Newbie questions about high CR and twin plug conversion

[RFP]

Good day,

I'm afraid that I've been away from Porsches for way too long! I have searched on this topic, but I really don't have the 'vocabulary' to understand a lot of what I read. So, I'm going to expose my ignorance and ask a couple of questions, not hoping for 'in depth' answers, but more for general guidance and information. So, here goes...

I have just purchased a 1987 Carrera coupe, just over 100,000 miles and in absolutely superb condition.

A few years ago (some 6,000 miles ago) the previous owner converted the car from 3.2 to 3.4, using JE pistons (10.5:1 CR), cams reground to 964, and SSI exhaust.

From what I read (and the little I understand!), I learn that the 10.5:1 CR with single plug heads is problematic... tuned to be 'safe' results in less-than-optimum performance.

So (finally my questions!); what is the simplest route to twin plug conversion? Can I simply have the heads (and valve covers) modified, bolt in a JBRacing twin distributor and go... or, is there more work needed?

Alternatively, should I just change the pistons to 9.5:1 CR and forget the twin plug idea?

Full disclosure: I have the title, but not the car... Intercity will be bringing it to me in a week or so.

Thanks for indulging an old geezer!

Rob

[Flieger]

The easy part is drilling/tapping the head and putting the spark plug in (assuming you already have the engine apart).

The expensive part is the twin plug distributor. Many people go with a crank fire or other form of electronic ignition to avoid the distributor cost. You could also do a 964 distributor. Or pay for the correct looking 12 terminal cap type.

[RFP]

Originally Posted by Flieger

The easy part is drilling/tapping the head and putting the spark plug in (assuming you already have the engine apart).

The expensive part is the twin plug distributor. Many people go with a crank fire or other form of electronic ignition to avoid the distributor cost. You could also do a 964 distributor. Or pay for the correct looking 12 terminal cap type.

Thanks, Flieger, for the helpful response. So, am I understanding this correctly, "do" the heads, then buy (~$1,500 + or -) a twin plug distributor and wire the sucker up... is that it?

Or, should I just lower the CR to 9.5:1 /

Rob

[DSPTurtle]

I'd skip the distributor and go right to an xdi system from Clewett. You can google that.

[Flieger]

Originally Posted by RFP

Thanks, Flieger, for the helpful response. So, am I understanding this correctly, "do" the heads, then buy (~$1,500 + or -) a twin plug distributor and wire the sucker up... is that it?

Or, should I just lower the CR to 9.5:1 /

Rob

Do the twin plug. Keep the compression.

[tocobill]

Originally Posted by DSPTurtle

I'd skip the distributor and go right to an xdi system from Clewett. You can google that.

But how could you say no to this ...

[Jcslocum]

We are doing this now...but very slowly. We have the 964 distributor, twin plug heads, and an Andial Motronic splitter. The Motronic can't run the twin plug by itself.