3.6L to 915 gearbox - Part List for Racing

[chstephens5219]

I have been searching and reading through multiple posts and am having difficulty trying to find a concise list of what is needed to mate a 915 gearbox to a 3.6L engine in a 1985 911.

No flames please, just looking for someone who has actually done this themselves and knows the specific parts! This is going into a 100% dedicated track car so I have no concerns on AC, heat, PS or other items that just add weight!

So far I know this:

1. Flywheel - can I re-use my 3.2L flywheel or are the others from Patrick or Timmons different from stock (besides weight)
   
2. Cross bar - I think this is a given to strengthen/fit into the 1985 chassis unless I misunderstand
   
3. Wiring - are there one or two wiring harness adapters required to add a 993 DME
   
4. Oil lines - what is needed to get to the stock oil tank
   
5. Exhaust - will straight headers from a 3.2L mate to the 3.6L block

Anything else I have missed? Thanks in advance.

Craig

[edbaus]

Craig,

I have an 87 911 with a 91 3.6L hooked up to a very strong 915 gearbox and I am running electromotive crank fire for fuel and spark.

1. You can use whatever 9 bolt flywheel you want. Either 3.0 or 3.2. That said, what are you running for fuel and spark computer. If you are running the 3.6L electronics, then you need to get the conversion unit for backdating from Patrick or the like. I do not need this with the electromotive and I run a lightened 3.0 flywheel.

2. Cross bar. I miss your meaning. I assume you mean in the rear of the motor. I use a standard 3.2L engine mount that I had to clearance for the pulley I have. It is welded to a custom bar to accomodate my semitube frame setup.

3. No idea.

4. Mine are all custom, but yours should still bolt to the same place on the block without any modification.

5. No, well maybe. You would need to flip the flanges on one side of the engine. So many cool header/exhaust options for the 993 though.

Throttle linkage is a challenge.

Shifter linkage may need to be modified. Let me think about that.

Maybe on the fuel lines.

Thanks

Ed

[chstephens5219]

Thank you Ed. I intend on using a 993 engine with a 993 DME for engine management (adding a SW chip).

My crossbar question may be stated incorrectly. From what I have read it appears some reinforcement and/or modification is required to the rear engine mounting brace/support. Any insights?

Craig

[KTL]

1. You need to understand why Ed said you can use your stock flywheel. His application has no need for the DME reference sensors. However in your case I believe you need to use a PMS-like conversion flywheel to trigger the reference sensors AND get your clutch positioned in a way that the clutch operation geometrically works with the 3.6 engine. I did a 3.6 de-install from a '78 SC (915 gearbox) into a '88 911, so this is how I have *some* firsthand knowledge of this

2. Ed is correct. The stock engine console (the part that bolts to the engine, not the flat spanner that bolts to the chassis) will work with some massaging. What you're thinking of is the modifications that are done to the stock 3.6 engine suspension.

3. In our conversion, we used no harness adapters whatsoever- note that our engine was a '93 3.6 from a 964 car. We simply followed Steve Timmons' instructions on how to rewire the existing wiring in the car to accept the 3.6 DME harness installation.

4. Our oil lines were the SSI-type oil lines that are so commonly used. The key to the 3.6 is what you do for the oil-in fitting that comes from the oil tank to the oil filter console on the 993 engine.

5. The exhaust from your 3.2 will not bolt up to the 993 3.6. You can flip the studs in the exhaust ports though. However that's a risky thing to do on account of breakage potential (high)

Ed's right about the throttle linkage. Patrick uses a custom made cable.

Shifter linkage is a non issue- straight bolt in hookup

Fuel lines are no problem in your car because of the 3.2 residual fuel system plumbing that is left when your 3.2 engine was removed. Our installation was a bolt on. However I don't know if the 3.6 donor engine had it's fuel line modified to hook up to the '78 car which coincidentally worked in our '88?

[KTL]

Here's some pics from the '88 install

[KTL]

Here's some pics from an '85 bodied 3.2 car made into a 3.6 Vram + 915 racecar. I was going to buy but was too slow to pull the trigger on & missed a good opportunity













Note that the second group of pics here shows a car that has a different oil line routing. That's because the car has a SmartRacing oil tank in the front trunk

[Steve@Rennsport]

I'd also recommend a transmission oil cooler & pump for track/racing applications.

[chstephens5219]

Great info and photos. I am looking forward to my project once I locate the "right" engine. Sounds as though a few items will be on my shopping list to complete the conversion.

Steve - where do you suggest locating a gearbox oil cooler? I already have a large cooler in the front bumper (RSR opening).

Craig

[Steve@Rennsport]

Originally Posted by chstephens5219

Steve - where do you suggest locating a gearbox oil cooler? I already have a large cooler in the front bumper (RSR opening).

Craig

Craig,

I prefer mounting the cooler under the engine grille on the left side. The fan pulls in a LOT of air when the car is moving and that makes it very effective.