911 SC engine upgrade. What would you do?

[Vereeken]

Originally Posted by wayner

JE. And Corrillo pistons at 9.5:1 are Max Moritz style and you can spec higher or lower compression

You would put these in the 3.2 conversion or in the standard 3.0?

[Vereeken]

Originally Posted by will hung

This is false. SSI's will still provide the heat needed for your auto heat. Auto heat is controlled in your interior. The heat exchangers around your exhaust provide the heat. SSI's provide more heat than the stock exchangers. On cool spring and fall nights, if I'm wearing flip flops and I have the foot well blowers on, I can burn my feet. And with their stainless construction, there is less of a chance of exhaust gases leaking into your interior if your exhaust develops a leak.

Plus, the sound. The sound a 911 makes on SSI's is worth the price of admission alone.

As far as power band. What I was getting at was the combination of 964 cams and SSI's created a broad power band from idle to red line and your rotating assembly is still stock.

If you don't need new P&C's, you will spend way less for a set of 964 cams and SSI's then you will for the short stroke 3.2 conversion. But it's your money.

I am not so sure of that. I understand the autoheat system pretty well as I managed to get it working instead of stomping up 1200€ for the box between the seats. The full autoheat system has a -inefficient- blower on top of the engine. I believe the SSI cancel that by the way they are installed and only uses air pushed by the fan to get the heat up front.

I do agree that the SSI exchange the heat better then the standard Dansk stuff Porsche used.

[wayner]

Originally Posted by Vereeken

You would put these in the 3.2 conversion or in the standard 3.0?

It depends on what size cylinders you use (stock or bored out.)
They are available in both bore sizes.

A 3.2 is a later 3.2 (carrera) engine
A 3.2 conversion is an earlier 3.0 converted to a 3.2 (short stroke) engine
Commonly referred to as simply a 3.2ss (versus the later 3.2 which has a longer stroke)

So if you have a 3.0, and you want more displacement, go to a 3.2ss, and chose whatever compression pistons you would like at that size

[Josh D]

Originally Posted by Vereeken

I am not so sure of that. I understand the autoheat system pretty well as I managed to get it working instead of stomping up 1200€ for the box between the seats. The full autoheat system has a -inefficient- blower on top of the engine. I believe the SSI cancel that by the way they are installed and only uses air pushed by the fan to get the heat up front.

I do agree that the SSI exchange the heat better then the standard Dansk stuff Porsche used.

I have early heat exchangers (same design as SSI, but in regular steel) with backdated heat and the autoheat controller, and trust me, it works just fine even without the supplemental blower. Even at temps as low as freezing, I can't run my autoheat setting any higher than 3 or my feet get too toasty. It auto adjusts with the engine speed and air volume just fine.

[will hung]

Originally Posted by Vereeken

I am not so sure of that. I understand the autoheat system pretty well as I managed to get it working instead of stomping up 1200€ for the box between the seats. The full autoheat system has a -inefficient- blower on top of the engine. I believe the SSI cancel that by the way they are installed and only uses air pushed by the fan to get the heat up front.

I do agree that the SSI exchange the heat better then the standard Dansk stuff Porsche used.

I am fully away of the auxiliary fan on top of the engine. SSI's replace your factory heat exchangers and that's it. You can leave your current heating system in exactly how it is now and it will work exactly the same. It will just operate hotter.

[wayner]

Originally Posted by will hung

It will just operate hotter.

(and less rustier...)

[will hung]

Originally Posted by wayner

(and less rustier...)

This is very true and why they were created. The original owner of SSI got sick and tired of patching the early heat exchangers he installed on his SC.

One thing to consider for the OP. What are your emissions laws where you live? You need to investigate what any planned mods will do to the legality of your car.

[jess p]

I have an 81 SC and I'm rebuilding the engine right now. I'm backdating the exhaust
to 74 which will give me 10 hp. Boat tailing the crank is good for 10 hp. I'm
removing the cis and installing 40mm webers for another 10 hp. 3.2 cylinders
with 22 mm wrist pins and different pistons and a 911S cams with a 78 dizzy
with a recurve and I'm looking at 300 hp and a flat torque curve

[chris_seven]

Do you think 300hp is achievable with 40IDA carbs? - it seems a bit optimistic.

[chris_seven]

Originally Posted by wayner

Speaking for myself, I don't know where the threshold is but from what I understand the main safety net for compression is twin plug heads.

We run 10.5: pistons using single plugs and the engine runs quite well but we also have S cams fitted.

I am not sure about what problems will occur due to running a higher compression with a 'softer' cam such as a 964.

Plug shrouding due to a high domed piston is a much bigger problem with the 2.0 litre where increasing compression much beyond 10.5 tends to reduce low end performance.

2.0 litre single plug race engine don't seem to get much beyond 200 hp and have poor low end performance.

The shallower chamber used in later engines is a little more forgiving and at 10.5:1 works quite well without twin plugs.

It would be good to compare single plug 9.5:1 and 10.5:1 engines to see what happens to the Torque behavior.

The pin offset is also interesting and I would be keen to find a table of different pin offsets with regard to bore and stroke combinations.

If I have understood correctly an offset pin will reduce the inertia loading regardless of the direction of the offset.

The thrust, however, will be different from side to side depending on the direction of the offset.

I guess most piston manufacturers believe that the inertia loading has the most importance as the thrust will change depending on which side of the engine is considered.

As far as I know none of the 911 pistons are 'handed' and I wonder if this is worth considering?

[Vereeken]

Thanks to everyone for suggestions and idea's.

I think i would like to go for the following set-up correct me if you see anything off:

On the original case to 3.2 with the use of 98mm pistons.

No 964 cam, standard SC cam retained.
Stock CIS retained.

On the pistons I understand I have the choice between JE and Carillo?

Are the standard SC con rods re-usable on this setup? I read on one of the posts an issue witht the pin?

What about compression? 9.5?

On the exhaust most likely SSI mated to a muffler 2 in 2 out.

What would this set-up run in the US money wise (labor plus parts) Ball park figure ofcourse.

Michel

[Jonny H]

Ok, Here's mine.

Euro 204 BHP
Standard 3.0 P&Cs
Standard CIS
964 cams
SSIs
Classic Retrofit CDI+ ignition.

This dyno run was against a standard low mileage (65K) SC which made 199 BHP on this dyno.

Green - standard SC
Orange - The same standard SC with CDI+ ignition (no ignition timing changes)
Blue - My SC as per above spec plus a little extra ignition advance.

I asked my builder to time the 964 cams for low down power. High RPM power doesn't deliver the fun IMO.

It turned out just how I wanted. A whole thick wedge of extra torque added where you feel it most.

[wayner]

Originally Posted by Vereeken

What would this set-up run in the US money wise (labor plus parts) Ball park figure ofcourse.

Michel

In addition to the cost of a stock build:

Other than the SSI and custom muffler, the piston increase and cylinder boring will add"only" a grand or so for pistons but up to and additional 3 grand or so for new cylinders or reboring and plating the old ones??

So, just go 9.5:1 pistons (assuming your bores are good) and its a little over a grand more

Or goes up to a 3.2 with pistons and cylinders for about 4grand more $US (or almost $7 grand for Mahle)
(the real big money is in gaskets and labour it seems. These engines take a lot of labour).

[Josh D]

Originally Posted by wayner

In addition to the cost of a stock build:

Other than the SSI and custom muffler, the piston increase and cylinder boring will add"only" a grand or so for pistons but up to and additional 3 grand or so for new cylinders or reboring and plating the old ones??

So, just go 9.5:1 pistons (assuming your bores are good) and its a little over a grand more

Or goes up to a 3.2 with pistons and cylinders for about 4grand more $US (or almost $7 grand for Mahle)
(the real big money is in gaskets and labour it seems. These engines take a lot of labour).

A bore and plate job is $900 with EBS if I remember correctly. But it's recommended you use 3.2 Carrera cylinders that don't have the compression ring groove the SC cylinders have. I found my set here on Pelican for $500. So I'm into 98mm nikasil plated cylinders for about $1500 w/shipping. I found my barely used 98mm Max Moritz pistons here on Pelican for $500 shipped. Total Seal rings were $250. So I'm into 98mm P&C's with rings for $2250.
Deals can be had if your not in a hurry, diligently watch the classifieds, and be ready to pounce when what you need pops up for sale.

[911SauCy]

Originally Posted by jess p

I have an 81 SC and I'm rebuilding the engine right now. I'm backdating the exhaust
to 74 which will give me 10 hp. Boat tailing the crank is good for 10 hp. I'm
removing the cis and installing 40mm webers for another 10 hp. 3.2 cylinders
with 22 mm wrist pins and different pistons and a 911S cams with a 78 dizzy
with a recurve and I'm looking at 300 hp and a flat torque curve

LOL, you'll never see 300hp with that set-up, never...sorry.

[Jonny H]

Lots of talk here.

Am I really the only modified SC owner here who can post an actual dyno plot?

['76 911S 3.0]

3.2ss (EBS 98mm bore cylinders, JE 9.5:1 98mm pistons), 964 camshafts, re-curved WUR, 4R CIS intake manifold.

[Vereeken]

Originally Posted by Josh D

A bore and plate job is $900 with EBS if I remember correctly. But it's recommended you use 3.2 Carrera cylinders that don't have the compression ring groove the SC cylinders have. I found my set here on Pelican for $500. So I'm into 98mm nikasil plated cylinders for about $1500 w/shipping. I found my barely used 98mm Max Moritz pistons here on Pelican for $500 shipped. Total Seal rings were $250. So I'm into 98mm P&C's with rings for $2250.
Deals can be had if your not in a hurry, diligently watch the classifieds, and be ready to pounce when what you need pops up for sale.

Yes indeed, but I like to get going. It seems the ring groove that is not on the 3.2 is still a nice thing to have. My engine builder would recommend havint it machined in....

[Josh D]

Originally Posted by '76 911S 3.0

3.2ss (EBS 98mm bore cylinders, JE 9.5:1 98mm pistons), 964 camshafts, re-curved WUR, 4R CIS intake manifold.

If that is at the wheels, that's an impressive torque peak. Nice and flat too.

[Url]

Vereeken, I'm an SC owner from Belgium as well

Who will do your engine build? Everything or will/can you assist?

I'll be following your adventure closely (Will you create a thread on PP?) as I'm looking to have my engine rebuilt in the coming years as well and was asking myself the same questions!