Light wiight flywheel?

[Jeff's First FFR]

Hi all,
I ordered and recieved my Tremec TKO 600 from Mike Forte as recommended by this forum. The experience was great. Thank you guys!
However he sent me a lightweight flywheel (12lbs). Just wondering if any of you have had experience with a lightweight flywheel. It is going on Blueprint 347. Any issues? Should i send it back and use the stock Ford flywheel?
BTW I just mounted Mikes bellhousing on the 347 and checked the runout: less than .002". Yea, don't have to use offset dowel pins.
Thank guys for all your help, advice and support. Factory Five Forum is the greatest.

[FF33rod]

I have a lightweight flywheel on my 347 as well. The lighter flywheels are going to be more responsive to changes in engine speed e.g. acceleration. Heavier weight ones have more inertia which may be helpful for lower power, lower displacement engines that might bog down a bit otherwise when you shift into a higher gear. That's what I know so far, will be interesting to see if there are other reasons for one vs the other as others chime in
Cheers
Steve

[NAZ]

The biggest difference you'll likely feel is a lightweight flywheel is easier to stall the engine when starting from a stop. If your driving style leans more toward leisurely you may stall the engine once in a while when lazily starting from a stop. It will improve acceleration performance and your ET slip would show it, however, unlikely your butt dyno will detect it. Not a real benefit for most civilized street orientated motorists but an absolute essential for a race car.

[mike223]

I'm less concerned about flywheel weight, and more concerned with flywheel metallurgy.

More precisely, I always pay extra for "steel" flywheels over "cast iron" flywheels (bargain).

I also always pay extra for an SFI scattershield (bargain).


Because in these cars - all that energy is "way too close for (my) comfort otherwise".

[NAZ]

I'm with you Mike.

[SJDave]

[QUOTE=Jeff's First FFR;368788]Hi all,
I ordered and recieved my Tremec TKO 600 from Mike Forte as recommended by this forum. The experience was great. Thank you guys!
However he sent me a lightweight flywheel (12lbs). Just wondering if any of you have had experience with a lightweight flywheel. It is going on Blueprint 347. Any issues? Should i send it back and use the stock Ford flywheel?

I've had both on my 347 over the last 10 years, I really didn't notice that big a difference, maybe in my head I thought it revved quicker with the lightweight, but my lap times around Laguna Seca were essentially the same in HPDE days. It's kind of misleading when then quote the "weight" of the flywheel, they should be quoting the "Moment of Inertia". On a rotary object, you use this value to calculate what angular acceleration results from an applied torque. So lower inertia is good for quicking rev building, worse for smooth casual driving around town.
NOTE: An aluminum flywheel still has STEEL friction surface for the clutch disc to contact and a Steel ring gear on the outside diameter to engage with the starter motor. The weight may be 40 - 50% less than an all steel flywheel, but I suspect the "moment of inertia" may be only 15-25% lower. That steel ring gear at that large radius adds a lot of angular inertia to overcome.
I searched briefly to see if Findanza or Quartermaster published Inertia numbers, NOPE...just weight. I guess 50% number makes the buyer think it's worth spending the money more for a lightweight clutch.
I also searched for the Inertia of a 5.7 liter engine to see how it compared to the "missing" clutch Inertia numbers...all those crank journals must be significant and I'm just wondering if it's EQUAL to the flywheel or 3X more?

If you decide to use it, be careful torquing the Pressure Plate to the Flywheel, the threads will be Helicoiled in the aluminum but you can damage them if you torque too high (yep tell me about it). Get the specification from the Flywheel Manufacturer.

[Megascott]

I've had both Stock cast iron, and aftermarket Tilton style super light flywheels in my previous Cobra (borrowed from my Super late model). I can say the performance is much better with the lightweight flywheel and clutch assembly, However, the Tilton 5.5" setup I had weighs around 10lbs fully populated and is minuscule in comparison to any stock flywheel and clutch setup. I doubt you will feel much difference with the 15lb flywheel in comparison to the stock ~20lb flywheel, however Mike should have sent an SFI rated flywheel, which the stock flywheel is not rated at. Much safer.

The super light setup (Tilton 5.5") is a lot harder to get the car moving and once moving if you do not get up to speed it will sometimes cause the motor to lope and the car can buck so it's either step in the gas, or push in on the clutch and shift down. The engine/drivetrain inertia is so light especially with Higher compression, it can and will cause the rear wheels to actually skid and loose traction if you just let off of the throttle. Imagine stepping on the throttle, doing a burn out, then taking your foot completely off of the throttle and doing a "reverse" burnout. In experienced Race Car driver knows to never fully let off on the throttle, An inexperienced driver can and will become completely out of control very quickly in this circumstance.

Stick with the stock weight SFI or even slightly lighter SFI rated clutch and flywheel, IMHO that is best for the street.

[GoDadGo]

I'm running a billet steel 28 pounds SFI approved flywheel that I had specially made by Centerforce. (I actually had them make me two of these suckers for a possible future project.)
Anyway, I wanted the heavy fly wheel to improve drive-ability, but felt like I NEEDED an SFI approve piece since nobody makes a blow proof bell housing for my transmission.
Personally if that is what Mike sent you, then that is what I'd likely run.

[mike223]

The engine/drivetrain inertia is so light especially with Higher compression, it can and will cause the rear wheels to actually skid and loose traction if you just let off of the throttle. Imagine stepping on the throttle, doing a burn out, then taking your foot completely off of the throttle and doing a "reverse" burnout. In experienced Race Car driver knows to never fully let off on the throttle, An inexperienced driver can and will become completely out of control very quickly in this circumstance.

These cars are very much inclined to this anyway - based on transferring weight off the rear axle alone - add in things to aggravate that tendency with care.

In addition to light flywheels + high compression already mentioned, another couple of things come to mind - mechanical secondary carbs + delete vacuum advance will also significantly add to drag at the rear wheels if the operator steps off the throttle "sloppy".


Works great if you know what you're doing with it (and treat it with the respect it deserves).


Big mistake if you're not expecting the reaction your driver input is going to induce...

[Bad Moose]

Like stated before, Lighter flywheel equals faster revving and a little loss in drivability on the lower end. With these cars as light as they are vs the size of the engine, you will not notice much.

My Cobra runs a light flywheel and on my TR3A we lightened the flywheel. Guess which one has the greatest loss of drivability. The 3, it sucks on take offs only, after that boy howdy she is fun to drive and raps out fast. I notice any weight differences with it when a passenger jumps in and so forth. Same weight as the Cobra, the three has 115hp and the Cobra 536hp. Hmmmmm, I don't think you'll mind the light flywheel enough to want go through the hoops to return it.

[caesarmascetti]

I have an aluminum flywheel in my Cobra also 12lbs, and I also have a 347 stroker, keep it love the way it revs and it's not at all difficult to drive at low rpms

[David Hodgkins]

I used to have a quartermaster lightweight flywheel and clutch and hated it around town. The car bucked at low RPMs and it was hard to pull away from a stop without chirping the tires. I switched back to a factory steel flywheel and spec clutch am glad I did.

[weendoggy]

Get an ACT flywheel. Steel, but lighter than stock. Very good. I use an aluminum one though and love it.

[FFRSpec72]

Get an ACT flywheel. Steel, but lighter than stock. Very good. I use an aluminum one though and love it.

I also use the ACT flywheel, very good quaility

[Mark Reynolds]

Fidanza aluminum flywheel on a Ford Racing 302/340 and would do it again. I think I have conked it out 2 or 3 times in 8k miles. 3.27:1 rear end and T-5.