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For info the car is a TR250.  Engine is not original but I have been informed that the number is correct for the TR250. Starter is new but not high torque  Battery is new. Car starts and ticks over fine so I a  sure timing etc is not far out. Head came loose with the car but is the American style with narrow manifold spacing. It looked like it had come from a machine shop not  diy refurb.

I have just checked the compression on my mg. It was a steady 75/76. This is an 1800 3 bearing engine with less than a 1000 miles on the clock and a Peter Burgess econotune head which is probably slightly higher compression than normal. (know I am spending too much time in the garage and not enough  driving).

So TR readings might not be as disastrous as first appeared .

From memory the bores didn't  look bad before I put the head on.  If the rings have been replaced is there a running in time for them to achieve  a good seal?

Many thanks for all the replies.

Eddie 

 

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 “If the rings have been replaced is there a running in time for them to achieve  a good seal?”

I can feel a BMEP bedding in session coming, I’m a great fan of it.

Mick Richards

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15 minutes ago, michaeldavis39 said:

What is a BMEP bedding in session Mick?

Here's a description, it's quite well known, and where "trophy"cars are involved (because they often don't get used as they should) "mind my hair, no faster than 50mph" the cars don't get enough use in the areas where the piston rings bed in.

The standard TR camshaft does not develop full torque until 3500 revs...which your car never achieves, people change up and use overdrive. The engine needs full torque to be used and for that to coincide with a full "loading" (where the engine is working hard) condition of the engine. The piston rings need this loading to be forced out sidewards to allow them to gouge out their complimentary grooves (we are talking microns) in the walls of the liners. Excessive revs are not what helps the piston rings bed in, but driving the car at revs over 3500 in top gear (4th) with your foot hard down to the floor...continually, allowing the car to develop speed and increase the revs DOES. 

This condition is well known and described as BMEP (Brake Mean Effective Pressure) Google it and you will find it described and how it works. Briefly the engine achieves it's most compression (which thrusts out the piston rings) on it's downward power stroke when the engine is loaded (working hard) and full throttle is continually applied. This is normally about the maximum torque area of your engine (3500 revs) where your engine mostly skirts apart from maybe an occasional foray but unlikely to be under full throttle in 4th.

You could ask a rolling road to load your cars engine and then in 4th at under 3000 revs apply full throttle and keep the throttle applied until the engine achieves maybe 4500 or 5000 revs even. Before power runs and with about 200 miles on the engine this is what we do on the race cars.This avoids any possible exceeding of road speed limits.

Alternatively I often (when bedding in race engines ) drive the car onto a motorway (car taxed and MOT tested). Then when you come upon a long uphill gradient (I have one within 3 miles of me) I change the car into 4th gear at about 2500 revs and floor the throttle and keep it buried as the car accelerates through the camshaft max torque are and when about 4500 revs are achieved (naturally making sure I do not exceed road speed limits). Because motorway gradients are long and of a consistent gradient when the revs are achieved, and then braking the car down in speed I can normally carry out this twice going uphill. Of course you must always keep an eye in the mirrors and also ahead to make sure your actions do not cause a danger to other road users. Then I come off at the next motorway junction and return back towards home going up the other side of the gradient and carry out the same procedure loading the engine and bedding the rings in. I normally invest maybe 1 hour carrying out the excercise. This is a lot more fun than stripping the engine and cheaper also ! Because this bedding in is carried out at a microscopic level it needs multiple applications, maybe a couple of times a week for about an hour over a month.

Interestingly my saloon road car tows my caravan and I can definately feel a difference after a 6 week caravan holiday towing covering maybe 2000 miles. The caravan loads the engine nicely and freshens up the bore conditions removing any glazing from the bores and beds the piston rings in.

Mick Richards

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On 10/17/2021 at 7:35 PM, Motorsport Mickey said:

Here's a description, it's quite well known, and where "trophy"cars are involved (because they often don't get used as they should) "mind my hair, no faster than 50mph" the cars don't get enough use in the areas where the piston rings bed in.

The standard TR camshaft does not develop full torque until 3500 revs...which your car never achieves, people change up and use overdrive. The engine needs full torque to be used and for that to coincide with a full "loading" (where the engine is working hard) condition of the engine. The piston rings need this loading to be forced out sidewards to allow them to gouge out their complimentary grooves (we are talking microns) in the walls of the liners. Excessive revs are not what helps the piston rings bed in, but driving the car at revs over 3500 in top gear (4th) with your foot hard down to the floor...continually, allowing the car to develop speed and increase the revs DOES. 

This condition is well known and described as BMEP (Brake Mean Effective Pressure) Google it and you will find it described and how it works. Briefly the engine achieves it's most compression (which thrusts out the piston rings) on it's downward power stroke when the engine is loaded (working hard) and full throttle is continually applied. This is normally about the maximum torque area of your engine (3500 revs) where your engine mostly skirts apart from maybe an occasional foray but unlikely to be under full throttle in 4th.

You could ask a rolling road to load your cars engine and then in 4th at under 3000 revs apply full throttle and keep the throttle applied until the engine achieves maybe 4500 or 5000 revs even. Before power runs and with about 200 miles on the engine this is what we do on the race cars.This avoids any possible exceeding of road speed limits.

Alternatively I often (when bedding in race engines ) drive the car onto a motorway (car taxed and MOT tested). Then when you come upon a long uphill gradient (I have one within 3 miles of me) I change the car into 4th gear at about 2500 revs and floor the throttle and keep it buried as the car accelerates through the camshaft max torque are and when about 4500 revs are achieved (naturally making sure I do not exceed road speed limits). Because motorway gradients are long and of a consistent gradient when the revs are achieved, and then braking the car down in speed I can normally carry out this twice going uphill. Of course you must always keep an eye in the mirrors and also ahead to make sure your actions do not cause a danger to other road users. Then I come off at the next motorway junction and return back towards home going up the other side of the gradient and carry out the same procedure loading the engine and bedding the rings in. I normally invest maybe 1 hour carrying out the excercise. This is a lot more fun than stripping the engine and cheaper also ! Because this bedding in is carried out at a microscopic level it needs multiple applications, maybe a couple of times a week for about an hour over a month.

Interestingly my saloon road car tows my caravan and I can definately feel a difference after a 6 week caravan holiday towing covering maybe 2000 miles. The caravan loads the engine nicely and freshens up the bore conditions removing any glazing from the bores and beds the piston rings in.

Mick Richards

As I have probably mentioned before, I am far from an expert, but even I can understand this clear explanation you provide. With great, much appreciated, generosity, I would like to add. To me, the pattern of not going up to higher rpm sounds like TR Fear of Cankshaft Breakage.

Ciao,

David

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14 minutes ago, DavidBee said:

As I have probably mentioned before, I am far from an expert, but even I can understand this clear explanation you provide. With great, much appreciated, generosity, I would like to add. To me, the pattern of not going up to higher rpm sounds like TR Fear of Cankshaft Breakage.

Ciao,

David

They can cope with quite a lot

this is 87mm, an original crank some 1970’s warm cam SU’s and a lightened flywheel.

go and enjoy.

 

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We learn something every day. Trouble is I tend to forget it the next day.

It is amazing what knowledge there is from the people on this forum.

I will try to do a blowdown test to see if I can get a better idea of the engine condition.

I have been offered a saloon 2.5 engine , supposedly in good condition, for little money and wonder if that would fit without too much work.

Thanks Eddie 

 

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Eddie, why?   Yes a saloon engine would fit fine, but you have shown yourself that the engine already in the 250 isnt in trouble.   What will another engine achieve?

By all means, accept the saloon engine, and rebuild it, correcting the many faults that may exist in an unknown, and if you wish, fitting upgrades, bore outs, head skims, flowing etc.wtc.   Then, decide if you want to swap or not, while enjoying the car in between days in the workshop!

John

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26 minutes ago, Eddie Trickett said:

We learn something every day. Trouble is I tend to forget it the next day.

It is amazing what knowledge there is from the people on this forum.

I will try to do a blowdown test to see if I can get a better idea of the engine condition.

I have been offered a saloon 2.5 engine , supposedly in good condition, for little money and wonder if that would fit without too much work.

Thanks Eddie 

 

Eddie

You should sort what you have the 250 has low compression if the head is std to get up to 10,1 you will need up to 86thou removing and rebuild it at the same time 

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