Triumph Stag V8 - Sticking Piston Rings

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Wed 2 Oct 2013 13:07
Triumph Stag V8 - Sticking Piston Rings - allanbennett

I have a 1976 Triumph Stag with the original engine which has done 86,000miles. The engine was lively and healthy until I unfortunately was unable to use the car and it was garaged for 2 years. I've started running it again and it goes as well as ever with the exception of a lot of oil burning and crankcase pressure which I never had before.

I'm more or less convinced that I have sticky rings on a couple of cylinders as the car runs like a rocket for 50 or 60 miles but then gradually starts to foul itself and run poorly whilst blue smoking under power. If I then change the plugs it's good for anothe 50 miles, but is still smoky and has significant breathing from the dipstick and oil filler cap.

It may be that the engine needs opened up, but this hasn't crept up gradually, which makes me think it's the result of being parked-up for a long time. Before I resort to taking the engine out, I'd like to try cleaning the pistons/rings - so I'm looking for suggestions please.

Thanks.

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Wed 2 Oct 2013 13:17
Triumph Stag V8 - Sticking Piston Rings - Collos25

Very very unlikely to have sticking piston rings most likely the cause of the oil usage is rotten seals in the head

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Wed 2 Oct 2013 13:24
Triumph Stag V8 - Sticking Piston Rings - RT

Very very unlikely to have sticking piston rings most likely the cause of the oil usage is rotten seals in the head

There's plenty of blow-by which points to rings, not valve stem seals.

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Wed 2 Oct 2013 13:23
Triumph Stag V8 - Sticking Piston Rings - RT

The old way of sorting this is:-

Wait for a cool day with a slight breeze when neighbours have the windows closed and no washing out - then remove the air cleaner, run the engine at fast idle and slowly pour a couple of bottles of Redex into the inlet - the resulting smoke screen would have done the Royal Navy proud at Jutland.

If that doesn't work you'll need tp strip the engine.

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Wed 2 Oct 2013 14:32
Triumph Stag V8 - Sticking Piston Rings - craig-pd130

An alternative approach to RT's method is to remove all the spark plugs and use a squirty oil can to inject about 10ml of Redex into each cylinder. Then with the plugs still out, turn the engine over slowly by hand (using the crank end nut) a couple of times to get the Redex around the bores and rings.

Then leave for a day for it to soak, etc (with plugs still out). Before refitting the plugs, give it a spin over on the starter for a couple of seconds. Then refit plugs, start and take it for a drive.

EDITED to add, which cylinders' plugs foul? Just a couple, or do they all get oily & sooty? If it's just a couple, then those are the cylinders that need action. If it's all of them, I'd think the problem could be elsewhere, what's the crankcase breather arrangement on the Stag?

Edited by craig-pd130 on 02/10/2013 at 14:35

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Wed 2 Oct 2013 16:47
Triumph Stag V8 - Sticking Piston Rings - focussed

There is an aerosol can additive availalable for de-coking and cleaning pistons, bores and rings on two and four stroke engines. It has been widely used for many years in the outboard marine industry and if used properly will do what is says on the tin.

http://www.mailspeedmarine.com/oil-lubricant-fuel-additive/quicksilver/power-tune738585.bhtml

Worth trying a couple of cans through the motor.

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Wed 2 Oct 2013 20:20
Triumph Stag V8 - Sticking Piston Rings - bathtub tom

I've seen Redex poured in the carb free up sticky valves, so I'd guess it's worth a try as it wouldn't cost much.

What would it do to cat equipped engine I wonder?

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Wed 2 Oct 2013 20:21
Triumph Stag V8 - Sticking Piston Rings - madf

I have used the "soak engine in redex for 2 days" treatment. You can expect to leave a smoke trail 100 meters long,10 meters high for half a mile...when you run the engine.

Best not to do in built up areas...

(It did not work)

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Wed 2 Oct 2013 21:08
Triumph Stag V8 - Sticking Piston Rings - Wolfan

It's possible that because it hasn't been run for 2 years that some of the rings had stuck to the bores and they broke when the engine was started again. I fear it might be an engine out job.

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Thu 3 Oct 2013 11:19
Triumph Stag V8 - Sticking Piston Rings - Galaxy

Stick an NSU Rotary or Ford V4 Engine in.

Problem Solved :)

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Thu 3 Oct 2013 11:58
Triumph Stag V8 - Sticking Piston Rings - craig-pd130

Stick an NSU Rotary or Ford V4 Engine in.

Problem Solved :)

Haha :) I seem to remember that the replacements of choice in the 70s were the Essex V6 or a Rover V8.

I thought the V4 transplant was for NSU RO80s once the warranties had expired?

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Thu 3 Oct 2013 12:38
Triumph Stag V8 - Sticking Piston Rings - RT

Stick an NSU Rotary or Ford V4 Engine in.

Problem Solved :)

Haha :) I seem to remember that the replacements of choice in the 70s were the Essex V6 or a Rover V8.

I thought the V4 transplant was for NSU RO80s once the warranties had expired?

Being the first production w***el, the NSU RO80 was the first to experience engine wear which marred an otherwise outstanding car.

The w***el isn't very big, physically, so space was limited and if my memory serves me well, the Ford V4 was the only engine that would fit the available space, because it was equally short.

ATTN - ADMIN - please fix this stupid censor software - this is the 21st century after all!

Edited by RT on 03/10/2013 at 12:39

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Thu 3 Oct 2013 14:08
Triumph Stag V8 - Sticking Piston Rings - allanbennett
Thanks for all these suggestions - even the ridiculous ones!

I think I'll give the 'Redex down the bores' thing a go at the weekend. After all, I really don't have anything to lose!
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Thu 3 Oct 2013 16:56
Triumph Stag V8 - Sticking Piston Rings - Collos25

Redex is very good for making smoke and nothing else it would need to poured down the plug holes in large quantities and left for a couple of days to have any effect .

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Thu 3 Oct 2013 17:05
Triumph Stag V8 - Sticking Piston Rings - thunderbird

Redex might not do any good but if the rings are damaged it cannot do much harm. You don't need much, instructions used to be on the bottle but it cannot perform the impossible.

If you happen to have a broken ring continuing to run the engine could score a bore if its not scored already. Then its rebore time. But on an engine this age a rebore and new pistons/rings might not be a bad idea instead of just replacing the rings which would probably never bed into the bores correctly. New rings, old bores can still use loads of oil.

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Thu 3 Oct 2013 18:47
Triumph Stag V8 - Sticking Piston Rings - Collos25

If you put redex or any additive into the tank or direct into the intake it will just burn in the top end of the engine it will never go into the bores.

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Thu 3 Oct 2013 21:02
Triumph Stag V8 - Sticking Piston Rings - Peter D

I would remove all the plugs and inject 20cc of petrol into each cylinder, turn over by hand 10 times and leave for 24 hrs. Then crank with the plugs out in bursts of 5 seconds 10 times, then replace the plugs and start it up. Run at idle to 5 mins then shut it down and do and oil and filter change.

Go for a run for 10 miles and see how she goes. I very much doubt you have any broken rings.

Regards Peter

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Fri 4 Oct 2013 23:55
Triumph Stag V8 - Sticking Piston Rings - Big John

>The w***el isn't very big, physically, so space was limited and if my memory serves me >well, the Ford V4 was the only engine that would fit the available space, because it was >equally short.

Hmm, I remember that the V4 also being a problem engine due to the balancer shafts to make it smoother - where have we heard this before ?

The V6 (Essex) was a lot better but still had a fibre cam wheel that used to fail - (usually with knocking noise before hand) and a hex drive shaft connectring the base of the distributor to the oil pump that used to eventually round off causing serious damage (usually seizing the crank) - likewise ?

Sorry - starting to show my age!

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Fri 4 Oct 2013 23:37
Triumph Stag V8 - Sticking Piston Rings - Big John

Does it burn a lot of oil (through exhaust) when first warmed up - e.g. 10 miles?

If it were piston rings it should be doing this shortly after startup not after 50 miles.

It shouldn't be blowing from the dipstick/ oil filler - are the oil breather pipes or where they are attached simply blocked with oil gunge? It's been a while but I seem to remember them being attached to the cam covers. If you get high crank case pressure it will blow oil past the valve oil seals (amongst others!) causing a smokey exhaust and potentially fowling plugs.

Under this circumstance on some cars i've seen the dipstick ejected!

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Sat 5 Oct 2013 15:10
Triumph Stag V8 - Sticking Piston Rings - Wolfan

The problem appears to be only on two cylinders so that would discount a fault with the breathing arrangement which leaves only piston or ring problems neither of which are likely to be cured without dismantling the engine.

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