The 915 is a lot stronger than most believe. I ran a few 3.6s and even a 965 turbo engine in front of bone stock gearboxes for many hard miles on the track and never had an issue with any of them. Smooth driving makes the difference. Jerky driving like at an AX is much harder on them.

Jack drives new GT2s and every other Porsche GT car on a weekly basis on a track. He works for Porsche. He can afford any of them. Why do you think he drives that lightweight vintage car? Because it’s more fun than a new one.

I tried to explain that earlier. The 915 is an amazing transmission, not just so-so or OK. Sometimes I wonder if I’m still even on a Porsche board w Mustang Sally and all of the other haters. :confused:

Many have grenaded 915s by adding enough boost - the huge torque of turboed 911 engine can do a number on some of the 915 components. Matt Monson once posted pics of some of the 915 gears side-by-side with 930 gears, and they were very slender in comparison.

Yes, as I stated earlier, the stock 915 is good for about 300HP. Hence, the 930 transmission. :cool:

Yes, you can kill a 915 with boost. But it has to be LOTS of boost, early. Mine is fine with 345 chp because I don't hole shot it. My kid's 2017 wrx is faster, off the line, but once I hit 3rd and twisties...

I said the same in post #68, and guess you had earlier on? Dayum, I'm too slow so it looks like I need more powwwaahhhhhh!!! :D

^so here is the crux of the matter as I see it. Building any hot rod is an expensive proposition. Building a 911 hot rod is even more expensive. People with tons of money can be cavalier about pumping cubic dollars into their project. If its someone without a ton of money doing this, they are devoted to the platform, to use your words. Yes the costs are insane, we just don't care because the air-cooled 911 platform does it for us.

You've already told us you're not wealthy. If you want to hot-rod the car, it will cost you a bunch of money no matter what. You can manage the cost down by doing work yourself, which will involve hours of intensive reading of forums, and books before you even turn a wrench. Those of us who have walked this path probably all have been rather obsessed about our projects (my wife referred to my 930 as "the mistress"). Less money is involved if you DIY, but this is just a different manifestation of the insanity.

The fact that you're struggling with the cost vs. performance equation suggests to the confirmed addicts here that you are perhaps not devoted to the platform. Perhaps that's unfair, and you're just venting your frustration that you don't have the money to build it into the hotrod of your dreams.

Do you love the way the car feels, sounds, smells, and drives? That's a good start. You have a small budget. I suggest that 1st you spend the $ and get the transaxle sorted so the car drives properly. If you find yourself falling deeper into love after that, throw some appropriate cams in there and see how it goes.

If you haven't done it already, please buy the 911 engine rebuild book by Wayne Dempsey, and Bruce Anderson's 911 Performance Handbook. Read them both, cover to cover.

I have a friend here in town that has a hot rodded Carrera 3.2. It’s a very cool car, I’m sure you’d like it, as it is both quite a bit lighter and quite a bit more powerful than stock. Most people wouldn’t recognize it as a Carrera 3.2, as it has a lot of the visual cues of the earlier cars. The cost to build it was well over 100 grand, roughly twice what you could buy his 996 turbo for, which will obliterate it in every measurable performance category and is both more reliable and more comfortable to drive at the same time.

That, in a nutshell is what we’re trying to tell you. If you want to hot rod your 911SC, go for it. It will cost you a lot more than you think, you may not be all that thrilled with the outcome, especially if you put a budget on it, but it is your car so have fun.

The books are a great idea. I have Wayne's book. Autographed at the Corvette Museum at The Visit 2.

My point was that a properly running and shifting stock 911SC might do it for this guy. How would he know?

I cannot leave any 911 stock, (unless it's an early S or other vintage screamer). It's a lot more rewarding and cost effective to remove weight and improve handling than to increase HP on those cars, however.

ANd javadog is correct, $100k is very easy to spend building a 911 hotrod. Most retro/backdate cars are waaaay more than that and still have stock engines. It's a rabbit hole.

For pure bang for the buck, it is hard to beat a Corvette if all you want is horsepower. If you want the driving magic of a air cooled 911, well, it is just expensive. It helps a ton to do the work yourself. I do most of the work on my cars. Partly for the money savings, but mostly because it is a big part of the hobby. I have a lot of money invested in my garage. Heat, air conditioning, scissor lift, beer fridge, and a bathroom out there. My wife sometimes says she is a garage widow. I reply all she has to do is open the door, there I am. Not out wasting money whacking a little while ball, not out at the lake pouring money into a hole in the water. It is playing with my cars that are going UP in value.

It has taken me a lifetime to collect the tools I have. I have worked on my old 914 with nothing more than basic hand tools, and done it in the driveway outside. It is way better to have the tools and the dedicated workspace. And even more important, a second car for daily driving so the project can sit in place for a while.

With old cars there is always something that can be fixed or tweaked to make it better. It is a hobby that will always have "just one more thing" to do.

My wife sometimes says she is a garage widow. I reply all she has to do is open the door, there I am. Not out wasting money whacking a little while ball, not out at the lake pouring money into a hole in the water.

We always have this conversation. I frequently have to remind her, that I do not drink, do drugs, gamble, golf, have mistresses, have a boat, collect star wars figures, take lavish vacations, or really have any other vices.
I play with cars, trucks, tractors, and houses . All of them are about making money, maintaining our home and properties, and doing something I enjoy . Id sell ( and have done so many times ) any , or all of them in an instant if I needed the cash for some family emergency , or for a future investment .
I remember telling her this when we first got serious and moved in together.
" You will never stop my from playing with cars . It is what I do, love , and who I am If you think you are going to try someday, or it becomes an issue, we should probably just end it now" .
She has been really good about it all over the years .

What is considered too much of a compression ratio to Turbo?

Fred, I had the same basic thing I told my wife I regards to looking at pretty women in public. I told her it was 100% pure instinct, and I have appreciated the female form since I went through puberty. I was like a dog on a chain, I would look, but never touch anyone but her. Other pretty women are just appetizers and my appetite is only for my wife.

Depends on how much boost you want to run, the ignition system (single or twin plug), and the cam profile to a degree as well. Over on the 930 forum, I think 8:1 or 8.5:1 is on the high end of the range for built air-cooled turbo engines. These cars typically run 12-15psi of boost.

Edit: if you're talking about turbo-charging an NA 911, I think the route is a low pressure turbo set up, 5-7psi.

Turbo pressure and CR are generally in an inverse relationship, i.e., the more boost you have, the lower CR needs to be. That is the reason for the crazy turbo lag on 930s and most older turbo cars, until manufacturers figured out how to stagger two small turbos so that boost came on partially @ low rpms.

Higher CR engines w low-boost turbos can be really sweet, I think that is what 991.2 cars have. They also have DI and really sophisticated engine management systems that keep everything optimal all the time, protect the engine from damage, etc...

None of that is germane to modding an old air-cooled 911, except the boost/CR ratio which never really changes.

^eggzactly:p

to expand on "sophisticated engine management" - a key element for high boost and higher static compression ratios living together peacefully on modern cars is knock sensing and the ability to retard ignition timing dynamically. That sort of tech can be added to an old air-cooled sled. There are standalone ignition system solutions like JS Safeguard, or most fully featured EFI/EM systems will have knock sensing options.

As Jacob said, .5 bar is great on a stock motor, no issues. .7 if you run an intercooler. E85 is safer, detonation wise, but who knows about what it does to the fuel system. Water injection is nice as well, you can do the .7 without the ic if you want. Safest route is ic, and water injection, and an maf...