3,0 sc engine and heads

[lupin..the..3rd]

hello,

I have noticed that the sc engines and heads come in different flavors. it seems there are higher compression and lower compression, larger valves and smaller valves, and then thick flange and thin flange for the exhaust headers.

Can someone tell me which SC engine or heads are the best for use with Weber IDA-3C carbs? And which year of SC they originally are from?

Thank you

[brads911sc]

Id pick up the phone and talk to Henry, Steve, Mike, or some other Pros...

Large Port were 78-79. Small Port 80-83.
Larger Port = Lower Torque.
Read somewhere on here that even the small port heads are good for 100+ horsepower than you could ever generate on a 3.0.

The pros will add more. Lots of other factors, compression ( a function of pistons and not heads), cams, etc that are probably more meaningful than simply whether heads are small or large port.

[Flat6pac]

The valves are all the same size.
The thick flange, smaller intake and exhaust are 80 to 83.
The thin flange are the 78/79 and the euro of the early 80s have the larger ports.
If you want really big ports, use Carrera 84 to 89 with the insulators to make the height correct.
Bruce

[PFM]

Lupin,

Brad's input is valid for the big and really big port heads if you can build the thing to go 9000 plus RPM to use the port cross section they can make big power. If you plan to build an engine that will live and work below 7500 RPM or so the small port heads are a great starting place. With a little work on the small ports on a 3.0 they can really scream. No pro here but have had heads on the flow bench and the dyno to compare things.

[Steve@Rennsport]

Originally Posted by lupin..the..3rd

hello,

I have noticed that the sc engines and heads come in different flavors. it seems there are higher compression and lower compression, larger valves and smaller valves, and then thick flange and thin flange for the exhaust headers.

Can someone tell me which SC engine or heads are the best for use with Weber IDA-3C carbs? And which year of SC they originally are from?

Thank you

Good question!

There are two SC heads: large ('78-'79) & small port ('80-'83). The CR's are determined by the pistons. Valve sizes are all identical so one chooses which one to use depending on what cams and RPM range you wish to run in. The car's usage is the main criteria for camshaft selection.

We can make small port heads into large ones pretty easily with a CNC program we have developed so this is no obstacle if thats what you need for your build. I'd need a LOT more detailed information to be able to offer a recommendation.

For high RPM engines, one can use Carrera heads (better than SC) or have a custom CNC job done to suit.

[Walt Fricke]

Lupin

The hot ticket in the SC world is the late Euro SC. It has the big ports and the 9.8/1 pistons. Just what you want if looking for horsepower. Of course, you will want an aftermarket exhaust system with a pair of 3 into 1 headers to get the most out of this, but it is the hot setup for SCs raced in Porsche Club Racing - so much so that guys with 3.2s complain early and often because they are in the same class.

If you want a street SC, none of this matters. Get any of them in good shape and with good leakdowns and records. Great car, and all the power anyone really could need for driving around town or across the country. And no need to switch to carburetors either.

You don't say whether you are thinking of the 40 or the 46mm carburetors. Bruce Anderson recommends 40s for this kind of thing. I ran 46s on my 2.7 and 2.8 race motors, and thought they really behaved just fine even down at lower RPMS. But I never did a proper street driving test with them. And in general the main benefit of going to carbs is the ability to run a hotter cam than the CIS will tolerate. Now you are on the slippery slope where fuel mileage is apt to go down, and the higher performance range moves up into higher RPMs than the 2,000 to 3,000 or so you will use crusing down the highways.

[lupin..the..3rd]

Originally Posted by Steve@Rennsport

Good question!

There are two SC heads: large ('78-'79) & small port ('80-'83). The CR's are determined by the pistons. Valve sizes are all identical so one chooses which one to use depending on what cams and RPM range you wish to run in. The car's usage is the main criteria for camshaft selection.

We can make small port heads into large ones pretty easily with a CNC program we have developed so this is no obstacle if thats what you need for your build. I'd need a LOT more detailed information to be able to offer a recommendation.

For high RPM engines, one can use Carrera heads (better than SC) or have a custom CNC job done to suit.

Excellent info, thanks very much Steve!

Originally Posted by Walt Fricke

You don't say whether you are thinking of the 40 or the 46mm carburetors. Bruce Anderson recommends 40s for this kind of thing. I ran 46s on my 2.7 and 2.8 race motors, and thought they really behaved just fine even down at lower RPMS. But I never did a proper street driving test with them. And in general the main benefit of going to carbs is the ability to run a hotter cam than the CIS will tolerate. Now you are on the slippery slope where fuel mileage is apt to go down, and the higher performance range moves up into higher RPMs than the 2,000 to 3,000 or so you will use crusing down the highways.

I'm looking at 40's. 46's seem to be quite rare these days. I've been tracking my 911 for 6 years now, and want to build a dedicated track car. It will be used for track days with various clubs, but not for racing. I want carbs, because well, I think they're cool and I want them. No other reason. Fuel economy and emissions are not on my radar. Car will be kept street legal and driven occasionally on the street, but it's main purpose will be for weekends at the track.