docmirror

Several of us have our engines apart, and are universally seeing a lot of carbon on the intakes, right up the head port into the intake, even beyond the point of the injector.

Seems weird to me. I can understand some carbon down near the valve and maybe a bit further up, but this goes quite a way. Reversion occurs when the piston starts up, and there is unburnt fuel/air left in the cylinder. This is usually on long duration cams, I wonder if that's the case, or if it's a oil vapor issue from the crankcase breather stuff.

Hmmmm......

John Veninger

Oil vapor from the breather system

BC

Remove the oil vapor, and you will have (nearly) no carbon. It seemed perfectly normal for Porsche in those days to have a car eat oil for breakfast, lunch, and a dolup for dinner. We now know better.

docmirror

Excellent. On my non-federalized Espada, there is a breather in the front, then a little oil collection canister with a open cell filter in it, then a draft tube that aims down at the front of the ground. Not very EPA, but keeps the insides clean.

Is there a cure for this malady? I would like to keep things in there cleaner, but the only choice I can see is some kind of dump overboard down by the rear of the engine. Again, not very EPA.

BPG_Austin

Doc, I remember seeing the same thing on my car while doing this job. Good thread to follow.

can't find the emotion, but it should be little guy eating popcorn inserted here.

Ben

RyanPerrella

Doc,

Let me know what you come up with to reduce oil injection from the intake. I notice our cars have no PCV valve which to my knowledge is a valve that lets air pass but prevents oil from doing so.

PCV valves are cheap ($2) and available in all sorts of sizes. I wonder if installing one of these valves on some of the oil/air lines like the ones on the passenger side valve covers would reduce the amount of oil ingested into the engine?

Anyone else thought of this?

LT Texan

The PCV connects downstream of the butterfly, so it sees vacuum. Hence positive crankcase ventallation. Problem is the oil vapor. Need to remove that. I had a chevy 327 that I rebuilt (no broken head studs) that would hold a vacuum in the crank. Turn off the engine and you could hear the air sneaking in. PCV is good for oil control, bad for effective oil pressure. I wouldn't put it on a 928. But a better catch can to remove the oil vapor I would. (why am I writing like yoda talks?)

FlyingDog

Provent or other air/oil separator. Drysump.

PorKen

Besides the valves, the lower intake legs get a sizeable oil crust on the interior walls, too, which restricts flow.

Not sure about mid-87 up, but early 32V with the metal oil tower have a PCV insert. PCV don't really restrict oil, unfortunately. Plus, there's two or three ways for oil to be sucked into the intake, besides that valve.



When I refreshed/cleaned my intake, I capped the cam cover ports, removed the PCV valve, and ran two 15mm hoses from the tower base into a 1" hose 'over the side'. My once oily intake is spotless, now.



I keep my oil level at the lower 'Fill' mark. This stops almost all oil ejection on the dyno.

docmirror

Yeah, we'd need to put a air/oil sep on it. Could be a problem with that as the Porsche doesn't have a down low oil return that isn't pressurized. Maybe a tap off the side of the dipstick would work. I have one on my airplane and it works pretty well. The only issue with the separator is it can't distinguish between oil and products of combustion. So, the oil tends to thin out if the car isn't driven for a while regularly.

RyanPerrella

Ken i never knew that about the PCV valve in the oil filler neck. I dont know if the later plastic ones have them. ow i wouldnt be surprised if they did, i never suspected that to be the spot for them. If they are integral then i think that would make the plastic oil filler neck a consumable item.

Where does most of the offending oil enter the intake manifold from? There must be some type of inline like oil/air separator that could work. It may not remove everything but wouldnt it reduce the amount of oil that gets through those rubber lines, or would it at some point block the line and cause some other issue?

FlyingDog

See post #8. 928 Specialists sells them.

RyanPerrella

i was thinking something cheaper though

Does the pro-vent deal make the GTS oil control upgrade on S4's obsolete?

Shane

I did pretty much the same thing Ken did, but routed my cam cover over as well instead of capping them.

David L. Lutz

My S4 is also torn down and I have the same build up Doc is talking about. I was going to convert my 87' with the GTS kit 928 specialists sells. This kit at least vents both sides. Do ya'll think this is some what of an improvement?