My 2.7l rebuild and tuning project

[CarreraEvo]

Hi all
I thought I'd do a write-up of my recently finished 2.7l rebuild and tuning project.

I have a 1974 US Carrera, completely stock apart from Carrera oil cooler in the front fender.

The project started with the engine making wierd noises last year.
So to investigate, I took it apart.
I didn't find the smoking gun, the only obvious reason was pulled head studs which caused leaking head gaskets.

I had rebuilt the engine some 8 years ago, and at that time, I determined that there indeed were some sort of steel inserts at the head studs, so I assumed that all was in order. Turns out it wasn't.

So.... while we're in there, right?

I decided to upgrade and tune the engine, I always wanted to tune the engine, and this was an obvious time to do it.

The project in headlines:
- Have case machined to fit case savers in place of the time certs.
- Oil bypass mod and Carrera oil pump
- Have heads machined to dual spark
- Find suitable COP's and matching a spark plug type
- New 10.5:1 JR pistons
- New cam profile and cam house mod
- MegaSquirt 2 DIY kit assembly and adaptation to my application
- Various sensors and idle valve for the MS2 application
- Wiring harness to match MS2 + engine sensors etc.
- Cam position sensor installation
- Find "some" ITBs and make it all fit
- Air filters

Case savers
Machining the case to install case savers was simple - I had a machine shop do it
As I understand it, installing time certs causes the material around the insert to be deformed a bit because the time certs are expanded during install.
So after the machine shop finished, I had to remove a bit of material for the cylinders to fit smoothly.
Other than that, this step was pretty easy.

Oil bypass mod
To do the oil bypass mod, I made a wooden jig to fix the case in the correct position.
IMG_1955+1958

I bought a 1/4 tap and made threads in the old oil duct. Then installed a plug with thread locker.
IMG_1957

I bought new springs etc. to adapt the the oil system. The part numbers I got from Waynes book (iirc).
I found a nice used Carrera oil pump from a local guy.
The sump plate had to go, and I bought a new one from Rennspeed.

Dual spark heads
The heads needed dual spark to match the high compression pistons.
A local machine shop did the job, fitted new valves and checked the valve guides.
I went with the old valve springs and retainers.
To check the springs, I used a kitchen scale and my friends hydraulic press.
I put a label on each spring 1-12 (small diameter) and 1-12 (large diameter). Then I compressed each spring initially 30mm and then 42mm - each time noting the weight on the scale.
These are the results:
(pic)
I then went on to match the small diameter springs with the large diameter springs to get the most even total spring load.
If this has a huge impact on things? I don't know, but it felt like the best way to go about it.

An issue that only dawned on me when I was about to install the head nuts was, that the new spark plugs got in the way!
IMG_2170 + 2171
The solution I found was to buy and install K-nuts in stead of the stock lower head nuts.

COPs
For COPs I went with the Bosch 0986221024 used in VAG cars. These need a smaller type spark plug though, so I decoded the Bosch system and ended up with Bosch FR5D as the type for me.
It seems these COPs grab the spark plug so well that I don't need any brackets to keep the lower ones in place. So far I've done about 2000km and no issues. I'll keep them under observation though.
I may need to buy or make some RSR style brackets...
IMG_2312

Pistons:
For pistons I went with the JR 10.5:1. They are an easy install - apart from the wrist pin lock rings, they are a NIGHTMARE! I ended up using the stock springs on one side of each piston.
It was simply not possible with my fat fingers to get the stiffer JR springs installed when the pistons was installed in the engine...

Cam profile and cam house mod:
I wanted an engine that was usable on the street, as I only do a few track days now and then. But I also wanted power
I sourced a set of used SC cams and sent them to CatCams for regrind. They told me that the most sporty they could do with those cams was their grind called "5200132".
So I went with that profile. Here are the profiles compared to others:
(Cam profiles)

I also had them grind down the bearing faces on the cam shafts to fit my cam houses.
Furthermore the SC cams have 4 bearings - the stock have 3. The cam houses has the 4th bearing though - but it has no oil duct!
So I drilled a hole through the oil duct and into the bearing and plugged the hole on the outside. Voila - I now have 4-bearing cam houses
No pictures of this, sorry

MegaSquirt2 DIY kit:
I bought the kit from diyautotune.com. It came with a very nice manual, all parts neatly packed in labeld plastic bags. So everything was actually quite easy to do.
As I needed 6 spark plug outputs, I had to make some extra output cirquits, but it's all in the manual.
I also wanted to go full sequential with the fuel, but the MS2 does not have enough outputs, so I had to leave it at untimed injection.
I'm told it has little practical effect anyway...
Oh and I forgot to make an internal wire, so my tacho didn't work. Once I installed the wire, the stock tacho worked just fine with the MS2.
All in all, it took quite some time to solder it all in place but other than that, it was pretty straight forward. And it all worked! Apart from some issues, I'll get back to later.


Various sensors etc.:
For sensors I needed these types:
- TPS
- Crank sensor + wheel
- Cam sensor
- Oil temperature
- Mainifold temperature
- WB O2 controller + sensor
- Idle valve

TPS:
I went with a Jenvey TP11, found it on ebay. Wiring was pretty easy. No issues.
Crank sensor + wheel I bought from Clewett Engineering, very nice stuff, wiring whent without problem.
For Cam sensor I bought a Bosch 0232103114 (Hall sensor). Wiring was not a problem, but it didn't work when I first started up. It turned out it needs a pull up resistor. It's in the MS2 manual (too)
Oil tempeature, I installed a Bosch 0281002412 in the hole where the CIS temperature switch once sat. No problems there.
Mainifold temperature, I installed a Bosch 0280130085 in the bottom plate of the air filters. No problems there.
IMG_2362
For WBO2, I had a PLX SM-AFR I once bought from our host. I installed that and hooked it up to the MS2. Here it's important to type in the correct values in TunerStudio, so the MS2 can read the signal correctly...!

Wiring harness:
With the MS2 kit, I had bought the wiring loom, which turned out to be a very nice thing.
I had set my mind on making the install as tidy as I could, so I ended up using a lot of time and effort.
One thing which was actually the greatest challenge of all was to find the correct connectors for the various sensors. DO NOT UNDERESTIMATE that task!
Finding a certain sensor is pretty easy, but where to buy the connector? Preferebly with some pig-tails, so you dont need to worry about special tools for the conenctors.
If anybody needs a complete list of connector types, where I bought them, let me know

Cam position sensor installation:
I removed one of the plugs on the front of the cam house. Then drilled and threaded one of the holes in the end of the cam shaft, so the sensor has something to detect.
A friend of mine then made a piece of aluminium to install the sensor in.
IMG_2190+2286

Idle valve:
For idle valve I chose the "556124A" used in VW Golf 2.
At first it worked fine - right up to the point, where the MS2 driver circuit blew because of too high current.
So I had to fix and then modify the MS2 as described in the hardware manual chapter 3.5.4.2. Again: RTFM (Read The ****ing Manual)....

ITB's:
At first I bought two sets of Thiumph ITBs and planned to installed those. But later I found JSR ITBs which to me looked much better and also should give some better peak power! The quality, design and materials seems to be of the highest standard. Here's an introduction to the ITBs:
NEW ITB's for our aircooled 911's
As for intake runners I went with EFI hardware 120mm.

Air filters:
Even if I like the look of the trumpets, I want my engine to last, so I need air filters.
I bought a set of Pipercross filters and adapted the plate to the trumpets.
The only disadvantage is, that trumpets and filter base plate are now assembled and cannot be taken apart again...
IMG_2344+2345

SO that's it for now.
I was on the dyno with the car yesterday. I had told myself to be content with 220, happy with 230 and very happy with anything above that.
It read 244hp @7000rpm and 263Nm @5800rpm - after some adjustment of the throttle linkage I went for an other dyno run: 271hp @ 7100rpm and 279Nm @ 6150rpm.
Turns out I'm very VERY happy now

EDIT: Pictures are in the next posts...
EDIT2: Chapter on idle valve added. HP numbers updated.

[CarreraEvo]

[CarreraEvo]

[CarreraEvo]

[Mixed76]

Nice work! Any pictures of the pistons or inside of the heads?

Sent from my Nokia 7.1 using Tapatalk

[lvporschepilot]

Great job! Can you tell us total ignition timing you are running?

[CarreraEvo]

Originally Posted by Mixed76

Nice work! Any pictures of the pistons or inside of the heads?

Sent from my Nokia 7.1 using Tapatalk

Thanks 😊
Sorry, no pics of heads or pistons. I tend to forget taking pictures 😬

[CarreraEvo]

Originally Posted by lvporschepilot

Great job! Can you tell us total ignition timing you are running?

Thanks 😊
Max advance is 27 iirc, but I’ll fire up the workshop pc and post the map in a few hours.

[CarreraEvo]

Here's the ignition and fuel tables

I'll have an other look at the fuelling around 2000 rpm and WOT... perhaps I can iron out the small dip in the tourque curve.

[lvporschepilot]

Outstanding looking build. Scary because it's almost identical to mine! Those look like dark red Bosch 22lbs injectors with 12 holes? I believe those are popular with the Jeep inline 6 crowd. I started with those but they were too small, so I went with Bosch 0280155931 (late 90s Corvette injector) which are ~25lbs using a Bosch 044 fuel pump which applies about 65lbs pressure.

The dilemma I currently have is gearbox ratios, gears 2-3-4 are perhaps a bit tall. Did you change ratios at all? Shifting 2nd gear at almost 8000rpm at some 74mph seems a bit steep for this engine. I would prefer 2nd pull to around 67-68mph as the SCRS ratios. Anyway here's my tune for reference.

It seems these heads, even with 39mm ports and very long duration cams (I run DC65 cams), hit a wall with regards to flow at about 6000-7000rpm. That appears to be peak flow per the fuel table anyway. Idles around 1200-1300 ok, lumpy, lots of overlap....

[CBRacerX]

Very nice project. I’d love to see a little more detail on the cam sensor setup and the ITB’s themselves. Great work with the twin plug.

[CarreraEvo]

Hi guys
It turned out that the throttle didn't open fully at last dyno run

Sooo after some adjusting, I went for an other go.

Here's the result: it went from 244-271 hp and 263-279 Nm, it's going to be a good weekend


@lvporschepilot
The injectors are Bosch 0 280 155 759.
Static flow at 3 bar, n-heptane factor [g / min]: 237
Used on Volvos among others.
Mine idles quite smoothly around 850-900.
Surprisingly actually, I'd have thought the idle would be much more rough with these HP numbers... but hey, I don't complain
Balancing these ITBs is very easy, the banks need no adjustment, so it's only to adjust the central linkage, so the banks open at the same time. And that's it!

@CBRacerX
I don't really have any more photos of the cam sensor setup, sorry.

Regarding the ITBs, it's JannikSadolinRacing (JSR) who makes them. You can find them on Facebook and Instagram.

[lvporschepilot]

Outstanding result! Any edits to ignition timing, or only fuel?

[CarreraEvo]

Originally Posted by lvporschepilot

Outstanding result! Any edits to ignition timing, or only fuel?

The main difference is that throttle now can open 100%. Before only around 85-90.

I tried to retard ignition above 4K RPM 3 degrees from base and then advance 3 degrees. Both gave lower performance ~ 5-8 hp less.

[brianjames1]

Great thread-
I have a 75 carerra roller in search of an engine. Thinking of buying a core 2.7
Thoughts on a newb with strong mech background doing a rebuild ?

[Trackrash]

Originally Posted by brianjames1

Great thread-
I have a 75 carerra roller in search of an engine. Thinking of buying a core 2.7
Thoughts on a newb with strong mech background doing a rebuild ?

The mag case motors can be a can of worms to rebuild due to the cases tendency to warp. Spend some time searching through this forum for more info. Search for ollies.

[jpnovak]

Very nice results.

[Mixed76]

Really impressed with both the peak power and the flatness of the torque curve. Very well done.

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[jpnovak]

Your torque dip at 2100 rpm is likely too rich. your 1600/1900rpm columns have a large jump in delivered fuel. This is an artifact of tip-in fueling on take-off.

Now that you have a torque curve you need to rescale your fuel table to add an RPM column at 2200rpm. Take away (or average the 4500/5100) a higher rpm column where your torque is flat.

This will give you resolution to improve your tuning as you ramp in torque.

Also, scale your load rows to match your engines total vacuum. Shift rows to add more resolution between 85-100kPa to better match your ITBs. use a datalog to set your lowest row at MAP-min value and scale accordingly.

[winders]

What is the displacement of this engine? What headers did you use?