fast camshaft specs

[roy4matra]

wow ... and 8.3 lift does not make  piston/valves interferences ?

No, I originally measured the clearances between the valves and pistons when rebuilding Graham's engine some years ago, so we knew we could go with more lift when we had the Piper cams made.  The Murena 2.2 engine now rebuilt in Colin's car has our new Piper camshaft with 8.3mm lift (11.37mm valve lift) and still has some clearance when running, and as can be seen and heard on his youtube videos, it goes well and sounds really good.

Roy

[GP]

I have the only car running with the Piper cam in it, unless Graham has been busy...? (do you have any events planned for next year with the Murena Graham? I am yet to see it in action...) It is good, very good, everyone who has driven it (who all have more experience of driving various Murena then me) says how good it is.
Here are some videos of it...
https://www.youtube.com/playlist?list=PLkkcMOq03tEgbCE2AzitiB7zyv-57QC0H

Hi Colin, no I have not fitted the Piper Cam as per your engine yet. Too mean to replace the Mecapart Head Gasket again £££££ Hah!
Another "no" I'm afraid as nothing planned for next year as yet.  A few other distractions/responsibilities have popped up.
Keep you posted when it does happen though?

Graham

[roy4matra]

Hey there! Welcome to the forum. Sad to hear about your contrôle technique experience. I have the following specs on file:

Sodemo gr 4:   Lift 7.75mm  Timing 30° 86° 78° 42°
Period (Inlet) 296° (Exhaust) 300°       Overlap 72°

I agree, the Holbay is a great cam shaft. Although it has less lift than the S-cam, the overlap helps the airflow and the performance might be even better. Also, it runs very well with the standard Solex 34CIC carb.

2020 Update:

I have now found my Politecnic brochure and the above specifications are not quite correct, so I would like to correct them for anyone else who is wanting to uprate their 2.2 engine, and is reading this thread.

The camshaft specification Anders lists above as the Sodemo Gr.4 cam is actually the data for the Politecnic Maxiroute camshaft and will only produce around 150-155 horsepower and cannot be a Group 4 cam producing 184cv.  The Group 4 Politecnic-Danielson kit which was supposed to produce 184 cv also had bronze valve guides and special sodium filled exhaust valves (for cooling) with twin concentric valve springs and special aluminium retainers. Whether these valves were larger and the head had a higher compression it does not say, but I suspect it did and also had a special high lift cam, higher than even the Piper 3777 because having spoken to experienced racing engine manufacturers, for this naturally aspirated 2.2 engine, the valves would need to be lifting over 12mm to produce around 185 horsepower.

We know that the Piper 3777 cam with 8.3mm cam lift and therefore 11.371 valve lift, plus wider timing will not produce more than approx. 160bhp so there is no way the Maxiroute cam with less lift could produce that claimed 184cv (181bhp) without extensive other modifications.  But the original Politecnic brochure does not claim the Politecnic-Danielson kit uses the Maxiroute cam.  The brochure simply lists what was available from them at the time and the options were:
1) Maxiroute reprofiled camshaft priced at 1,990 FF in exchange for your old cam.
2) Politecnic-Danielson complete Gr.4 kit priced at 7,500 FF.  (yes French Francs which shows how old this brochure is!)
You can see from the price difference here, that the Gr.4 kit contained a lot more as it cost approx. 3.5 times as much as the reprofiled Maxiroute cam!

Roy

[Murena1400]

I have the correct information on this matter.

The Politecnic Gr.4 set consisted of a special hemispherical head, with bigger valves, double springs, modified intake ports, small spark plugs and a wider exhaust.
It was delivered with a special camshaft, which was available in two stages, 184cv and 200cv. (these figures are real figures as on bench tests).

A few of these heads were made for the Rallye Monte Carlo cars, and later for some rallyecross operations.

Whatever was left they put for sale on their brochure, (in numbers not more than 2 sets). The last set was bought by us in 2001 and put on a Murena S.
(The photos of the engine bay of a Murena S with double Dellorto's is in fact our car).

These are really potent kits and are not comparable to whatever is on the market today.

[roy4matra]

I have the correct information on this matter.

The Politecnic Gr.4 set consisted of a special hemispherical head, with bigger valves, double springs, modified intake ports, small spark plugs and a wider exhaust.
It was delivered with a special camshaft, which was available in two stages, 184cv and 200cv. (these figures are real figures as on bench tests).

A few of these heads were made for the Rallye Monte Carlo cars, and later for some rallyecross operations.

Whatever was left they put for sale on their brochure, (in numbers not more than 2 sets). The last set was bought by us in 2001 and put on a Murena S.
(The photos of the engine bay of a Murena S with double Dellorto's is in fact our car).

These are really potent kits and are not comparable to whatever is on the market today.

Thank you for your reply and the confirmation of the true facts.

When you say the photos of the engine bay are of your car, what photos?  I see no photos here, or are you referring to the photos in that an old Politecnic brochure?

Roy

[Murena1400]

Roy,

The photographs of the Murena S engine bay on the Politecnic website are in fact of our Murena.

But it seems the photograph is gone, there are still some photo's on the "Moteur complet" page (the right one, with the carburettors, it is the special head.)

[Henk]

Hello,

I'm Henk Scholte from the Netherlands. I am restoring my Matra Murena 2.2 from 1983 which is almost done. I had a donor car so lots of extra parts and therefore a spare engine.
This one will be repaired. The camshaft looks quite good, and I want it machined to the Holbay specs. I allready found a machine shop for this. As I understand the Holbay will work fine with the standard Solex carb.

What i'm unsure about is the ignition. Will this have to be changed also, or is adjusting the timing enough?

Thanks.

Henk

[roy4matra]

Hello,

I'm Henk Scholte from the Netherlands. I am restoring my Matra Murena 2.2 from 1983 which is almost done. I had a donor car so lots of extra parts and therefore a spare engine.
This one will be repaired. The camshaft looks quite good, and I want it machined to the Holbay specs. I allready found a machine shop for this. As I understand the Holbay will work fine with the standard Solex carb.

What i'm unsure about is the ignition. Will this have to be changed also, or is adjusting the timing enough?

Thanks.

Hello Henk,

No, the ignition doesn't need to be changed, it is fine just as it was originally.  You don't even need to adjust the timing.

I have run a Murena 2.2 for many years and many thousands of kilometres with a standard Solex 34 CICF carb. a standard camshaft reprofiled by Holbay to their 58C profile, commonly named the Tornado cam, a four-into-one gas flowed exhaust manifold and stainless steel silencer with one tail pipe on the left like the original. It has the original Bosch distributor, standard electronic specification 12v coil, standard amplifier, and standard 10 degree BTDC static timing, using NGK BP6ES plugs and it runs fine. It also has a lightened flywheel. It produces around 140 genuine bhp. The Murena 2.2S was rated at 100 kW on the Certificat de Conformité and that, when it is correctly converted to bhp, is only 134 bhp. The claims of 142 bhp are erroneous as the incorrect conversion factor was used in all the Matra advertising. This has all been detailed on my website for years.

I have owned a genuine 'Prep 142' and driven a genuine 'S' and I know mine is slightly quicker as well as being better on fuel economy since the 34 CICF down-draught carb. is more economical than two twin side-draught carbs. in normal fast driving, and I get between 10 litres per 100km (worst) and 7.1 litres per 100km (best) (that is between 28 mpg and 40 mpg!) and I mostly drive fast but I do have the high 5th gear fitted which I pioneered! I would normally easily achieve 8 litres per 100km or say 34-35 mpg on a run. Even before I fitted the high 5th gear I would easily get 8.7 litres per 100km (33 mpg).

Roy

[Henk]

Sounds great Roy!

What I want/need to do is first get the Murena driveable, get the gas installation removed  from the carregistration and then the APK (MOT in England). Then the car is road legal. This is almost done!

In the main time I will revise the second cilinderhead and fit it with the Holbay cam. Make a good exhaust and get the 2nd flywheel machined. When all that's done exchange the original with the revised one, and off course fit the new flowed exhaust and lightened flywheel. This will take a couple of months. Enough to get used to the Murena and notice a difference in performance.

Thank you very much!

Henk

[Henk]

I've send the cam to the machineshop last week for regrinding it to the Holbay specs. I noticed one of the camlobes is badly worn, as is clearly shown in the picture. Only one, the others are fine. How is that possibl.... So not a moment to soon. I expect the cam back in a few weeks. Before it's back I will clean the engine and prepare everything so I can fit the faster camshaft quickly.

[JL]

That does not look particulary good, when you fit the new/reground cam you will need to fit either new followers or get the existing ones refaced(if they are in good enough condition). I would also check that valve and spring assembly to make sure that there is no undue stiffness or sticking to cause that amount of wear also do not be surprised if there is not enough of that cam lobe left to allow a regrind.

Good Luck
John

[roy4matra]

I've send the cam to the machineshop last week for regrinding it to the Holbay specs. I noticed one of the camlobes is badly worn, as is clearly shown in the picture. Only one, the others are fine. How is that possible...

First thing Henk, have you removed all the rocker arms and kept them in order so you know exactly which position they came from?  Have you checked that all the exhaust rocker arms are the ones with oil holes on the underside as this lubricates the system on that side?  The inlet rocker arms don't, or should not, have an oil hole on their underside.  They have oil fed from the rocker shaft internally.  Having both sides correct is very important.  Over 90% of all the engines I have stripped, with cam wear on various lobes, have been previously rebuilt by someone who did not keep them in the correct place and there were arms with oil holes on the inlet side and some without on the exhaust side!

With that amount of wear even on only one lobe and rocker arm - and that rocker arm will be bad and should be replaced too as I doubt it can be refurbished, but if they do manage, it will certainly need the case hardening to be redone.  I have seen this so many times and it shows how many people overhauling engines don't really know how!  Also with that amount of wear, all the material that has come off will have circulated with the oil and you need to check everything for wear now.  Particularly the oil pump, and all bearings on the crankshaft, as well as totally cleaning out the oil system to get rid of the abrasive oil and metal swarf mix.

As JL has already said, I would be surprised if they can recover that cam because of the amount of wear on that one lobe, but if they have rebuilt it up and reground it, they must have also redone the case hardening.  Make sure they have done that to all the lobes.  But you must not rebuild this now without refurbishing all the rocker arm pads.  You do not use worn rocker arms against a newly reground cam, because it will not last if you do.  I know at least two owners that did that and the cams were shot in less than 10,000 km.

Roy

[Henk]

Thanks for the input guys.

Thanks to this site I am aware of the order of the rocker arms. These were mounted in the right order. I removed and cleaned them and I will put them in back in the correct way. The rocker arm of the worn lobe was also damaged. This was not as bad as the lobe and it could be salvaged by a light regrinding, hardening and polishing. The other arms will be regrind also. All valves are cleaned and polished, and the springs are alle fine. I also refurbished the waterpump, again with help to the info on this site.

But I found this cilinder head wasn't original. The upper engine mount mounting points are welded on, so it's probably from a Tagora or 180. The head of the 2nd motor however is original. This one is also been totally refurbished (as above) and is as new.

Further the oil has been removed, engine and pump cleaned and new oilfilter mounted. I found no pieces of metal in the old oil. Hopefully the filter caught the particles. I will change the oil and filter after a few rides, to be sure.

The cam itself is now at a specialist who will be welding the worn lobe, than regrind it to the Holbay specs and give it a hardening treatment.
I expect to have it back in a week or 2. Can't wait to put it in the car.