How long will these last ? Grady ?

[pjv911]

Also will these offer notable difference ? The price seems pretty fair but im wondering if these are releliable enough for street use at about 2k miles a year .

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=4516192585&fromMakeTrack=true

Kurt Williams

[Craig 930 RS]

It sez they are "race approved"

[ianc]

Probably not that long running against a steel chain.

But the question is, why would you want them? Trying to save a couple ounces?

ianc

[pjv911]

Its the same theory as a lightweight flywheel . a NEW COMPLETE SET OF STOCK OEM STEEL GEARS WOULD RUN OVER(dam cap lock) $300. Why not spend a little extra provided they will hold up . In theory they should last . They tend to last on moto x bikes . Thats a steel chain and aluminum gears without lubrication , plus some sand . Paul wier has been relisting(on ebay) an incomplete set for the past year now . He wants much more money too. I figure if porsche used them there must be an advantage . Question is will they last . Grady is the one guy on this board that my have first hand feedback on these . I guess he is not online tonight.

Kurt Williams

Kurt Williams

[pjv911]

Also its much more than ounces . I would figure a 2 lbs savings at least .

Kurt Williams

[thabaer]

Originally posted by pjv911
[B]Its the same theory as a lightweight flywheel /B]

But about 1% as significant ? OK, that's just a wild guess but probably not far off the mark: they rotate at 1/2 the rate on a much shorter lever arm, thinner, perforated....

Unless you've really run out of things to try I'd look to other components first with more $$$bang.

Good sick-puppy quotient though

[sketchers356]

Since the cam gears etc are hard conected to the flywheel wont lightening them do the same as lightening the flywheel, a much easier task imho. Seems like a waste of money to me .

[Grady Clay]

Kurt,

I have three sets in three 2.5 (91x66) race engines with stock steel chains. One has at least 300 hours which would work out to some where in the 10-20K mi range for the street. They have not shown any wear and don’t leave any tell-tale aluminum in the sump or filter. You just have to remember these engines were disassembled for inspection, bearings and rings every 25 hours. They were always running in the 6-8500 RPM range.

To answer your question, yes they would work and are cool parts.

Buy them and hang them in a shadow box and use steel sprockets. The down side of using the aluminum sprockets is they have less rotational inertia, greater inertia is important for the valve train at idle and low RPM. That is why a failed chain tensioner rattles at low RPM and not at high RPM. The 4-cam Carreras (547, 692, 587, and more) had actual flywheels on the camshafts to protect the drive gears at the expense of light weight and low rotational inertia.

You have to remember that these aluminum sprockets were just part of an overall package of light weight parts – Ti rods & bolts, Ti jackshaft, 906 rocker arms with valve adjusting caps, light clutch & flywheel, and more. The purpose was to reduce the rotational inertia to allow for greater angular acceleration. Of course it also lightened the overall engine and additionally had FG tin and Ti hardware, etc.

Best,
Grady

[Craig 930 RS]

Damn. Now THAT was a definitive answer. Love it -

[Grady Clay]

Come on - - - I hate making “definitive” answers. This is a DISCUSSION Forum. I make at least one technical mistake per month and don’t mind being hauled on the carpet for my opinions. Please feel free to question anything I post. The spice of life is arguing one’s position. I regularly play “devil’s advocate” and am known to change my position upon reflection or contrary evidence.

Best,
Grady