oil control expander woes

[bentvalves]

this will be the 3rd time where in the process of assembling an engine, I come to the conclusion that the supplied oil control expander, is too large for the bore, and end up reusing the original expander with new rails.

the first sign for me is the expander seemingly not dropping down into the pistons groove far enough. the second symptom is the bore being "burnished" with streak marks after rotating the engine a few times by hand and excessive drag.

what gives?? I am not trying to modify a brand new expander, so I move forward and reuse the original.

do you guys notice these things leaving marks up and down the bore sometimes?

anyone else see what I'm sometimes seeing?

viewtopic.php?f=1&t=57899

you know what? if the engine were to be run under load, i am almost positive the resulting "burnishing" would look alot like that there bore!

[PRH]

I’ve only encountered it once.
It was with some Total Seal for 4.500 bore.
After assembling the 3 pieces on the piston I really couldn’t get it started in the taper ring compressor.

They had the same type of expander as what came out of the motor(Hastings), and after comparing the old vs new side by side, the new ones had one additional “corrugation”.

I did as you did and just reused to old expanders.

[Elroy]

Is it a non-common bore size? I've run into it on less than common bore under or oversizes. I feel like sometimes they may not have one made specifically for that bores size or close so they include one from the closest one a size up(which may be quite a jump)...to err on the safe side, and the drag is horrible. I've had to modify them or order the next size down to try and get something that wasn't so tight and draggy.

[bentvalves]

Is it a non-common bore size? I've run into it on less than common bore under or oversizes. I feel like sometimes they may not have one made specifically for that bores size or close so they include one from the closest one a size up(which may be quite a jump)...to err on the safe side, and the drag is horrible. I've had to modify them or order the next size down to try and get something that wasn't so tight and draggy.

hi elroy. when you modified the expander did you use dikes to clip a nibble off or did you grind it off with a stone or belt? 81mm bore btw.

[Elroy]

hi elroy. when you modified the expander did you use dikes to clip a nibble off or did you grind it off with a stone or belt? 81mm bore btw.

3.189 bore or so...not terribly common depending on thickness and radial I have used several methods to play with expanders over the years. Bending tabs(ss50)...cutting with dykes. Now that I have an electric ring grinder I have been using that with good results...can be delicate

[dwilliams]

I ran into it a few times. There's no harm in re-using an expander as long as the radial width of the oil rings matches.

If an engine is harder to turn over than I expect, the oil rings are the first thing I check. Remove them and check the torque with just the top and second rings...

I've seen some absurd tension on those rings, too. Everyone has their own ideas about reasonable turning torque, but if the engine gets hard to turn, STOP! Any engine I ever put together with rings that made it hard to turn over, came back, usually with lots of ring wear and signs of overheating. It was an expensive lesson.

[n2xlr8n]

May be helpful, may not:

viewtopic.php?f=1&t=48872

[BillK]

what gives?? I am not trying to modify a brand new expander, so I move forward and reuse the original.

Just curious why you would do that instead of stopping and calling the ring manufacturer to find out what the deal is ???

Personally I would never mix up parts on rings like that. I dont have that kind of luck

[bentvalves]

because Dawn at hastings has retired and there is no longer anybody to speak to, you have to e-mail them and wait back for a response and yada-yada.

even when you have a less than ideal part in your hand, tech support is always gonna tell you that you are good to go anyways.

But Dawn sure was one smart lady that knew a thing or two about piston rings and cylinder wall finishes

[BillK]

because Dawn at Hastings has retired and there is no longer anybody to speak to
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But Dawn sure was one smart lady that knew a thing or two about piston rings and cylinder wall finishes

That is absolutely the truth. She has saved my rear end many times over the years.