring on one side. The opposite side doesn't look as bad. This cylinder has the worst scoring on the cylinder walls.

IMG_8626 - closeup of the scoring on the lower half of the piston, with metal fragment visible

IMG_8749 - cylinder #4 showing scoring on the rear side. I can catch a nail in the scores.

IMG_8635: rod big end bearing wear - this is the upper bearing half - showing strange wear pattern

IMG_8461: rod big end bearing - lower bearing half (cap bearing shell) showing wear along the edges

 

[mightyohm]

A couple more pictures of the piston scoring.

IMG_8613: piston #4 showing area above the wrist pin on the worst side.

IMG_8653: piston #1 for comparison - one score line shown. cyl #1 had no visible scoring on the cylinder walls

 

[RootesRooter]

Guess I'd start by carefully inspecting the rings for damage or missing chunks. Do the tops of the pistons show any damage/indentations? Did you notice any problems while installing the new pistons in the cylinders?

Could you capture all the pieces of the silver metal fragments you can find from the pan and take a pic? Just seeing the quantity and average size might help.

You may have just drawn the short straw on your trip and sucked a chunk(s) of debris thru the stock wire mesh air filters.

Re bearings. After a high-speed, 2,000+ mile trip after a short break-in period, I'm not sure your bearing wear is abnormal, but I'll defer to those more knowledgable with 1592's.

 

[beamdream]

Sadly it seems that something has gone through the lube system, I guess now its a bit academic as to what it was.

From what I see in your photos, if it were me, I would be pulling the engine right down; no telling how far the metal has carried through the entire lube system and where the damage has spread; have you cut the filter open to see what`s inside?

Oh and I might be checking the piston to wall clearance.