Let the repair begin

[Nickodell]

Matilda's restoration progress so far:

I got the 030 oversize pistons ,complete with installed rings, from Sunbeam Specs. (They were made in Israel, so I hope they don't explode!) plus a complete top-end gasket/seal set. I also got the hard-to-find cap bolt nuts from Summit Racing (thanks, Scott). They didn't describe them as "locking," so in desperation I bought some Loctite and hoped that this would work, but on receiving the nuts saw that the shrink-wrap description said "Locking." And so they are. Finally, I bought a piston ring compressor and ridge reamer locally.

I experimented with inverting the cylinder head and filling the combustion chambers with oil, to see if by a miracle the valves were still seating, and lo and behold, the oil was still there two days later. It's incredible that the top ring on #1 and likely on #2 also could come off, get mashed up by the pistons and then go out of the exhaust without getting caught between valve and seat.

Note the indentations on #1, and even a couple of shiny dents and more battering on #2. My guess is that bits of #1's busted ring got sucked into #2 cylinder on the inlet stroke, then out the exhaust.

 

[Tom H]

Good luck, Nick. I hope it all comes out well and Matilda is on the road.

It looks to me that the bits that did the battering were fairly small. When this happened to me the broken ring piece was about 1/4" long and made bigger dents. Great that the valves are undamaged. Do you plan to do anything to the head? Depending on how dented it is you should maybe at least polish the dented area and smooth the dents.

Tom

 

[Nickodell]

I'm just going to remove as much carbon as I can and clean out the scale from inside the water passages. The dents are small. I was tempted to remove the valves and polish their crowns and stems, then grind them into the seats and replace the springs, but since they're obviously OK I'll just get rid of the carbon/lead buildup on the crowns and replace the stem seals. I'm not even sure that just replacing the pistons/rings is going to work, so I'm skipping more ambitious work.

You may know the answer to this one. My old (1964) Floyd Clymer workshop manual says that as the top compression ring is chrome plated, one needs to remove the glaze from the cylinder walls or the ring will never bed itself in.

Any comments on that, anyone? I bought a ridge reamer; it has arms that expands like an umbrella, each one with a rounded stone on the end mounted in a way that it can pivot. I bought it because I thought I detected a ridge at the top of each cylinder wall, and wanted to be sure the new top ring wouldn't hit anything like this, but now from the manual I'm wondering if I should run it up and down the entire cylinders to de-glaze them.

Clymer recommends mixing a couple of tablespoonsful of scouring powder with a pint of motor oil and running each piston up and down the cylinder with this compound on top. I don't fancy that idea.

 

[pcmenten]

Regarding chrome rings, I knew a guy who rebuilt a 327 with chrome rings and the rings never did seat. I thought the work was done at a shop so I can't vouch for the cylinder wall prep. I go for iron rings just because they do a good job of seating.

Ridge reamers are pretty crude devices. They are usually used for a 'rings and bearings' overhaul. When I find crud built up on cyinder walls, including rust, I get a straight razor blade and use it (carefully) like a scraper to clean the cylinder walls. You might try that to remove the 'ridge' you are seeing at the top of the cylinder. It might just be built-up carbon.

If you need to refinish the cylinder walls, I'd look for a ball hone. Reverse the direction periodically because the metal it removes gets smeared. Reversing it will knock the smeared bits away. Wipe the cylinder walls afterward with white rags until the rags come clean.

Never heard of the scouring powder/oil technique. Makes me wonder if you couldn't just use some sort of medium grade polishing compound and a buffing wheel on a drill to de-glaze cylinder walls.

I'm skeptical that something would travel up one intake and out another. It could happen, but I would also be looking for some other root cause of the foreign material in the cylinders.

Good luck.

Paul

 

[bashby]

About 4-decades ago I used a ridge reamer to do just that and a bore hone (3-stones) to cross-hatch the cylinder walls; cleaned it out with soap and water, wiped it down with motor oil. I then installed chrome rings and carefully seated them (at the time it was recommended to use non-detergent oil for the 1st 1,000 miles to seat the rings). Drove that Dodge Slant-6 hard for the next 65k miles and never had another problem with it before selling to go to college.

 

[coupe]

A ridge reamer has blades on it to scrape the top edge of the cylinder which does not get worn by the piston rings. three stones on the expandable spring loaded unit is just a hone used to deglase the cylinder and put the break in cross hatch lines in the cylinder wall, which mate the rings while holding an oil film for lubrication of the rings during brakein. The reamer is used to even or true the cyl. top of the cyl to the now worn wall from x number of miles on the engine. with the ridge removed you can hone the cyl. from top to bottom properly with no area untouched due to that high spot at the top. That idea of some type of paste and an up and down motion is nuts, the cross hatch should be about 45 degrees up and down is not the best. You can use kerosene and a light oil mix to hone, you want to cut but still lube the hone. Wipe ing with a clean rag only gets most of the metal and grit out of the block walls, if the ehgine is broken down wash with hot water and soap, dry, and coat with oil.
Yes soap and water, you dont want extra metal and stone in the oil, you get enough of the rings and cyl. breakin as it is. A lot of people will decry the wash but it is reccomended by many engine builders! The only time we ever used scouring powder was when we had a glazed wall on a dozer and it was fed in the intake in dry form it did help but there was a lot more engine to experiment with.
coupe

 

[Nickodell]

Thanks for putting me straight, guys. Yes, looking at the tool again it's clearly marked "Cylinder Hone," not ridge reamer. Thanks for all the helpful tips and advice.

 

[Series3Scott]

Nick, keep the tool anyway - you can use it to rebuild wheel cylinders, brake and clutch masters and slaves.

 

[mikephillips]

Probably not Scott. If he bought one to do engine cylinders it's probably too big to fit into the brake cylinders.

 

[Nickodell]

Nick, keep the tool anyway - you can use it to rebuild wheel cylinders, brake and clutch masters and slaves.

Masters and slaves. Hmm. Not into that kind of thing

I have some chains, though.

 

[RootesRacer]

It is my opinion that a reasonably well kept 1725 is not going to have a ridge to speak of anyhow since the blocks are high in chromium.

In all the Rootes engines Ive torn down, Ive never had one you could catch your fingernail on once the carbon was scraped off.

Your mileage may of course vary.

 

[Nickodell]

It is my opinion that a reasonably well kept 1725 is not going to have a ridge to speak of anyhow since the blocks are high in chromium.

In all the Rootes engines Ive torn down, Ive never had one you could catch your fingernail on once the carbon was scraped off.

Your mileage may of course vary.

I've scraped the carbon deposits off and you're right, there is no ridge that one can feel at all. I got the sump off this afternoon (I remembered to drain it first this time - the first bottom-end job I ever did, on my MG TD, I forgot to do this and ended up deluged in oil) and the #1 piston out.

You wouldn't believe the wreckage. The top two rings were broken; almost all of the top one had gone, but the second ring was still there in pieces. The top ring had battered the piston wall so much I'm surprised a chunk of the crown hadn't come off. I'll post some pictures when I have all the pistons out.