when to rebuild?

[Mike Usiskin]

Hi all,

My '72 911T/E has done 86000 miles and is generally happy

but perhaps not..

3 things

1, she's a smoker, a little on tickover, occasionally, but when I rev it past 40thou she smokes like a good 'un, she stops smoking once the rev sdrop below 4 again. Any ideas?
2, Also after I've cut the engine after a decent run i always get smoke in the cabin, which makes it tough for the kids in the back
3, there is always a smell of oil etc in the cabin. Personally I love it but it does get complaints. Any suggestions

Basically I'm wondering wether to have a leakdown and/or compression test with a view to getting the engine rebuilt as needed. Are the issues i've mentioned likely to be dealt with with a rebulid?

comments/brickbats/ideas anticipated


regards

Mike

[davidppp]

Hello, Mike.

Not easy IMHO.
The only really catastophic failure you risk is a velve head coming off due to lack of cooling..very rare ...

So the rebuild would be timed by your toleration really, ..

If iyt were mine I'd leave well alone I think, assuming no more than normal road use..

On the othe heand if its tracked or really thrashed...RS spec calls!

Kind regards
david

[impmad2000]

It sounds like what you have is a perfectly good, used 911 motor. Use it and enjoy it as it is. When you are ready, then get it reconditioned. Look after the servicing and regular oil changes and my guess is that it will continue to run great just as it is for years to come.
I'd recommend fixing the cause of the oil smoke if you can ! is there an oil leak that drips on the hot exhaust manifold somewhere ? Check out the timing cover gaskets...

Cheers
Tim

[Barry]

I'm with Tim: check out those valve cover gaskets: there are some silicon ones available (in the states I think) that should stop the covers leaking. It's very likely these that allow oil to drop into the heat exchangers giving your smoke and oil smell in the car.

The leakdown or at least compression test is always worth doing, there's no real down-side to this, and it gives you some quantitive figures to compare to in the future (i.e. if one cylinder is gradually dropping compared to the rest, or is wildly different to the others, you know you've got a problem developing).

As for the smoking from the exhaust, as you know, it's likely to be bore wear or valve guides. Either way, improving your oil certainly won't hurt. It's often well worth trying increasing the viscosity. What are you running? (I'm sure we've had this subject before ).

Oh yes, oil pressure and temperature O.K.?

[Barry]

Also, jst worth a quick check on the oil breathing system: its probably fine, but if blocked (kinked breather hose etc) it might encourage crankcase pressure to creep up, forcing oil mist past the rings ...

[2.4TE]

I'm with Barry- check the breather pipes connected to the air box. There's a small one attach to the bottom side of the airbox. Make suure it's not blocked: mine was on my 72 TE when I first got it. If you redline it in say 2nd and then let it slow down on the overun, does it smoke badly (on the overun)? If so could be valve guides, if not, keep driving it!

[Mike Usiskin]

Hi,

Yes, thats basically it. When I redline it (or near to it) in 2nd or 3rd she smokes like a chimney on the overrun, as i back off under 4thou again the smoking stops.

re the interior smoke, is the consensus that there must be oil dripping onto the heat exchangers from somewhere?

thanks again

mike

[Barry]

Yes, it's usually coming from either the upper or lower rocker box covers, as I say you can get silicon gaskets that will probably sort it. (discussion here:
http://www.ddk-online.com/phpBB2/viewtopic.php?t=7479.

The alternative if to use the later 930 'Turbo' valve covers: they are heavily ribbed, so don't distort nearly as much as the early ones.

If you went the silicon gaskets route, just put your existing covers across some wet-n-dry covered glass, and make sure that they are as flat as possible .