Fuhrmann to Mezger

[ChrisW.]

At what point did it change and what are the differences ?

I seem to recall with the 930 Turbo but ?

Was the 911 3.0 Fuhrmann, or Mezger ?

[C4ME]

I thought Fuhrmann was the designer of the 356 4 cylinder engine and Mezger designed the original 2.0 litre 901 engine for the 911 in 1964. So all aircooled 911 engines were Mezger.

[C4ME]

PS the 930 was part of the change from a magnesium crankcase to an aluminium crankcase, having been aluminium for the original 1964 2.0 engine but going to magnesium for the last year of the 2.0 plus then the 2.2, 2.4 and 2.7 engines. The 3.0 RS, 930 Turbo and Carrera 3 engines were then aluminium as were all later versions.

[ChrisW.]

Interesting, that would certainly tidy things up ...

So all six cylinder engines were Mezger based I guess on the 356 engines from Fuhrmann.

It's my recollection that the Magnesium crankcases were problematical .... they often needed to be line-bored and shuttle-pinned to make them more stable.

The 3R crankcases were magnesium ... the 5R's were the crossover ... and then there was a 7R ? Aluminium ?

The step change as I understand it came with the 930 Turbo engine which had 5 main bearings (instead of 3) and set the scene for the 3.2 and beyond ...

[SRT Hellcat]

I believe that even the first 2 litre 911 engines were five main bearing cranks. Some 2.7RS engines were mag and a some were aluminium

[Yellow491]

From memory
Selenium alloy was used,which minimses internal corrosion,mags do corrode internaly as well as externally
The early sand cast cases were /are good.
3.0ltr carrera and turbo used the alloy instead of mag cases.
mag cases went through many changes,mainly internal strengthening up to the 7r cases,shuffle pinning etc was only necessary if pushing the size or output of the engine ,or prudent on a rebuild as they are getting old now.
They were great if used as designed,but once stretching the output,like anything else they need modifications.
I had a 906 engine 2.0ltr mag case,234bhp,reliable as anything,just built a 904 2.0 6 engine,and searched down a rare late 2.0 ltr 7r cases,as this had all the 2.7 strengthening with the 2.0 cylinder size apertures,shuffle pinned and other mods,so should be super strong and reliable with a target bhp of 240 in a 700kg car
The 2.8rsr used mag cases,reasonably reliable for the abuse they got.

[ChrisW.]

Many thanks (Paul ?) ... I was being a little lazy but wanted to get an alternative conversation going ...

I will hunt out the info on the 930 bottom-end and feel very much more comfortable with all the six cylinder engines being Mezger. I was hunting for a transition that had already happened ... 'hardly surprising that I couldn't find it !

[Yellow491]

ChrisW. said:

Many thanks (Paul ?) ... I was being a little lazy but wanted to get an alternative conversation going ...

I will hunt out the info on the 930 bottom-end and feel very much more comfortable with all the six cylinder engines being Mezger. I was hunting for a transition that had already happened ... 'hardly surprising that I couldn't find it !

Bit more interesting than the fortune tellers of future pricing,devalue,doom and gloom and of course now experts on the covid,only happens on PH
The 930 bottom end is fairly bomb proof,uprated oil pump is always good,and the bigger spacing of the head bolts for extra cc capacity and so on.
Are you building something
Yes its paul

[C4ME]

If you have time on your hands at the moment then two books

How To Rebuild And Modify Porsche 911 Engines 1965 - 1989
Wayne Dempsey
ISBN 0752748310872

Porsche 911 Performance Handbook 1963 - 1998
Bruce Anderson
ISBN 9780760331804

Have a lot of information between them on the engines, crankcases,
pistons and barrels, short and long stroke cranks and performance engine options. They are not perfect and have some inaccuracies but a good source of knowledge.

Edited by C4ME on Monday 6th April 17:59

[BertBert]

Yellow491 said:

,just built a 904 2.0 6 engine,and searched down a rare late 2.0 ltr 7r cases,as this had all the 2.7 strengthening with the 2.0 cylinder size apertures,shuffle pinned and other mods,so should be super strong and reliable with a target bhp of 240 in a 700kg car

Sounds interesting. I've got a 2.0 on carbs in my 69t which is reputedly an E spec. It certainly has injector holes in the head. I want to do a rebuild and turn it into something with more oomph. Happy to get more at higher revs, so thinking S spec, maybe out to 2.2. how would you your approach it?

Cheers
Bert

[Yellow491]

BertBert said:

Yellow491 said:

,just built a 904 2.0 6 engine,and searched down a rare late 2.0 ltr 7r cases,as this had all the 2.7 strengthening with the 2.0 cylinder size apertures,shuffle pinned and other mods,so should be super strong and reliable with a target bhp of 240 in a 700kg car

Sounds interesting. I've got a 2.0 on carbs in my 69t which is reputedly an E spec. It certainly has injector holes in the head. I want to do a rebuild and turn it into something with more oomph. Happy to get more at higher revs, so thinking S spec, maybe out to 2.2. how would you your approach it?

Cheers
Bert

Something interesting would be s heads or rework your e heads, s or better comp pistons,i am running a genuine 10.5 comp ratio,DC cams from the usa,happy to share my spec of cams,better than 906/rsr cams with a better spread of torque and all the way upto 8200rpm.E cams are ok but have limitations.
Also using carrillo rods,cases all gasflowed,pinned and oil bypass mod,big oil pump,New factory steel head studs,tall manifolds and 46 webbers with necked down venturis,40,s will do a good job if set up correctly and in good condition.The real expensive part is running lwt rockers,i run factory 964 rsr lwt adjustable rockers,there are non factory rockers on the market but some have proven not reliable,can use modded 993 rockers or even better early forged rockers with max revs of say 7800,mine are good to 8500 plus! But they are more than 400 each.
Twin spark also,not for much performance gain,but safer on the engine with carbs and getting a consistant and safe fuel burn,and keeps the pistons upright and square.
Building a good 2.0 screamer can get expensive,but when done properly, well reliable and produce good power.
Also had all rotating parts balanced at Jud,says it all really,a very important part of the build to get a fully balanced engine for the high rpm at consisant throttle,as in flat out for long periods.
Hope some of this is usefull.

[ChrisW.]

I really wish i had the skills to do this but ... regretfully not !

Although I have developed my GT4, it has all been a careful selection of expert work by others ...

But I do admire and enjoy the engineering heritage of Porsche ... hence my interest ...

[ChrisW.]

OK ... well a little research has been done using Peter Morgan's Ultimate Buyers guide 911 (1964-1989).

The original 2.0l six had a 7 main bearing crankshaft with 8 main bearings ... one outboard of the intermediate shaft drive gear !

The '73 2.7 was close to it's limit without modification even in 7R version ... producing 210bhp (6500 rpm) and 188 ft lbs (5100 rpm) ...

This figure wasn't exceeded (naturally aspirated) until the 3.2 arrived in 1984 !!!

But the numbers are interesting and the 930 Turbo bottom end (930/20) was a big step-up from 2.7RS (911/83) ...
New Aluminium crankcase / Nikasil liners / 4 journal camshaft housing / ... no benefit from line boring and shuffle pinning. It was described as offering bullet proof reliability with the 3.3 Turbo ... see below

'73 2.7 911/83 210(6500) / 188(5100)
'76 3.0 930/02 200(6000) / 188(4200)
'78 3.0 930/03 180(5500) / 196(5250)
'80 3.0 930/09 188(5500) / 196(5250)
'81 3.0 930/10 204 (5900) / 197(?)
'84 3.2 930/20 231(5900) / 210(4800)

930 Turbo
'75 3.0 930/20 260(5500) / 252(4000) ... no intercooler.
'78 3.3 930/60 300(5500) / 304(4000) ... intercooler !

QED ... the 911/83 bottom end simply could not provide a reliable solution for the turbocharged motors that started in 1975 ...

[C4ME]

ChrisW. said:

QED ... the 911/83 bottom end simply could not provide a reliable solution for the turbocharged motors that started in 1975 ...

Yes it had pretty much reached its limit by the time of the 2.7RS. It was very much over engineered in the original 2.0 form but had steadily become more stressed as engine size and power had increased. The 930 crankcase reset the bar (back to being over engineered).

A 930 crankcase with a 2.0 66mm crankshaft is an extremely bullet proof basis for building a short stroke big bore high performance engine. The disadvantage is the extra weight over the earlier mag cases so it is a case of picking the right one for the engine you want to build.

[Yellow491]

Not sure where you are going with this chris.
The early 930/sc cases are allowed for fia spec engine builds of 3.0ltr rsr etc,but once you stretch these cases out to 3,4/3.5,they start having issues and pin the cases etc is required.
The main restriction was head stud spacing/vs capicity vs weekness between the thinner walls of the cylinder apertures.
The best cases are the 964/993,even these have there limits once boundaries are pushed,my 993gt2r i used to race,the large main bearing at the back of the engine next to the flywheel,would get that much flex from the crank etc,it would oval the bearing! With a honest 530bhp.
As said anderson book is more usefull than the morgan books,i have 2 spare Anderson books,happy to send you one to read if you want.
Anderson used to do some great open forum workshops on engine builds and modifications.

[ChrisW.]

Many thanks

Where I am going with this is the conversation, I'm not en engineer but the engineering fascinates me ... and yes please to borrowing the Anderson book if I may ...

I have pulled out a book I have on the '74 RS3.0 (106 built of which 50 were converted to RSR) ... according to Peter Morgan many more engines were produced than cars ... in the customer car the compression ratio was 9.8:1 producing 230bhp at 6200rpm and 203 ft lbs at 5000 rpm. In RSR 911/74 spec the compression ratio was 10.3:1 producing 315 bhp at 8000 rpm and 240 ft lbs at 6500 rpm ... so was this based on the 930 if 911/74 ?

In the middle is the 2.8 911/72 producing 300bhp at 8000 rpm and 222 ft lbs at 6500 rpm.

It took most of it's underpinnings from the 2.8 RSR with brakes from the 917 .... Porsche were really flying in this time

I have the Gruber and Konradsheim Rs book (no 120/3000 and signed) which I now have the time to read again ...

Edited by ChrisW. on Saturday 11th April 19:07

Edited by ChrisW. on Saturday 11th April 19:14