question about rebuild plans
 

Here's the situation: '79sc euro, 115k miles, rarely smokes at startup but sometimes smokes during idle. Oil consumption seems normal or slightly high (I haven't measured carefully). I don't know what type cylinders I have yet, but I assume alusil. Doesn't leak a drop of oil. The car starts and runs well.

Obviously the valve guides are shot. So I am planning to start a rebuild soon. I was originally thinking about tearing it down to the crank and doing it all. But I just tested the compression, and the cylinders are all within 3% of each other (150-154 psi). I haven't done a leakdown test because I don't have the equipment.

Now I'm not so sure about the full rebuild. I'd really like to check the main and layshaft bearings. So I think I should carefully remove the cylinders and try not to disturb the rings. Has anybody tried this and had it work? Any opinions?

Also, has anyone else seen compression numbers within 3% on an SC engine this old? I am a bit surprised. It makes me think that the PO had it rebuilt already, but I don't have any receipts and this woman was unlikely to have done it herself.

I've done quite a bit of reading on the board and I know about the trials that some of you have gone through when it comes to re-ringing or not. Thanks for your opinions,

Just my 2 cents...

I would definitely do a leak down to give as much info as possible. If all cylinders are leaking the same amount, then your compression would be fairly consistent across each cylinder too.

Having said that, if you are not burning oil, running poor, ... why tear anything down? Or are you (planning) on using the car mostly on the track where you really want to make sure everything works 100%?

Again, JMHO, at this age & milesage, if you do open her up, most people would do a pretty complete rebuild (i.e. $$$$$). But, if there's no sign of breakage / leakage / burning oil, and if you are not heavily taxing the car a lot (i.e. on the track), then why fix it when it ain't broken?

Thanks for your input.

It smokes sometimes at idle, and that's generally an indication that the valve guides are going bad. There is a faint valve tic also. So I thought that if I have to do a top-end rebuild, I might as well do it all. The problem is that I would hate to disturb alusil cylinders that are perfectly functional because they may or may not reseat.

I only put 4-5k miles on the car each year, so now I'm leaning towards a top end rebuild only.

I did only top-end rebuild on my car. My wrench said a bottom-end rebuild would probably be a waste of money. (I haven't heard of any crank bearing failures on non-racecar SC's.) Although there have been a lot of posts on this topic (top-end versus total rebuild) in the past.
- Bill

Many here will tell you to go into the case, and do the whole thing.
Easy to say if you're the one spending the money.

On my 80k 3.0, I took a couple of rods off (case intact) and measured. No measurable wear. Let sleeping dogs.....