Engine and Transmission Tech

tips, technology, tools and techniques related to vehicle driveline components

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BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5759 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Ideal Flywheel Weight?
Posted by: BlownMGB-V8
Date: October 22, 2015 11:56AM

The simple answer is "yes" but...
I'm guessing this is one of the 10.5" units and the capacity varies widely based on the components used. At the bottom end with organic linings and a very streetable nature they quote about 400 HP, but you aren't using that one are you. From there they go way up to over 1200 HP.

Since capacity is a function of both clamping and heat dissipation (as well as lining material), to lighten the intermediate or slider plate would at least theoretically reduce the capacity somewhat since you remove mass and therefore heat absorbing capacity. So like most things it's a matter of balance. If you have excess capacity or high temp linings you might be able to do a great deal here.

But first a safety concern. What material is the slider made from? If billet, no worries, but to lighten is to weaken and this must be remembered. I highly doubt they used cast but there is no guarantee. Best to check. You can do that with a drill or a grinder.

Quite a few of these come with rather large holes in them. You might be able to drill to lighten. Below a certain size, the bore of the hole will add more surface area than the ends take away which may help in heat dissipation. You obviously need to keep enough of a web to maintain the strength of the ring.

The flywheel and the pressure ring are the other high weight areas, and for the same reasons. It is possible to remove weight in all three places but cautiously, as you do not want the thing flying apart at redline.

But since you are in the neighborhood of 450 HP you should be able to do something with it I would think.

Jim


DiDueColpi
Fred Key
West coast - Canada
(1259 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
What if the Hokey Pokey really is what it's all about?

authors avatar
Re: Ideal Flywheel Weight?
Posted by: DiDueColpi
Date: October 22, 2015 12:20PM

To get a good idea of what Jim is talking about. Check out the Centerforce Dyad clutches.
They have the perimeter of the flywheel lightened as well as the floater.


Blown v8
Bryan Phipps

(47 posts)

Registered:
03/10/2013 04:52PM

Main British Car:


Re: Ideal Flywheel Weight?
Posted by: Blown v8
Date: October 22, 2015 12:24PM

It is one of the 10.5" units,I bought it about 12 years ago,allegedly capable of taking over 600lb of torque !
Flywheel is steel,and came with the clutch,weighing it at 20lb,
image.jpgj
The rest of the clutch weighs in at 26 .25ib, yes the floater has holes in it,I didn't weigh it,but it's not heavy
image.jpg
image.jpg
The clutch came complete but without the throw out bearing ! Gearbox is a cosworth T5 with Quaife internals
Giving the engine a refresh over the winter,new shells,roller cam,and new Pistons (forged) as picture tells what's happening with the TA heads and 0.650" lift
image.jpg
I will be getting the bottom end balanced,and any saving of weight will be a bonus !
Thank you
Bryan


roverman
Art Gertz
Winchester, CA.
(2974 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Ideal Flywheel Weight? Too much Wait !
Posted by: roverman
Date: October 22, 2015 05:16PM

Fed Ex lost my Fidanza insert in Bloomington, CA., but won't admit it. USPS had my carburetor kits, 40 mi. away in Ontario, but sent them up the coast, 5 different stops. What is happening to our carriers-people ? They better hurry-up, before I fergit,," what is this insert for" ?


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5759 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Ideal Flywheel Weight?
Posted by: BlownMGB-V8
Date: October 22, 2015 06:39PM

You could take a good bit of weight off that flywheel yet. I've seen skeletonised steel flywheels down around 15 lbs easy. Anything outside of the PP attachments and the clutch face is only to attach the ring gear. Almost all of that could be machined away. The clutch surface does not have to be more than 3/8" thick, the web to the crank could be thinner than that and have holes. There could be holes in the clutch face as well.

Note, the PP is available with an aluminum pressure ring at a reasonable price:
[www.google.com]

Jim


BMC
Brian Mc Cullough
Forest Lake, Minnesota, USA
(379 posts)

Registered:
10/30/2007 02:27AM

Main British Car:
1980 MGB '95 3.4L 'L32' SFI V6, GM V6T5 & 3.42 Limi

authors avatar
Re: Ideal Flywheel Weight?
Posted by: BMC
Date: January 12, 2016 11:03PM

Although this thread was started two years ago, I thought I would give a simple and short weigh in.


First, it is not just the crankshaft that makes up the rotating weight. It is anything spinning inside and outside the engine including the crankshaft, big ends, balancer, timing chain, camshaft and everything. The further out, the more it will effect things= outer edge of the flywheel and the balancer are good items to point out.

I have used steel and aluminum flywheels and have seen no negative effect on engines that are essentially built to use on the street.

I hear and read from many people who most likely have zero experience with very light flywheels who believe with all their heart that a light flywheel is doom and gloom, especially the MG and other people in the as-it-were factory built car crowd. Some believe that a little weight off the factory flywheel is okay but not too much. My experience says otherwise but it is something that costs money and there are some other items that money is better spent on first.

My personal 3.4L powered MGB and an S10 pickup I have both have aluminum flywheels- no problems. Although everything was identical on both vehicles, it was actually more noticeable on the S10!

Speaking of the S10, with the pickup weighing in at around 2,800 pounds, adding a 200 pound fibreglass top, driver, passenger, fuel, a few spares, my very tiny tandem axle trailer and an MGB V6 to the trailer, the GVW is somewhere around 7,200 lbs. The only time I noticed any change was when pulling away from a dead stop at the top of any hill. This usually at a stop light coming off the freeway. I have to slip the clutch for an extra second- but then again, the rear end gearing is so tall (high speed) that it needed to be slipped at that point anyways. The power of that engine in that truck going down the road is not effected negatively either but it does not have the braking power in that small vehicle to stop the trailer but that's a different story.

Point is- weight of a flywheel under many circumstances I believe can be lighter than the average internet mechanic realizes. As others have said, your findings may differ.

-BMC.


roverman
Art Gertz
Winchester, CA.
(2974 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Ideal Flywheel Weight? Got Dual Mass ?
Posted by: roverman
Date: February 27, 2016 01:03PM

Anyone using one ? Late oem Corvette/ others ? I'm told less "lurch" ? Like a highly effective torsional hub, in the clutch disk ?

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