Is there a way to preserve new valve guides?

[patkeefe]

Dr Island:
My apologies also. The feeble mind may not recall the exact nomenclature correctly. I think the mixed-film region is the actual wedgie part, like where you hammer the revs up really quickly, and the angular acceleration squishes out some of the oil from the journals. So, you don't get the full hydro effects, but have not retreated to stricly relying on the boundary lubrication. Aside: recall the no slip condition at the boundary layer for moving fluids.
Pat

[island911]

Originally posted by patkeefe
.. .. The feeble mind may not recall the exact nomenclature correctly.. . .

That's what I was thinking about myself.

When I said hydrostatic I meant pressure fed. Like most all the bearings in an engine. . . .as opossed to what I believe hydrodynamic is; oiled bushing types (like a furnace blower motor (for example) where you squirt a little oil on a felt wick, or in a resivior . ... and magically it spins just about forever

. . .or, like the cams. They have to drag the oil between the surfaces (hydrodynamic)

[island911]

Okay, this blurp from marks std mech egr handbook

When the rubbing surfaces are separated from each other by a very thin film of lubricant , the friction is that of boundary (or greasy) lubrication. The lubrication depends in this case, on the strong adhesion of the lubricant to the material of the rubbing surfaces; the layers of lubricant slip over each other instead of the dry surfaces.

A journal when starting,reversing, or turning at very low speed under a heavy load is an example of the condition that will cause boundary lubrication. Other examples are gear teeth (especially hypoid gears), cutting tools, wire-drawing dies, power screws, bridge trunnions, and the running-in process of most lubricated surfaces.

When the lubrication is arranged so that the rubbing surfaces are separated by a fluid film, and the load on the surfaces is carried entirely by the hydrostatic or hydrodynamic pressure in the film, the friction is that of complete (or viscous) lubrication. In this case, the frictional losses are due solely to the internal fluid friction in the film.

Oil ring bearings,bearings with forced feed of oil, pivoted shoe-type thrust and journal bearings, bearings operating in an oil bath, hydrostatic oil pads, oil lifts,and step bearings are instances of complete lubrication.

Incomplete lubrication or mixed lubrication takes place when the load on the rubbing surfaces is carried partly by a fluid viscous film and partly by areas of boundary lubrication. The friction is intermediate between that of fluid and boundary lubrication. Incomplete lubrication exists in bearings with drop-feed, waste-packed, or wick-fed lubrication,or on parallel-surface bearings.

[patkeefe]

I love it when everybody is correct.
Where was the internet when I went to school?

http://www.engineersedge.com/lubrication/lubrication_knowledge_menu.shtml

[island911]

Geez .. . or even better, there's this "internet" thing . . full of information. :O

per: http://www.engineering.com/content/ContentDisplay?contentId=41005002

Plain bearings can be classified into two types: hydrodynamic bearings and hydrostatic bearings. Hydrodynamic bearings attained lift between the mating surfaces by wedging lubricant into the contact area with a relatively high rotational speed. The disadvantage of this design is the lack of lubricant on the surfaces when the shaft begins to rotate. Thus machineries that utilize this type of bearings should not be subjected to a high load during startup.

Hydrostatics bearings utilize an external source to force lubricant into the contact. They are used in heavily loaded and slow moving machines where the rotation speed is not great enough to form full film lubrication. Below is a summary of the most commonly used plain bearings; with the first three being hydrodynamic bearings and the last one is hydrostatic bearing.

phew . ... you had me worried there for a moment.

[island911]

LOL

Alright . .this is getting weird.

[patkeefe]

Agreed

[snowman]

MY 2 cents worth on all of the above:

All 911 engines have always had hardened valve SEATS, the seats are the part that leaded gas lubed back when domestic cars did not have hardened seats. Leaded gas helps raise the octane, allowing use of high compression ratios, but otherwise just gums up the engine, big time. avation gas and race gas both have about 2 grams per gallon of lead. If you mix 120 octane race gas with an equal ammount of say 90 octane unleaded gas you will get say 115 octane gas, higher than expected for a 50/50 mix but always lower than 120 octane no matter what the ratio.

Finally ALL 911 engines will run better on unleaded than leaded, except for the octane issue. If you have a low compression 911 and a choice of leaded or unleaded, unleaded is much better. If you could boost the octane sufficiently on a high compression 911, unleaded would be a better choice. There are no unleaded issues with valves on any 911 engine.

[snowman]

The valve guides used in 911 engines have a dry lube capability due to the bronze, consequently they do not have a real start up issue, like the rod and main bearings or camshaft and lifters do. 911 valve guides will outlast the rest of the engine if proper clearences are used and proper cross hatching is machined into them when installed. The clearences are such that there should be no warm up issues with the guides. There are warm up issues with the rest of the engine, especially if it has forged pistons in it. Valve lash is also a warm up issue. A 15 minute plus warm up is highly recommenced before any agressive driving or high revs.

Keeping valve lift under 0.4" is also significant for valve guide wear. I have the opinion, a result of measuring head flows of several 911 heads, that there is no reason for any street 911 to ever have more than 0.4" lift as nothing is gained by doing so. If you are a racer a serious racer and you just have to have 601 HP instead of 600 HP then go for it (more than 0.4".lift) but the guides will wear out MUCH faster.

As to valve seals, they are a good thing. They never seal to well. If you do get to much oil down the guides it will gum up the valve, cause detonation and otherwise be a bad thing to have.

[movin]

Avoid any motor oils that contain phosphorous additives; usually older dino oils did have it. Phosphorous additives will increase valve guide wear if the guides are made from bronze alloy. Most newer oils have deleted it because it also decreases O2 sensor life, and kills catalytic converters.

[stlrj]

You can make all the arguements you want about lubrication but in the end the only explanation for the premature valve guide wear on the 3.2 engines can be traced to over rich conditions that resulted in abnormally high cylinder head temperatures.

General Aviation has all the data when you run an air cooled engine rich of peak EGT, meaning richer than your 02 sensor range.

Joe

[H.G.P.]

Originally posted by stlrj
You can make all the arguements you want about lubrication but in the end the only explanation for the premature valve guide wear on the 3.2 engines can be traced to over rich conditions that resulted in abnormally high cylinder head temperatures.

General Aviation has all the data when you run an air cooled engine rich of peak EGT, meaning richer than your 02 sensor range.

Joe

What about too much advance?

So today I ride about only 4 miles or less to work, definitely not a 15 minute drive.

Did check the compression gauge constantly. From start up to work, tried to keep 60-100 on the compression gauge. So did I avoid lugging, and did the components get "hydro-lubed."??

(Also then took the long drive home, about 12 minutes or so. Today cool in the 50s, and the temp gauge never got close to say 130 or so.)

[stlrj]

What about too much advance?

That's more a detonation issue which would not be good for your pistons.

[Oldporsche]

After the theory and stuff, I do know several things about 911 motors after taking care of them for 30+ years.

Motors will wear a lot without oil pressure.

The best temperature I have found to operate 2.7L and smaller motors is 176F.

Often I have changed oil to remove water from the crankcase.

Silicone bronze guides are better than the earlier ones. Honing them to proper size throughout their length is preferable to reaming them.

Good luck,
David Duffield

[RoninLB]

Mobil1 has higher heat performance than Dino oil.

high EGT means hotter exhaust valves, means higher valve guide heat, means thinner oil boundary layer.

a rich fuel mix cools EGT.. other things being equal.

[RoninLB]

Originally posted by H.G.P.
(Also then took the long drive home, about 12 minutes or so. Today cool in the 50s, and the temp gauge never got close to say 130 or so.)

my engine needs about 10-15mi to warm up. I'd change oil every 2k mi with your routine.

[snowman]

I beg to differ with over rich conditions being a problem that will cause overheating. Running LEAN will cause overheating, serious overheating and overheating will cause serious premature wear on almost all engine components. Ronin LB is right on the money.

[patkeefe]

HGP:
When I was a kid a bought an old Dodge from a guy for $50. He used it exclusively to commute to work, which was about a mile from his house. He got in, drove to work, got in at work, drove home. It never warmed up.
So the first day I have it, I drive to a friends house, we go cruising around, and after about half an hour I hear an ungodly racket from the engine. Turns out all of the rods were knocking. The guy I got it from probably knew this all along. As long as it never got up to operating temp, nothing expanded, the oil was still thick and it was quiet. This story exemplifies the one and only good thing which can happen from insufficient warmup. Everything else is bad, which has likely been noted somewhere in this thread. Condensation, oil contamination from rich idle mix, et al.
I would even consider one range hotter spark plugs for that routine, but that could be flirting with disaster in a 911. I'll bet others on this board are much more objectively experienced with hotter plugs than I am.
Pat

[H.G.P.]

Originally posted by patkeefe
HGP:
When I was a kid a bought an old Dodge from a guy for $50. He used it exclusively to commute to work, which was about a mile from his house. He got in, drove to work, got in at work, drove home. It never warmed up.
So the first day I have it, I drive to a friends house, we go cruising around, and after about half an hour I hear an ungodly racket from the engine. Turns out all of the rods were knocking. The guy I got it from probably knew this all along. As long as it never got up to operating temp, nothing expanded, the oil was still thick and it was quiet. This story exemplifies the one and only good thing which can happen from insufficient warmup. Everything else is bad, which has likely been noted somewhere in this thread. Condensation, oil contamination from rich idle mix, et al.
I would even consider one range hotter spark plugs for that routine, but that could be flirting with disaster in a 911. I'll bet others on this board are much more objectively experienced with hotter plugs than I am.
Pat

So my goal of keeping the compression gauge up to 60-100 isn't sufficient for flow?

I'm using Castrol 10W-40, but still deciding on the oil change routine, as the engine has recently been rebuilt.

I have been able to run the car enough to reach if I recall, around 210 deg. at the max. But not all the time, as the outside temperature has been in the 50s here for many days too.

I do know when the temp reaches 180 on the gauge, the thermostat kicks right in and holds it there for some time. So my goal with the 2.0 E engine stock would be what temperature as a warm-up parameter?

[patkeefe]

HGP:
My concern on your behalf is not getting proper warm up by only driving four miles to work (I am jealous about that; I go 30). The gauges on my SC don't have any numbers, but until iI get out of the little "warm up"arc on the bottom left of the gauge, the car runs like crap ( I have CIS idle problems, hunting at warm up). My car never runs more than halfway up the gauge, nor dit it for the PO who had it for 23 years. And, I don't have an external oil cooler.

You have probably had the car for a while (correct me if I'm wrong). You know how it functions, and it's nuances, and how you've done it in the past. Continue doing that and all will likely be well.

I would second Ronin's opinion that if you do use it under marginal warmup conditons frequently, accelerate the oil change schedule. I use Castrol also, 20W-50 GTX. BTW, have you changed the oil since rebuild?
Pat