Need your expert opinion on different alternatives to motor setup
 

Hi SmileWavy

I am going to overhaul my engine. I have a Porsche 911 from 1980 with the stock 180HK. Since I am doing this costly measure I hope to do some simple modifications to drain some extra HK from the engine.

I am considering to different alternatives and this is where i need the expertise from you pelican guys!!

Option 1: Change the 3.0L cylinder and piston set for a 3.2L bolt on cylinder and piston set. And then combine this with a SSI exhaust.

Option 2: If i have the Nikasil cylinders! Then change the original pistons with JE pistons with 10.5 comp. Combine the JE pistons with 964 cams. Also here mount an SSI exhaust. To meet the new high comp I am thinking about installing an MDS unit to gain more spark.

So I need somee feedback on what you guys think about the different options. Also if someeone have done the option 2? Do you think this is to high a comp? Do you think the JE piston will work with the 964 cams?

And finally do option 1 or 2 give the most boost out of the engine?

I hope you guys have somee good answers for me!!! :D:D:D:D

Thank you!

I dont see what option 1 does as a benefit
Bruce

Option 1 will give an extra 20 - 25 HP and more low end torque. I would also think about having the cams reground to a 964 profile.

Option 2 will require twin plugging, a switch to carbs or MFI/EFI, a more aggressive cam than 964 and will get very expensive. You can get close to 280 HP with this option depending on cams and headwork

So you say that changing the volume to 3.2 to get a greater displacement and a higher comp ratio will not do anything for the power?? :confused:
Guess I am left with only one option then?

So if I go with the 9.8 comp instead I could drop the carbs right? I am reading the Wayne R Dempsey "How to rebuild and modify". There it says that you could use the 9.8 piston with 964 cam and the SSI exhaust. The given power increase is between 30-50HP. Is this realistic in your eyes?:confused:

The displacement increase to 3.2 is good for about 7% increase in power. Let's call it 12 HP The increased CR will add a couple more say 15 total. The SSI's will be good for another 15 and the 964 cams maybe 5 HP
So you have a total of maybe 35 or so increased HP

You havent added the 3.2 crank and rods, on a 3.0, adding 3,2 pistons doesnt do anything except lower the 3.2 compression and add machine work to the 3.0 rods.
Bruce

I think what Bruce is trying to get across is that the 3.0 and 3.2 both have a 95mm piston bore. The difference in the 3.0 and 3.2 was a stroke change from 70.4 to a 74.4.

I assumed he meant the 3.2 short stroke (ie 98 mm P&C's).

Yes, sorry for the confusion!:( I meant the 3.2 P/C conversion when you increase the bore to 98mm.

Hi,
I am in the same boat. I bought a non-running '79 real cheap thinking it would start right up after I fixed the fuel leak... two weeks later and I find 7 broken exh studs and a few rusty valves. So, total rebuild in my future. CIS is not looking to be in good shape so new EFI (or carbs). It came with PermaTune ignition. not sure if this works either.
I was thinking about swapping in a good used 3.2. Now, I'm not sure. A rebuilt 3.0 w/ new EFI and MSD(?) would be better then a stock 3.2 I'm thinking.

Will you keep CIS?? What is your budget?

Andrew