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Author Topic: fast camshaft specs  (Read 2004 times)
roy4matra
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« Reply #15 on: November 06, 2019, 04:49:24 pm »

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. Smiley

Roy
« Last Edit: November 09, 2019, 09:10:47 am by roy4matra » Logged

GP
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« Reply #16 on: November 07, 2019, 08:01:18 pm »

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
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roy4matra
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« Reply #17 on: March 29, 2020, 05:00:33 pm »

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
« Last Edit: March 30, 2020, 11:17:42 am by roy4matra » Logged

Murena1400
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« Reply #18 on: July 31, 2020, 01:58:16 pm »

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.
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roy4matra
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« Reply #19 on: August 04, 2020, 12:40:07 am »

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
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Murena1400
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« Reply #20 on: August 04, 2020, 07:47:19 am »

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.)
« Last Edit: August 04, 2020, 07:51:49 am by Murena1400 » Logged
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