Is a lighter flywheel right for your classic?

While completing an overdrive transmission conversion on our 1973 Triumph Spitfire–look for the full story in a future issue–we took the opportunity to make an upgrade, one you’ll never spot on the showfield.

While the transmission was out, we traded the stock steel flywheel for a lightweight aluminum piece from Fidanza Performance. The result? Eight pounds of weight shed. We cut the flywheel’s mass nearly in half.

Lightweight flywheels are commonly found on race tracks, so why did we install one in our street car? Because this Spitfire is meant for spirited drives on back roads, not long slogs in rush-hour traffic. The stock, heavy flywheel was putting a serious damper on the little four-cylinder’s lively nature.

We paired Fidanza’s aluminum flywheel–figure about $430 for the one we installed–with a stock replacement clutch. It’s a remove-and-replace operation that doesn’t require any fabrication or fiddling. Leaving from a stop now requires a little extra throttle, but we haven’t noticed any major decrease in drivability.

But the payoff: a huge increase in the engine’s playfulness when running through the gears. Now, finally, the drivetrain feels worthy of a sports car.

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Comments

wspohn SuperDork
10/21/22 11:58 a.m.

The issue that alloy flywheels raise is the thin steel friction surface attached by screws to the alloy - they can warp or come unglued/unpegged.

I have almost always gone the way that doesn't have that possible issue and usually costs less anyway - lightening the stock steel flywheel. Same result, less expense, no risk in regard to the friction surface. Check around - sometimes the factory wheel used on a slightly different (sportier?) model is interchangeable ( early MGB are lighter and interchangeabke with MGA for instance).

You can get pretty close to alloy wheel weights if desired, by windowing the periphery of the flywheel. This is an MGB race wheel.

Another issue with an alloy wheel can be the steel ring gear coming adrift while in use - we routinely braze the ring gears to the flywheel on lightened steel wheels before balancing so that can't happen, but you can't do that with an alloy wheel.

A lighter flywheel can have a profound effect - an Austin Healey 100 used a stock flywheel that weighed just on 40 lbs. Talk about agricultural - they took the engine straight out of a commerical vehicle without lightening it.

Alloy flywheels have been used in racing for many decades - I ran one on one of my MG engines that came from an Elva Courier - they had homologated it for Le Mans - and I'm not saying that they are necessarily risky, just that there are other ways of getting there for a street car.

sir_mike Reader
10/21/22 7:17 p.m.

On both my 1600 Cortina's I took a lot of weight off the flywheels w/o any issues.Just don't take off too much I guess.

Noddaz PowerDork
10/22/22 10:36 a.m.

While my 1997 Jetta is not a classic, I did have the following conversation with the local VW machine shop when I had the flywheel resurfaced.

Shop: you want this lightened also?

Me: no, I just need it resurfaced.

Shop: you don't want to lighten it?

Me: no. Just resurface it. It is stock. It is a daily driver.

Shop: so don't lighten it. Only resurface it.

Me: correct.

The Shop seemed really confused that I didn't want that done.

Bradlee New Reader
10/23/22 3:43 p.m.

I put that same Fidanza in my TR6. 'about 9 or 10 pounds i think. The stock one was about 22lbs? It revs up and down much quicker but you have to feather the clutch much more from a stop.

JoeTR6 Dork
10/23/22 7:05 p.m.

A Fidanza flywheel is working great on my TR6. It's fine for a fast street car and makes the engine much more willing to rev. Since I had a stack of stock flywheels, I did consider having one of those lightened. But getting it anywhere near 10 lbs. would be difficult without removing too much material. I previously used an aluminum flywheel in an autocross TR6 that was run hard for over a decade without incident.

Kubotai New Reader
10/24/22 10:07 a.m.

Add one more to the list with a Fidanza on my TR6. I like it and have never had any issues with it.

RobMason New Reader
10/27/22 8:30 a.m.

Went from 29lbs on my stock flywheel to 11lb Fidanza on my MGA 1500. Also a MGB competition pressure plate and Volvo P1800 clutch disk

Engine revs faster and pulls quicker through 1st and 2nd gear which is perfect for stop and go traffic and Autocross

It does increase vibration though - especially with new competition engine and trans mounts. I can feel engine impulses through the gearshift and at certain RPM through the wheel and seat from harmonics. Very, very minor and minimal, but there.