tveltman

I have determined that my oil burning problem is inside the engine, either in blowby past the rings or through the valvetrain. I haven't yet done a leakdown test, but my compression numbers are okay, and my gut feeling is that the problem is in the valvetrain. Apparently you can pull the heads with the engine in place, which due to my particular situation would be preferrable. Assuming the problem is in fact all in the valves, and that I am willing to flail with removing the heads in situ, is there any reason not to? I was thinking that it might be better to do the rings and bearings at the same time, but of course that would necessitate removing the engine, which I can do, but is kind of a pain to do by yourself. Any advice for or against? Should I pull the engine, or just try for the valves?

Thanks!

blown 87

These engines can be oil thirsty when nothing is wrong, how much is yours using?

Nicole

Is the issue with removing the engine that you don't have enough hands, or is it an issue of space or tools?

There are lots of very savvy 928 owners in this area, and we've done wrenching parties before. I would be surprised, if you could not find any local help.

Shark_Week

from recent experience, i would say just pull that engine. i did most of the preliminary disassembly and had a buddy come help with the final pull. not difficult. as Nicole says you should have no problem finding someone to help. probably a lot more interesting with others involved

Lizard928

If you do decide to rebuild the bottom I have a set of S4 rings that I will let go at a good price.

And if you are going to pull the heads. Pull the entire motor.

Also if you are using a lot of oil consider upgrading the breather system so that it does not connect to the intake manifold as I have seen most ingest a lot of oil this way when driven hard.

tveltman

Lizard, thanks for the advice. I actually have already installed a sharkvent kit and it is working flawlessly. The engine is very clearly burning oil over 3k RPM, and I am absolutely certain that there is no ingestion through the intake, as there is no puddle of oil in the throttle body where there was before I installed the sharkvent.

Greg, the engine uses a quart between 350 and 450 miles. This is not a GTS, and so I have been told this is way too much. Obviously, I agree, and it's definitely a smokescreen type of consumption, so no way that it is right.

The issue of pulling the engine is mostly space/tools. I moved out here for grad school, and I have no garage and no special tools. I don't mind pulling the engine, I've done it before, I figure most of the tools needed are the ones I've got (wrenches, ratchets, etc), so I would just need to rent a hoist, get some jackstands and go at it. I'm sure I could get a dolly from the university for a week or so and use it to wheel my engine to the elevator and up into my room where I can rebuild it there. I'm just not thrilled about trying to do all this with a fairly deficient workspace. I hadn't considered a "rebuild party" but that could be a potential solution. I suppose I will just take everyone's advice and yank the engine.

Do I need a special ring compressor for the rings? I've seen the DIY valve disassembly tool, and it looks pretty straightforward to make. Are there any other tools I am forgetting about that I need to investigate?

Also, what else should I be looking to replace? Car has 130k miles. I was thinking:
knock sensors
motor mounts
fuel lines
injectors (I think a couple are leaking anyhow)
(I just did TB/WP about 7000 miles ago, so I don't think they need replacing, unless someone disagrees)
rings/bearings/valve guides/valve seals

I'd like to generate a parts list and get everything together before I even open her up. In and out and back in is the way I'd like to have it go, as little downtime as possible.

EDIT: Should I replace the motormounts with the solid alloy type or the solid rubber type? I'm personally leaning towards solid alloy but I am curious if anyone has advice against.

Thanks!

blown 87

Sounds like you need to build the motor if it is smoking and using a quart in 350 miles, that is too much.
I personally would not use solid metal motor mounts on a street car.

I am with every one else, pull the motor and as far as what else to replace, let your funding guide you, cause it can get expensive in a hurry.

David L. Lutz

You do not need a "special" ring compressor. It was my 1st ring job, and it was uneventful. However, with all the cleaning and replacing of items I didn't plan on in the beginning it ending up being a 6 month long project. Point being you probably need to plan a little extra time.

One item you need to put on your list is a gasket set. The set is much cheeper than buying even 1/3rd the items separate.

Lizard928

well I hate to be the bearer of bad news.....

if your motor is consuming that much oil and you have already done the breather, then I can say with almost certainty that you have 1 or 2 cylinders with scratched walls.....

I had an 86 engine (put down 310 to the wheels) that had a single cylinder with a ton of scratches on it. And it did not consume that much even at the track with higher RPMS.

I can say with around 98% certainty that you are looking at more than a reringing job.

A leakdown test will tell you more though. Make sure you leave the oil fill cap off to hear all the air passing.

Also consider contacting Namasgt (i think thats his username) he may have a line on a block.

Or consider getting a good used motor. There is one in seattle craigslist for $2500.

tveltman

David, you hit the nail right on the head. I want to figure out what I need to replace, and what I should replace, so I can gather it all up in one go.

tveltman

Oof. That IS bad news. Maybe I should have bought one from 928 intl while they were 50% off used parts.

blown 87

That is excellent advise all around, but if you do look for a used engine, call Namasgt first.

tveltman

Colin, aren't there different tolerance group pistons? Would it be reasonable to expect that I could get a new block and drop everything in and have it work?

tveltman

Okay, I'm trying to evaluate my options now. If I were to pull the engine and rebuild it, how much should I expect to pay to get it bored out, and can anyone recommend a shop in or around the bay area? I figure if I have to bore it, I might as well see about upgrading to 6L with some 968 pistons, since I would have to buy oversize pistons anyhow. Thanks in advance for the advice!

PS does anyone in the area happen to have a borescope that we could visually check the scratched-wall hypothesis. I know that you all have a lot more experience with these engines than I, but I would prefer to be certain that that is indeed my problem before opening up a giant can-o-worms.

karl ruiter

You can get boroscopes on ebay for pretty cheap, but I think it may be hard to see what is going on. I got one to look inside my current motor and could not see squat. Seems like you need to pull the heads whatever the case so why not just do that and see what's up. Try not to worry too much about problems you don't yet know you have.

If you have a scratched wall you can just take the one hole out to the first oversize. The pistons in all oversizes weigh exactly the same so you would just need to do the scratched one. Not sure what it would cost to do one hole. I was quoted $300 to do all 8. I would guess 1 would be about half that since most of the work is getting it setup on the machine.

When I pulled the heads off mine I did see some scratching, and I decided to do the whole motor. But once I got the pistons out I noticed that the old oil rings were really brittle. Most of them were either broken or broke when I pulled the pistons. The new oil rings were nothing like that. Not sure if that normally happens or if this points to an overheating or what. In retrospect, I think I could have just changed the rings and been fine. Many have said (Greg Brown included, I think) that you can have what seems like a lot of scratching and be fine.

I'm not sure why everyone seems to jumping from your oil consumption to a scratched block. These cars are pretty hard on valve guides and seals. It might be that a valve grind and guides and seals is all you need.

I think people are pointing towards pulling the motor becase, in general, it will take less time to pull the motor, do the work and put that motor back in, than to do the work with the motor in the car. But if circumstances point you towards wanting to do it with the motor in there is absolutly nothing wrong with that. You can do a fine job with the motor in. It will just take a little more time.