Spun Bearing Pics

[Dan Himan]

I finally got around to dis-assemble my spare engine, and as i suspected, spun #2 bearing.



I was really happy to find my cylinder walls are still in good shape.
The question is how to proceed? I know I need to have the crank checked. Do I have the rod resurfaced? I realize that I will need an oversized bearing, can I just do the one rod?

[Dan Himan]

What is a crossed drilled crank, any pics? I read that the crank scrapper helps avoid this spun bearing issue. Is this correct? I did install one in my 87 S. I did not have the money to get the tray. The crank seems to spin fine with no play, is it possible to reuse the main bearings (not the rod bearing)?

[desertt5]

Subscribing. I am sure I lost or am about to lose #2. Comp check read only 80psi or something like that. I only have the head off so far. Cylinder walls look good too. Head at the shop being checked out as of today. Not sure what I am going to do with it. The rest of it is getting parted.

[Pete R]

I would take the crank out and have it magnafluxed, measured and polished. You could bring the con rod to whoever does your crank and have them look at it. It's so torn down now, not doing main bearings is not very cost effective. It may has well all be fresh. A cross drilled crank reroutes the oil passage so it flows easier to the #2 bearing at high rpms.

[John_AZ]

Originally Posted by Dan Himan

What is a crossed drilled crank, any pics? ?

Pics:

Rennlist Discussion Forums - View Single Post - Re-ring question for the guru's

More info Member Dare rennlist (his pic link also)

The following post contains a very helpful picture of a 928 crank that has cross drilled oil passages in both the main and rod bearings. Although a 928 crank is considerably different from a 944 crank, I think the picture does a good job of illustrating the routing of oil passages in a crankshaft and the concept of crossdrilling.

http://forums.rennlist.com/rennforums/3855652-post10.html

On the 944 crank the main bearings are all cross drilled. However the rod bearings are only 'half-drilled'--i.e. the passages don't go all the way through. Cross drilling the crank involves drilling the rod oil passages through to the other side of the journal and chamfering the edges of the new oil feed hole. Typically this is only done on the #2 and #3 bearings.
__________________
Jay


John

[vdubr928]

Originally Posted by desertt5

Subscribing. I am sure I lost or am about to lose #2. Comp check read only 80psi or something like that. I only have the head off so far. Cylinder walls look good too. Head at the shop being checked out as of today. Not sure what I am going to do with it. The rest of it is getting parted.

Rod bearings will ABSOLUTELY NOT affect compression. Its either intact or broken. If it was broken compression would be 0. You have a different problem.


Crank scraper keeps oil in the pan. Thus making the pump less likely to starve. For sure helps prevent bearing failure. This also frees up hp because the crank isn't carrying that extra weight.

Cross drilling also helps oiling.

Windage tray will help cut down on oil in suspension and free up even more hp.

These are all positive things. I would ditch the cross drill but do the windage tray and scraper.

[vdubr928]

No. You can't just do one. Maybe you can but really bad idea. Keep it simple. The crank will need to be polished at least.

[Techno Duck]

Personally, with the amount of used parts floating around for these cars i would replace the crank with a used one (all 2.5L cranks are the same and dime a dozen) and find yourself a spare 16v rod. By the time you factor in the cost of machine work for your damaged parts and the cost of oversized rod bearings (about $100 each from Porsche) i think its more worthwhile to go this route.

You should take the girdle off anyhow to flush out the oil passages aswell as the oil cooler. You dont need to replace the mains but with the girdle already off you are only $180 away from replacing them.

What is your intended use for this motor when you get it running? If this is strictly a street engine i would save the money and only baffle the pan and replace the pickup tube. Even if you intend to track and want to do this on a relative tight budget, i would go crank scraper and crossdrill at most. The windage tray from IJ is not cheap.

[vdubr928]

True. I probably have some stock rods.

[333pg333]

btw, what oil have you been using?

[krystar]

remember when u put it back together that the girdle surface needs to have sealant applied before bolt it back together. AND the front need to have sealed too before the oil pump goes on. that cost me a boatload of hassle and a trip to the shop.

when i had mine apart, i crossdrilled #2 and #3, polished, new rod bearings, new rod nuts (important!), new mains, new pilot bearing, new front main seal, new rear main seal. do it all while it's apart. my oil pan was already baffled, pickup tube already reinforced.

[Dan Himan]

I purchased the 87 S with a seized engine, and just replaced. I plan on rebuilding the spare just for street. I definitely want the engine to perform and last. Replacing the crank and rod sound like the way to go. Scraper and tray install for sure. The cross drill seems like it could compromise the crank.
The 88 S might need rings and rod bearings, still runs strong, I might replace with engine in place. I don't know, maybe wait till the replacement engine is done. It sure is nice to have options thou.

[Dan Himan]

Originally Posted by vdubr928

True. I probably have some stock rods.

I would need the 1 S rod, right (higher compression)? The other 3 look good. I did notice the numbering on the parts, all 86. I am going to do some measuring tonight.

Thanks everyone for chiming in.