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PostPosted: Sun Nov 04, 2018 6:55 pm 
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While I haven't inspected every C Porsche ever produced, it is my belief that all 356's had vented valve covers. The non-vented valve covers were introduced with 912's as part of the closed crankcase ventilation system mandated by the U.S. government to sell cars over here. Before this closed system was required, there was no reason to introduce non-vented valve covers.
Look inside your old valve covers. There is a small screen, usually quite mangled by this time, that leads to a passage exiting outside the cover. Of course S90 valve covers had fancier vent systems with sliding balls to close the vent when driving hard. All these vents barfed lots of oil out the cover and were a pain to clean up, therefore owners would block the vents, or get 912 covers after they came out. Yes, your motor will vent adequately through the oil filler's downtube if you change to 912 valve covers; but if you rev your motor like David and me, I think more venting is better.

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PostPosted: Sun Nov 04, 2018 7:32 pm 
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My `C` (131 899) - Engine No. 716 676 had Rocker Covers vented with the Ball and Mesh system

The engine is original to the car and had 40,837 miles on it when I purchased it

It is a RHD car very near the end of production

Of course Porsche may have been clearing the bins

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PostPosted: Sun Nov 04, 2018 10:51 pm 
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Ron LaDow wrote:
"My Euro S90 has vented covers, and I think I’ve about had it with cleaning up that mess." - Jim
"My Euro-spec SC had vented covers when I got it about 10 years ago. It no longer has vented covers ..." - Greg.

First, Greg: Did your Euro-heater car vent the case to the right hand carb? Inquiring minds...

Yes - still has the original hose, too
I haven't had any oil related issues with the non-vented covers - you can see in the picture though that the air filter is oily - filters better that way!


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PostPosted: Sun Nov 04, 2018 11:03 pm 
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Craig Richter wrote:
While I haven't inspected every C Porsche ever produced, it is my belief that all 356's had vented valve covers. The non-vented valve covers were introduced with 912's as part of the closed crankcase ventilation system mandated by the U.S. government to sell cars over here.

Craig, I've had at least 8 Cs (a couple of SCs, also). Except for the odd 'one-side vented' rocker boxes (likely replacement), they were all non-vented. The weight of the evidence I've seen says cars with the case-to-carb vent had nice, dry, non-vented rocker boxes.

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PostPosted: Sun Nov 04, 2018 11:07 pm 
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Greg Bryan wrote:
Ron LaDow wrote:
[...]First, Greg: Did your Euro-heater car vent the case to the right hand carb? Inquiring minds...

Yes - still has the original hose, too
I haven't had any oil related issues with the non-vented covers - you can see in the picture though that the air filter is oily - filters better that way!

I had assumed it was the US specs which required the change; thanks for the info.
And since those things only keep out the rocks and the stray sparrow, it's good to see the oiling kills two birds with one stone.

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PostPosted: Mon Nov 05, 2018 12:05 am 
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Thanks for the info, guys. I have no problem being corrected. I've never owned one of the "new cars".

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PostPosted: Mon Nov 05, 2018 11:08 am 
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Further to Mike Smiths RHD 356C, my 356C with a CoA completion date of June 12th 1964 Chassis 129856 engine 713839 was fitted with vented rocker covers which I have plugged with silicone rubber plugs held in place with a spring and washer holding the ball against the plug. (It can be returned to vented form easily). This has eliminated the small amount of oil that inevitably used to be emitted onto the "J" tube where it burns off. The crankcase breather goes to the RH carburettor and that seems to adequately deal with any oil vapours and the small bit of emulsion in cold weather.
I was told that as my car is one of the early 356C models (plain hubcaps) Porsche probably used up any Super 90 rocker covers they had in stock and only changed to the non vented covers when the old stock was used up. (Fake News ?)

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PostPosted: Mon Nov 05, 2018 12:53 pm 
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There shouldn't be a little filter on the oil filler vent/tube, unless you like breathing the oil vapors via the fan, even w/the heat system is shut off! The extra line on the 912 filler can is for wet(?) oil return.

The C series started w/the 'closed' vent system when the USA rules went into effect and continued on the 912s and all the rest of Porsches from then on.

For the early crankcase breathing, the 'downpipe' is vented below the case while the later breathers is connected w/a hose connected to the right carb air filter; It also can be vented downward, but if the engine is having a lotta blow-by, it'll wet the underside incl. the exhaust!


I've used vented or non-vented valve covers--pending on which car series to be correct for concours.
I did close some vented covers w/oil resistant RTV (when I ran out of vented covers) preventing leaks.


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PostPosted: Thu Nov 08, 2018 9:42 am 
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My 61 1600 Super Coupe with original engine has vented covers with screen, ball and cotter pin. Quite messy, always oil covered. No venting from the oil fill to the right carburetor. Would venting from oil fill to right carb air intake (as pictured above) allow me to close the valve cover vents. Would this work properly on my engine?


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PostPosted: Thu Nov 08, 2018 10:20 am 
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You can close the vents without changing anything else, in fact I believe it would be best to not change anything else.

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PostPosted: Thu Nov 08, 2018 10:55 pm 
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Craig Richter wrote:
You can close the vents without changing anything else, in fact I believe it would be best to not change anything else.
From memory, you can flatten the vents from the inside (against some sort of anvil). Probably not 100%; I did a bit of brazing to make sure.

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PostPosted: Fri Nov 09, 2018 4:59 am 
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Quote:
My `C` (131 899) - Engine No. 716 676 had Rocker Covers vented with the Ball and Mesh system

The engine is original to the car and had 40,837 miles on it when I purchased it

It is a RHD car very near the end of production

Of course Porsche may have been clearing the bins


I guess that I should have also said that by engine breaths in the Standard `C` way, from the Oil Filler box into the R/H Air Cleaner below the Paper Element - it uses the Convoluted Plastic Hose

I have never experienced any Oil leakage from the Rocker Covers

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PostPosted: Sat Nov 10, 2018 11:50 am 
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Ron
I will have to try that next time valve covers are off.


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PostPosted: Sat Nov 10, 2018 12:09 pm 
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BTW, the S90 ball-checked valve covers won't fit on engine heads having the casting changed to a blind center hole boss for the long bolt thru the intake manifold.


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PostPosted: Sat Nov 10, 2018 12:26 pm 
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My latest message didn't take place on the post/reply(?), so here's a repeat;

Actually there were/are 3-versions of valve covers:
1st is vented #546 04 020,
2nd is S90 w/ball check vent #616 104 043 01,
3rd is non-vented (for USA only) #597 104 305 00.

There were some SCs and early 912s having the S90 covers, but the later cylinder heads had a blind hole casting change for the center long bolt retaining the intake manifold to prevent any leakage.


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