Judging cylinder bore wear and pistons

[911hillclimber]

posting this on the '2.4 and before' section for greater visibility.

I am bracing myself to fully re-build my beloved 3.2 engine in my 73T, it has 140K on the clock, never been apart and runs perfectly, but getting a little blue smoke on start-up, and getting close to at least a top end rebuild, probably the whole lot as oil pressure is 'ok'.
I'm ok with doing the engine, but the cost crunch lies with the cylinders.

To gauge the wear I will do a leak-down test etc first, but one apart I was going to slide some new rings down the bores, about a 1/3 in from the top and see what the ring gap is.
If to spec, then is it reasonable to assume the bores/pistons are ok for the build?
I am looking to avoid the cost of new P&B of course.

I don't have access to the micrometers so looking to this simple method instead (which may be folly in itself).
Any comments please?
Graham.

[chris68]

I'm near Burton on Trent. I've micrometers and bore gauges. Happy to check them if you fancy a trip out.

Chris

[911hillclimber]

Thank you Chris, feeling the waters at the mo and checking the costs for the bits!
If it comes apart will contact you.

[PeterK]

To gauge the wear I will do a leak-down test etc first, but one apart I was going to slide some new rings down the bores, about a 1/3 in from the top and see what the ring gap is.
If to spec, then is it reasonable to assume the bores/pistons are ok for the build?

Graham.

A ponder....... I always thought that ring sizes were not consistent (small gaps), and that you had to slide them down the bore and then adjust your ring-gaps to spec. If that's the case, you slide a set of new rings and the gap is to spec, is that because the cylinder is not worn or might it be that the cylinder is worn but the rings are too tight, thereby cancelling each other out ??

I suppose that as long as the final gap is to spec, then maybe that's fine.....

Just a thought. I also have a set of bore gauges and micrometer and am happy to pop them in the post if needed.
Peter

[911hillclimber]

Indeed Peter, the worn bores could be worn oval, but I can check that with callipers.
Miles away from stripping it yet, just seen new p&b are not tooooo £££££££££.
Pause for thoughts first, but will keep your offer in mind!

[Cortina]

If I was in your shoes ......................

.......... I would just keep driving it ! (assuming leak down test is OK) .... a wee bit of smoke on start up is not the end of the world exactly ??

(All this assumes performance and therefore power is still "pleasing you")

[911hillclimber]

I'm happy with it, like the idea of it having 140K miles and all undisturbed, no oil leaks anywhere, 30 mpg and starts perfectly.
However, the Boss feels it is heading for unreliability (and hence reluctant to go out in it), and having the Boxster does not help.

It went in the car @ 66K miles in 1996 ish, did 12 years being thrashed on the hills, and cruising ever since.
New oil every 12 months no matter the miles, so about 3K miles per oil change on average.

[Cortina]

............... and it's heading for unreliability because ..........................................

??

time to keep quiet me thinks ......................

[hot66]

Just tell her you rebuilt it one Saturday ... then continue driving as is

[mycar]

[911hillclimber]

So often James you prove you live in a very different world to me!

Is it heading to be unreliable?

140K on a 3.2 sounds like it is getting to the end of it's first life.
However, the trips we do are quite long, rarely short, most over 100 miles and the thing just goes on and on boxed-in on Midland roads, so 60 maybe 70 tops mostly lugging at 40/50 so the car takes that in it's stride, very '3.2' I think.

She also knows I have to have a project on the go as time consuming as possible during the day, and with the Honda cb drawing to a close, the next project will be looming.
Thus, instead of another bike, it would be far more beneficial to do the 911 engine, that will keep me busy for a while and have real value when done.

The costs of the engine and another bike are about the same, the work also so there is the background thinking.

The 3.2 only needs a top end if I want to improve it as I read that they take out valve guides quite quickly, so a strip to the short block would be possible and hence the p&b question arises.

Looking at the cost of parts on type911 all the parts are to order, so I assume they are coming from Porsche direct so some cost saving there too maybe.

[jwhillracer]

I'm happy with it, like the idea of it having 140K miles and all undisturbed, no oil leaks anywhere, 30 mpg and starts perfectly.
However, the Boss feels it is heading for unreliability (and hence reluctant to go out in it), and having the Boxster does not help.

It went in the car @ 66K miles in 1996 ish, did 12 years being thrashed on the hills, and cruising ever since.
New oil every 12 months no matter the miles, so about 3K miles per oil change on average.

Using the same logic, maybe you ought to have open-heart surgery before you start the engine rebuild.
I know you are quite fit, but you're getting on a bit, and have quite a few miles under your belt.
Maybe you wouldn't be able to stand the stresses of an engine rebuild and all of the niggly problems that will come afterwards during de-snagging?

Or is it best just to get on with it and enjoy life?

Take care!!

JW

[Lightweight_911]

... I have to have a project on the go as time consuming as possible during the day ...

I have a feeling that this is the real reason & you use your wife as justification !

.

[Bootsy]

... I have to have a project on the go as time consuming as possible during the day ...

I have a feeling that this is the real reason & you use your wife as justification !

.

Or Mrs Hillclimber has to make sure you have a project on the go that is as time consuming as possible?

[911hillclimber]

50:50 boh think.
Doing the engine would satisfy me, ahd she would not haveto put up with me 'project-free' which, by all accounts is not a pleasant atmosphere.

Best project would be to re-build the Lola's 3.2 to rev reliably to 7600 or better, 8000 red line.

That would be quite easy, the engine is solid right now bar one cam tower oil drip on each side ( ) all my own work, change the hardware bolts, change the rods, change the pistons, change the cams.
Doesn't sound too expensive if you read it fast enough....