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how often do you take your engine up to maximum revs?


jenevers

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38 minutes ago, OptedOut said:

 

That’s way over the maintenance requirements in my manual. They imply a decoke etc  every 1500 hrs and bearings every 6000.

I suspect stationary engines with fixed speeds may require less maintenance , less coke up and cool running.

However I never decoked Thaxteds engine in 16 years and god knows how many hours. Towing the butty probably helped, and no please pass at tick over nonsense.

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5 hours ago, MartynG said:

I have never taken my engines  to full revs.

May have gone to 3500rpm occasionally . Max is 3900rpm.

Mostly cruse at 3200rpm when going fast which is about 22Knots.

You are being too kind too it!!

 

Get it wound up to WOT and give it a good clear out. It will do it the world of good.

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On 22/11/2020 at 18:42, Athy said:

I have no idea how long that takes.

Less than a minute. My 4LW  soon builds up to 45 pounds oil pressure. But even then I would never over-rev the engine.
There used to be a TV advert (Castrol GTX?) showing an engine screaming in pain when someone revved it up from cold ?

Edited by jenevers
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LPWS4, used to run at 1k for a couple of mins then into gear and gradually increase revs until running temp, after cruising for an hour or more and ready to switch off a quick blast to max revs in neutral, allow to tick over them shut down. Never revving to max risks broken rings if after a few thousand hours engine running it is revved to max, the higher the revs the more the con rods stretch and rings will hit the wear ridge at the top of the cylinders. 

Never exceed previously selected max revs on a high hours/mileage engine. 

 

ETA: Revving to max with a cold engine is the worst thing you can do. 

Edited by nb Innisfree
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15 hours ago, BWM said:

I suspect that the pistons would end up in a different postcode!

 

Reminds of an article in the car club magazine when I was rallying back in the 70's.

 

One member had a "Broadspeed Bullet", a 3 litre Ford Capri with a turbocharger and other mods to improve performance. To reduce the compression ratio, the head gaskets were replaced with thicker ones. He decided to replace these with the originals...

 

The car really flew but as he increased the revs there was a load bang, smoke and the engine stopped.

 

In the club magazine he described the reason for his retirement as "total electrical failure - a conrod escaped from the engine and cut through the battery cable"! ???

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53 minutes ago, cuthound said:

 

Reminds of an article in the car club magazine when I was rallying back in the 70's.

 

One member had a "Broadspeed Bullet", a 3 litre Ford Capri with a turbocharger and other mods to improve performance. To reduce the compression ratio, the head gaskets were replaced with thicker ones. He decided to replace these with the originals...

 

The car really flew but as he increased the revs there was a load bang, smoke and the engine stopped.

 

In the club magazine he described the reason for his retirement as "total electrical failure - a conrod escaped from the engine and cut through the battery cable"! ???

The 3 litre V6 was an extremely expensive unit to tune, and without a full on balance was very happy to chuck a rod through the block. I used to replace them with a rover V8, cheap to tune and the weight saving improved braking and handling! Had a firm called real steel just up the road, was like a kid in a sweet shop.

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19 hours ago, nb Innisfree said:

 Never revving to max risks broken rings if after a few thousand hours engine running it is revved to max, the higher the revs the more the con rods stretch and rings will hit the wear ridge at the top of the cylinders. 

 

 

 

That’s something I’ve never heard of before. Con rods stretching? Is that an accepted fact?

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1 hour ago, jenevers said:

That’s something I’ve never heard of before. Con rods stretching? Is that an accepted fact?

I have heard it said that as the piston goes across TDC in a racing engine the effective weight of the piston moving up whilst the con-rod moves down is in excess of 5 tons and that is with special light pistons. The two oil control ring and three compression ring pistons are far heavier to start with. So I am sure the rods will tend to stretch at high revs. I suspect in this respect an old long stroke engine will put far less stress on the rod than a modern over square whiz bang one.

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1 hour ago, Tony Brooks said:

I have heard it said that as the piston goes across TDC in a racing engine the effective weight of the piston moving up whilst the con-rod moves down is in excess of 5 tons and that is with special light pistons. The two oil control ring and three compression ring pistons are far heavier to start with. So I am sure the rods will tend to stretch at high revs. I suspect in this respect an old long stroke engine will put far less stress on the rod than a modern over square whiz bang one.

Remember this is supposed to be about Gardner engines!!!!

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1 hour ago, jenevers said:

Remember this is supposed to be about Gardner engines!!!!

Yes, I was answering @jenevers post, and I bet it will have long five ring pistons that may have iron cast in. That is why I said a long stroke engine is likely to be less susceptible than a modern over square one. Actually  I would be more concerned about the big end bolts.

Edited by Tony Brooks
change more to less - did contradict my last post
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On 24/11/2020 at 17:27, nb Innisfree said:

LPWS4, used to run at 1k for a couple of mins then into gear and gradually increase revs until running temp, after cruising for an hour or more and ready to switch off a quick blast to max revs in neutral, allow to tick over them shut down. Never revving to max risks broken rings if after a few thousand hours engine running it is revved to max, the higher the revs the more the con rods stretch and rings will hit the wear ridge at the top of the cylinders. 

Never exceed previously selected max revs on a high hours/mileage engine. 

 

ETA: Revving to max with a cold engine is the worst thing you can do. 

Very unlikely to have con rods stretch on anything but a highly tuned race engine, and most rod faliures happen on sudden closure of the throttle.

 With a diesel engine it would be much more likely for rings to fail when over revving an engine with poor compression, as you lose the cushioning effect at tdc.

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4 hours ago, BWM said:

Very unlikely to have con rods stretch on anything but a highly tuned race engine, and most rod faliures happen on sudden closure of the throttle.

 With a diesel engine it would be much more likely for rings to fail when over revving an engine with poor compression, as you lose the cushioning effect at tdc.

Conrod must stretch to some extent, the faster they travel the more they stretch, microscopically maybe but its still there. I recall a relative buying a Triumph Herald many years ago that suffered broken rings when they hit a wear ridge in the bores, caused by being revved higher than the previous owners gentle driving. It was cured by fitting 'ridge dodger' rings which had a step in the top of the upper ring, not uncommon back then, though I don't know if they are still avaliable. 

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When the loco Mallard got the world speed record of 126 mph it busted it's inside cylinder cover and valve chest covers by over running of the con rod and valve gear at that speed. The engine had to be taken off its train at Peterborough.

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8 hours ago, bizzard said:

When the loco Mallard got the world speed record of 126 mph it busted it's inside cylinder cover and valve chest covers by over running of the con rod and valve gear at that speed. The engine had to be taken off its train at Peterborough.

I thought it was the crank that had shifted?

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19 hours ago, OptedOut said:

"as you lose the cushioning effect at tdc."

 

The cushioning effect is not present during the TDC at the exhaust/suction stroke with a 4 stroke engine.

Splitting hairs. The cushioning effect is achieved just prior to the piston arriving at tdc (compression), which is relevant to my comment.

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On 25/11/2020 at 10:24, BWM said:

The 3 litre V6 was an extremely expensive unit to tune, and without a full on balance was very happy to chuck a rod through the block. I used to replace them with a rover V8, cheap to tune and the weight saving improved braking and handling! Had a firm called real steel just up the road, was like a kid in a sweet shop.

 

The company that sponsored my rallying Mini used to earn most of their profits transplanting Rover V8 lumps into Triumph Stags!

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49 minutes ago, cuthound said:

 

The company that sponsored my rallying Mini used to earn most of their profits transplanting Rover V8 lumps into Triumph Stags!

Definitely a good swap, the triumph was an untunable and underpowered lump! I was told that the Triumph V8 was basically two of their four pots grafted together, a product of desperation by their designers. 

 I owned one briefly, still the only car i've ever run out of fuel in - twice!

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