Cam chains

[Nick Paul]

Anybody know the difference between standard cam chains and sport versions I assume sport type are lighter / stronger but not sure?

 

[chrishak]

Looking forward to the answer to this one - I didn't think there was such a thing as a "sport" engine for a Carrera 3.2. There was a Club Sport engine of course, but that's unique to the CS version and consists of lighter valves and a re-map, allowing a higher rev limit (plus various other rumoured, but never confirmed, mods.)
The 3.2 Carrera Sport had suspension and aero mods but nothing else as far as I am aware.

 

[911 targa]

Again Cris you are correct,sportchains never heard of these.
Asyou know my car is a sport with a M30 race package,which makes matchsticks feel like speedhumps.
Paul

 

[Beaky]

Ditto the above, in all my research never came across Sports Chain, perhaps this maybe referring to say the 964 cam modification as opposed to chains.

On the CS, I'm also led believe that the engines were blue printed

 

[vitesse]

As an ex Renold Engineer,I have never heard of sport chains-when I worked there ,Porsche used Renold Chains,in their engines usually British Standard 3/8" pitch Duplex (double row) chain always made to tight tolerances with straight sideplates (for tensioners).

Hans Renold invented the bush/roller chain & the British Standard was based on his designs,which combine the best balance of tensile strength,weight & bearing pin/bush areas to give suitable life with HP rating.

Overall life is determined by both component wear capability (which is dictated by case hardening depths on the pin/bush) & fatigue life & generally chains normally wear out before reaching their fatigue life-obviously steels used are slightly special & metallurgical advances plus control of tolerances have helped chains to keep up with engine power advances-it is becoming more common for camshaft drives to revert back to chain from belt as engine powers increase with smaller engines these days.

Yes ,you can increase strengths & this would cope with higher peak loads in camshaft drives but then the wear factor still restricts the life which is no good for road cars.

However on racing motorcycles,where all you want is a chain to last the race with certainty,then strengths are increased,rollers softened so they don't crack etc but then changed every race.

 

[911 targa]

WOW

 

[chrishak]

ORIGINAL: 911 targa

WOW

WOW indeed. I said it would be an interesting thread!

 

[vitesse]

I wouldn't accord "wow" to some of my knowledge -however correctly engineered camshaft drives having sensible sprocket centres ,sensible sprocket sizes .oil fed automatic adjusters,chain damping blades should give troublefree performance,when you consider that a typical 1.5ft chain length has 378 precision manufactured components with appropriate heat treatment,centreless grinding,end softened bearing pins,interference fits & each production length of chain run in on special machines under load in an oil bath.

Correct alignment is a requisite & with the correct sprocket tooth profile,wear equating to 2% can be accommodated but at this point ,the chain would be at its wear life as all case hardening will have been used up,but this would be expected to also mean engine life .

Of course 1 bad drive example is the cam to cam drive on the 16 valve 944/968 engines -very short centres coupled with small sprockets & the use of a connecting link which allows the link to alternately stretch/contract-bad for fatigue.