3.2 engine build
 

I'm planning on rebuilding the 3.2 in my 84 911. I want to add displacement, PMO efi, and maximize naturally aspirated performance. I have several questions:

- can I change the cylinders/pistons to get 3.4 without machining?

- what are the best cams for this engine?

- what will the performance gains be if I upgrade to twin plug heads and distributor?

Thanks in advance people!

3.4 is derived from your cylinders opened to 98mm then nikisil coated. That gives you a choice of compressions. Your choice of compression leads to the cams that you will need.
If the compression is high enough, over 10/1, you need dual plugs and ignition, weather distributor of electromotive.
This is how the 964 and 993 run with such high compressions.
Bruce

Thanks, Bruce.

Where is the best place to buy larger cylinder/pistons, cams, and dual plug heads?

In reading Wayne's book, he references a 3.5L upgrade to the 3.2 using 100mm Mahle pistons, S cams, and twin plug ignition. He rates it as one of the "best normally aspirated engines you can build". Sounds good to me, but I'll have to save my pennies!

Mark,

You might want to look at Ed Hughes engine build on Rennlist forum...
He put up a whole thread on a 3.4 engine build ...
The rebuild begins.... - Rennlist Discussion Forums

Regards,

Got PM

I'm running 98mm Nickie cylinders to get 3.4 on my turbo build, along with Omega pistons.

Of course, most of my setup isn't what you'd run, but I'm very happy with the setup I've got. I went up to Omegas factory in Birmingham (UK, not Alabama) and spent a few hours with Fred, the now semi-retired founder of the company. Wow. What an experience, a very VERY knowledgeable chap. He was itching to show me around but had contracts in place with his clients that prevented him from doing so...all very hush hush, specifically for a certain leading F1 engine supplier...silver in colour...They've also made every piston that Ducati works teams have used in the modern era; I actually held Rossis and Haydens 2012 piston, both as a stage 1 extrusion and a finished item, before they ever got into this years engines. I believe Steve @ Rennsport distributes them in the US? They are a thing of beauty, especially when the subtle detail of the manufacturing process is explained.

The Nickies, again, look very nice and Charles is a good guy. Can't comment so much on these yet, but they're a good match for the pistons with regards to thermal expansion rates (same alloy), and have a higher fin count for better heat displacement.

...of course, I've not yet fired up the engine, so these are just my thoughts on where I'm at, at the moment...if it all goes tits-up in an oily cloud of smoke, I'll have to revisit this thread and edit my opinions, lol! :D:p

Forgot to say, with heads, again Steve @ Rennsport and Bill DiCondia (sp?) at Xtreme Heads would be the folk I would contact (I'm sure there are many more over there - I'm in the UK...our forum Mod, 304065 I know has a very good relationship with a shop near him in NY).

Unfortunately I didn't go this route, and very much regret not biting the bullet and shipping my heads Stateside.

The answer to your questions;
1. Yes, you will need 98mm bores to size up to 3.4 liters.
2. Depends on the build as Bruce points out. A good start for a street engine would be something along the lines of a GE 80 or similar with at least 10.5 CR.
3. Again as Bruce said, twin plug becomes necessary with higher compression. Higher compression allows for more aggressive cams which lead to...

You might want to consider PMO 50 mm carbs. They work great on the street as long as you don't have emissions to worry about; I think a better bang for the buck. JE pistons are a good choice and affordable. Twin plug machine work is pretty straight forward and can be done at a number of shops in the US. Aaron Burnham at Rennsport does good work and is priced fairly. Aaron also makes a pretty nice conversion for your distributor to a twelve wire setup using a Jaguar cap and custom rotor. JB racing makes a nice piece that is completely new made from billet.