Time for a rebuild...

[Rick Lee]

As I feared, my high oil consumption was not a fluke or the result of a mere mixture problem. Almost overnight I went from using 1 qt. of Castrol 20/50 per 1200 miles to 1 qt. per 500-600 miles. She has 86,500 miles on her and still pulls very strong with no (more) oil leaks. So I had a leakdown done, which came back all 94-97%, but with a vacuum leak on cylinder #5. Got the intake manifold gaskets replaced (had no time for a DIY - shameful I know) and then mixture leaned out a bit. Wrench told me to run her hard for 1000 miles and keep an eye on the oil. Well, yesterday I put my 1000th mile on her since that job and used almost 2 qts. in doing so. It was mostly spirited highway driving over two weekend round trips from DC to NJ/Philly. So wrench say it's about time for some headwork. But since I have no garage, I'm leaning toward a another 3.2 swap. For about the same amount I'd spend on a top end (plus handing my engine off as a core), I can get a fully rebuilt and upgraded 3.2 and have the swap done in a day. I'm leaning toward this option, as the seller is very reputable and having my car always at my disposal is worth something to me. Having a wrench do a top end will take a while and is always susceptible to the "hey, your P's & C's are shot and it's gonna be another $2k" sort of phone call. I hate to give up so easily, but I just can't bear the thought of renting garage space and spending every minute of two mos. worth of nights and weekends doing a top end and still being out a few grand. A 3.6 is just cost prohibitive for me now, but another 3.2 is within reach. I hope I don't drop a valve between now and when I can get this job done sometime next month.

[Jim Richards]

Sorry to hear the bad news, Richard. The rebuilt 3.2 sounds like a reasonably cost effective way to go. Will you get any warranty on it? Are you going to be back in the saddle for the next fun run?

[Bill Verburg]

IMH(and completely unbiased)O, You really ought to think about a 3.6 a bit more.

[gr8fl4porsche]

My 87 has about 85,000 miles and is now suddenly burning a quart in about 500 miles. Started after a nice dose of Mobil 1. A couple of months ago it was using about a quart in 900 miles with dino oil. I am now starting to budget for a thorough top end job and maybe new rings. I am worried I may get carried away and also do rod bolts, exhaust, cams, etc.

First I am going to try some dino oil and see if oil consumption goes back to normal.

An engine swap will void the matching numbers game if you are interested in perserving a future 'classic' sports car. I plan on keeping my little baby forever and adding a couple of sisters to keep her company in the garage.

[schulr]

Richard, from what I understand, 500 to 600 miles per qt is completely within spec. Why not save the money and just carry a few qts of oil in the trunk. I am using about 600/qt and the engine runs great other than the vales being a bit noisy.

I do like the idea of a rebult 3.2 over tearing down the existing engine. Any concern about the numbers not matching for resale issues?

Bob

[john walker's workshop]

the average valve grind cost is around $3000. add $500 for rings, rod bearings and rod bolts while it's apart. a rebuilt engine for the same amount is not really "rebuilt". a real rebuild will be in the $8000 range.
compared to the cost of a quart of oil every 600 miles, as long as it runs well, doesn't oil foul plugs, and doesn't smoke out the neighborhood, why not just keep driving it?

[TimT]

as long as it runs well, doesn't oil foul plugs, and doesn't smoke out the neighborhood, why not just keep driving it?

Sage advice as usual

[Jim T]

Psychologically, it would be difficult for me to enjoy my 911 if it was burning a quart every 600 miles, even though that technically is on the spec borderline. Unless I wasn't planning on keeping the car much longer.

That's a good amount of burning oil, and in my mind the writing would be on the wall. If I were planning on keeping the car for a while, I personally would fix it and fully enjoy the car with its rebuilt engine for many years to come.

But that's just me - I obsess over these kinds of things and that gives me no choice.

[Rick Lee]

Bill, I thought about your 3.6 and that's a fair price. But when I factor in all the other stuff I'd have to get for the install and then try to get $3000-$3500 for my engine, I'd still be out $7k when it's all said and done.

JW, your word is law in my book. But do I need to worry about dropping a valve? I'd rather nip this in the bud while I have the money (and no wife) to deal with it, than take my chances with destroying my engine. I take it to high speeds every day and high rpm's every shift (after warm up of course). I don't want some cool-looking car I have to be careful about driving too hard. For the money and sweat this car gets out of me, I want to be able to drive the hell out of her every time I get in. I don't mind adding oil all the time and it doesn't smoke very much. But when do I say when? It has a few other issues too, which puzzle me a bit. I get a decent back fire when going from 1st to 2nd at high rpm's and also when shifting down from 3rd to 2nd. I'm afraid bad things lurk in my engine.

[Doug E]

Richard - sounds like your car needs another therapy session , oops I mean Fun Run, to exonerate all the gremlins

[Rick Lee]

I've done about 12-15 hrs. of fun runs over the past two weekends. If there are still demons to be exorcised, hard driving ain't gonna cut it. But no worry - I'm in for 11/17 even if I have to Fred Flintstone it. I may end up behind Kurt (Green912) that way.

[Bill Douglas]

Richard, if you are planning on swapping the engine out anyway; why not do the evil of all evils and throw some engine additives in like Motor Up or Wynns for Oil etc. It can't do any harm and it worked well on a car of mine in the past.

[cstreit]

WHy would you drop a valve burning oil? Factory spec is one quart every 1000 km's.... Sounds pretty normal to me... Even to the Obsessive-Compulsive type

[Rick Lee]

Originally posted by cstreit
WHy would you drop a valve burning oil? Factory spec is one quart every 1000 km's.... Sounds pretty normal to me... Even to the Obsessive-Compulsive type

Well, if I have valve guide wear, doesn't that increase the risk of dropping a valve? I don't know much about this stuff. But my oil consumption seemed to double almost overnight and I don't think any band-aid solutions are gonna make it any better or prolong its life. I am a total engine hypochondriac admittedly, but I don't want to make it any worse than it has to be. Most people I've asked think those factory specs are a little too liberal. I mean, how would you feel if you went from 1 qt per 1200 miles to twice that in a period of about 3 wks? Would the factory specs console you?

[HarryD]

Richard,

My guy uses 1 qt/200-300 miles. I KNOW I have shot valves guides but when I discuss it with my wrench and he tells me that as long as I limit my visits to red line, I can go for a long time. The biggest down factor is the HUGE blue cloud on decelleration. That said, at the end of this years AutoX series (two more events), it'as off to the shop for a bit of freshenng.

If your leakdowns are good and the blue clould is small, I would put the $$ aside and wait. From what I can gather, the job will cost the same and the downside risk is very small. As an experment, try Kendall or Valvoline Racing instead of Castrol, the change in additives may help a bit.

Good luck.

[speeder]

Someone more knowledgable will correct me if neccesary, but I believe that the amount of valve guide wear that will allow some oil through at high temps is a long way from "dropping a valve". In fact, it is the little keeper on top of the spring that holds the valve, it would take a lot of lateral movement to somehow shake it loose.

A question as well; does anybody ever try just changing the valve stem seals in 911s? It can be done w/ engine in car, not a big job, it's worked for me in other vehicles, (to reduce oil burning/consumption). If those are cooked and hard, and it seems likely w/ our head temps, oil will pass through and go by PERFECT valve guides. At least in other engines. Just wondering.

It does not seem very likely that your valve guides "all of a sudden" went bad, and consumption goes up from one oil change to the next. Experts?

[john walker's workshop]

"dropping a valve" is when the valve head parts company with the stem, and the resulting damage potentially can kill everything in the engine (worst case scenario). the keepers have been known to pop out during the chaos of an over-rev, but that's another story. the 2.7 engines with their copper valve guides were the worst ones, due to the massive guide wear that would allow the valve head to be walked back and forth a half inch or more. the valve's contact with the guide and seat is the only way for it to conduct it's heat to the head. 3.2s tend to wear the valve stem along with the guide, and the resulting side slop breaks the stem seals, which get hard with age, and don't like to move sideways.
the vacuum created by the volume of gas going thru the port will cause oil to be sucked thru the guide, especially the exhaust guide, which is close to the oil in the bottom of the cam tower. the guide wear in 3.2s is nowhere near the 2.7s, due to better guide material.
my recommendation to people who have this oil use problem is to put up with it until it gets to the point where the car smokes more than normal, or a plug oil fouls, but some people can put up with this longer than others, so it's your call.
remember, one quart of oil in 300 miles, is 10 quarts in 3000, (normal oil change interval). i've done lots of major engine repairs because people were ignorant of this oil use problem, and never checked the level between services. that's how i got such a screamin' deal on my 87 cab.

[Rick Lee]

Now that's what I was looking for! Again, I don't mind adding oil all the time and I keep very meticulous track of date and mileage on anything I put in or on my car. I check very regularly, so I will keep on top of it and maybe just delay the pain a while longer.

[JavaBrewer]

Richard,

Again we're on the same page it seems. My 86 with 110K has the exact same symptoms. A local respected P-car shop that recently looked at my car echoed John Walker's viewpoint to a tee. Sure I could drop a large bucket of cash to make the smoke go away but do I really want to or maybe more importantly need to? If I'm gonna do that I have to really consider the total $$ figure I'd have invested in the car vs. what the same figure would get me in the marketplace. If push comes to shove I would have a hard time justifying a 3.2 rebuild over a 3.6 transplant anyway.

Good luck.

[silverc4s]

Richard,
What weight of oil are/were you using??? 15w 50? Did you keep to the same weight when you changed from dino to synth oil?