How big can 911 motors get?

[Wrecked944]

I read recently that the bore centers on the Porsche flat six have not changed since the very first 911's were produced. If this is true, would it not place a hard upper limit on the displacement of 911 motors? I've never heard of or read about a 911 motor greater than 3.8 liters. So is this as large as they can possible grow?

And is this continuity in size the reason you can put a relatively modern 3.6 into an early car designed for a 2.7?

[ischmitz]

I think I once came across a 4.0 liter big bore kit when Googeling around.

[Amac]

I agree, 4.0 liter is the largest I've seen.
I think cooling is a problem on anything larger.

[Porschekid962]

you can go bigger than 4 litres, the factory did it. they took two flat six engines, created a common crankshaft, threw it together after many hours of engineering work and the 917 fat twelve was born! haha. as far as a 6 banger, 4 litres is the largest displacement i have ever heard about as well, the 3.8 seems to make more sense since the factory made a 3.8 engine once.

[Rick Lee]

I saw a 4.0 liter engine with my own eyes. While touring Ruf, they had a 3.2 Carrera engine on a bench, which they were boring out to 4.0 liters. I wish I could take that one for a spin.

[xlr8]

[thabaer]

Russ, you one sick puppy!

Howza 'bout oval pistons ala Honda GP bike

[larry47us]

So, uhhhhh, Russ. That is the crankshaft on the new Porsche engine?

larry

[vash]

i wonder what the package of plastigauge looks like for that crankshaft?

[Az911]

CMW used to have a 4.0l kit. I think that was the kit with the CF pistions.

[JeremyD]

Anybody out there have a 4.0 running?

[ischmitz]

Originally posted by unfixed
i wonder what the package of plastigauge looks like for that crankshaft?

and I wonder what the rev limit is on that engine, 200 RPM maybe

[Randy Webb]

It depends on how this engine is defined. If you used higher strength materials but the same design and bore centers you could probably go beoynd 4 L.

It is not the bore centers but the overall size and mounting points that allow the ease of engine swapping we enjoy. In fact, the 911 engines have been getting smaller over the years and the rear seat is expanding - witness the 996. A few more decades and tey'll turn the 911 into a true 4 seater - but by then I expect we will all be driving "skateboard" design fuel cell cars with very low centers of gravity and enormous handling and accel. potentials.

[Bill Verburg]

I looked at a 993 Cup car last week w/ a cheater 4 liter. Supposedly a factory motor.

CMW used to offer a 4 liter kit w/ billet heads. Dr. Timmins has one I believe.

[juan ruiz]

Long ago I saw something about a 4.2 Liters I heard of 4.5 liter but dont have any inf to back that up.

[john_colasante]

Originally posted by Bill Verburg
I looked at a 993 Cup car last week w/ a cheater 4 liter.

I'm sure when it was racing it was "bone stock". We'll be waiting for you at the scrutineering impound Bill...

[Bill Verburg]

No it wasn't racing in PCA and I did pass on it.

[Jack Olsen]

CMW used to make both 4.0 and 4.2 kits. I'm not sure the company's still around. Their web site has disappeared.

[ttweed]

Originally posted by Jeremy964
Anybody out there have a 4.0 running?

Kenny Rumbaugh from Scott's Porsche in Chula Vista has a 4.0 in his full race 914. He claimed 400HP and 320 ft.lbs. out of it. I believe he stroked a 3.8, though, as opposed to using larger jugs. It was for sale a while back. I have run with him at WSIR and Spring Mountain, and the car is very fast.

TT

[thabaer]

Originally posted by Randy Webb
A few more decades and tey'll turn the 911 into a true 4 seater

Just read a report this morning that has Porsche saying they are already working on it to compete w/ M5s and E55s.