Weight savings for a 64.5 mustang....

[Joey120373]

In my case a 50lb reduction in "driver weight" would be a BIG gain!!!!

LOL, I always avoid this subject, but since it was brought up...
I always grin when I see long threads on weight loss for performance reasons....only to see a 300 lb driver.  Seems nobody wants to go to THAT extreme to gain some weight savings..lol  At 140 lbs, I figure I already have a .10 ET advantage on most people..lol

One hint; if you have a fold down rear seat, you can save a quick and easy 50+ pounds by ditching it and either making it a 2 seater or putting in a basic rear seat. An aluminum radiator is another easy weight loss. Fiberglass hood and bumpers is another easy savings. Factory Mustang bumpers are worthless for protection anyway, especially in the front.

Yep! Couldn’t agree more! I’m not a small guy but I am down about 40 pounds from a year ago, another 15-20 to go. 220 or so now.
Bumpers are a good call, and I need at least 1 new front quarter panel.

[Falcon67]

If you are interested in "weight" as limiting performance, you need to focus on rotating weight.  That is 5 times more effective than eating salads or using aluminum bolts.  Drive shaft, internal trans parts, wheels, rear end gears, etc, etc.  Rotating mass eats power.  Doesn't hurt to lose statis weight, but the average is 100 lbs static to gain about .01 in the 1/4.  You can gain 10~100 times that with just a converter change.

[Joey120373]

If you are interested in "weight" as limiting performance, you need to focus on rotating weight.  That is 5 times more effective than eating salads or using aluminum bolts.  Drive shaft, internal trans parts, wheels, rear end gears, etc, etc.  Rotating mass eats power.  Doesn't hurt to lose statis weight, but the average is 100 lbs static to gain about .01 in the 1/4.  You can gain 10~100 times that with just a converter change.

I knew rotating weight was more beneficial to cut than static, just didn’t know it was that much.
I’ve been seriously considering spending $1600-$2000 on one of the “ultra light” crank forgings, as well as a light weight balancer and flywheel/clutch. To me that seems a better use of money than an alloy block. Of course those same parts in an aluminum block is better, but cost IS an issue.

[gt350hr]

   I have a new aluminum ring Romac balancer for a small block . PM if interested.

[jayb]

You have to be careful about rotating weight, I've done lots of moment of inertia calculations on that and the results in most cases are not that big.  Where you can really save on rotating weight is the wheels and tires, and the flywheel, those two items will have a big effect.  The reason is that the inertia of the parts increases with the square of the radius, so the larger the diameter, the bigger the power gain (or loss) potential.  An aluminum flywheel will pick you up a significant amount of HP over a steel flywheel.  A lightweight wheel and tire combo will help even more.  Cranks, rods, harmonic balancers, axles and driveshafts, not so much.  Here's a post I did quite a while back, explaining this issue:

There's a recent message on the forum regarding using an aluminum flywheel versus a steel flywheel in a performance application.  To quantify this you need to do a torque calculation using something called the moment of inertia of the flywheel.  I thought it might be of general interest here to show this calculation, at least if you are an FE tech geek like me 

For the purposes of an example, let's pretend that we have a choice of two flywheels, a 15 pound aluminum flywheel or a 40 pound steel flywheel.  The 40 pound flywheel has more inertia, and will be harder to accelerate than the 15 pound flywheel.  How much more torque will it take to accelerate the 40 pound flywheel at 1000 RPM per second than the 15 pound flywheel?

First, we have to calculate the center of mass of the flywheels.  This is the imaginary ring, some distance from the center of each flywheel, where if all the weight of the flywheel was concentrated it would behave the same under acceleration as the flywheel itself.  The easiest way to do that is to find the imaginary ring where half the flywheel's weight is outside the ring, and half is inside the ring.  If we approximate the flywheel as a simple disc 13" in diameter, the diameter of the imaginary ring is 0.707 X 13", or 9.19".  We actually will need the radius of this ring, which is 4.595".

Next we have to calculate the moment of inertia of each flywheel, but we need to get the values into a form that we can use.  In English units, this means that we will calculate the moment of inertia in slug-feet.  In order to do this, we have to convert the radius of our imaginary ring to feet, which is 4.595/12, or 0.383 feet.  We also have to calculate the mass of the flywheels, by dividing their weight in pounds by the acceleration due to gravity, 32.2 feet per second per second.  For the aluminum flywheel, this is 15/32.2, or 0.466, and for the steel flywheel this is 40/32.2, or 1.242.  Moment of inertia is the mass times the radius of the ring squared:

Moment of inertia of aluminum flywheel = 0.466 X 0.383 X 0.383 = 0.068

Moment of inertial of the steel flywheel = 1.242 X 0.383 X 0.383 = 0.182

To calculate the torque required, we have to multiply the acceleration rate by the moment of inertia.  We need the acceleration rate in radians per second per second, but we have it in rotations per minute per second.  To convert one rotation to radians, multiply by 6.28, and to convert minutes to seconds, divide by 60.  So, 1000 RPM (Rotations per minute) per second = (1000 X 6.28)/60, or 104.66 radians per second per second.

Torque required to accelerate the 15 pound aluminum flywheel at 1000 RPM per second is 0.068 X 104.66 = 7.12 lb-ft of torque.

Torque required to accelerate the 40 pound steel flywheel at 1000 RPM per second is 0.182 X 104.66 = 19.05 lb-ft of torque.

So, if you switch out the 15 pound aluminum flywheel in your 428CJ Mustang and replace it with a 40 pound steel flywheel, as you accelerate in third gear at 1000 RPM per second, you have lost about 12 lb-ft of torque all along the acceleration curve.  In terms of horsepower, at 3000 RPM this is a 6.85 HP loss, and at 7000 RPM it is a 16 HP loss.

This calculation can be applied to any part of the rotational drive components of the vehicle, including the driveshaft, axles, transmission components, wheels and tires, and of course the reciprocating assembly.  For anything other than a round disc, the center of mass portion of the calculation is more complex, but an estimate can be made in most cases.

Hope this is of some general interest 

[Joey120373]

Fantastic post there Jay, thanks.

That leads  to the next big question I have, smaller diameter clutches, single or multiple disk.
An aluminum flywheel is on my list, it has one now that’s ~ 40 years old.
But seems to me bolting up a large, heavy clutch to that light weight flywheel is taking a step in the wrong direction.

I’ve seen some really sexy looking multi disk, light weight clutches for modern vehicles, some of them look to have aluminum cover plates too.
But google “light weight clutch for a Ford 302” and all I see are big center force clutches as far as the eye can see, or full race sprint car stuff. Seems to me there ought to be something in the middle that doesn’t cost $1600-$2000.
Dunno, but seems to me that would be a worthwhile expense at 2 to 3 times what a “good” stock replacement clutch would cost.
I remember the engine masters episode where they took a basically stick motor, and dynoed it with a heavy stock dampener and flywheel, and then with basically a hub at either end. The way the lighter stuff revved on the dyno still gives me goosebumps thinking about it.

[rockhouse66]

Very small diameter multi-disc clutches are the norm for fully developed high performance engines.  Some of the motivation may be packaging, but the dynamic advantages are real, as Jay has illustrated.

[cjshaker]

Just remember, there is no free lunch. Going to trick lightweight rotational parts means you better have a really fat wallet (except for maybe wheels). Stuff gets expensive, quick, when you start looking at lightweight engine components, carbon fiber driveshafts, gun drilled axles, lightweight pressure plates and other driveline parts. There can also be a sacrifice in longevity and durability. Short skirt lightweight pistons will have a limited lifespan compared to a 'regular' performance piston that is more stable in the bore. Carbon fiber driveshafts are prone to damage and can not be repaired. Lightweight housings and third members wear out quicker. You get the idea.

Other stuff just might not make sense, in a given scenario. A short stroke small block with a manual trans and a fat cam can get dicey on the street with a lightweight flywheel. A heavier flywheel smooths out the idle and takeoff and makes the car more street friendly. Not saying an aluminum flywheel won't work, but there are tradeoffs, and they have to be taken into account with the overall combo.

As for the rotational math on flywheels, I'd be interested in hearing back to back comparisons. There's no shortage of instances where theory and what the math says, doesn't match reality in ET gains. Just a 'devils advocate' question to ask yourself; is it worth living with a combo that is nearly impossible to drive on the streets, just to gain .01 or .02 in ET?

Remember, you started out by saying "This will be a road cruising daily driver." Most of the trick stuff being discussed here does not belong on a daily driver. It's fun bench racing though...lol Personally, I'd stick with removing what you don't need, maybe throw some fiberglass at it (hood, decklid, bumpers), relocate some weight with the battery in the trunk to make the car more balanced. You would definitely feel the difference, and you won't sacrifice anything.

[Joey120373]

.  As for the rotational math on flywheels, I'd be interested in hearing back to back comparisons. There's no shortage of instances where theory and what the math says, doesn't match reality in ET gains. Just a 'devils advocate' question to ask yourself; is it worth living with a combo that is nearly impossible to drive on the streets, just to gain .01 or .02 in ET?     

Good points, as for some of the things mentioned, carbo fiber or even aluminum drive shaft, I’m thinking “nah” , just don’t see the benefit justifying the cost, for all the reasons mentioned.
As far as making a 302 based engine too wild for the street, don’t think that’s possible with any reasonable fore thought. Light weight Mahle pistons, I beam rods, light crank, balancer and flywheel/clutch, all those are going to be lighter for sure but I doubt so much lighter than stock that it’s going to make it un-drivable.  Overly large heads, cam and CR, guessing that would do it. Could be wrong. And, for me, it’s not about an ET, if I were going for an ET, I would be chasing HP, cause “it is a lot cheaper than carbon fiber” .
Would be looking at shoe horning a bigger motor in there or power adders or both. For me it’s as much about making the car more responsive as it is quicker. Reducing unsprung weight and rotating mass on a 55 year old car, within reason, I’m guessing will only do good.

[Joe-JDC]

In back to back dyno testing with 26# flywheel vs. 34# flywheel, the torque curve was more round with no dips with the 36# flywheel, and horsepower difference was not measurable.  Acceleration rate was quicker by less than a second after everything was optimized.  Just my experience, but maybe we needed more of a difference in flywheel weight to see the horsepower advantage, if any.  Joe-JDC

[Gaugster]

The flywheel (I.e. Manual) argument has some secondary considerations. At least that's what I've been led to believe. A heavy flywheel will have more stored energy in a drag race launch situation. When the clutch is dropped that energy can result in a more powerful launch. This may or may not result in a faster overall ET. Perhaps with a lower trap speed but it gets real vehicle specific. This is probably true for an automatic (flexplate) using a stutter box.

Of course you can just increase the launch RPM to compensate for a lighter flywheel. As always it's the combination of vehicle and powertrain that gets the win light.

[blykins]

So, you all know my thoughts on aluminum blocks, and I'm not here to re-hash that.   

However, if you look at it from a cost efficiency standpoint, a brand new Ford Racing cast iron Boss block is $2200.  A new Dart cast iron block is similar (if they can ever get away from their 14 week delivery backorder right now).  A Dart aluminum block is $6800.   You could quite literally buy 3 cast iron blocks for the cost of one aluminum block.  That money would go a long way toward lightening the car, driveline, rotating assembly, or even adding *a lot* of horsepower by cylinder head porting, forced induction, etc. 

There is a big difference in weight between the aluminum and cast iron aftermarket Ford 302 blocks, because the aftermarket blocks are quite beefy.   I've had the aluminum Dart Ford 302 blocks in here and I could quite literally pick one up off the floor with one finger, when the block was sitting on the floor on its bellhousing flange.  They weigh about 85 lbs.   The Dart cast iron blocks weigh 160 with a 4" bore.  It goes down a bit when you take them to a 4.125-4.170" bore.

The aftermarket cast iron blocks will support 370-380 cubes with a 3.400" crankshaft.   "Streetable" horsepower would be around 475-500 in that trim. 

[frnkeore]

Of course, another way to save 170 lb, is to dump the Mustang and build on a early Falcon (6 cyl, 2390 vs 2562 curb wt).

There is very little difference between the two, the Mustang is built on the basic Falcon chassis. The Falcon wheel base is 3" longer but, everything on the chassis, will swap from one to the other.

With a lot of time and money, you could come up with a 2000 lb, SBF car.

[TomP]

Or a Lotus Super7, I think you could get that below 1200lbs with an aluminum SBF ... but i'd think he was wanting to know abou the Mustang. All the hardtops compared to sedans are heavy because of the way the door and quarter window mechanisms are.
 The door glass and vent window frames are heavy.... there is weight to be saved there.

[Joey120373]

. There is a big difference in weight between the aluminum and cast iron aftermarket Ford 302 blocks, because the aftermarket blocks are quite beefy.   I've had the aluminum Dart Ford 302 blocks in here and I could quite literally pick one up off the floor with one finger, when the block was sitting on the floor on its bellhousing flange.  They weigh about 85 lbs.   The Dart cast iron blocks weigh 160 with a 4" bore.  It goes down a bit when you take them to a 4.125-4.170" bore.

The aftermarket cast iron blocks will support 370-380 cubes with a 3.400" crankshaft.   "Streetable" horsepower would be around 475-500 in that trim.       

Seems I have to keep reminding myself of these things, you are quite correct. An extra 4K to save 65 pounds is a tad bit on the unreasonable side. I know the aftermarket iron blocks are heavier than a stick block, but how much heavier? 20-30 pounds? Seems to me that’s a good trade off for more cubes and a bullet proof block.