stuck piston rings

[johnf48]

Hi Guys -

First of all it's good to be back on the CSC Forum after an absence of 5 years!

My Lomax 223 "Demented Wasp" has been off road for last 3 years while I have played with model boats and other classic cars; and I am now re-commissioning it with a "new" - ie only 25K miles engine. - The old engine was beginning to lose power and burn oil after 160K total miles.
Having got the heads and barrels off (both initially stuck together - this engine seems in dirty but excellent condition. Pistons also removed from con-rods but 4 of total 6 rings firmly stuck in their grooves. Been soaking in bath of heating-oil last 2 days but still no change.

Can anybody please help on this one?? John (ex NE Rep & Gen Sec)

[2cY]

Have you tried thumping the sides of the piston /rings with a block of softwood (say a 12" length of 1-1/2" x 1-1/2").?

I know it sounds drastic but I generally do that after I've run around them with the (high speed) fine wire wheel to clear any surface crud away.

Cup the piston in one hand and use the flat side of the block of wood square onto the pistons.. more to resonate shock than to hammer them. That makes sense if you practice on a piece of tube with the block first. Try hitting the tube in such a way as to get it to resonate. You sort of strike with a bounce, with the block ..rather than hit and hold it.

The softwood transfers a resonating shock better than a rubber hammer, is less local an impact than a hide, copper or lead hammer, and doesn't damage like a steel hammer.

I also use carb cleaner + penetrating oil. The carb clean thins the penetrating oil even further to enable it to wick into any void. Repeating this (squirt or each) as you shock the piston/rings with the block of wood. Probably carb cleaner + your heating oil will do much the same. If you can remove the loose piston rings - then that would be best so as to not hammer those. Otherwise you need to hold those tight into their groove where you are thumping. You don't want to hit any part of the piston ring as it pops out of the groove, so be watchful.

Hope that helps.
Pete

[notsmartcar]

How about heating the piston up , a small expansion may make all the difference

[hutchii]

From memory (not my strongest point) the C of E for aluminium is roughly double that of steel. So if you immerse the pistons in your heating oil and raise the temperature the small gap created should free the rings.

I've never needed to try it, but a friend assures me that Coke poured into seized cylinders works wonders at freeing pistons.
Might be worth a try.

[Ken Hanna]

Hmm,
in my experience, 'stuck piston rings' on an A series engine are usually the result of a partial seizure as a result of overheating.
With four out of the six rings affected, that possibility must be strong...
Is there any evidence of scuffing of the cylinder bores and/or the piston surfaces?

[johnf48]

Many thanks guys - all 3 replies are extremely useful - will try hot heating oil, carb cleaner and a block of softwood (on an old piston first) - tomorrow.

Will keep everybody advised.

Ken - bores, pistons and rings seem in excellent condition with no sign of previous overheating. The engine seems not to have turned over for at least the last 6 years and was difficult to turn initially. Rings seem firmly stuck in their channels.

John

[2cY]

^ "Will keep everybody advised."

[johnf48]

Hi Guys,

First of all my sincere apologies for not coming back on this forum sooner - Now that I officially an old TOGG I have become truly terrible at remembering passwords!

To cut a long story short I tried all the suggested remedies for the stuck piston rings with mixed results. One piston I freed after heating (see below!) with small screwdrivers but in doing so broke 2 rings. The other I freed all 3 rings using heat alone - from a propane blowlamp. Previous efforts with hot paraffin heated up on my camp cooker almost burnt my garage down due to spontaneous combustion -- (do this as I did OUTSIDE - in the pouring rain!) Even so it would not go out until all the oil was gone ----- so much for me passing a 2 week RAF Fire Officers' course three whole decades back.

I have now rebuilt the engine using new barrels and 9/1 pistons with rings from ECAS and have also overhauled the heads as 2 valves needed grinding in.
I have now also refitted the engine back into the Wasp and am about to start connecting everything up. Hope for first start-up in a week or so.
Should have quite a long list of bits and pieces for sale before too long as I really need to clear out the garage!
with best wishes - John