996 engine rebuld at home - Camshaft question

Hiya Everyone, Newbie here. I have used the site loads over the past six months during the tear down of the engine. But am at a bit of a stumbling block with the rebuild. basically the engine rolled a main journal bearing (next to number No 6) and then made a bit of a mess of things. The crank was totalled, so I sourced a replacement and had it checked over. I have installed new shells and all the usual parts that could be worn from debris, like chains guides, oil jets etc. Also having new sleeves and pistons put in as there was some scoring on the bores (nothing from the bearing, normal wear) so seemed sensible while I as in there. So...... it has kind of ended up as a full rebuild with new parts....... the wife is well happy! I am now getting the heads ready, so have installed new stem seals etc but since noticed after close inspection that the cams have wear marks. I now think I have an issue, as I understand that these are matched parts, so simply sourcing a second hand part may not be ok..... In reflection I should have checked the cams over, but didn't so I am where I am now. So questions are as follows, 1. Can I fit another (second hand) cam into the head 2. Do the photos of mine look normal for a 95k engine 3. will I get away with using the ones in the photo Sorry to sound stupid or tight, this is the first 911 rebuild I have done and the UK Indi's are proper expensive, as are new parts, especially when you have two kids and a broken Porsche...... doh! Anything you can say to help would be greatly appreciated. Cheers Sam

It does look like you have excessive wear there. The cams are interchangable so you should be able to get a suitable replacement. AutoFarm maybe? It's the camcovers that are machined in place & best to stay together for life. Don't forget to mike the cam lobes also!

ok that's great news actually, makes more sense now. I was wondering why all three parts were so tightly matched. I am up Manchester tomorrow so can check out Hartech and maybe Douglas valley and see what they have. More money no doubt, but rather safe than sorry I guess. Thanks for the advice ill let you know how I get on

What do the cam bearing surfaces look like?

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I have the same question. Agree that looks like quite a bit of wear compared with my own cams (120K miles). Since they are steel but ride directly in the soft aluminum head/valve cover with no bearings I would turn my attention to those surfaces.

Looks like you had some debris pass through... I'd be more concerned with the cam tunnels and journal caps in the heads.

thanks for the comments. I will take a photo in a minute and post it. Our of interest, are the tunnels or cam cover plated with anything?

Ok so here are the photos of the worse ones I can see. If I go get them measured, what clearances am I looking at as maximum if I can get these marks polished out? Or is this a rather depressing new head requirements?

There's no plating... Just a high silicon aluminum is used that can't be easily restored. Clearance should be .001- .0015" at maximum. These are my specifications, factory specs do not exist for this engine.

You can measure them if you want, but based on the appearance of the camshaft and the rough surface of the alum. camshaft bearings my opinion is the cam is shot as is the head. I know of no way (well, there is always a way if you have access to a horizontal boring mill and are prepared to re-line bore the camshaft bearings a bit oversize and source a cam with oversized bearings) to repair that damage. Also, JR brought up a good point and one I have to reinforce. Debris got on the clean side of the engine. That's never good. If you proceed with this rebuild you have to be very sure all of that debris was flushed out. There is no way to know this has been done though. There is a lot of faith involved. The debris can be insidious. For instance a piece blocks a piston oil jet. The cylinder/piston runs hot and the bore scores. Or oil flow to a main/rod bearing is restricted and the bearing seizes. Really, an engine that has experienced debris on the clean side is not a good candidate to rebuild.

Crickey! Ok thanks guys, not great news for me then. I will give it all some thought and see what I can figure out. Appreciate all the balanced opinions. Just so that I know, if I get the cases lined, is it possible to ensure they are debris free? or are some oil ways hidden? bearing in mind that the engine is at component level I figured I should be able to it in all the hideaways....... The crank and cradle are replacements so I know they hasn't got any debris in, and these have been split and cleaned just to be sure. So maybe I can get away with replacement heads........ and all the others bits like guides etc. Not ideal, but am working out if I'm too far in to stop or if I start over. I guess I now for next time (fingers crossed there isn't a next time), because of the bearing failure I was more interested in the bottom end initially.

Macster, please STOP giving out advice on this thread! The cam bearings can easily be re sized. Under cut the head and/or the cover and then line bore to factory (in this case Jake's) specs. Cleaning a block isn't that difficult either. But it will take time and probably a trip to have it dipped and ultrasound cleaned.