1975 911s 2.7 engine rebuild and options

[mpieretti]

I have a stock, mint black 1975 911s targa on the road with a 2.7 running the CIS fuel system pictured below. A few years ago I added large*ribbed solid brass oil lines from elephant racing to an original 28 tube brass oil cooler. That cooler is a piece of art, but unfortunately is hidden away in the front*right wheel well. This set up*mitigated my high temps (pretty well).See this car on page 95 of Pelican's Ultimate Targa Thread*https://forums.pelicanparts.com/porsche-911-technical-forum/170660-ultimate-targa-thread-95.html

I also have a white 1975 911s coupe that has its 2.7 engine at my machine shop being evaluated. I bought it 8 years ago for $5k knowing the engine was shot.
I am waiting for the machinist to check the*block to see if it's in spec. He's also evaluating 5 cylinders and to see if the crankshaft is bent, out*of round and or salvageable.

My mechanic thinks the rod bearing on the crankshaft failed allowing the piston to overtravel. The piston then hit a valve and damaged the head, also causing the piston to crack and lose metal into the cylinder. The cylinder is heavily scored and there is metal in the sump. Also, the hole in the timing case cover* that accepts the carerra tensioner is out of round from a bolt working itself loose and the timing chain sliding the tensioner back and forth within the case.* This may have started the entire chain reaction failure. We don't know. This happened BEFORE I bought the car from my friend who is a mechanic certified by Porsche USA in Georgia.

Originally*I planned to rebuild the 2.7 engine and put carburetors on this one. Have a black stock 911 and a white outlaw coupe with carburetors. I also like the idea (because*the white paint is imperfect) of fitting this one out like the 1974 East African Safari Rally 911. Though it would save some money on paint, interior etc without really devalaluig the car, because it could always be be brought back to full stock later if my kids wanted to take that route. For now it would get it back on the road so me and my 3 boys could drive the two of them in tandem on weekends.
I plan to use this thread to seek advice*and document my project.*As it stands now my boys and I feel like we are looking at 2 options, and a third which has likely already been eliminated.

Option 1
Rebuild the 911 motor (or buy another 2.7 core for parts if my machinist says the case and or crank shaft*is irreparable). Shelve the CIS fuel system for carburetors. Buy new or machine existing pistons, cylinders, rods, crankshaft, case and*timing cases etc.* Upgrade to a Carrera cooler centered in the front bumper valance.

Option 2
Ahhh... go the small block chevy route-- the way my mechanic who I bought the car from planned to do. He knew all too well the damage to the engine and cost to rework it. This was 10 years ago... and with current prices, it might make more sense to go original. I also am not thrilled about listening to V8 muscle car. I much prefer the wur and smell of the original oil cooled engine back there... but I already have one of those that is really just a weekend driver. It might be nice to have an everyday driver*I could take 7 hours to NH over the green mountains in VT. I don't think I can*do that with my black targa.

Option 3
Likely too much proprietary work to do on my own, but I've read that people*are doing this to later model 911s: putting in a turbo charged V6 250hp Audi 2.7 engine.* Renn 27 sells kits for 996* and later, not not my 1975. Got off the phone with them this am. This option is kind of cool to have an audi motor in a "rally" looking 911. But then I would get into the whole ECU issue and have to modernise the car that way as*well.... too crazy I guess. Though I find it appealing for price, reliability*and country of origin similarities.

Thanks all

[mpieretti]

I will update this post when I get word back from my machinist about status of my many questionable parts.

[mpieretti]

East African Safari Rally Porsche 911s

Something inspired by this:
https://petrolicious.com/articles/heres-how-one-man-saved-two-east-african-safari-rally-porsche-911s

but not nearly as involved

[PeteKz]

Option 4: install an SC 3.0 or Carrerra 3.2 engine. Rebuilding one of these is cheaper than rebuilding a 2.7, and they are much more durable. Also can get more power with reliability. Induction is your choice. Put the original numbered engine or case on the shelf for "the next guy"

Re the V8 conversion: The vendors claim that the Chebby LS engine weighs about the same or less than the Porsche engine. That's bogus. I've measured the weights of several engines, and I guarandamtee you that installing a LS engine will add at least 50lbs, more like 100lbs when it's all installed. Remember, you need to install a cooling system too, and chop up the car to add plumbing and radiator(s).

If you like the idea of a high power, high torque V8 pushing you around, I understand that, and by all means go for it. Just don't justify it by thinking it will save you weight or money/time.

[bbturbo]

I second option 4: the SC motor base, then boost it for some more juice. That's what I'd do! Of course, it's very easy for us to spend your money. Either way, enjoy the process, that's all that matters.

[75 911s]

I've had multiple 3.0,3.2 and 2.7 motors machined. Yes the 2.7 is slightly more expensive to machine but in the grand scheme of things, it's a few hundred bucks more. In a build that runs 10k min, that extra 2.7 machine cost on the case shouldn't really be a consideration imho. All the other parts are the same costs. The 2.7 is lighter, revs better and is period correct.

LS swap in these cars is a crime. It costs way more than you think and it kills the heart and soul of these cars.

With higher compression, single plug, and early PMO 40s, this would be a dream to drive.

Here's my suggestion:

Drop the engine, send the trans out to Bill Rader here in Vegas and have it refreshed.

If you are doing the engine disassembly, you can save a bit of money. Obviously, buy Wayne's book as it shows you step by step how to disassemble and rebuild a 2.7 motor.

Get the case, heads, crank, cam towers, rockers and rods to the best machine shop you can find that specializes in this stuff.

Buy new Pistons and cylinders. Have the heads ported to S spec 36mm intake, 35mm exhaust I think from memory.

Buy new web cams for carbs. Upgrade to the oil fed tensioners (or don't)

Run SSI with a good muffler. Run the original CDI box, with an RS curve Dizzy.

You will love that motor and other Porsche air cooled guys will love this motor, and it will look and weigh appropriately for this cool Targa. It will also sound amazing.

[PeteKz]

Duane, let me politely disagree that the difference in machining costs for a 2.7 is only a few hundred dollars more than a 3.0/3.2. The magnesium cases all need to be machined 3 different ways if they have significant miles on them. The aluminum cases usually don't need any. So the difference in machining cost is thousands of dollars (not to mention the months of delay). And it goes from there: If the aluminum case is in good shape, the crank and rods most probably are good too and so are the bearing shells (yes, I prefer to reuse known good bearings instead of taking a risk with poorly made new ones). Pistons and cylinders probably are reusable, etc.

[mpieretti]

Does anyone have a line on a 3.0 or 3.2 engine?

I have been looking for this engine but have not come up with anything under 20k so that’s really out of the range for what I want to do. I have sourced another 2.7 for 4500 which I’m considering.

What are the 3 ways a 2.7 needs to be machined?
The more information I have when I see my machinist this week, the better off I will be.

Thank you

[PeteKz]

That was just an offhand remark. The operations that come to mind include:

The case needs to be measured and machined flat at the case mating surfaces.
Then the main bearings and intermediate shaft bearings need to be align-bored
Then the the cylinder spigot surfaces need to be decked to the same height
Then case inserts installed for the head studs.
Shuffle pins are optional, but recommended if you are building a high power engine on a mag case.
I'm sure I'm leaving something out.

[zztot]

Don’t believe in V8 conversions in 911s. Heresy but doubt you will be burned at the cross. However your car your choice!