New pistons Petter PJ2, block after short time engine running. Clearance?

[Rob PetterPJ2]

Just came across this Vid which explains how to do rings gaps which may be helpful for new engine builders.

https://www.youtube.com/watch?v=gs0Fg3tvhoc

That's a video about fire arms, Glort!

[dieselgman]

PJ1 and PJ2 ring end gap  .029 to .037 inch
bump clearance .036 to .042
bore 3.8175 to 3.8185 inch

dieselgman

[Rob PetterPJ2]

PJ1 and PJ2 ring end gap  .029 to .037 inch
bump clearance .036 to .042
bore 3.8175 to 3.8185 inch

dieselgman

Thanks, dieselgman, for these exact numbers!
I'm happy to see that the present bump clearance of my PJ2 engine is exactly in the middle of the two numbers you gave.
Coming tuesday I'll have the time to check the rest.
Cheers,
Rob

[ajaffa1]

Hey Rob, Glort is right as usual ( I hate him,  ). There is a chance of scoring in the bores, it is very unlikely to be severe. Do you have a cylinder honing tool? They are not expensive and can usually be purchased at you local automart or tool store. They fit into an electric drill, give the cylinders a quick hone to remove any scoring/high spots. Then wash out any residue with soap and water, please be diligent in doing this as metal particles and carborundum have no place in a cylinder or engine.

Adjust the ring gap and reassemble, all should be good. Recommend using flushing oil when doing the first oil change, I also recommend that you do the first oil change at half the running time stated in the manual.

Bob

[Rob PetterPJ2]

Does anyone have a tip for the best way to remove the piston rings? I'd of course do it extremely careful, but I don't know what I don't know. The scraper ring has a spring in the gap. Would that thing cause a problem?

[Rob PetterPJ2]

How many times have you run the thing when it locked up? Was it ever under load or making any power as in above idle?
Locking up an engine like that is a mechanical cringe fest.  Hopefully nothing bad has happened.

Also you will probably want new head gaskets as well. 

Hi Glort
I ran the engine a few times with no load. The first time it stopped itself after 2 minutes. The second time, I stopped it when it slowed down. The third time I had it run as slow as possible, no load. It then slowed down after 9-10 minutes so I turned it off. After each time it was impossible to turn the flywheel by hand, for like a minute or two.

The head gaskets I cut from material with metal thread in it, especially made for the hottest parts of an engine. Don't know the name of it. It's been awhile that I bought it. But yes, I'll cut new ones.

I'm very curious to see what the ring gaps are, tomorrow!

[Rob PetterPJ2]

PJ1 and PJ2 ring end gap  .029 to .037 inch
bump clearance .036 to .042
bore 3.8175 to 3.8185 inch

dieselgman

Hey dieselgman, I just measured the gaps of the first pistons' rings, when taken from the piston and put into the cylinder at the top side, and that was a bit over 0,4 mm, less than 0,45 mm being around 0,0165 inches.
(Photo attached to next post)
So, then indeed, the gaps are too small. They'd need double the size.

It means that ajaffa1 was spot on with his first comment!

Now shit happened. I still broke the 4th ring, the scraper ring. Dang! Got a bit confident I guess after the first three went OK. So, I'll see if Jim Perkins has one for me, part from the manual and an oil banjo bolt (replacing a wrong one put in by the life boat's former mechanic) he'll mail to me.
I still have the old pistons with intact rings, but they're a fraction thinner. I guess, worn a bit. What you think, guys? Would that indeed be a cause a problem?

I also see the tiniest vertical scratches, all the way down, in the wall of the first cylinder I just removed. How would I know which scratch is severe enough to demand new honing? And what if a second honing means a tinier wider cylinder, for the same pistons?

[Rob PetterPJ2]

If you se a line ( or several) run your fingernail across them and see if you can feel them.  If you can, will definitely need a hone, if you can't.... probably OK.

Be interesting to see some pics of the rings in the bore, the insides of the bores and the piston walls.

Hi Glort,
I now see you already gave an instruction to see if the scratches caused by too cramped piston rings are a problem. Most of them I can not feel with the nail. One I felt, though. I'll check again, all around.

[Rob PetterPJ2]

As far as using the old rings, it would seem likley that they overbored the cylinders when they did them and the pistons are also larger. You'll need to know what size they went over.

When you rebuilt the engine, Did you do any of the bearings or just the top end? Also, did you get the specs for the head bolts and torque them down with a tension wrench in the correct order to the right specs? If not, best you do this time.

Ah, yes, of course. The engine revision guys said they'd order slightly bigger pistons, because of the honing.

I didn't do any bearings. I took the cylinders off, and removed the pistons. Nothing else.

And with the reassembly I followed instructions for how to bolt in the right order as I wrote earlier. No 'force meter', but an instruction of how the force used should feel/ I don't have all the specialists' tools.

I MAY BUY ME ONE, though, after reading about the importance of it (protecting the gaskets).

[Rob PetterPJ2]

Have a look at the pistons. They may have something like +.005 stamped in the crown. Might also be .010 if the bores were heavily scored or worn to start with.

The new pistons say 020 at their top side.... I guess that's 0.020 inch extra, then.
The old pistons have "196695  S" engraved, there. Now what can that mean?

[Rob PetterPJ2]

You might want to feel the Rods and make sure there is no freeplay in the bearings. If there is any detectable movement especially in the big end, You'll want to do those as well whether it's a big job or not. Otherwise you could do damage and be pulling the whole thing down again anyway pretty soon.

You're not making me happy with this... I expect horizontal movement to be not a problem (even a necessity). Vertical it would be problematic. Before I did not feel any vertical freeplay, when I checked it for that purpose.

[ajaffa1]

Hey Rob, looks like you may have dodged a bullet if the scoring is only very minor. A cylinder honing tool should fix the problem without having to do another re-bore. A tool like this is cheaply available in the UK https://www.ebay.co.uk/itm/CAR-ENGINE-CYLINDER-BRAKE-HONE-BORE-HONING-FLEXI-SHAFT-TOOL-51MM-TO-178MM/222367752202?epid=1146057264&hash=item33c626a00a:g:Ur8AAOSw2xRYbWnC:rk:3:pf:0

I know the purists are going to start throwing spanners at me for recommending such a low tech solution but you are only trying to knock the high spots of the scoring.

After honing clean the cylinders and then clean them again! (detergent and water and lots of clean rags) Now check the piston ring gaps and adjust as needed.

If you contact the machine shop that provided the pistons, their supplier should be able to send out a replacement piston ring. Might be worth asking for a complete set in case you break any more during assembly.

Glort is right about checking for play in the big end bearings, does your engine have a crankcase door? If it does then the cost of a new gasket and a pair of white metal bearing shells is a no brainer.

Bob

[sirpedrosa]

Greattings to all

Sometimes I feel the same as Rob, but the guys around here have a long-standing experience - that's what I call masters.

I'm afraid the workshop where Rob had the job done knows less about it than he does.

As we say - a problem never comes alone! and maybe they've seen the bottom of Rob's pocket.

And also, as I had already said: "the machine works as it wants and not as we wish!"

Of course sometimes we doubt what our eyes are seeing, but the engine starts to take its weight in gold! and that does not cheer anyone.

Rob, dismantle the whole engine and resemble it again, each step makes sure that the whole assembly rotates freely - attention to the clearences because the engine heats up.

I'm sure it will get better!

Cheers
VP

[Rob PetterPJ2]

Now I'm confused. In a catalogue in Dutch, the "schraper-veer", which, to me, seemed the Dutch word for scraper ring, is not the one I thought it was.

The one I broke was the 4th one, at the bottom side of the piston. It hides a spiral in it, that goes all around the piston and it has horizontal slits in its side. The Dutch catalogue has another name for it, with the word for "oil" in it.

What's its proper name in English, for the bottom ring that I broke?

Jim Perkins says he may have one, the plus .020 size. He's going to send me some stuff anyway. Otherwise I contact the online lister-petter shop.

[Rob PetterPJ2]

Hi guys!
This video shows a honing tool. I knew it was something like that, but would this size be OK for my bigger cylinders?
https://youtu.be/-NRUZNX0IAg?t=642
Indeed, I'm not going to buy new pistons. They were expensive: 245 euro each. But I could do some light honing, to just get that one hardly noticeable scratch away, right?

I took both cylinders off, with the finger nail I can detect just one light scratch. Other lines are visible but I can't feel them, and I'm quite a sensitive guy, really ;-)! Most of my working hours so far were spent on illustration and design.

I let the pistons sitting on their rods and the crankshaft. There's really no vertical 'play' of the pistons. All the pistons can do is move sideways, over the pins they're attached to the rods with. The rods can not tilt one bit. I see no reason to dig into the block and take it all apart.

I got all other rings off the pistons without breaking any. Did that with sliding them up over three thin metal strips, one of them being a valve clearance feeler gauge.

I'll wait for the manual to arrive in the mail (and stuff) before adjusting the gap of the piston rings. The manual I was using so far, of a one cylinder air cooled Lister LD, actually had measures of the gaps equal to the ones of the new piston rings.

I'll ad the flyer for this engine (earlier I wrote it weighed 300 lb, but that's in kilos. It weighs 611 lb).
I also ad a photo of the boat it sits in, parked in an Amsterdam canal. It was an open life boat coming from a cruise ship. I build the cabin over it. Last summer I painted the black figures at the white hull. The wooden roof part and windows can be taken all off in 2 minutes. There it also has a fire place in it, for wood fire, oh yes! So, that's why I need this engine to work again. I missed 3 months of boating fun already!