3.0 small valve vs 3.0 big valve vs. 3.2 heads for 3.2SS

[Sicklyscott]

Hi -

I starting to pull parts together for a 3.2ss build to go into my '80 SC. I plan on using PMO ITBs with a twin plug setup and higher compression with hopes of a 7,000 rpm redline.

Which is the better option to go with? I'm under the opinion that at the end of the day I'll need to do a decent amount of work to all of these with twin plugging and the bigger P&Cs.

Any help / advice / experience is appreciated.

-S

[Flat6pac]

All the valves are the same size.
Bruce

[jpnovak]

Do you have heads now? The options for me would be based on what heads I had and what cams would be in the build. The cam choice would be determined by the driving style, usage and gearing. If you are driving mostly track and have stock gears you would favor a cam and port setting that would put the power band at higher rpm. If you are driving mostly street then you would favor a cam with lower rpm power band matched with stock gears.

The small port heads are too small to use for a 3.0 at 7K rpm when combined with a cam that will actually make power to 7K. The stock SC cam is not a suitable candidate. However, these have the most meat in them and are very good candidates for some nice CNC port work.

The large port heads will work well here. Though I would not go any larger in cam than a DC40 (Mod_S) or similar. These would peak HP right below 7K with minimal fall off. I would just clean up the flow around the valve guide and run them.

The 3.2 Carrera heads would be the best choice. With most cam choices to 7K rpm you would not do much more than drill for the second plug.

[Sicklyscott]

I have small port heads. I also have 46mm PMO ITBs.

As for cam I was thinking a S cam or the DC62 cam. This will mostly be street driven with a couple Motorsport events a year (for now). It will have stock gearing with slightly taller rear wheels.

I love high rpm motors mostly for that linear feel and the lovely sounds it makes. To your point it'll see duty mostly on the street and won't need up top performance.

[Steve@Rennsport]

Originally Posted by Sicklyscott

I have small port heads. I also have 46mm PMO ITBs.

As for cam I was thinking a S cam or the DC62 cam. This will mostly be street driven with a couple Motorsport events a year (for now). It will have stock gearing with slightly taller rear wheels.

I love high rpm motors mostly for that linear feel and the lovely sounds it makes. To your point it'll see duty mostly on the street and won't need up top performance.

As you might already know, you will need either big-port heads or Carrera heads in order to enjoy the benefits of either of those cam profiles. Since you have stoick gearing, I'd recommend the milder grind in order to maintain as much low & mid-range torque as possible.

FWIW, your small-port heads can be CNC'ed into big-port ones and due to the precision this process achieves, these actually flow better than factory ones.

[fred cook]

I used a set of Carrera heads when I built my 3.3SS engine. I'm very pleased with the performance as it pulls quite well all the way up to the 7000 rpm redline. There is an old saying about engines...."Horsepower is in the heads". Probably one of the better places in an engine to spend some extra dollars! Good luck.

[mreid]

Fred, what cams did you use?

My 3.2ss uses DC80 (104 lsa) with 46 pmo carbs, 10.5-1, twin plug, ported 3.2 heads.

[fred cook]

Originally Posted by mreid

Fred, what cams did you use?

My 3.2ss uses DC80 (104 lsa) with 46 pmo carbs, 10.5-1, twin plug, ported 3.2 heads.

My engine is much like yours. I used the 3.0 block, crank, rods and oil pump. Carrera heads w/twin plugs, LN Engineering slip fit cylinders, Mahle 10.1:1 pistons, SSI exhausts and a somewhat modified CIS system. Cams are original Porsche 964 units. Ignition is by Electromotive XDi system. I also have a/c on this engine, but haven't gotten around to charging it yet. Runs good!