Neat Post of the day: Porsche 911 3-Valve Engine!

[Wayne 962]

A very kind fellow emailed me a few months ago asking me to put this up on the site. I got very busy and sidetracked by a few important things (server failures, kid in hospital, etc - everything's fine now), and I'm just starting to catch up. This stuff was / is too cool to let go, so here it is, more info to come:

[Wayne 962]

[Wayne 962]

I?ve never posted, but from time to time, I?ve provided pics or info-material to certain board members.

I was infected by the Porsche virus, when I was a young boy, as one of my neighbours had several Porsche race cars. I spent countless hours at his little shop starring at the cars. Already during those days, I started collecting Porsche related stuff. I have a collection of old articles and road/track tests from various European magazines and I?m pretty sure that some of them could be of interest for the community.

In addition to that, an Italian friend of mine who is a 70 year old engine builder with a particular addiction to Porsche opened his archive to me. In his long career, he was involved in countless projects from the tiny Abarth engines, up to the Subaru commissioned F1 turbo and NA engines from Motori Moderni, but his real passion were and still are Porsche cars. He started hill climb racing with a 904 and in the 70ies, he raced with the 934 and 935. He built some really particular things, such as a 3-Valve, DOHC, slide valve MFI Porsche flat 6 from 1968 (I have many pics)? In the mid 80ties, he built his own Porsche-956-engined Group C car. Last year, he closed his shop and he only works for some old customers, now. He?s currently building a nice 3.0 RSR replica and he?s going to rebuild a 935 engine pretty soon. He has tons of (black and white) pics from the good old days, for example from his Targa Florio participations?

I'm convinced that a part of the material has not been published on other forums and some project pics were never posted, for sure. As I already said, I?ve seen a lot of enthusiasm and knowledge on your board and if you are interested, I?m willed to share my material with you. I prefer to remain in the background and I would leave it up to you to select the right occasion for posting.

What do you think of it?

the 3-valve engine is based on a porsche 911 2.0 engine

cylinders 6
induction valves 12
exhaust valves 6
distributor marelli - twin plug
cams 4 (4 bearings)
bore 80 mm
stroke 66 mm
max rpm 9.000
slide valve set up carrera 10 (910)
intake stacks 917
mfi pump: Carrera 10 - bosch
spark plugs: 2 x10 mm/cyl
distributor: Carrera 10 - marelli
wiring loom: Marelli
cooling fan set up: Carrera 10
exhaust: 3in1+ 3in1 headers with carrera 10 megaphones
oil-pump: Carrera 10
flywheel: Custom steel
induction ports: 38 mm
induction valves: 2 x 33 mm
exhaust port: 42,5 mm
exhaust valves: 1 x 39,5 mm
valve springs: Double
c/r: 12,5 : 1
piston rings: Top 1,5mm l
second 1,5mm
oil control 3mm
con rods: Carrera 10 titanium
crankshaft: Carrera 10
engine case: Carrera10
cam housings: Cast alusil
valve covers 4 magnesium with integrated oiling channels


a second version of the engine was planned with gear-driven cams, a shorter stroke with a special crank and a 83mm bore.
They paid particular attention to the cam oiling and the oil cooling capacity of the engine was nearly doubled.

I hope you like it. More to come.

-end

[BURN-BROS]

Very cool Wayne, thanks for posting! Love the splayed intake .

[sc_rufctr]

Awesome info... You can see someone's blood sweat and tears in those castings.

The machining is a bit rough but these are prototypes so that's to be expected.

[djpateman]

The source may be a treasure trove of impressive information and photos. This should be carefully developed.

[CBRacerX]

Fascinating! There is some recent activity around new tech 4 valve air cooled heads in the Engine Rebuilding forum - this would fit right in.

[jcge]

Very interesting - maintaining a single exhaust valve to maintain air cooling. (no overheat between two exhaust seats)

2.0L @ 9000rpm and 12.5:1 CR = .........

[TRE Cup]

thank you wayne!
awesome !!

[Winter]

One of the things I love about this forum are the constant surprises that can be found here complimented by the great info that allows me to get my hands dirty and work on my car by myself.

From Pesto's car with a very troubled history, to this engine, to the hint I got from someone to look really hard in the tangled mess of wiring under my dash for a wire that might need to be connected to my hazard switch and thus make my blinkers start 'a blinking, this forum has it all!

Thanks to Wayne and everyone else who makes it such an interesting place to pass the time!

---

Tom '75 targa

[Zeke]

dayumm!

[carrera turbo]

see what happens i was looking for something else and now im sucked into another thread to take more time from the cars i need to attend to.

but man do i enjoy stuff like this keep it coming


cheers ed

[Beetspeed]

Originally Posted by jcge

Very interesting - maintaining a single exhaust valve to maintain air cooling. (no overheat between two exhaust seats)

Exactly. From what I learned, that was the reason Porsche did not use 4-valve heads on aircooled engines.
Ludwig Apfelbeck's thoughts as well as he made a 3 valve twin spark OHC head for the type 4 engine, which could probably be used on a 911 motor as well...

www.apfelbeck.nl

[wesayso]

Thanks for pointing me to this thread Beetspeed
There are definitely similarities between these heads and Apfelbeck's Type IV heads:



The dual camshaft on the above 911 heads are cool though! Nice stuff... one wonders if there aren't many more undiscovered gems and projects like these hidden in old sheds...

[Francosporto3C]

The difference in thermal pressure on the exhaust valve area is related to the 911 3V being DOHC and the Apfelbeck 3V being SOHC. The exhaust valve bulk together with casings for plugs and studs will become more disadvantageous for SOHC because DOHC setup allows both plugs positioned away from the exhaust bulk providing more open space for coolant closely along the very hot exhaust valve casing. Obviously 4V setup concentrates even more bulk that will be poorly accessible for cooling air especially in between the canals and seats. So alternatively twin exhaust canals should be situated well apart from each other often interfering with the existing studs. Now one realizes the need for water as coolant being more effective in cramped areas such as in between exhaust canals.
So considering both enjoyable constructive jobs Apfelbeck did a fantastic job upgrading Beatles to almost Porsche level while the 911 3V upgrade design exercise only makes sense on Porsche level for maintaining air as coolant medium ……. saving weight but loosing surplus thermal absorption compared to water as coolant.

[jpnovak]

Very cool.

Looks like an M96 prototype.

[fred cook]

Noticed that the intake guides are cut back to the port surface while the exhaust guide extends down into the exhaust port just above the exhaust valve head. Makes one wonder if the intake ports were flow tested and needed some help to match the flow characteristics of the larger exhaust port. Or, perhaps the larger head on the exhaust valve needed a longer guide for more support. Also, the intake and exhaust valves appear to be at a steeper angle in relation to each other with the spark plug hole located where the intake charge would get an optimum spark from both plugs. Some very good design work here!

[dkirk]

Thank you Wayne - very interesting!

[darcher]

Very cool but I have a question: does anyone retrofit roller cam followers to get around the lower Zinc and Phosphorus in the oil now? Detroit engine builders and hotrodders do it all the time both on OHC and pushrod engines...

[Tippy]

Pants are tighter....