Update by Tim Suddard to the
Elva Mk VI project car
Sep 16, 2022
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Elva,
ARP,
Tilton,
Pegasus Auto,
Elva Mk VI
Photography by Tim Suddard
Our Elva Mk VI sports racer had a new flywheel and new bellhousing assembly. We had to source a clutch to finish off this part of the driveline.
In period, the car probably raced with a VW Beetle clutch assembly. Our early Hewland transaxle uses 13/16-inch input shafts with 24 splines–same as an early Beetle.
But racing clutch technology has come a long way since then, and we went with a standard, known quantity: a 7.25-inch Tilton Engineering clutch assembly sourced from Pegasus Auto Racing.
[When is it time to upgrade your clutch?]
The 7.25-inch Tilton clutch has become very common in the racing world as it offers plenty of clamp load, smooth engagement, relatively low cost (about $600 for an assembly with a single disc) and with low weight (5.6 pounds for our setup).
These Tilton clutches can be tailored for each application, too, via the spring rates and number of discs. For our use, we went with a single-disc setup and, to preserve our thrust bearings, the softest springs offered.
[Project Corvette Z06: Why a Multi-Disc Clutch Saves Weight While Increasing Clamp Load]
Tilton rates these springs up to 200 lb.-ft. of torque, while our engine will make about half that. We should have plenty of headspace.
Pegasus offers a chart that shows how the 7.5-inch Tilton clutch can be tailored for different needs, all the way up to 1230 lb.-ft. of torque. More discs and stiffer springs simply increase capacity. (On our 500-horsepower V8 Mustang, for example, we opted for twin discs.)
Some part numbers for our setup: TE 66-001HW for the clutch assembly and part No. TE-64185-V-32 for the cerametallic disc.
We finished off the installation with ARP hardware and a custom-made pilot bushing fabricated by a local machine shop.
one thing to think about in going from an old style clutch to a racing clutch is whether the other components of the drivetrain will be affected. You mention the clamping springs and the thrust bearings, good thinking, but what about getting rid of the springs in the clutch disc itself? These take up some of the engagement shock - these small clutches tend to be more like an on-off switch - and it may put more stress on the transmission, differential, etc.
The story does indicate one of the features is smooth engagement, so I am going to guess it will be fine.
Noddaz said:The story does indicate one of the features is smooth engagement, so I am going to guess it will be fine.
Yeah, based on talking to those who have already been down this road, we should be in good shape.
Now to button up the driveline–more updates to come–and then the rest of the car.
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