Worn valve guides?

[safe]

3 of my exhaust ports look like this, the other 3 are dry, clean and nice.



Due for a top end rebuild?

And yes, it smokes a bit...

[old man neri]

What is your oil consumption like?

[safe]

Originally Posted by old man neri

What is your oil consumption like?

I don't keep record of it. On the 2500 miles (~300 at the track) I put on it this summer, 4-5 quarts at least maybe up to 8.
After a track day I may have to top it up a quart or more, but on the street a quart goes a long way.

[old man neri]

8 quarts in 2500mi? That's something like 315mi/quart. That's pretty high from what I have heard.

[1982911SCTarga]

What's the mileage and history of your car, Magnus? Has the engine been apart before? Lots of possible while-you're-in-theres with a '77.

Brian

[safe]

112-113.000 miles, never been apart, aside from chains and tensioners. I have talked to most POs. Before me the car has probably had a pretty relaxed life.

[RoninLB]

113,000 miles was far enough for my 2.7.

If you also need rings it may be a good time to split the case or just get another engine.

I rebuilt and made sure to have the case line bored by a Porsche experienced machinist.

[74-911]

Originally Posted by RoninLB

113,000 miles was far enough for my 2.7.

If you also need rings it may be a good time to split the case or just get another engine.

I rebuilt and made sure to have the case line bored by a Porsche experienced machinist.

When I had my 2.7 rebuilt at 90K miles, the valve guides were in such bad shape we had to replace all 6 exhaust valves. Note: Many of the 90K miles were put on the car in S. Texas (very hot climate) and the car had no external oil cooler.

[JeremyD]

Similiar to what mine looked like before I started my top end. I'd start monitoring your oil consumption. When it gets (or if it is) around 300-400 miles per qt - time to dig in.

[safe]

I have another engine ready (well, soon) to go in. I might need the old engine once every second year for inspection so I'm keeping it and I was entertaining the thought of rebuilding just the heads for fun. But I wont be putting a lot of miles on so I might just leave it as is.

[RoninLB]

If I was looking for a cheap way to buy some miles I'd just replace the exhaust valve seals.

[84toy]

Originally Posted by safe

3 of my exhaust ports look like this, the other 3 are dry, clean and nice.

Due for a top end rebuild?

And yes, it smokes a bit...

The short answer.....Yes. If oil is pouring out of the guides that bad, the seals and/or guides are wiped out. Can you still drive it?....sure. However I suspect the guide has significant wear and the valve slopping around in a large hole invites extreme valve seat wear and possible valve breakage.

I recently pulled an engine down that had .014" wear in the guides vs the appropriate .002. The oil in the port was less than yours and it didn't use that much oil. When finished, the engine was much quieter.....pic for you

[cgarr]

If you let it go too long your seats can get beat so out of round that they may not be able to cut them round again.

[Rot 911]

Originally Posted by cgarr

If you let it go too long your seats can get beat so out of round that they may not be able to cut them round again.

Or this can happen, like on my 3.2 with worn valve guides:

[safe]

I have known for a while that they probably been a little worn... It has problem holding the valve adjustment, it gets noisy quite quick. Not sure if that's related.

Maybe I just change the seals and baby it, if everything goes to plan it will only be used 10-15 miles every second year.

That's nasty Kurt!

I keep being surprised how well these engines run despite all kind of wear and tear.

[livi]

Fingers crossed, Magnus.

[porschenut]

Originally Posted by safe

It has problem holding the valve adjustment, it gets noisy quite quick. Not sure if that's related.

Yeah, it's related for sure. Valves not staying adjusted is one of the tell-tale signs of worn-out valve guides.

[vreference]

I can't wait to measure my wear - I hope to hold the world record for most worn (but still intact) 911 valve-guides very soon.

This seems like an appropriate place to ask - Does anyone know any specifics I could ask my local machine shop (or anything that makes installing guides in these heads different from any other aluminum head)? I've used them for years for domestic stuff and they build a lot of race motors but I suspect their Porsche experience is limited. Still, I can't imagine they aren't up to this task unless someone can offer some information to the contrary.

[JB36]

Originally Posted by cgarr

If you let it go too long your seats can get beat so out of round that they may not be able to cut them round again.

I've been told my valve guides are wearing out which is causing some noise. The valves were adjusted about 5k miles ago. The valve seats getting beat out of round has me wondering how long I can go before a top end job. My oil consumption is very good. At least 1 quart per 1K miles and maybe even a bit more. Which is going to come first....physical damage or higher oil consumption?

[RoninLB]

Originally Posted by vreference

(or anything that makes installing guides in these heads different from any other aluminum head)?

I'm not a P machinist but I do know that you just can't just slam them in. May be same routine for other manufacture Al heads but I don't know. It's been discussed here very rarely. I'd find out exactly how to do them before proceeding.