Valve guides

[Hnichols]

My new to me '88 burns oil -- I'd have to guess it burns a qt. every 500 miles or so, though I haven't driven it enough to be accurate. I knew when I bought it that the valve guides were showing wear, but I didn't know it would burn this much oil. It's got 113K and the records suggest that the previous three owners maintained it properly. Otherwise it runs beautifully. It had excellent compression numbers.

So what do you guys think: I can live with the oil consumption indefinitely, and I'd like to put off opening up the motor until something forces me to. I know that worn guides compromise the valves' ability to dissipate heat, and that in theory one could overheat and break. But that strikes me as an extreme case scenario -- or is it?

Also: What is the estimated cost of having someone replace the guides and regrind the valves (assuming I can reuse the valves)? Zimmerman's book cites $2500 for the basic valve job, but that might be out of date. And how much can you save be dropping the motor your self and removing the heads?

Thanks in advance!
Hugh

[RSTarga]

I'd guess closer to 4k for a top end job. You'ld probably want to do the studs while your in there. I'd just wait until it bothered me.

[CCM911]

I was just at a shop and had a tech educate me on this very subject. You should be OK for now. As the condition persists, the oil that leaks down the stem of the valve will begin to "coke" or harden into chunks, which will then prevent your valve from fully closing. At this point your performance will drop off considerably, and you will know it is time to go in and fix.

In any case, you will be looking at new valve guides, seals, and either new valve seats, or if there is no damage, machining of the valve seats and valves.

If you look at how the rockers work, you will understand that what is happening is that when the rocker opens the valve, there is top to bottom stress, which in turn ovals out your valve guide which ultimately will allow too much oil to flow down the valve stem.

So keep your eyes open, enjoy the car, and start saving for a top end refresh. If you have not already done so, join the PCA and attend some meetings. You will meet folks that will most likely assist in dropping your engine and trans when the time comes. This will save you some money.

This is not the end of the world. It will not break the bank if you do most of the prep work yourself.

Best of luck.

[john walker's workshop]

$4K is average in this area, valve grind only. the longer the valve beats around on the valve seat due to worn guides, the worse the seats get. the valve starts to wobble around and hit on one side of the seat as it closes. basically dragging itself in, which wears a section of the seat away, instead of closing precisely on the seat. some of the exhaust seats take a lot of cutting to clean up properly on those 3.2s, even at 100K. i sometimes wonder if the heads can take another valve grind down the road.

[wholberg]

My 87 started to show signs of a bad valve guide at about 100K in cylinder #1 only. None of the other cylinders ever showed a problem, but by 140K #1 was fouling out the plug in a couple of hundred miles and shortly thereafter quit firing on that cylinder entirely. I say run it until it becomes a problem (like dropping to 5 cylinders in the middle of a 300 mile trip - the car still runs but not that great) and then fix it. You might get 30 or 40K miles before that happens.

[gregwils]

I remember being bummed when my new to me car was found to be in love with oil. My car was about 400m/qt when I did a top end. I ended doing the non-machine shop work myself and ended up spending about $2,500 on parts, but wish that I had spent another $500.

If it were me, I would probably try to get to it in the few thousand miles. If you're at 500/qt, it needs work and isn't going to get better on it's own.

You could buy a new car, have fewer maintenance issues, but have much higher depreciation. You 911 will require regular repairs/restoration, but the price is stable and may even appreciate with inflation.



John Walker's prices are really fair, so don't be surprised if you get a $5k quote.

[88911coupe]

$4,000!?, I wish I'd had that quote, I was quoted $8-10k by a well known indy here in Dallas about 3-4 years ago for a top end only!, waited a while and ended up doing complete rebuild myself.

[cuchanonM]

I was just at a shop and had a tech educate me on this very subject.

[James Brown]

if you diy it you could save several grand. but as you know, while your in there can get pricy. ask for a price for a naked head (with valves and springs attached). good learning experience also. Be firm with yourself and replace things that are only in need.

[911dean]

Sounds like a great winters project. LIke previously stated it's not going to get better and might compound the problem if you wait. I could probably help you drop the engine. I've never done it on a 911 though, but certain I could.
Dean

[wholberg]

I got estimates of about $4500 for a simple valve job, but my top end rebuild wound up at about $8500. I was looking for maximum reliability and 100K+ before tearing it down again, so it included all new valves and springs (a couple of exhaust valves were questionable), new 964 cam (old one had minor pits, regrinding was almost the same price), new studs (none broken, but just in case), rebuilding injectors, new fuel and oil lines, and a host of other "if it's not going to last 100K, replace it" repairs.

It will take me about 10 years to put 100K on it, and if I take care of it, I should be able to go considerably farther than that. I figure I would have been able to do it for about half the price if I had done most of the work myself, but I just did not have the time. And, if it was not my daily driver, I probably would not have spent as much.

[Hnichols]

Thanks for the good advice, guys. Since the mileage is not that high and the car otherwise runs well, I will try to resist the "while you're in there" expenses. Maybe a winter project if I confirm the oil consumption is as bad as I suspect.

Hugh