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Author Topic: 2.2 cam shaft? Way down on power......  (Read 2070 times)
Colin
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« on: August 25, 2015, 09:23:23 pm »

Hello, I am new to Murena ownership, I have just bought a 1983 2.2, which although on the road, has not been used for 15 years.
Having replaced the big end shells, sump gasket etc, and rebuilt the carbs (Dellorto 40), I took the car to my local rolling road to have it set up. Disappointingly the car only made 67BHP when they had done all they could. They suspect, a worn cam shaft, and or weak valve springs.
So, as yet, I have not removed the rocker cover. Are new cam shafts readily available? And is there a hotter option, from the “S” or similar?
Thanks in advance......
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Oetker
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« Reply #1 on: August 26, 2015, 04:54:51 am »

They can look like this if your unlucky.

Pic Pete Speed

The camshafts from Politecnic for S and 2.2 engines are out of stock.
They only have the fast Sodemo camshaft in stock but they are almost 600 Euro.

http://www.politecnic.com/piecesmoteur.htm

Maybe ask around at carjoy or Simon but I doubt they have one.

www.carjoy.nl

http://www.simon-auto.de/


Herman





« Last Edit: August 26, 2015, 11:11:41 am by Oetker » Logged

I feel like Jonah, only my fish looks different.
Murena 2.2 Red 1982. Murena 1.6 black on places.
krede
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« Reply #2 on: August 26, 2015, 07:19:57 am »

Simon is usually very helpful, and just because the part you need isn't in his catalogue , doesn't mean that he cant supply you with one. I would send him a mail if you need some parts.

The cam you see on the picture is from a peugeot 505 turbo that I took apart a couple of years ago (basically the same engine) I have dismantled a few of them and ALL had worn cams.
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Jon Weywadt
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« Reply #3 on: August 26, 2015, 10:54:57 am »

Hello, I am new to Murena ownership, I have just bought a 1983 2.2, which although on the road, has not been used for 15 years.
Having replaced the big end shells, sump gasket etc, and rebuilt the carbs (Dellorto 40), I took the car to my local rolling road to have it set up. Disappointingly the car only made 67BHP when they had done all they could. They suspect, a worn cam shaft, and or weak valve springs.
So, as yet, I have not removed the rocker cover. Are new cam shafts readily available? And is there a hotter option, from the “S” or similar?
Thanks in advance......

First, welcome to the circle of Matra Murena owners. It is a seriously fun car to drive. Once fixed you will enjoy it. Grin

I would be surprised if your cam is so worn. Have you checked the compression in the cylinders? I think the most likely cause for the loss of power is worn piston rings, or worn valve seats.

Once you take the head apart and inspect the cam shaft, if it looks ok you can improve power by re-profiling the cam to Holbay 58C specs. I did, and I can really feel the difference. Grin It goes from zero to a speeding ticket much faster now. Cool
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roy4matra
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« Reply #4 on: August 26, 2015, 04:42:36 pm »

Hello, I am new to Murena ownership, I have just bought a 1983 2.2, which although on the road, has not been used for 15 years.
Having replaced the big end shells, sump gasket etc, and rebuilt the carbs (Dellorto 40), I took the car to my local rolling road to have it set up. Disappointingly the car only made 67BHP when they had done all they could. They suspect, a worn cam shaft, and or weak valve springs.
So, as yet, I have not removed the rocker cover. Are new cam shafts readily available? And is there a hotter option, from the “S” or similar?
Thanks in advance......

First, welcome to the circle of Matra Murena owners. It is a seriously fun car to drive. Once fixed you will enjoy it. Grin

I would be surprised if your cam is so worn. Have you checked the compression in the cylinders? I think the most likely cause for the loss of power is worn piston rings, or worn valve seats.

Once you take the head apart and inspect the cam shaft, if it looks ok you can improve power by re-profiling the cam to Holbay 58C specs. I did, and I can really feel the difference. Grin It goes from zero to a speeding ticket much faster now. Cool

Just to clarify on that last statement Colin - you don't have to remove the head or take it apart to inspect the camshaft, obviously you only need to remove the cam cover which is fairly easy.  Then you can inspect all the cam lobes and see if they are badly worn or not.  If they are then you will have to find another but if they are still good, then you need to find out if you have good compression first.  The fact that you say 'when they had done all they could' regarding getting it set up on the rolling road, they should have already checked the obvious things like valve clearances and compressions but if they did then they should have seen if it had any drastic cam wear.  The fact that they only 'suspect' it might have cam wear, suggests they did not even check the valve clearances!  How can you set up an engine on the rolling road when you don't even know if the basics are correct?!  The level of mechanics knowledge seems to get worse all the time.

Anyway, you need to check the basics first but there is a good possibility that the cam may be worn like that in the photo.  These cars need really good quality oil and regular maintenance, and to give you my own example I've owned my Murena 2.2 from new, used fully synthetic Mobil oil in the engine from new, and have done all my own maintenance correctly as per the book, (I am a profession technician) and I have never suffered any wear on my camshaft.  I have never even had to adjust the valve clearances (because there was no wear).

One of the biggest faults I have seen is owners fitting re-profiled camshafts without having the rockers refurbished too, or fitting new ones; and this leads always to cam wear.  If new are having one surface reground (i.e. the cam lobes. then you MUST have the mating surfaces (the rocker pads) also reground.

So if you have to replace the camshaft you will need to either fit new rocker arms or have them refurbished, if you want the cam to last.  Also note that the rockers on the inlet side and the exhaust side are different.  Every engine I have stripped that others have rebuilt have some of these rocker arms in the wrong place and that will also lead to wear as the exhaust ones have oil holes which the inlet do not.

Roy
« Last Edit: August 26, 2015, 04:48:56 pm by roy4matra » Logged

Jon Weywadt
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« Reply #5 on: August 26, 2015, 06:08:36 pm »

----
Just to clarify on that last statement Colin - you don't have to remove the head or take it apart to inspect the camshaft,
----
Roy
Thanks Roy, for keeping me straight  Embarrassed
Checking the compression would be the first step and only require removal of the spark plugs.
I was assuming that Colin would find worn valve seats or piston rings and would have to take the head off to fix that.

Roy,
is there a way to determine if the piston rings are worn, rather than the valve seats? Could the piston rings be checked by setting the pistons so they are all a bit down in the cylinder, pour a bit of oil into each cylinder and then pressurise the crank case to see if and how bad it bubbles around the pistons?  Huh
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roy4matra
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« Reply #6 on: September 04, 2015, 09:01:01 am »

Roy,
is there a way to determine if the piston rings are worn, rather than the valve seats? Could the piston rings be checked by setting the pistons so they are all a bit down in the cylinder, pour a bit of oil into each cylinder and then pressurise the crank case to see if and how bad it bubbles around the pistons?  Huh

The normally accepted way to check if it is valve seat leakage or piston ring leakage, is to use some engine oil in the bore particularly with flat topped pistons which ours are.

You check the compression of one cylinder as normal first and record that low reading.  Then you pour some oil in that bore and immediately check it again.  If the compression reading increases, you have some bore wear/piston ring problems.  If the reading does not change it is the valve seats that are more the problem.

The idea is that oil you pour into the cylinder will temporarily seal the gap between the piston and bore and if it was leaking before it will result in a brief increase in compression.

However, we have a slight problem in that our engine is angled over so the oil will mainly be around the lower edge and won't be as effective - the test was original designed when engines were upright!

This is one reason why a running vacuum test is better.  Valve sealing problems show a different result to piston/bore sealing problems, and with the engine running it gives you a better idea.  Obviously if the engine won't run, or runs so poorly that it is difficult to get steady revs or response to a blipped throttle, then this is not much use.

However, after checking basics, you can usually sense where your problem lies.  An almost complete loss of compression is usually valves whilst a substantial loss but giving say 50-80 psi will probably be piston bore, assuming the engine looks dirty inside.  The dirt is carbon that has been getting into the engine via the leaking pistons/bores.  Even with that lack of sealing the gap is small enough that you still get some compression.

If the problem is with the valves, or say a valve had burnt a section out of it, the compression loss is almost complete yet the inside of the engine can remain clean as the piston rings will still stop the carbon getting into the block.

Roy
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Colin
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« Reply #7 on: September 04, 2015, 08:22:27 pm »

Thanks for the guidance so far... as yet I have not had time to do any further investigations.... Is there anyone in the UK who can be recommended to carry out a full engine rebuild? Due to mobility problems this is not something I can do myself. I assume that this may be the way to go, as the car has done 170k km, so there will be wear in a lot of it, when we replaced the big end shells, there was evidence of wear on the crankshaft, and the new shells have quietened it down, it is still a little rattley. 
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roy4matra
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« Reply #8 on: September 05, 2015, 07:12:25 pm »

Thanks for the guidance so far... as yet I have not had time to do any further investigations.... Is there anyone in the UK who can be recommended to carry out a full engine rebuild?

That's me Colin.

Quote
Due to mobility problems this is not something I can do myself. I assume that this may be the way to go, as the car has done 170k km, so there will be wear in a lot of it, when we replaced the big end shells, there was evidence of wear on the crankshaft, and the new shells have quietened it down, it is still a little rattley.  

Yes, it sounds like it needs a rebuild.

If you contact me directly by my club email ( roy at matraclub.org.uk ) we can discuss it further.  I think you will find there are others on here who can verify my work.

Roy
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GP
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« Reply #9 on: September 06, 2015, 11:12:17 am »

Hi Colin,

I highly recommend Roy.

http://www.matrasport.dk/forum/index.php/topic,2158.0.html

If you go elsewhere you will most likely have all sorts of problems occur.

Regards,

Graham
« Last Edit: September 06, 2015, 11:17:19 am by GP » Logged
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