Hi Daniel!!

Great pic!!! From the pic it actually looks to me like the bearing is larger in outer diameter than the crank pulley which means bearing RPM will be less than engine RPM. Here's two other pics from goober's site which seem to show the same thing to me:





If the bearing is smaller, the difference is quite small. If we assume the radius of the crank pulley is 3 cm (think that's pretty close from a very rough measurement on the cam pulley w/ timing belt cover on - ~6cm) at 7500 RPM on the crank (the start of redline on my tach) a bearing w/ a radius 3.5 mm smaller (2.65 cm) would be turning at ~ 8500 RPM and the SKF handles brief excursions to 8500 right? At 7000 RPM a bearing that much smaller would be under 8000 RPM ...

I haven't heard from anyone on crank pulley diameter (or cam pulley diameter - should be twice the crank). Let's see what the weekend brings. Thinking about it I'd be very surprised SKF would offer a fully sealed replacement bearing that didn't at least meet original specs so my speed worries are likely not worth the effort :-) Bearings look bigger in the pics anyway ...

Best regards,

Bryan

I have to get the exact diameter when i remove the bearings and the belt.. Bud I dont think the 3205 bearing should be a problem, even if i rew the car to 7500... Do you have some news Bryan?

Best regards Daniel

Hi Daniel!!

No updates unfortunately, still trying to get measurements on the crank pulley diameter or the cam pulley diameter. I have some inquiries out further a field, but no 'bites' yet. Once we have either the crank puley diameter (preferable) or the cam pulley diameter, we can compare that to the 'galoppino' - sprocket? covering the bearing which is (rough measurement at the moment) ~ 7 cm in diameter. That, I think, is the critical dimension as that diameter should 'control' the RPM of the bearing ... I looked at the parts breakout again and then at my car and realized there is a cover w/ a spacer on either side (which may help a bit in sealing) over the bearing and this is what is in contact with the belt. Bearing diameter is 5.2cm, the cover is obviously larger.

If you get your car apart, we should certainly be able to answer this concern. Again, I think it is a red herring - why would SKF make a new bearing that doesn't meet the specs of the old part? The folks I am talking to at SKF are definitely recommending a fully sealed bearing - the 2RS1 designation you have. They also say the TN9 designation is a special glass fibre cage - when the bearing loses grease it will still rotate for a while in this cage and screech loudly to warn you of impending failure. the 5205-A2Z bearing I have will simply fail ... Not good.

Please let me know what you find when you can get at your car and make some measurements. I'll do the same if my inquiries 'bear fruit'.

Thanks and best regards,

Bryan
'74 P250S S/N 15622
Indianapolis Indiana USA
blissinindy@yahoo.com

Hello Bryan

Thank
you fro all your effort and great answers!

It seems to me thet the 3205 bearing i have is the way to go.. That it will make a sound before failure seems to be the best, instead of just breaking.. Does it just fail, with no further warnings the 5205 bearing? that seems no good..

I just have to wait and get my mechanic to meassure the size of the crankpulley.. If the Crankpulley is the same size or smaller than the outer diameter of the bearing there should be no problems with the 3295 bearing I have right?

My mechanic will look at my car in the end of this month, so I hope to get som more answers then..

Best regards

Daniel

Hi Daniel!!

Still not able to get any definitive measurements - looks like we'll have to wait for your mechanic. In the meantime I did see this eBay auction:

http://cgi.ebay.com/ebaymotors/Lambo...ayphotohosting

eBay item number 140116118416.

Ignore the title on the auction and look at the bearing box. The Lambo part number marked is 8502501 - that's the part number for the 4 bearings. The SKF part number on the box is exactly what you have: 3205 A 2RS1 TN9/MT33.

Remember, the bearing rides in a housing and it is the housing radius relative to the crank pulley radius that is key.

I think you are on a good track!! Let us know what your mechanic finds.

Best regards,

Bryan
'74 P250S S/N 15622
Indianapolis Indiana USA
blissinindy@yahoo.com

Hi Bryan

Thats the one... I've seen those bearings on ebay before.. This must be the bearing to use?

Have you talket with Chelle about what bearings they did use in their blue urraco? I talked with Caleb and he mensioned that you know eachother...

Daniel,

I really apologize for being out of touch for soooo looonnngg!!! I've been ill. Am getting better and getting back into the car.

What's news on your bearings and your gearbox (!!) for that matter?

Found some old correspondence w/ Kim. She used SKF 3205 ATN9 bearings. Same size as those you have, but not sealed. My memory says a Lambo dealer gave her the SKF part number.

Best regards and again I apologize for not responding way sooner!!!

Bryan
'74 P250S S/N 15622
Indianapolis Indiana USA
blissinindy@yahoo.com

I didn’t see this thread before, but reading it very quickly you seem to be on the right track. To calculate the rpm’s of the idler wheels you have to measure the outer diameter of the belt when it is wrapped on the crank pulley and then compare it to the diameter of the idler wheel: rpm of idler pulley = Dc/Di * rpm of engine.

There are open, shielded and sealed bearings. Since the idler wheels are quite exposed, sealed bearings are the best to use, however they typically also have the lowest rpm rating (to maintain seal integrity).

Unfortunately I am not familiar with the details of rpm ratings. Except for the sealing, I find it hard to believe that they are independent of the load and the idler wheels are not loaded very hard. Also, the typical failure more is quite “soft”, typically starting with a noisy bearing. In other words I wouldn’t be too concerned about exceeding the rpm limit slightly.

Brian, in the last picture your engine appears to have a lot of calcium deposits in the cooling area, which is not good for the cooling performance. I hope it has been cleaned out since the picture.

Laust

Hi Laust!!

Sorry for the tardy reply!! I am still on the mend and not keeping up w/ the threads on all sites ...

Been a bit sidetracked on the idler bearings. Have realized that there will be plenty of re-chroming folks at Auburn this year (which is pretty close to me) so I decided to pull my chrome and stainless trim and take it up to get quotes, dicker and get it redone ... Will get back to the idler bearings soon ...

Nice to know about the typical failure mode!! I did pull the idler bearing for the dizzy/alternator belt. It looked 'clean as a whistle'. The steel shield is not bad (not a perfect seal of course) and the outer housing that fits around the bearing provides some protection against incursion ... Particularly given what you're saying about audible warning of failures, I'm probably okay w/ what I have, but I think I'll replace them anyway ... it's been a while on the belts, even though the car hasn't driven much in that time ... :-(

That's not my engine btw, that's Goober's in Australia ... friend of Daniel's w/ lots of good pics posted on the net ... That being said, I looked at the pics again and I don't see the deposits ... There's a lot of variance in the lighting, perhaps I am mistaking deposits for glare? Could you let me know which pic shows the deposits so I can learn what to look for?

Thanks as always :-)

Bryan
'74 P250S S/N 15622
Indianapolis Indiana USA
blissinindy@yahoo.com