MatraSport Forum

Each model => Murena => Topic started by: Anders Dinsen on July 29, 2025, 05:52:38 am

Title: Murena 2.2 / Chrysler 2L cam shaft specifications
Post by: Anders Dinsen on July 29, 2025, 05:52:38 am

Just out of couriosity, I’ve been keeping a list of cam data for the Murena 2.2 engine. Recently I discussed with Youri from this forum that it would be a good idea to share them here. I’ll be updating this list if I receive corrections or details on performance or engine configurations, so please send it to me. Please feel free to use the thread to discuss and share stories about the cams and engine configurations.

Type	Lift (mm)	Timing	LCA inlet exhaust	Periods inlet exhaust	Overlap	Timing lift	Clearance inlet exhaust (mm)	Engine configuration
Stock	6.5	19°12'/56°48' 54°48'/13°12'	108° 110°	256° 248°	32°24'	TBD	0.2 0.3	Bosch distributor and single Solex carburettor.
K142	7.4	27°/72° 69°30'/29°30'	112°50' 110°	279° 279°	56°30'	TBD	0.2 0.3	Murena S, twin Solex ADDHE 40, Ducellier distributor, stock cylinder head.
Politecnic Maxiroute/Gr.4	7.75	30°/86° 78°/42°	118° 108°	296° 300°	72°	TBD	TBD	200 hp claimed on cars entered for Rally Monte Carlo with 47x40 valves, ported head, large intake, 50 DCO/SP carbs
Holbay Tornado 58C	7.06	39°/77° 79°/37°	109° 111°	296° 296°	76°	TBD	0.25 0.3	Fastroad cam with stock head, carburettor, and distributor
Danielson K230	7.45	21°/77° 85°/24°	118° 120°50'	278° 289°	45°	TBD	TBD	Turbo
JRD No 1	7.0	34°/71° 68°/32°	106°	285° 280°	66°	0.5	0.25 0.30	Designed for a racing class defined by Simca with Chrysler 2L engine and Lola or Chevron chassis
JRD No 10	TBD	31°/62° 58°/35°	105.5° 101.5°	273° 273°	66°	0.5	TBD	For rally
Condrillier	7.5	35°/85° 85°/35°	115°	300° 300°	70°	TBD	TBD	Designed by Condrillier as a fast road camshaft
Piper 3777	8.3	46˚/72˚ 74˚/44˚ (estimated)	109 111	298˚ 298˚	88˚	10 thou = 0.25mm	0.25 0.30	TBD

Notes:

Lift is measured on the cam. Rocker arms multiply this by a ratio and the clearance is subtracted from that number to get the lift the engine sees at the valves.

Timing lift is the lift (on cam) by which the periods are measured.

Unless there’s an adjustable cam sprocket installed in the engine, cam timing is fixed.

Timing angles are specified as: Inlet opening BTDC; inlet closing ATDC; exhaust opening BBDC; exhaust closing ABDC.


Some definitions:

LCA: Lobe Centreline Angle
TDC: Top Dead Center, piston at the highest point
BDC: Bottom Center, piston at lowest point
BTDC: Before Top Center, i.e. while piston rising
ATDC: After Top Center, i.e. while piston lowering
BBDC: Before Bottom Center, i.e while piston lowering
ABDC: After Bottom Center, i.e. while piston risinng


Acknowledgements:

Thanks to Youri Nieuwenhuizen for actually measuring and verifying the data on the K142, Danielson, JRD and Condrillier cams, and for calculating LCA's
Thanks to Roy Gillard for supplying me data on Holbay, K142, Stock, and Piper 3777 cams.

Title: Re: Murena 2.2 / Chrysler 2L cam shaft specifications
Post by: Anders Dinsen on August 05, 2025, 04:31:13 pm

So I thought I'd be interesting to see some actual performance documentation to start a discussion. This is a dyno run performed in 2009 with my Holbay cam on a stock unmodified head, twin Weber 40 DCOE carburettors, 4-in-1 stainless exhaust, and unmodified 2.2 Bosch distributor. It's many years ago, but I remember that we ran out of main jets or airs so we felt the top end could have been a bit better. My notes are not complete, but this is what I ran in the car until I started my restoration. I've only dynoed it this once so far:

Idle advance: 15 degrees
Venturi: 36
Idle jet 45F8
Main jet: 130
Emulsion tube: F9
Air corrector: 200

Title: Re: Murena 2.2 / Chrysler 2L cam shaft specifications
Post by: Anders Dinsen on August 21, 2025, 08:43:04 am

The objective of the cam is to time the airflow through the cylinder head by opening and closing the valves. There's a lot of theory and expeirence behind cam tuning, much more than I'm competent to explain, but I wanted to share these photos which Youri (Murena1400) has kindly shared with me and given me permission to post here as they show the channels the air is passing through when entering or exiting the cylinder.

The primary restriction on the 2.2 head is the inlet valve seat. The cross sectional area of the opening is simple to calculate by calculating the area of the circle inside the valve seat minus the valve stem circle area. The area of the valve opening is given by the lift of the valve multiplied by the valve seat circumference.

Increasing the inner diameter of the valve seat will increase both areas. Theory says that a restriction has effect on airflow when airspeeds become sonic as it's not possible to accelerate air molecules beyond the speed of sound. Remember that air flows into the head in pulses so the restriction can be said to "cap" the top of the pulses. Turbolence created by edges and the like also restrict a little, but generally turbulence in the inlet is desired as it assists mixing of air and fuel in the cylinder.

The pictures are of cut-throughs of an unmodified head.

Exhaust is even more limited as the exhaust valve (and valve seat) is significantly smaller. Exhaust restrictions affect performance far less than inlet on a normally aspirated 4 stroke engine.