3.0L modification

[Doug Steinel]

Thinking of rebuilding my '82 SC 3.0L. Have been devouring Wayne's book. In the section which describes "Wayne's Top Engine Picks" I am intrigued by the 3.0L which loses the CIS for carbs and goes to the 95 MM JE pistons with a Ratio of 10:1. Has anyone tried this or had any experience with this mod?

[Wayne 962]

It's a good, quick engine, with improved throttle response over the stock engine. What information are you looking for exactly?

-Wayne

[Doug Steinel]

First, I want to thank Wayne for the quick response and the wonderful book. I rebuit a 911n engine in the 1980s and it was a bear without Wayne's book, even with a brother who is a Porsche mechanic and my adviser. It is a huge undertaking for a backyarder like me and a gamble since if you screw it up, you could be looking at an $8 grand loss. I think Wayne's book will be the catalyst for many more attempts. The Porsche shops won't like Wayne for this. Also must thank him for this Forum where people like us who the world thinks is nuts can communicate.

My car is a street car and maybe will see some PCA track events. It is a 1977 911 with an '82 SC motor. In my state it qualifies as a "historic car" and thus is exempt from all mechanical isnpections and smog tests. That gets my imagination whirling.

Some questions I have about the modifications:
1)I would use the JE 95mm pistons. Their website isn't helpful at getting info on them, but I assume that a simple phone call would do. How about cylinders? My guess is that I would tear down my engine and then inspect the ones in there. If they are alusil, then I scrap them and find a new set. If they are nikasil, I mic them and if they are within spec, I can use those. Do I have those contingencies right? If I have to replace the cylinders, are they hard to come by without buying the pistons with them?

2) Compresion ratio-- Wayne's book has it at 10:1 which is pushing the limit of street gas and avoidance of a dual plug ignition which would add $2500 to the project. But Wayne's 10:1 is only his best estimate. Machining of the case, etc. can change that. I am thinking if I can measure the CR in a dry assembly, I can then set the CR at a tolerable level by changing the copper gaskets between the cylinder and the case. Am I thinking down the right road here?

3) The S Cams. Do I regrind my SC cams to S specs or get early S cams? Am I right to think that I can't use the early S cams because they will have 3 bearings whereas my cam housing will have 4? The picture in Wayne's book on pg. 64 seems to show that I could use the early cam which would ride on 3 of the 4 bearing journals. Not sure about this issue.

4) distributor issues. Do I simply ship my distributor out to a reputable shop to be re-curved? How do they know what to do with it, since my engine is not stock and will be sitting on my engine stand in my garage?

5) estimated ball park cost: If I squirrel away $10 grand (my wife will love that!), can I cover the costs? The carbs and manifold add about $3K from Wayne's $8k estimate, but his estimate has a lot of case work that you need for a 2.7L which I avoid because I have the 3.0L aluminum case. Am I in the ball park here?

Sorry for the lengthy reply, but you have to get the planning right at the beginning or you will have headaches down the road.

[cstreit]

Doug,

If you're going with JE pistons, you can always order a semi-custom set to drop the compression to 9.5-9.8:1 and give yourself some breathing room. I'm not sure I'd go 10:1 with single plug. It may work fine on cooler days or with good 93 octane, but a tank of bad gas and/or a really hot day could introduce detonation. Also keep in mind that you probably have Alusil cylinders meaning you will have to buy Nikasil cylinders or have yours replated.

I have a similar race motor to what you are thinking...

3.0L case with Mahle RSR 10:1 compression pistons
46mm webers with heads matchced and early 39mm/36mm ports
WebCam 120/104 cams
Twin plug, titanium valve keepers, racing springs.
Case windage mod's.

For a nice streetable car, I see two good options: (there are probably many more)

1. Make sure the compression is 9.8:1 or less
2. Use a milder cam than an "S" to make the car less peaky and take advantage of the 3.0L torque
3. Use 40mm Webers for the same reason
4. Upgrade the exhaust to a higher flowing system like a B&B or SSI setup.

This should get you in the 230 HP range.

OR

1. You could keep the CIS and avoid emissions and cold-start issues
2. Upgrade to the 98mm pistons to get more displacement.
3. Use a 964 or Webcam 20/21 cam,
4. Free flowing exhaust. Probably the same horespower.

You can just have your existing cam reground for about $650. You're right about not using a 2.7 or early style cam. Different cam sproket nut configuration anyway.

Plenty of places to recurve the diz. Rennsport for example.

A starting budget:

$3000 for Pistons and Cylinders (purchaing Mahle or JE's with replated cylinders)
$650 cams
$300 diz recurve (guessing)
$1000 exhaust (guessing again)
$250 misc gaskets, etc..
$1500 for webers (if you choose that route)
+25% for fudge factor

So you're looking at $6500-$8000.

[viejopatron]

Hey Doug,

Read your post and I've the same question as I’m rebuilding a 930/16 and intend to install Webers and Pre-74 exhaust. Chris's post was very useful. As I understand it the 3.0 piston crown is intended to work with the CIS. Sooo.... hypothetically speaking, how much loss is there using those pistons with Webers? Maybe someone out there “knows”. Doug, did you contact J&E? I’d like to hear status on your project.

Gary

[Wayne 962]

"Loss" is not a good method of thinking about it. Just think of it as not getting as much performance as you can. The best solution is to go with some JEs that you can run with a hot cam like an 'S' cam. Say good-bye to any notion of passing smog though...

-Wayne

[A Quiet Boom]

cstreit, you mentioned replating alusil cylinders, I'm assuming repalting with Nickasil? Is this expensive and who does it? I'm contemplating low comp JE's for my SC for use with a turbo. I have Alusils now and the budget doesn't allow for new cyls at this point.

[Doug Steinel]

Gary,

I am only in the planning stage. My stock 3.0L engine has 120K on it and runs as you might expect a stock 3..0L to run. It pulls very strong till about 5k and then runs out of breath. It burns 1Q of oill every 450 miles, so I thinking rebuild is in the future, but not the immediate future. I have not contacted JE but, Eugene at Pelican has posted a note that Pelican sells JE pistons for $750 a set and cylinders for $2k. Not bad. In my state of Maryland my 911 is considered a "historic" car so is exempt from smog tests. This gets the imagination going...

Doug