Engine Rebuild questions

[AlfonsoR]

Have a few questions for my first engine rebuild for my 89 Carrera 3.2, ~100,000 miles, I am going through a rebuild because I am finding small aluminum bits in the oil. I have not dropped the engine yet, so...

1. should i replace the tensioners? These puppies are 363 each. Do I really need new? I am planning on replacing chains, ramps, idlers and sprockets.

2. oil lines. There are a few lines in the oil circuit with rubber as part of the line. Again, is it recommended to replace these? The line going from engine block oil pressure line to oil tank is leaking at the fitting. It's not available through our host, so was planning on sending it to Amazon hose, unless there is another fix.

3. the PO had the heads rebuilt by a non-porsche shop. They replaced a few exh valves and all of the valve guides, that was roughly 10k miles ago. I dropped the exhaust and noticed the number 5 exhaust has a bit of an oil film. Would a quality Porsche head shop be able to tell if the guides are of decent quality or is it better to bite the bullet, and have them all replaced? I know, I know, it might be the rings too.

4. again regarding the heads, with 100k miles, would replacing all the exhaust valves make sense? I have seen some people comment that they do this as a rule. What is recommended here?


Thanks,
Alfonso

[yelcab1]

1. No, re use the old one unless you see obvious signs of failure
2. Pelican has all the hoses for an 89. There are 2 crimped ones from the thermostat and one S hose at the bottom to the oil tank. I just replaced those and bought them from Pelican
3. you are assuming that a Porsche shop would do a perfect job? No, that is not always the case. My valve job by a very respected machine shop had one leaky exhaust seal
4. I think people replace exhaust guides as a matter of course. I don't see the needs to replace the valves if they are still usable.

[Lapkritis]

aluminum bits in the oil... how big are we talking here?

[simsalabim]

Heads done just 10k miles ago? just have guide clearances and other tolerances checked by a good local machine shop, repair as/if needed, new seals and run it?

Check your old receipts for what was done during the last top-end head job for background before doing it all over again for something minor.

Why doing complete rebuild after a top end rebuild just 10k miles ago on a 100k mi car?

[Lapkritis]

Because something is being chewed up it sounds like... gotta find out what that something is before you get a bigger problem.

[AlfonsoR]

aluminum bits in the oil... how big are we talking here?

The ones that were coming out with the oil drain are roughly twice the size of a pin head. No recognizeable shape, non-magnetic and fairly bright so I assume aluminum. The few, maybe 10, in the oil filter with 5000 miles are speck or gliter size, very small. Only one was a longer sliver, possibly off the pump gear.

So it looks like hardly any of the aluminum is getting into the oil filter.

Lapkritis is right, opening the engine to see what's going on. Also got several oil leaks.

[Lapkritis]

I'd check compression before disassembly - hopefully cyl 5 isn't scuffing piston on jug but that would be my suspicion. If you have access to an optical mechanics scope then I would look in there first. Harbor Freight sells them IIRC.

[AlfonsoR]

Thanks for the advise. I will take a cold leak-down check. Not sure if that will tell me anything unless something is really bad, but at least I can compare to the values I get after assembly.

Still want to disassemble to check the bottom end out. Want to look at all the bearings and want to install ARP rod bolts.

[justinp71]

Alfonso-
I wouldn't be surprised if the aluminum bits aren't from cams riding on the cam housing. Especially if the motor was just rebuilt, they probably put in the oil restrictors to the oil lines going into the cam housings. The cams run directly on the aluminum cam housing with no bearings, so I wouldn't be too surprised by getting a few aluminum bits in the oil. Maybe pull the restrictors out, check and if you find the updated ones with the smaller holes, drill them out to a larger diameter, clean, re-insert and check the oil again after 1000 miles or so. Note this will show a decrease in oil pressure on the gauge, as long as you have ~1bar per 1k rpm you're good.

It's also possible to get aluminum in the oil from the intermediate shaft gears meshing, if you have a noise in the middle of the motor it could be that you have too much backlash on those gears. From what I've read before its just a little noisy, but not sure how imperative it is to fix.