Carrera 3.0 engine rebuild

[Jesse911]

After my 3 year project of backdating my '76 911 I will now do the engine. During the backdate process I did a regular service because the condition of the engine was unknown (bought the car running but that was it). The engine is a 930/02 Carrera 3.0.



The engine pulled strong and took me all the ways to the Alps last September. However as the engine had sit for maybe 10 years + some of the gaskets were failing. As the looks of the engine were also a bit less compared to the rest of the car I want to rebuild it and add EFI with ITBS.

The ITB/EFI part I already figured out now just the engine .

Taken the engine apart and will get the case, crank, heads and rods to a machine shop this week. They will check all measurements. Preliminary measurements by me show that the crank, rods and case are all STD size and no obvious signs of problems.

Somewhere in the history of this car the nikasil cylinders have been replaced by alusil cylinders.. And piston no6 was put in 180 degrees wrong..

I will have my cylinders checked if they can be plated with nikasil. If not I will have to get new cylinders. I'm considering the 3.1 set made by Supertech (Henry) but I will have to check the costs of shipping and taxes to Europe.

If I stay with 95mm I will go for JE or Wossner pistons with 10 - 10.5-1 CR. We got good quality fuel here so I can stay single plug.

What I would like to have some advise on. What camshaft would be good for 95% street driving and keeping in mind I will have ITBs.

Also does my case or crank (6 bolt) need any mods when getting more HP from this engine.

If you guys are interested I can make this a complete rebuild topic. BTW I will be building this engine myself.

Thanks

[Bill Verburg]

Put a '73-74 RS cam in it same as was used in the 3.0RS

[Jesse911]

Thanks Bill will look into that.

I see a popular cam here is the DC40. Would that work?

Close to me we have Cat Cams which also have some cams for the 911. How can I compare the cams? The duration is the same as the DC40 but it has a different lobe angle and slightly less lift.

http://www.catcams.com/products/camshafts/datasheet.aspx?ENGINE_id=252&CAMSETUP_id=1034&Language=english

[Rosco_NZ]

I think the mod-S version of the S cam works well. My 2.7RS spec engine seems to love it … webcam 464/465

[Bill Verburg]

Originally Posted by Jesse911

Thanks Bill will look into that.

I see a popular cam here is the DC40. Would that work?

Close to me we have Cat Cams which also have some cams for the 911. How can I compare the cams? The duration is the same as the DC40 but it has a different lobe angle and slightly less lift.

http://www.catcams.com/products/camshafts/datasheet.aspx?ENGINE_id=252&CAMSETUP_id=1034&Language=english

DC-4- mod S, sure similar to the S/RS but w/ more lift, be sure of piston clearance

These are every nice street cams for 3.0 to 3.2 as long as you have ITBs or carbs

[Richey]

You will be disappointed with the DC40's , you do not need the more torque and HP from 3000 to 5000 that the modS's provide with a 3.0 liter engine . the engine displacement provides enough . I don't even like the DC40's in a 2.2 liter , the engine signs off after 5500 rpm instead of the S cam's added push to 7000 , but this is a subjective opinion .

[mikedsilva]

For what it's worth, I ran Mod S in my 3.0 carrera... single plug.. 10.2:1 compression.
Ran fantastic. Itbs, efi.

Great torque from 3500 all the way to 7k

[Richey]

As I said , it becomes subjective , "ran fantastic " is subjective . I believe it would have been more fun with true S cams .

[Rosco_NZ]

Mod-S provides both Tq & HP gains in most displacements, very surprised a 2.2 would 'sign off' after 5000 rpms .. not my experience in 2.7. Strong 2.2S compression and exhaust should make it work well.

[Jesse911]

Thanks guys.

I talked to a local cam grinder here in Europe as the shipping/import taxes make USA camshafts really expensive and went with his advice.




For pistons. I see JE pistons now also have a 10:1 piston in 4032 which can be run with a tighter clearance and should be a better match with the Mahle cylinders.

Any pro's or con's besides that instead of going for their 2618 pistons?

[stownsen914]

One note - the wider lobe centers of that Cat grind might be aimed at a single throttle body application. I believe you mentioned running ITBs, which opens the door for more aggressive cam grinds.

[Henry Schmidt]

Originally Posted by Richey

As I said , it becomes subjective , "ran fantastic " is subjective . I believe it would have been more fun with true S cams .

This is a silly comment. The Mod "S" cam has proven to be far superior to the factory "S" in almost every aspect. If you found limited performance above 5K in a 2.2 engine you did something wrong.

Dima designed the Mod"S" cam to overcome Porsche's propensity towards high duration low lift cams in their search to reduce cam/rocker parasitic loss.

[Henry Schmidt]

Originally Posted by stownsen914

One note - the wider lobe centers of that Cat grind might be aimed at a single throttle body application. I believe you mentioned running ITBs, which opens the door for more aggressive cam grinds.

Agreed. That CAT cam profile listed above would perform better with a 106 LC.
Given your compression ratio and piston preferences, you should have no issues with a narrower lobe center as far as piston to valve clearance.

One caveat: A new build like this always requires careful attention to build tolerances.

[Neil Harvey]

Originally Posted by Jesse911

Thanks guys.

I talked to a local cam grinder here in Europe as the shipping/import taxes make USA camshafts really expensive and went with his advice.




For pistons. I see JE pistons now also have a 10:1 piston in 4032 which can be run with a tighter clearance and should be a better match with the Mahle cylinders.

Any pro's or con's besides that instead of going for their 2618 pistons?

If I can add my 2C's worth.

Go with the local Cam company as they will be able to answer any questions you have after any use, in case it may require some changes. Lift and duration numbers along with LCA's are 3 of the factors that produce changes in performance. There are a lot more factors in a lobe design that contribute to the performance.

Going with known cam designs is always a good idea when you want simple choices. Unfortunately, many of the historic proven designs are copies on top of copies and not close to the original.

When I decided to get back into the Cam supply business I decided that new engineered designs would be our focus. So all new designs are A symmetrical using all modern camshaft engineering we have learned over the past years. I saw no point in offering the same as everyone else.

The internet is full of opinions, me too, but we do not know what you have, how you drive etc. Go with what you have as a starting point and then ask your supplier for any recommendations.

When choosing the Piston, make sure you provide the Piston maker with the Valve drops and ask the Cam supplier for the Valve lifts each side of TDC from 20°. This way you can be sure the valve pockets and clearances will be ok.

[dedyplay]

Great job , look forward to completion..

[Richey]

I replaced the Mod S camshafts in the 2.2 engine with stock S cams , definitely more zip after 5500 to 7000 rpm which I wanted , so nothing was done wrong , but less torque / horsepower between 3000 and 5000 ,
so the choice becomes subjective as to what a person likes .

[Rosco_NZ]

I’d suggest less between 5500 & 7000 too. It just appears to come in harder when there’s so little there before …

[Rosco_NZ]

Not the general consensus. I’d suggest less between 5500 & 7000 too. It just appears to come in harder when there’s relatively little there before …

[Henry Schmidt]

Originally Posted by Richey

I replaced the Mod S camshafts in the 2.2 engine with stock S cams , definitely more zip after 5500 to 7000 rpm which I wanted , so nothing was done wrong , but less torque / horsepower between 3000 and 5000 ,
so the choice becomes subjective as to what a person likes .

Perhaps tuning for different cams was required....if all you did was swap cams.
These are your projects and as the builder you can choose any combination of parts you choose.

Like others have said, perhaps seat of the pants can be deceptive.
We've built these early engines (both road and track) and because of this long term commitment to air-cooled 911 engines we've had the opportunity to dyno all mannor of combinations.
As far as 911S vs Mos "S" the performance is objective not subjective.
Some where in our files, we have dyno sheets that confirm this performance enhancement.

A little story: years ago we had a 914/6 customer that could afford to experiment.
We built him a long stroke 2.5 and a short stroke 2.5. The dyno showed they made the same peak horse power [right around 265hp] but did it differently.
After a weekend of testing, the customer was sure the short stroke engine was quicker. (Seat of the pants)
What surprised the driver was the long stroke motor trimmed the lap times by almost 2 seconds.
Of course there are a plethora of factors that affect performance but seat of the pants is deceptive.

[Richey]

As I said , what a person likes , not necessarily the fastest , I like the original 2.2S personality , but interesting story about the 2.5 liter engines . I think Porsche also experimented with 2.5's in the ST and used the short stroke version , but a different time and a different track .