2.7 Carrera with case 901.101.101.5R

HKZ Bob · HKZ Bob's Garage

Dear Folks,
I´m building an 2.7 Carrera 210 HP out of an engine which is not original anymore.

My question is about the case.
Can I use a 5R Case for my project

What´s the differences of all the attached cases

3R
4R

My 5R

7R
8R

Greetings Bob

Steve@Rennsport · 02-07-2007, 09:46 AM

Bob:

3R, 4R, and 5R case halves are all pretty much identical and interchangable as long as the main bearing bores are true.

The 7R cases have additional stiffening ribs and are preferred for high HP applications.

AFAIK, 8R's were never made,...

HKZ Bob · HKZ Bob's Garage

Is the 5R case suitable for an 210 hp version.

Eagledriver · 02-07-2007, 02:05 PM

Bob,

I had an RS replica (210HP) engine that was built on a 4R case (1972 911T). The engine had 8 years and about 70k miles on it when I bought it. I started racing with it and after a couple of years the case cracked. It cracked in an unusual place though and was due to the original builder being over aggressive on his windage mods.

Having said all that I'd find a nice 7R case to build my engine on. That is what I replaced the cracked case with. Chances are your 5R would be fine but I don't think it's worth taking the chance. I think you can find a 7R case for around 500 dollars. That is a small price to pay compared to the cost to build the engine.

-Andy

Eagledriver · 02-07-2007, 02:06 PM

You'll probably save money on machining because most 7R cases have the larger spigots that you'll need.

-Andy

Steve@Rennsport · 02-07-2007, 02:21 PM

Quote:

Originally posted by HKZ Bob
Is the 5R case suitable for an 210 hp version.

Yessir, it is.

My own 245 HP 2.7 currently uses a 4R/5R case and has done quite well since I built the motor in 1979.

HKZ Bob · HKZ Bob's Garage

Thank you for all the great comments.

Eagledriver.
You'll probably save money on machining because most 7R cases have the larger spigots that you'll need.

But what is a spigot ?

It cracked in an unusual place though and was due to the original builder being over aggressive on his windage mods.

Where did you case broke ? windage mods.

I think you can find a 7R case for around 500 dollars. That is a small price to pay compared to the cost to build the engine.

What year & what model used 7R cases ?

Thank you

Eagledriver · 02-08-2007, 07:42 AM

Spigots are the holes the cylinders go into. The 5R case you have will have smaller spigots than a 7R from 74-77. You would have to have the spigots bored out on your case. A 7R case from 73 will have the smaller spigots (these are for 2.4 engines)

Windage mods are case mods to improve airflow inside the case. It is supposed to increase the HP of the engine. It involves grinding away at areas in the case that restrict airflow behind the pistons. In my case the builder ground away too much material near the spigot of the number 4 cylinder and the case cracked where the headstud attaches.

74-77 cases will work. I like 74 cases because those engines ran cooler (less smog equipment) and 77 cases because they had dilivar lower case studs (less stress on case).

You have alot of reading to do in order to make an informed decision on your engine. I'd start with Waynes book and Bruce Anderson's 911 performance handbook.

-Andy

HKZ Bob · HKZ Bob's Garage

Andy I am located in Germany so some vocablelury is not known.
My 5R case fits to 90mm cylinders. Does the org. 5R cases came with 84 mm.

robert

Eagledriver · 02-09-2007, 07:05 PM

Sorry about the language barrier. I think your case has been modified if it fits 90mm cylinders. As far as I know all 2.7 engines (90mm cylinders) had 7R cases. Yes the 5R was for smaller engines with 84mm cylinders.

-Andy

HKZ Bob · HKZ Bob's Garage

Eagledriver do you know who the oil pimp supplier of porsche is.

HKZ Bob · HKZ Bob's Garage

J P Stein · 02-10-2007, 09:27 AM

The 5R I've seen had the wide spigot lands of the 7R and also the external webing around the fly wheel. They don't have the internal webing at the main bearings....nor the oil bypass mod of the 76-77 7R. A 5R is less likely to be distorted than
a 7R. 3Rs (with the narrow spigot lands) are just flat scary when it comes to 90 mm cyls.

That said, I'd use a 7R as mag cases need all the help they can get. Keeping the mag case motors cool is the most important part of the equation, IMO.

Eagledriver · 02-10-2007, 08:27 PM

I don't know who makes the oil pumps. I've always used the old ones on my engines. I'd try to talk to a mail order place about a new or rebuilt one. If Pelican can't help I'd try Engine Builders Supply. They have a website and you should be able to get a phone number off that. I know you are in Germany so this is difficult. Maybe there is a local Porsche repair shop that could help. Sorry I don't have more information for you.

-Andy