Source for tapered 84mm ring compressor in UK

[fergus]

I am having a difficult job installing some 84mm pistons which are fitted with 3 piece oil control rings when using one of the ratchet type ring compressors. Even when compressed, these are not truly round, so allow the lowest of the thin oil control rings to catch on the top of the liner.

Is anyone aware of any *sensibly priced* UK stockists of the tapered sleeve type ring compression tools? Alternatively, if anyone has an 84mm bore tool I could borrow, I would be willing to provide a deposit equal to the cost of the tool, plus some beer money!

[stevieturbo]

fergus said:

I am having a difficult job installing some 84mm pistons which are fitted with 3 piece oil control rings when using one of the ratchet type ring compressors. Even when compressed, these are not truly round, so allow the lowest of the thin oil control rings to catch on the top of the liner.

Is anyone aware of any *sensibly priced* UK stockists of the tapered sleeve type ring compression tools? Alternatively, if anyone has an 84mm bore tool I could borrow, I would be willing to provide a deposit equal to the cost of the tool, plus some beer money!

It really will be a case of hunting around.

Performance Unlimited in York might stock some, Co-ord sport are also supposed to be stockists for that type of thing ( although seem to carry little stock of stuff you actually need )

Maybe Nevlock Engine components ?

Or at a push, get a local machine shop to turn one out on a lathe.

Although if your bore is good and there is a sensible chamfer on the top edge, the crappy old piston ring compressors should work ok.
I actually tried one of those wrinkle band ones last time around...and whilst I did break a ring, it was my own fault. It's easy to want to tighten the compressor like mad....which is often not the correct thing to do in order for it to maintain it's roundness for allowing the piston to pass correctly.

[fergus]

stevieturbo said:

Or at a push, get a local machine shop to turn one out on a lathe.

Although if your bore is good and there is a sensible chamfer on the top edge, the crappy old piston ring compressors should work ok.

Cheers. I think getting an old liner put on a lathe to generate a taper / long chamfer at the top is probably the most cost effective thing to do.

Unfortunately, the chamfer on the top of the new liners is only about 1mm deep with a 45 degree angle on it, so isn't really safe to use to push the rings into the piston without risking damaging them.

[Mignon]

Simples. Do what I've done to every performance engine I've ever built for 30 years. Get yourself a fine toothed round shank metal file that's not too big, 3mm in diameter is fine and 6" long, and some 80 grit wet and dry paper or 1" cloth roll. Go round the chamfer with the file carefully blending out the bottom edge with a sort of rolling hand motion that aims to produce an elliptical curve merging into the vertical of the bore. It's much easier than it sounds with a few seconds practice. Then tear off a bit of emery 2" long x 1" wide and with that on the ball of your thumb and holding the trailing end with the forefinger just gently blend your filing into a nice smooth scratch free curve.

The next step is using the ring compressor properly.

Pistons step up in diameter immediately below the oil ring. If you have the bottom edge of the compressor band too low down the skirt there will be a gap that the rings protrude from and that's when they snag on the top of the bore. You want the compressor just a couple of mm below the oil ring so it's only compressing the ring land area. Don't knock the piston into the bore. With the shaft of a wooden hammer position the piston and push it smoothly down with a continuous motion. If it snags then stop and do it all again. A little practice and any piston should slide into place as easy as pie. Make sure everything is copiously oiled first including the inside of the compressor band. Don't evertighten the compressor. It only needs to be nipped if it's in the right position on the piston.

[fergus]

Mignon said:

Simples. Do what I've done to every performance engine I've ever built for 30 years. Get yourself a fine toothed round shank metal file that's not too big, 3mm in diameter is fine and 6" long, and some 80 grit wet and dry paper or 1" cloth roll. Go round the chamfer with the file carefully blending out the bottom edge with a sort of rolling hand motion that aims to produce an elliptical curve merging into the vertical of the bore. It's much easier than it sounds with a few seconds practice. Then tear off a bit of emery 2" long x 1" wide and with that on the ball of your thumb and holding the trailing end with the forefinger just gently blend your filing into a nice smooth scratch free curve.

The next step is using the ring compressor properly.

Pistons step up in diameter immediately below the oil ring. If you have the bottom edge of the compressor band too low down the skirt there will be a gap that the rings protrude from and that's when they snag on the top of the bore. You want the compressor just a couple of mm below the oil ring so it's only compressing the ring land area. Don't knock the piston into the bore. With the shaft of a wooden hammer position the piston and push it smoothly down with a continuous motion. If it snags then stop and do it all again. A little practice and any piston should slide into place as easy as pie. Make sure everything is copiously oiled first including the inside of the compressor band. Don't evertighten the compressor. It only needs to be nipped if it's in the right position on the piston.

thanks for the tips.

[Boosted LS1]

fergus said:

stevieturbo said:

Or at a push, get a local machine shop to turn one out on a lathe.

Although if your bore is good and there is a sensible chamfer on the top edge, the crappy old piston ring compressors should work ok.

Cheers. I think getting an old liner put on a lathe to generate a taper / long chamfer at the top is probably the most cost effective thing to do.

Unfortunately, the chamfer on the top of the new liners is only about 1mm deep with a 45 degree angle on it, so isn't really safe to use to push the rings into the piston without risking damaging them.

It only needs to be 1mm deep. I used to make a champher with a half round file which I then smoothed off with a flapwheel in a drill. Never force the pistons home, sometimes they need a gentle rock but use persuasion instead of force.

[SoCalDave]

Best to have it customised then to fit the sizing.

[fergus]

I used an old liner, with a reverse chamfer cut into the base and a large taper machine into the top, after the liner had been cut down to around 70mm deep. A spray of lube, and the pistons (along with their very thin 3 piece oil control rings) slide straight in with no drama.