Pistons require identification help

[Bee-Za]

Hi
Can anyone identify the pistons in the picture. I’d got an incomplete engine off an auction site. Compression was stated as ok. But when I put the palm of my hand over one of the barrels there is a poor suction.
Any other suggestions of how to check the compression without the head on please advise.
Problems getting the photo sent

The pistol have

Pistons. 
30 7/63
67-1606 BSA
1 N/M  OS
I’m hoping to order new rings if possible

[Swarfcut]

  By my reckoning they are 8.26:1 Compression Ratio  from the part no  67 1606.   Date code 30/7/1963   Nominal Bore 70mm plus 1mm oversize, but measure to make sure. Ring Set consists of 2  Plain Compression Rings 1/16" deep, One Oil Ring 1/8" deep. Size to suit honed bore size.

 A hand over an open bore is a poor test. If the compression rings still fit in their piston grooves without excessive up and down movement in the piston grooves, they will work well enough to get a runner, but may blow smoke.

  With the head off it is a easy job to pull off the barrel and see what you've got. Broken, worn or missing rings are to be expected!

 Swarfy.

[RichardL]

What picture? I believe Swarfy is seeing into the inside of your head.

Richard L.

[Bee-Za]

Thanks Swarfcut for “reading my complete post”.
I’ll remove the barrels for further inspection.
I would be looking at replacing the rings. I did have them off late last year. The rings were showing rust and one ring was very difficult to free. I with lots of WD40 kept it free and have continued to WD40 and oil the barrels.
After this time the problematic piston has got better. But will remove and measure this time.

[JulianS]

67 1606  is 9:1

[Bee-Za]

Pistons pretty dirty. Bought these pistons ring pliers. Absolutely useless. Even after I ground them down to fit the piston circular profile I could only remove the top 2 rings after a struggle. The bottom ring had to be removed with my thumbs . Ultrasonic cleaning at present

[RichardL]

This is the type you mean, right? I have the same type and find it pretty easy for the compression rings and sketchy for the oil ring. Can't recall right now if it actually worked for oil. I don't think of it as completely useless, but will be looking to move up next time.

Sad you had to lose your thumbs. (No good emoticon for "weak joke.")

Richard L.

[muskrat]

G'day Richard.
In the thousands of re-ring jobs I've done I've never used ring pliers (don't have a pair) and  don't recall breaking a ring on or off. Getting the barrels on is a different story "that smoke should settle down soon"
G'day Bee-Za.
Double check the ring grooves with the new rings. If the clearance is too large the rings will flutter meaning they won't seal and/or break.
Cheers

[orabanda]

The only piston ring I have broken (ever) was when I used the new you-beaut piston ring pliers identical to those shown by our respected contributor Richard L.

They have been consigned to the bottom of the draw labelled "great idea, but.....", never to be used again.

To quote the gynecologist, I will continue to use my fingers.

Richard

[RichardL]

For the record, I was just identifying the pliers Bee-za was mentioning, while confessing that I,  too, own a pair.  I will take the friendly warnings from down under seriously.

Richard L.

[Bee-Za]

Ring gap measures 1.16 mm which is 0.046 inch.
My bsa manual states it should be 0.013 inch.
Was thinking of getting +50 rings and file down to suit.
Reflection shows a wee bit of scoring but I’ll live with that.
The pistons are still getting the ultrasonic treatment. Most of them are spotless. But inside the back of the ring grooves still have hard black coke.
I guess it’s been caused by the short rings. Any thoughts??

[RDfella]

Dunno if you'll find +.050" rings, but although not perfect, not unknown to do what you're suggesting.
That hard carbon has to go or it could give insufficient clearance for the new rings. It's very hard, so suggest you get a new 12" hacksaw blade and grind the sides so there's no 'set' on the teeth to damage the piston lands and gently use that.

[muskrat]

G'day Bee-Za.
Are they new rings with that gap?
+50 isn't available that I can find. Trihard T120 +10 are that size but not 100% sure if their the same thickness. Research needed https://tinyurl.com/y59uwahy
Also need to make sure the bore isn't tapered and there's no ridge at the top.
Cheers

[Bee-Za]

That gap of  0.046 is the gap of the rings which I took out.
Slight difference between top and bottom of both barrels. I’ll use my honing tool to attack the lip.
Thanks RDfella for the tip. There must be some chemical out there which breaks up carbon buildup. I’ve tried paint stripper and back to metal rust eater. The latter  being the best so far. But there has to be something. ????

[berger]

bee-za patience and care is what you need using RD's method, and don't forget the lip at the bottom of the barrels will also break rings. a mate of mine said " they will close up" I said the oil ring will break straight away . guess what