Introduction & Turbo 2.7L Project

[dah72094]

Hello all,

Long time lurker here...thought I would introduce my project of the past 12 years and ask for some advice based on where I would like to go in the next steps of the adventure.

I purchased this car back in 2010 as a running and driving project with the hope of using it as a platform to learn on and keep long term. It has been everything I hoped for and more. The car is a 1975 U.S. spec 911 Carrera Targa, number 112 of 174 built that year. It is a numbers matching car minus the transaxle which was replaced at some point in its life. It was also painted Guards Red, as it was originally Grand Prix White with gold stripes. I have touched about every nut and bolt on it, from rebuilding the suspension, to dropping the engine and transaxle to replace the clutch. I am a huge fan of the 934, and have taken some of my favorite aspects of that car and combined them with the '75 Carrera. Some specs are listed below:

Suspension:
- Elephant Racing rubber bushings (sport hardness)
- 21mm & 30mm Sway Away solid torsion bars
- Stock 20mm and 18mm sway bars
- Koni 1039 Sport and 1214 Sport Shocks

Engine:
- Stock 2.7L S-spec with Bosch CIS
- Carrera chain tensioners
- 1x Bosch 044 fuel pump, raised system pressure to 95psi, running a mix of 93
and 110 octane
- GReddy Type-S BOV vented to atmosphere
- 934 headers with dual 930 wastegates and custom 0.4 bar springs
- Twin scroll T3 housing KKK OM422A turbo for testing purposes
- 123Ignition distributor with factory 2.7 S advance curve, vacuum advance,
and addition boost retard setup
- Retrofit CDI+ ignition box, using default settings.
- Clewett Engineering ignition wires
- Elephant Racing Widemouth oil cooler

Transaxle:
- 1976 mag case 915/44 with 7/31 R&P and open diff.

Wheels & Tires:
- 15x7 and 15x8 Fuchs with 205/60-15 and 225/60-15 tires.

I have been extremely happy with the current setup, however the engine has excessive blowby, smokes heavily under load, and is in need of a rebuilt. The case to my knowledge has never been split. Cold compression test results are as follows:

#1 142 psi
#2 60 psi
#3 162 psi
#4 152 psi
#5 140 psi
#6 82 psi

I knew this day would come eventually, as it has been turbocharged for the past 10 years, so I am trying not to be too disappointed... I am assuming it is the rings or pulled head studs. I have not done a wet compression or leak down test yet.

...So in light of that, I would like to start making plans to rebuild it, and put together a list of things that should be done to meet my goals. I would really like to keep the mag case and 2.7L of displacement, spin it up to 7K rpm, and make 275-300hp at the crank. I currently have a set of brand new (from the 80s) Arias flat top pistons for it. I am debating whether to source another 7R case and put the original one to the side with the other original parts, or use the numbers matching case. I know I will need to at least have the case line bored and have case savers installed; what additional work needs to be done to it to allow it to take 7K rpm reliably, and what other bottom end components should be upgraded over stock? I plan to run 934 cams specifically because I love the way they sound, and plan to use a 928 CIS fuel head using the extra 2 injectors for boost enrichment. Will the stock 2.7L S heads flow enough air to make that kind of power at a moderate boost level? Should I look into porting? Will the 3 bearing cam towers be ok with that aggressive cam profile? What should I use for valve springs? I still have much to learn but I am excited to start the next chapter of this project. I appreciate any advice you all might give, and if I am crazy for wanting to go this route you can tell me.

Thank you all. Pelican Parts and this community have been a tremendous help.

[TitoJones]

Whoa. That exhaust and waste gate setup is trick as hell. Cool build.

[Rusty911]

I would put the mag case on the shelf and invest in an aluminum ghat will work with your other engine components if you can find one. In long run you’ll be better off with that much torque and horsepower.

[Uwon]

Originally Posted by Rusty911

I would put the mag case on the shelf and invest in an aluminum ghat will work with your other engine components if you can find one. In long run you’ll be better off with that much torque and horsepower.

I would agree with Rusty. SC/3.2 cases are very robust and will likely aliviate many problems associated with the 2.7.

My own experience with a 3.2 to 3.4 turbo conversion with many, many track and road miles is that it’s difficult to get any power past 6,200 rpm, especially on warm/hot days. So I would not sweat about reaching 7K. Your power band will likely be around 3k-6k with starvation setting in quickly after that, unless you go into a twin turbo setup.

You will easily reach and surpass 300 hp, depending on how much boost you have it set at. In my case .5 bar is street drivable, .9 simply dangerous.

BTW, I would worry about that turbo oil drain line which appears, from that angle of the pic, to be too close to the exhaust header.

M2CW
Cheers,
Johan

[Coastr]

Why are you planning to stick with cis? I would think the first thing you want is efi on a setup like that. And maybe a water/air intercooler

[mepstein]

You want to talk to this guy.
https://forums.pelicanparts.com/porsche-911-technical-forum/1114118-299hp-300ftlbs-my-2-7-turbo-setup-wheels.html

[jpnovak]

I think you may now hold the record for longest living 2.7 turbo. Well done!

Personally, I would ditch CIS and go EFI in your next evolution of this engine build.

I absolutely love the visual of that exhaust setup.

I am curious how you bring the pressure side of the turbo into the engine bay. The up pipe looks like it will run right into the rear cross member of the car There is not a lot of room between the engine console cross bar and car.

[dah72094]

Thanks guys for the suggestions and links! My biggest reason for wanting to stick with the 7R case is cost. A 3.0L turbo aluminum case is out of my budget unfortunately, and the 3.0L SC case won't work with my current engine components.

I love CIS for its symplicity. It is mechanical, easy to adjust, and reliable, and the 934 made 485 hp with a variation of it. I would really like to continue using it, even if I need to move on to a larger fuel head. I don't expect the driveabilty of EFI with the radical cams and CIS, but that is something I can live with.

I am using aircraft flex tubing on the intake side of the turbo to get it to the turbo inlet, and some aluminum tubing with silicone adapters on the compressor side. This was kind of a proof of concept I put together 2 years ago when I had the engine out to fix oil leaks & replace the clutch. It is a little crude, but it all fits behind the bumper. I was worried about the tubing length from the air metering plate to the throttle body, but the throttle response is still excellent. The car is very driveable, getting full boost at 3500rpm.

[911 SLANT]

Any video of motor running. Love to here how it sounds

[dah72094]

Here are a couple for ya. The video of it going down the road was right after I put it back together about 2 years ago. I've been meaning to record some onboard footage...

https://youtube.com/shorts/7T1mISNBt4w?feature=share

https://youtu.be/BI6Orm77iDI

[tonytuzz]

Bump for updates?

[Kevin Stewart]

Nice

[dah72094]

Last year I started planning and collecting parts to build a custom 2.7L turbo engine off of a 911/85 (1977 2.7L S) since it has the 47mm 4 bearing cam towers, aluminum chain housings, etc, so I could put my numbers matching '75 2.7L on the shelf. I found a running engine with 278k miles on it in Atlanta and brought it home, but it had great compression and ran so well that I decided to dress it up, put it in the car, and run it N/A with my old rsr style headers and some glasspacks, keeping the CIS. I dressed it up like I had the turbo engine and installed it, been enjoying it like it is since.



I don't know that I will turbocharge it again, as I had a once in a lifetime opportunity to chase my dream and buy a 934/5 race car replica shortly after that which had been off the track for nearly 20 years. It has been an incredible project and it has been giving me my turbo fix since... I am currently in the process of putting the 934 header/turbo setup on it with ITBs. It has a 3.4L based of off an '88 3.3L 930 engine.

[TopTuning]

Originally Posted by mepstein

You want to talk to this guy.
https://forums.pelicanparts.com/porsche-911-technical-forum/1114118-299hp-300ftlbs-my-2-7-turbo-setup-wheels.html