Leakdown Test Results

[hot-growler]

Following a gradual loss of power I performed a Leakdown Test on my TR6 engine and found a loss of compression coming mainly via the rings into the block.

My question is is does wear happen equally to the rings and the bore or more one than other? It seems a moderately cheaper job to re ring only thus restoring 50% of the loss cheaply. Or is this incorrect thinking/false economy and should I have a rebore with new OS pistons and rings? Oil pressure good so would probably leave bottom end.

I will get valves recut to restore any compression loss through head.

Thanks for any replies.

[BlueTR3A-5EKT]

 De coke and re do valves.

re ring and flex-hone the bores

fit new be and main and thrust bearings as required

inspect and recon oil pump

these few actions would re vitalise the engine.

All can be done with engine in car.  

Fiddly doing crank bearings upside down

 

Cheers

Peter W

[Motorsport Mickey]

^ + 1 with Peter. 

You don't say how many miles the engines done or years the engines been together, perhaps you've only had the car for a year or two ? When you've got the head off just check for a wear ridge on the top of the cylinder bores, not uncommon to have a 2 or 3 thou ridge worn into the cylinder walls, if so your replacement piston rings bought need to have a "ridge dodger" top ring. That's a stepped ring with maybe a 10 thou step on the top edge which allows the cylinder bore ridge to be accommodated without the new top ring impacting and breaking on it, they work well and are an  accepted fitment on engine rebuilds.

Mick Richards

[hot-growler]

Had the car at least 17 years, and in the time haven't done much with the engine, just fuel & ignition  systems replaced. Mileage was 78,000 but milometer broken when purchased so, more likely to be nearer 90,000. 

Will lift the head to assess if any lip.

Where can I purchase the stepped rings from? Any preference to make?

Thanks for advice.

 

[ntc]

It will need rebore pistons and rings or you will be back there asap

[DRD]

1 hour ago, ntc said:

It will need rebore pistons and rings or you will be back there asap

Yep anything else is just a false economy.

[Peter Cobbold]

6 hours ago, hot-growler said:

Had the car at least 17 years, and in the time haven't done much with the engine, just fuel & ignition  systems replaced. Mileage was 78,000 but milometer broken when purchased so, more likely to be nearer 90,000. 

Will lift the head to assess if any lip.

Where can I purchase the stepped rings from? Any preference to make?

Thanks for advice.

 

Thats less than 1000 miles per year. I would try an Italian tune up to get some heat into the pistons and free any stuck rings.

90k is nothing, mine went to 180k , daily driving, before needing a rebore.

Peter

Edited August 15, 2019 by Peter Cobbold

[harlequin]

Last winter I did exactly what PeterW described. On inspection the bores had no lip which is understandable as the surface of the bores is far greater than that of the rings.

The big ends have to come out anyway to do the rings so you can inspect the journals and for the cost of a set of shells just change them. The front main bearing cannot be removed with the block in the car but the others are easy to do along with the thrust  washers 

I used Grant rings which seem ok, personally I would avoid using County rings.

Having said all that before opening the bonnet try Peter Cobbold's Italian tune up! Have a day out and get 100 miles on the clock and use the motorway 

George

[hot-growler]

makes sense the idea of gummed up rings cos when i bought it it felt great and compressions were high. the number of miles driven shouldn't have caused much power loss. will give it some serious welly on our next weekend away