Rebuilding a 964 3.6 liter Hot Rod Engine

[ScottKelly911]

Well, it's quite unfortunate, but I've blown my engine. Not sure how much Damage I did, but it still runs, so I'm hoping it's not too bad. Any case, since I have to open it up, what are my options? The car is not my daily driver, it would be used on weekends and occasional track days. I'd like it to be stout and reliable and only have to do this once. Here's my current thoughts:
1. Rebuild back to stock Specs and have a good solid engine and enjoy what I've been enjoying with the wonderful Power to weight ratio in my '72 with mostly stock 3.6 964 engine.

2. Build it up as a 3.8 liter. If I do this, what is needed to complete the conversion and what kind of power would the end result be? Obviously I'd have to source 3.8 pistons and cylinders, what else is needed for this conversion?

3. This is where the hot rodder ideas will really help! Build it up using parts to get the most power possible Titanium valves/valve springs/retainers? Titanium Connecting Rods? Different Pistons? Bigger cams? I've got an Eaton 90 Supercharger just waiting to be set on top of her if I go this route. If I add the SC, what else should I do, lower compression ratio so I can run more boost? Bigger injectors?

Any and all suggestions will be considered, the only stipulation is that I will be using my current engine as the base to build upon. If anyone here has built a Hot Rodded 3.6/3.8 please let me know what you did and what kind of power you got out of it. I've had the 3.6 964 in my car since about '98 and was very happy with the power increase over the stock 2.4 liter But if I'm gonna build up the engine, I figure I might as well get some more power out of it. Thanks in advance!
~Scott

[Steve@Rennsport]

Scott,

Perhaps unwittingly, you've asked some HUGE questions with a lot of variables. A 3.6 and/or 3.8 can make anything from 260 HP to 400+HP, and its going to depend on this:

1) Precisely,...what are your engine longevity expectations? 25K, 50K, 100K, more?

2) What is your budget?

The answers will frame whats possible to do,.....

[ScottKelly911]

Steve, thanks, you're right, there are a ton of variables that will go into this. My idea is an engine that will give near to stock longevity (engine has about 120K pretty hard miles). I'm not looking for a high strung track only engine. Just something with an added kick while maintaining good reliability, so I'd say 50-100k miles sounds about right and easily obtainable as these engines are near bullet proof and documented to be as good as the SC/Carrera engines as far as reliability. I'm sure had I taken care of the Valve guides and had the heads machined and put in the gasket (common problem for the 964 engines) dealt with, my engine would have gotten many more miles from it. My car doesn't have any emissions restrictions, so I'm lucky enough to have added quite a few ponies due to the deletion of cats and added a much more free flowing exhaust. So I was making I'm sure quite a few extra HP over a stock 964 since the exhaust on them was pretty restrictive. It's hard to find a lot of info on building up this engine to extract more power out of it other than exhaust mods. I believe Jerry Woods did some cams a while back that got more power to be used on this engine, GE100s? When I went to the Smart Racing site, it says none available, so I'm a little at a loss as far as that goes whether or not they're still available.

[Steve W]

Scott, from your description, realistically what I see is that 3.8s dialed in make about 17 more hp than a 3.6, or about 4.5 to 5.5% more torque and power throughout the range assuming similar mechanical configurations. For the upper end of higher strung streetable motors, normally I see about 260 rwhp from a 3.6 on a Dynojet (about 290+ hp from the engine), and 275 rwhp from a 3.8 (~309 hp engine). More can be had from race gas and headers with an open exhaust but that sounds like it would exceed your design objectives. Much beyond this and you'd have to change out the entire induction and fuel management system.

If you need to replace your p's and c's then going to a 3.8 would be a no brainer, but if not, only you can decide if the additional cost is worth the gain.

[Steve@Rennsport]

Scott,

FYI,..GE-100 cams are quite aggressive and suitable only for racing engines. They are certainly not compatible with any OEM 3.6 intake system.

A lightly modified, properly built, 964 3.6 can make 300 BHP with a good exhaust, RS cams, bigger intake valves, some intake mods, and good software. A 3.8 will make a little more power and more torque everywhere across the RPM range. These engines exhibit excellent drivability and with good maintenance and oil temp control, can last well beyond 100K.

Engines used for the track should get some uprated components such as valve springs and retainers as well as better rod bolts and bearings.

[175K911]

Scott, I've been going back and forth on a similar thought process for my '86 which is 95% track. But in my case either build my 3.2 to a hotrod 3.4 or get a 3.6 and do some mild upgrades to it. Ultimately I just bought a used 3.6 and will be tearing it down and sending heads, barrels and rods to Steve Weiner to do his magic. My goal was 290-300 hp on 93 octane pump fuel.

Steve offers great insight and asks some good questions as well. In my case we're going to basically build a 964RS engine with different valves, cams, headwork, valve springs, titanium retainers, balanced and properly rebuild rods with ARP bolts, European Racing headers. I'm sticking with stock pistons and barrels, and just ExtrudeHoning the intake. Should have a good idle, strong power band from 3500-7000 and have loads of torque. And have an engine that's good for a long time, or until I get bored and do something different.

[Bill Verburg]

As Steve says it all depends on budget and what you want in the end.

For street use torque is king, go w/ 3.8-4.0 p/c(you want some mild cams anyway and stock pistons limit cam choice) and some mild cams like the ss, GT2, or GE40 cams, toss the 964 heads and cam carriers -use 993 versions w/ Ti keepers and RS or better valves, use Pauter rods, DLC coated bearings etc. Motec w/ stock intake can work w/ these setups or have a custom chip burned for Motronic.

Of course at each step of the way there are far more expensive options that produce more gains, as Steve says up into the 400hp range can be had from a still streetable motor but it's going to cost a lot. ~300 can be had at a fairly reasonable price(as these things go)

[JeremyD]

If your thinking of using a SC I would definitely base my P & C on this decision. I'd talk to Charles over at LN or Mike Bruns at JB Racing. You'll probably be restricted with the head flow of the 964 heads - so look at some of the aftermarket 993 heads.

You have three of the best minds on this board with Steve Wong, Steve Weiner and Bill Verburg. I see motec in your future. Not having emissions gives you lots of choices on cams - but to really get the most out of cams you will need to dump the stock intake/engine management.

I guess it all depends on how much "while I'm in there" your wallet can take.