3.5 Litre Engine

[Mark Crowe]

I am looking to build a 3.5 liter naturally aspirated motor for my 911, can anyone advise the route they took to build a similar engine, pistons and barrels ( make, MAHLE, KS , other?) what sort of induction system, custom manifolds, modified 3.2, or others?


Anny watch outs?


Any advise on exhaust systems and cams?

Thanks

[1meansc]

Hi Mark
I have recently finished the build of a 3.5 l 911 motor. The build specs are as follows:
3.2 carrera base motor
964 cylinders - reconditiond
100 mm JE pistons - high compression
GT3 oil pump & 964 piston squirters
Twin spark & midified cylinder heads
Equal length exhaust
ITB - custom with long induction length
Sequential injection & ignition
Everything balanced & lightened where possible

This has turned out to quite an interesting build. A few minor problems encountered with the 964 cylinders, and not the more expensive 100mm non 964 cylinders. But this is still dooable, with a bit of creativity.

PM me for the details if you want.

Please remember that this was almost a money is no object build, with ultimate performance in mind. I will be opening the motor after every 30 to 50 hours.

Good luck.

[EarlySport]

I was under the impression that the head stud spacing was different for 964 cylinders vs. a 3.2 case?

What machine work is neccessary to run these?

[efhughes3]

search for Carrera3.5L as a user here. Ralph built a well-publicised motor as you describe 3 or so years ago.

[1meansc]

The most difficult part of the build was machining the cylinders to suite the 3.2 stud spacing, as well are the O ring groove in the base of the 964 cylinders, and making clearance for the case through bolts, that will interfere with the 964 cylinders.

I would recommend either Nickies made to suite, or locate the Mahle cylinders that were made with the 105mm spigot, and 100mm bore, but on the 3.2 stud spacing.

[JP911]

Your ultimate goal with the motor will be key to any recommendations. Is this motor going to be primarily used on the street, track, a mix of both? Any emissions regulations to consider?

Here's my experience:
I thought this would be a 99% street motor and it was built as such. I now use it mostly on the track, with some light street driving. I simply underestimated my Porsche addiction and the alure of track days.

3.0 case
Early 3.0 heads (larger intake and exhaust ports)
3.2/3.3 crank and rods
ARP rod bolts and head studs
GT3 oil pump
Mahle 100mm cylinders
Mahle 100mm DME pistons (9.8:1 compression)
964 cams
Twin plugged (964 distributor converted for mechanical advance)
Two 6-pin CDI boxes and stock coils
993 heat exchangers
Triad muffler

The motor originally had early CIS, but it just didn't breathe enough. I switched to 46mm PMOs and the engine came to life. The car is very streetable and performs well on the track, but I left alot on the table by not going with a hotter cam. I looked into making the change to a mod-S cam, but with the motronic pistons I'll have clearance problems. The engine has gobs of torque, pulls like mad, and the throttle response with the carbs is simply amazing.

If I were to do things all over again I would go with carbureted pistons and a hotter cam, but that's about it. I suppose I could have done better by starting with a 3.2 instead of a 3.0, but it's all academic at this point. Best of luck with your project!

[Steve@Rennsport]

Mark:

Jon's input on his 3.5 motor is excellent and such a setup makes a great street engine.

You did not say anything about how your 3.5 would be used so its difficult to offer specific suggestions,....

Jon's build is well done and the only thing I would offer is that if such a combination is going to see much track use, I would strongly recommend either Pauter or Carrillo rods and having the crank cross-drilled with the modified center main bearings for better oiling. Of course, camshaft choices are based on the application.

[JeremyD]

Originally Posted by efhughes3

search for Carrera3.5L as a user here. Ralph built a well-publicised motor as you describe 3 or so years ago.

3.2 to 3.5 - Part II

I think he has one of the ultimate 3.5 engines. and Jeff Alton has one of the better 3.4 engines -

3.4 build part 2!

[Jeff Alton]

Thanks Jeremy, mine is pretty, but let me get it tuned before we put it into the "one of the better" categories.. Yours aint to shabby either!

Cheers

[Mark Crowe]

Thanks for the input and links to previous threads. To answer some of the questions- I am going to be using mainly on the street, and am looking for around 300 HP, but with a snappy throttle response.

I have access to both 3 liter and 3.2 litre engine casings and heads, and the condition of these will determine the base for the exact specification of the end motor.

[Jeff Alton]

Well, my limited experience with the ITB's suggest they are the ticket for the snappy throttle response you are after.

Cheers

[Mark Crowe]

Jeff,

Can you give me some information on ITB's- they are not that common in our neck of the woods!

Thanks

[Jeff Alton]

Mark,

The ITB's have one throttle for each cylinder. Search my name and "build" and you will see my threads with pics of my instalation.

Running such system requires an aftermarket ECU, of which many are available. I went with a Microtech (know more for rotaries than porsches, but a master tuner is about 1 mile from here...)

I am using 48mm Jenvey throttles on my motor with custom linkage and custom port matched manifolds. However I am doing some Beta testing shortly on a new set up and may be selling the Jenveys.

Other places to look for ITB's include TWM.

http://www.twminduction.com/
http://www.jenvey.co.uk/

Cheers

[JeremyD]

I would also look at Mark Haggarts (NATCHAMP)

ITB's Anyone ?

he makes some quality stuff!

[Jeff Alton]

Those are the ones I will be testing......

Cheers

[Mark Crowe]

Thanks, the way to go!

[Facey]

hey
been busy.... but i also have a 3.5L
mines based on the 3.3L 930 case, which isn't different from your options.
i used the 74mm crank with 100mm Mahle P&C's.
mod-s cam
46mm webers
etc....etc...
made 278rwhp with B&B headers.... it feels similar but with mroe mid range with georges european racing headers.

is a great engine no matter what i think. Bigger discplacement, and it realllllllyyyy revs fast...magnified by the low gear ratio in my 915....

keep us updated.