Valve seals or top end rebuild?

[Steve Marshall]

I've got an 86 Carrera bone stock with about 118K miles. I'm running VR1 20/50. It smokes at idle on hot days, which is most days in central Texas. Otherwise it runs great and is regularly maintained. Im assuming the smoke is caused by leaky valve seals?

The question is: Should I replace just the valve seals or do a top end rebuild?

[darrin]

what's your oil consumption?

Wouldn't you need to pull the cylinder heads to get the valve seats sent out? Once all's apart, you should be able to determine what else is worn and requires refurbishment -- "conventional wisdom" seems to be that once you've pulled the top end apart, best to refurbish and renew all worn parts

[HarryD]

Hard to say. If it is just sitting when smoking, I would be thinking rings. A compression and leak down test may help to isolate the culprit. If it was valves, I would expect smoke on acceleration or deceleration.

[john walker's workshop]

With that many miles, the guides are likely worn. Top end in your future.

[Steve Marshall]

I'm probably using about a quart every 2000 to 2500 miles. Are there longer life seals and guides available? Are 3.2's prone premature guide/seal wear?

[HarryD]

If that is your oil consumption and you are NOT having fuel dilution of your oil, I would just move on and keep an eye on your oil consumption.

[darrin]

Originally Posted by HarryD

If that is your oil consumption and you are NOT having fuel dilution of your oil, I would just move on and keep an eye on your oil consumption.

^^ this!

under 500 mile per quart oil consumption (and very laterally loose valves) caused me to have my 86 3.2 top end rebuilt to address prematurely worn valve guides at around 80k -- something that some (but not all) 3.2s of our vintage are susceptible to. Since you're seeing a bit of smoke at idle (do you still run a cat?), worth checking oil to make sure you're not getting excessive fuel blow-by from worn piston rings

[rwest]

A leak down test would be very useful in seeing if your valves and rings are good.

[911pcars]

Valve guide wear on 3.2 engines seems to be a common occurrence. Look for visual signs such as oil consumption (2500 mi/qt = good, oil on intake and/or exh ports or both, oil fouling or deposits on spark plugs, etc.).

Can access the valve train and inspect for valve stem wobble (valve closed). If just valve seals are bad, can remove springs in situ and replace. Perform all the usual engine structural tests first (compression, leak down) so you have an idea before you dig in further.

If your only symptom is a quart every 2500, I’d just drive and enjoy the ride. Excessive exuberance or cash does make some people more sensitive.

Sherwood

[Steve Marshall]

darrin - I don't run the cat anymore and when I took it off I noticed the smoke. I forgot about that.

Leak down test will be my next step for sure.

[kyngfish]

I was under the impression that a leak down test told you nothing about your valve guides. Only if the valves weren’t seating correctly. Oil consumption and lateral play would be the only real ways to diagnose.

[911pcars]

Originally Posted by kyngfish

I was under the impression that a leak down test told you nothing about your valve guides. Only if the valves weren’t seating correctly. Oil consumption and lateral play would be the only real ways to diagnose.

Wouldn’t you want to know if the basic engine was in decent condition before replacing the valve seals? New valve seals on an engine needing a valve job or new piston rings is.......premature to say it mildly.

Sherwood

[john walker's workshop]

Worn valve seats are usually the direct result of worn guides. So is smoking. At your mileage, I rarely see piston/clyinder/ring issues, other than maybe carboned up oil return slots in oil rings.
The seals used on a 3.2 and others are the brown rubber with a steel sleeve that are difficult to remove even when the head is on the bench, disassembled, so replacing them in situ isn't going to be a cake walk. Mmm, cake.

[darrin]

Originally Posted by Steve Marshall

darrin - I don't run the cat anymore and when I took it off I noticed the smoke. I forgot about that.

Leak down test will be my next step for sure.

I'd start by having your oil checked for unusual gasoline dilution (e.g. blow by from bad rings) -- if your oil's OK and you're only seeng a quart of oil consumed every 2-3k, I'd consider yourself lucky and call it a day

[Steve Marshall]

Originally Posted by john walker's workshop

At your mileage, I rarely see piston/clyinder/ring issues, other than maybe carboned up oil return slots in oil rings.

I was curious about this. Is a typical top end rebuild just rework the heads? What about chains? Piston rings? I guess a leak down would determine if the rings are bad?

[Steve Marshall]

Originally Posted by darrin

I'd start by having your oil checked for unusual gasoline dilution (e.g. blow by from bad rings) -- if your oil's OK and you're only seeng a quart of oil consumed every 2-3k, I'd consider yourself lucky and call it a day

No gas in oil. I still have some carbureted cars where the floats will occasionally stick so I'm familiar gas in oil. My natural inclination is to just keep driving it. But when do you know it's time for the rebuild?

[darrin]

"when do you know it's time for the rebuild" -- either when you have the $$$ to perform upgrades that require a teardown (e.g. new cams/bigger p/c, more displacement) OR when your oil consumption is a LOT higher -- I did my top end when I was adding a quart every other tank (i.e. around 600 miles per quart) -- others wait even longer (a quart per tank) before doing so.

Keep in mind that the premature valve guide wear issue only affected a (small?) percentage of Carreras from our vintage (I too have a meteor grey '86 that did require a top end rebuild) -- the folks that went through this do tend to be vocal