Clutch, Flywheel, and 5-speed...oh,my!

[tarheelbob]

Hello! First real post related to my 1976 2002. This little car was picked up on BAT, and has a great engine with dual side-draft DCOE 45Webers, 10.5:1 Ross racing pistons, tubular headers, an E21 head, and a hot .302-degree cam. This is pertinent to my questions. I've gotten my hands on a nice Getrag 245 5-speed and want to do the full conversion. The car is going up on it's stands for a full brake system rebuild and a full front/rear suspension upgrade and refresh. Both sub-frames will be dropped. While I am in there, the transmission will be addressed.

 

I need input on the following:

Given the hot cam and higher horsepower motor, am I well-advised to go with the 228mm tii flywheel with something like the Sachs Performance Clutch kit? The car will not be a track car, and will be "fast street", at most. I'm concerned about the loss of low-end torque in the lower rev range due to the cam set-up, and wondering whether a heavier flywheel will actually help with that. 

 

I do not know what is in there right now given the PO engine rebuild and stock 4-speed transmission. It functions fine with no discernible slip, but will be replaced with a good fit for the 5-speed.

 

I am tempted to stay with a new 215mm diameter set-up, and maybe a Stage 1 clutch upgrade, with a lightened, but not aluminum, flywheel. Thoughts?

 

- Bob

[Son of Marty]

You'll be fine with the 215mm clutch set up, with the proper choke size for the webers  you'll have near stock  low end torque and a much stronger mid and upper power. You might want to get a lsd unit if one hasn't already been fitted.

Edited October 30, 2023 by Son of Marty

[tarheelbob]

Thanks! Have already started the inquiries into a 3.91 ratio LSD. It's a "must" with this build. After a bunch of reading and researching, I was feeling that a good, stout, 215mm set-up would be a decent fit. I appreciate the feedback.

 

Oh, and I'll have a local race shop help me really dial in the timing and carb set-up on a chassis dyno once I get her road worthy. I can get the Webers in the ballpark, but a need a really good baseline.

 

- Bob

[tarheelbob]

Will a 215mm clutch/flywheel (stock, HD., or Stage 1) designed for the OEM 4-speed, still fit with Getrag 245 5-speed, or do I need a specific set-up? What variations should I be aware of for the fitment between the two transmissions?

 

- Bob

[Son of Marty]

The clutch assembly will change over just fine you'll need to match the throw out bearing to the transmission.

[Alexander]

15 hours ago, Son of Marty said:

The clutch assembly will change over just fine you'll need to match the throw out bearing to the transmission.

Yes, it's the same clutch assembly except for the throw-out bearing. The throw-out bearing for the

245/5 speed 215mmclutch assembly is the same critical height. It just has the tabs for the actuating lever  at a different location since the the 320i transmissions, both 4 speed and 5 speed, use a actuating lever which differs from the ones on the 02s.  

Edited October 30, 2023 by Alexander

[tarheelbob]

@Son of Marty and @Alexander

 

Thanks,guys. You answered my questions (for now), straight to the point. There will be more, I promise.

 

- Bob

[visionaut]

IMHO, with 10.5 pistons, a 302 cam, DCOE 45s & headers it’s clearly a higher rpm power set-up, and will likely run best with at least 36mm chokes. You can try to choke it down to 30/32 chokes, and run an adjustable cam timing gear, and other tweaks to build back low-end torque, but you’ll give up most of your power bump.
 

What’s the plan for an ignition upgrade to go along with the power goodies? I’d recommend you look into an MSD box or similar.

 

nice car, good luck!

 

Tom

 

 

[tarheelbob]

Thanks, Tom. Vey helpful, and I'll keep this in mind when I go for tuning set-up.

 

The car has an MSD electronic ignition, Ireland Engineering intake manifold, and electronic fuel pump.

 

- Bob

[TobyB]

Quote

 hot .302-degree cam.

well, cool it off, then.

 

10.5:1 is going to be right up against detonation on pump gas,

especially with that conservative a cam

(depending on the other cam numbers- lift and overlap, particularly)

since it will have a very high static compression at low speeds.

Your timing curve will have to be pretty conservative at significant throttle

openings at low revs.  

 

You don't say your redline.  That's also germane to the choke discussion ahead.

And to the clutch choice- last I looked, only radial- strap pressure plates were available

for the 215, and they don't survive shifting hard above stock revs.

The VW bunny crowd has a hell of a time with them.

At one time, longitudinal strap 215's were in the aftermarket- but that was quite a while ago.

 

And check your fuel pressure.

 

t

 

[tarheelbob]

@TobyB

 

Thanks. The car came with this nicely upgraded engine, and runs very well, but I have not been able to really stretch it due to the lousy brakes and suspension situation. I'll keep all this in mind when I deep dive into timing and tuning.

 

As to fuel pressure, definitely need a fuel pressure gauge for the electronic pump. Webers are very particular and need low pressure fuel delivery in the 2.5 - 3.5 psi range. I need that visibility, yes.

 

- Bob

[wheelieking]

On 10/29/2023 at 5:09 PM, tarheelbob said:

 

 

I am tempted to stay with a new 215mm diameter set-up, and maybe a Stage 1 clutch upgrade, with a lightened, but not aluminum, flywheel. Thoughts?

 

 

Very nice car!! 

 

If it helps for reference, I have a rebuilt 10.4:1 engine with a weber 38/38, a ~282 cam, headers and forged pistons.  I went with the 228mm aluminum flywheel and I have no problems at all.  As @TobyB points out the timing at low RPM and large open throttle positions is right on the edge.  I had to back the timing off quite a bit.