A10 non detergent to detergent

[fenderman!]

I have a 1955 road rocket...the sledge trap in the crankshaft has not been taken apart and cleaned...I've switched to a detergent oil.i understand damage may occur as the detergent oil may release dirt from the trap and go thru the engine perhaps causing damage.is there a way to filter the return oil coming back to the tank and capture any contaminents?

[DAVE BRADY]

Hi,

A cartridge filter can be fitted in the return to the tank and will 'clean' the oil.  The risk with what you are doing is that the route for the sludge is through the big ends before to gets to the sump to be pumped through the filter.  If there are no harmful particles and the sludge dissolves rather than breaks up you may get away with it.  If there are abrasive particles the big end shells will be subject to advanced wear and if the sludge breaks up it could actually block the oil ways so staving the shells of oil.

Dave.

[Bess]

Hi,
    Lots of A10 specific concerns, advise, and ideas on the A7/A10 forum:

https://www.a7a10.net/forum/index.php?topic=5859.msg121058#msg121058

Also worth reading service sheet July 1961, No 81, found in the members area.

Best wishes...

[fenderman!]

Thanks Dave although I'm confused.Once the particulars are out of the trap,there going to go wherever they go anyway..Retrieving it in a filter before it ends up in oil tank.Is switching to detergent oil a mistake without knowing how much is built up in the trap?

[DAVE BRADY]

Hi,

I would say yes, it is a mistake.  The only way for the sludge to go is through the big ends and any abrasive particles will all most certainly cause damage to the shells.  You could still fit a filter to prevent more sludge build up but perhaps hold off on the detergent oil.  Do you know the mileage of the engine?

Dave.

[fenderman!]

I recently had it bored .060 over,with new pistons, new connecting rod bushings lapped valves..Its only been run about 2 hrs total with less than a mile on the road.i believe the rings are somewhat seated..is it too late to switch back to non-detergent oil? Do not want to cause any damage.

[DAVE BRADY]

Hi Fenderman,

I would switch back to non-detergent but still fit the filter and a sump plate with a magnetic plug.
Top photo showing almost blocked sludge trap but oil still getting through but eventually it will block up stopping the oil from getting through.
Next photo is of a crank still with a way to go before getting critical.
I do not know the history of these engines.
The third photo is of a high mileage (60,000 miles ish) small journal crank with a filter fitted and detergent oil used from rebuild.  Even still a bit sludge has built up as this is how the centrifugal sludge trap works.  If no filter had been used this crank would almost certainly have filled up and failed but his mileage.

Dave.