lightened flywheels

[seniorchristo]

Does anyone have an opinion on the advantages and /or disadvantages of a lightened flywheel for a street engine? For example Burton's offers a 6 bolt steel flywheel at 6.5kg., reasonably priced compared to aluminum. It seems to me the disadvantage would be a less smooth idle.
Thanks,
Chris

[elancoupe]

Hi Chris,

I run a steel flywheel on mine, if that helps.

[seniorchristo]

Steel as in standard or lightweight? What are your observations?
Thanks Mike

[msd1107]

6.5 kg is not that much lighter than stock.

Years ago I got the Fidanza aluminum flywheel, which is substantially lighter. I did not notice any problems idling or low speed operation, even in LA's mobile parking lot traffic.

David
1968 36/7988

[elancoupe]

Steel as in standard or lightweight? What are your observations?
Thanks Mike

It's lightened steel. Does it make a difference? Not sure. Less weight is always good.

I tend to think of engine builds as complete packages, and the flywheel was recommended as part of the engine build. The advice of those with great experience building these motors is my guiding force.

[seniorchristo]

David
You're right, a standard flywheel is roughly 6.5kg (14.3 lbs.). I did a little research and found this which covers the subject pretty well.
lotus-twincam-f39/lightened-flywheel-t19796.html

[archigator]

I've had a Fidanza aluminum flywheel for over 10 years, and I've had no trouble at all. It did take some getting used to initially, when taking off from a stop, but now its second nature.

Gary
'71 Sprint FHC
Miami, Florida

[Davidb]

I fitted the Fidanza flywheel and also a 3.55 diff. There is a slight hesitation when pulling away from a standstill but it is minor and easily adjusted for. I have exactly one weekends experience driving the car though!

When I spoke to Fidanza they still had several aluminium Elan flywheels on the shelf despite them not being in the catalog any more.

[cabc26b]

Chris,

I found the super-light option to be aggravating on the street ( light Aluminum flywheel and Tilton race clutch, total weight similar to a stock clutch cover ). Tricky to get going but intoxicating acceleration - I went backwards to a steel flywheel and AP race clutch , well mannered , but neutered. Looking for middle ground at present .

George.

[Certified Lotus]

Chris, I have an aluminum flywheel in my S1. No issues from my perspective, but I have had aluminum fly wheels in my last 2 Lotus' and am installing in my Europa Twin Cam. They do get a little getting used to upon starting from a standstill, but the acceleration is very much worth the learning curve.

[SJ Lambert]

Anyone got a torque figure for clutch cover bolts (5/16"UNC) into an aluminium flywheel? I presume around 10-12 ft/lbs but less than 15?

[2cams70]

Doesn't make any difference whether it's steel or aluminium it's being screwed into. The bolt needs to be in tension a fixed amount to prevent loosening regardless of what it's screwed into - assuming it's the same size and grade.

[SJ Lambert]

I vaguely recall Dave Bean telling me not to give 'em too much curry into aluminium though - I'd just as soon use a high strength loctite (like 272) & go conservative on tightening them than use a torque figure that would endanger stripping a thread....

[SJ Lambert]

Even Fidanza in their aluminium flywheel installation instructions say maintain OEM tightening specs for clutch cover bolts - doesn't compute if going from a UNF to UNC thread though & the material you're screwing into can make a difference

[rgh0]

A T6 temper aluminum flywheel tensile strength is greater than the original cast iron and similar to a steel flywheel.

A UNF thread develops a higher tensile bolt load at the same torque than a UNC thread on average but the variation in load versus torque due to lubrication and surface finish factors is greater than variation due to thread type so it is a lottery to some degree where you end up.

In general the original Lotus specs will be OK whether UNF or UNC and whether steel or aluminium or cast iron. i also use loctite on those bolts.

cheers
Rohan