centre lube cams

[obrut]

the 2.0 motor in my new 1969 911E has 906 centre lube cams (as well as a bunch of other 906 trickery...). however, the centre lube oil components are not present.

any idea what components i would need to add the centre lube setup?

also, if i stick to a 'sensible' rev limit (say 7500 rpm) will the centre lube oiling really make much of a difference?

[gumba]

You need the 906 cam chain housing covers that are set up to feed the cams. The 906 cams also used a special cam nut. I had 906 cams in my 2.8 twin plug. Came alive at 4500 and pulled to over 7500. I ended up selling the cams as I was told there were better cams to use. Here is a link to some shots of the cam covers, and the cams.
http://www.pbase.com/9146gt/my9146gt_engine_906_chainbox_housings
http://www.pbase.com/9146gt/my9146gt_engine_906_camshafts

[obrut]

thanks!

[MBEngineering]

HI obrut which cam nuts are on the cams 46 or 41mm , if you have 46mm you will need tool No' P203 to remove the nuts, if you have 41mm nuts, tool No'P139 (if you can find one) , as gumba has said the 906 cams have a small nut and a fine thread. What other bits has the motor got on it ??

regards mike

[obrut]

hi mike

i haven't yet got any paperwork from the PO. however, from a chat, it has the original (but modified) MFI, bored out mag stacks, 906 centre lube cams, 906 titanium Rods, 906 Mahle forged pistons, pinned & dowelled crankcase, 40 mm ported & polished ports and matched primaries and pipes with short headers and two big oval mufflers. it also has a close ratio 5 speed 901 gearbox with factory lightweight gears.

its magic to drive and revs like crazy. pretty easy/tractable to drive from 2500 to 5000rpm, then a big surge when the cams kick in at about 5500rpm.

[obrut]

ps. no idea on the cam nut sizes as i haven't opened it up (and hopefully won't have to for a long time)

[Porschekid962]

That sounds like a pretty fun little motor you have got yourself there. Just one word of caution. Titanium has an extremely short service/fatigue lifecycle. It might be in your best interest to shelve those Ti rods now before one lets go. As of today the factory puts a 40 hour time limit on the Ti con rods in DP and RSR motors. The small end begins to elongate and the large end goes out of round as well. Just a heads up.

Center lube cams are slowly making a comeback in motorsports, shame no one makes some updated chainbox covers with center lube cam fittings on them...

[MBEngineering]

HI obrut if at any stage you have to pull it apart give me a shout .

regards mike

[kenikh]

Originally posted by Porschekid962
That sounds like a pretty fun little motor you have got yourself there. Just one word of caution. Titanium has an extremely short service/fatigue lifecycle. It might be in your best interest to shelve those Ti rods now before one lets go. As of today the factory puts a 40 hour time limit on the Ti con rods in DP and RSR motors. The small end begins to elongate and the large end goes out of round as well. Just a heads up.

Center lube cams are slowly making a comeback in motorsports, shame no one makes some updated chainbox covers with center lube cam fittings on them...

I have been in Porschekids camp on Ti rods for a long time, but I am starting to waver. If the 997 can run Ti rods on that HUGE stroke (yes, I know some have let go, but those have been on race cars), 2 liter cars with occasional runs to 8000 RPM should have a long service life. Having heard of a number of cars running original 906 Ti rods from day one until today, I think it is safe to assume that the 906 Ti rods are good.

[chris_seven]

The theoretical problem with Ti rods is that unlike steel Titanium does not have a well defined Fatigue Endurance Limit and aero engine parts made out of these material tend to have a finite service life and i believe this is why they were given a 40 hour life.

Providing the rod is in a good mechanical condition, ie straight and not cracked it is possible to deal with the fatigue life issue.

After the rod has been measured to make sure that the ends are in tolerance I would have the rod crack detected and I would tend to used an FAA approved test house.

The rods can then be treated using controlled shot peening which will eliminate the surface dislocations that lead to the initiation of a fatigue crack. This process needs to be carefully controlled and we have a company here in the UK that has developed this technique for reclaiming 'end of life' aero parts and have CAA/FAA approval. The research that they have done shows excellent results and they have carried out a detailed series of experiments to prove the technique.

Cost is about $300 per set of rods and this includes supply of nylon coated side plates used to protect the thermal or plasma moly coating and the bores of the eyes. The rods would need to be assembled with reduced head bolts to allow access to the radii.

I am sure that ther must be companies in the US with the same capability, probably somewher near Indianapolis of Cincinnati.

If not I can ask the guys they use if they have an American Partner.

[Porschekid962]

I am all for using go fast goodies as much as possible. The main reason I brought up the rods was this is a motor that has an unknown internal condition. If it was known then making a decision would be much easier. In terms of comparison I understand this motor wont be flogged about as much as an RSR of today but also take into account the fact that the RSR pistons are extremely lightweight versus the older units. I am not sure if shot peening the rods would be advantageous, perhaps a very fine shot peen as the rods on most motorsport engines I have seen are treated a different way and its not shot peening. My main worry with these rods would be with the large and especially small end being out of round. Aside from that if they pass an FAA certed test I wouldnt have qualms about using them.

Just a fun aside, there is a reputable rod maker that has a special metal which is some house blend they came up with. They are capable of manufacturing a steel rod to the point where the difference between a Ti and steel rod is negligable. Standard I beam racing style rod with no nuts, just bolts.

That reminds me, perhaps I am rambling. I consulted my Bamsey history of the F1 v10 book and through many of his interviews one of the initial problems with Ti rods was galling where the bolt and nut made contact with the Ti, just another thing to look for. This was solved with a Ti bolt and a crushable Ti washer under the nut before the nut itself was elminated from the design.

cheers

[obrut]

kenik

i'm with you on this one. this motor was very carefully built about 8 years ago and has only done about 2000 kms since (including 5 or 6 short races shifting at 7500 rpm)

"Having heard of a number of cars running original 906 Ti rods from day one until today"

agreed - and we must remember that these rods were not built to the 'minimum size' requirements of an F1 rod

i'm happy to keep 7500 as my shift point and i'm sure it will last for many years (of light race/street use) to come.

[tadd]

Porschekid:
I'm not so sure I agree with your logic on piston mass. As you well know, the newer motors are rather large bore (100 mm or so?). Even with slipper skirts and flat tops, I would still bet that an 80 mm piston will contain at an absolute maximum as much material as a 100 mm piston. Area does follow a square dependance so as the bore increases, the material in the piston grows (and thus mass) quickly. I would have to say that a 2.0 is swinging a lot less material around than you late model big bore guys. Less mass, less forces from spinning at 8k.

By their nature rods are a near perfect choice for Ti - very few interfaces to gall or induce surface defects. Titanium used to be traditionally polished as it is notch sensitive. So, remove all surface defects to below a certain size by polishing, and no stress concentration points for a failure mode. Shot peening is better than polishing by an order of magnitude, IIRC, (as I am sure you also know by putting the surface into compression). Now a force not only needs a defect site to start propagation at but also the force level has to be larger than the compressive force in the surface treatment. What Chris is bringing to the table is way, way keweler. Your Ti rods are 'worn' out since after so many trillion cycles, you have a bunch of surface defect that the compressive layer is keeping in check. Eventually statistics catches up with you - enough surface defects and one will eventually garner enough energy to 'break free'. However, as I understand it, these folks can just re-shot peen the surface, and for a waving of hands argument, 'beat out' those surface defects. No more surface fatigue buildup = 'as new' $300 ti rod set! I have not seen the data, but tossing out a guess, I would think the process should be repeatable several times. If this were true, one might almost consider the process as a prophylactic measure.

There are some new steel recipies that are quite a bit less dense than say 300M, that close the gap with Ti, but that gap is still about 25% (unless this is something within the last 6 months I have not seen. I went and bought my Ti rods and thus stopped looking ). The 'lightweight' steels carried a premium on something like 300M and were less stress riser friendly to boot. So in balance, Ti was still the material for me. To be honest, best I have been told, Ti has an artifically high price thanks to a USA tarrif. The Russians and the Indians make quite a bit of the stuff anymore - it should be competive in price with the high end steels if not cheaper. IIRC, there was a $500 material surcharge to cover the tarrif when I had my rods made a few months ago. It is an amazing material when used correctly.

tadd

[chris_seven]

As Tadd explains the idea of using controlled shot peening is to remove the deftect sites that have been created by the cyclic stresses.

The idea of using a small diameter shot is not isn't guaranteed to be the correct approach. The idea is to introduce residual surface compressive stresses in a controlled manner. The size of shot, the velocity of the shot and the screening used to remove broken particles is all part of the procedure. Any change to these parameters many not produce the desired result which is why I would always leave this work to a company that has good experience in this field and has carried out a defined test programme.

Just crack detecteing a Titanium component isn't quite good enough. A components fatigue life is always dominated by the number of fatigue cycles needed to initiate a crack. Once the crack has formed then life will be very short and the component is essentially scrap.

I am unaware of ant Non destructive test that will determine the amount of fatige damage that has accumulated prior to crack initiation, hence the reason for using shot peening.

If the rods were new then it would be easier to determing the service life, particulalry with modern data loggers but shot peening is still a good insurance policy.

I am sure that there are other surface treatments that could be applied to new rods but in virtually every case these treatments will rely on introducing compressive residual stresses in the component as a means of improving fatigue crack initiation life.

I would always try to select a component manufactured from a know alloy with good data about k theshold stresses and fatigue crack growth rates. Developing special steels is a complex business which has a very high cost and carrying out the relevant fatigue tests takes quite a long time.

I would think that S300M is not a bad choice as it is well qualified and there is good data available but there are probably some of the Maraging Steels that may offer a beter performance but at a significantly higher price.

I don't think that the density variation of the ferrous alloys used for making rods will have any significant impact on component weight it will just be a fatigue strength issue.

With regard to Titanium costs it may be worth looking at the Indian market.

http://www.midhani.com/Products_Gr.htm

Midhani have manufactured a wide range of specialist aero engine alloys for about the last 15 years and thier Titanium Alloys have been developed using Russian formulations.

I spent a few years working with these guys and helped with the installation of their fatigue testing labs.