As some of you know I'm in the midst of sorting out why the T5 in my '65 Valiant has, apparently, two 4th gears and no OD (see: I'm baffled, T5 puzzlement) and along the way I'm having to wade into the clutch, at least enough to get a disc with the right spline count in it. BTW the disc for a 2.2L 4cyl S-10 has the right splines (1-1/8 - 26) and is the same 9.125" OD. Or it's supposed to be, the new disc isn't here yet so that I can confirm.

Since the flywheel needs resurfacing and I need to make a new pilot bearing holder I pulled it. If it weren't iron I'd cut off the "Inertia Ring" (weight where it has the most effect) on the front side of it. All of those old stories about exploding iron flywheels make me nearly nervous to not try it even though I could chuck it up and have it cut in an hour. Which leads me to my question, how light is light enough for spirited street/mtn roads driving? It will likely never be drag raced in my hands, not at all worried about leaving the line. The 3.75 first and the 3.73 axle should be more than enough.

Wilcap only makes their steel flywheels like the OE flywheel, a lighter version isn't available. This particular iron flywheel weighs 19.6 lbs. From the way that the engine behaved I thought sure this was a 30 pounder. Was I wrong to not consider an aluminum flywheel? I don't need a twitchy road racer, just something "sporting" to drive.

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Thom

Cross-threaded is tighter than Lock-tite

Do you have a picture of the front of your flywheel?

There are two versions of the smaller flywheel, one has a heavier outer ring and one that has a flatter ring (the light version)...Nothing says you can't have the outer ring machined down a little... your 1st gear and the rear ratio will be a bit excessive...I'm out of 1st gear in the first 10' with the 3.09 and 4.56 ratios, by just letting up on the clutch...things are better leaving in daily traffic in 2nd (1.67 and 4.56), but I also have built for torque and use a heavy flywheel to help the car launch and leave at street rpm.

Just dropped it off to have it surfaced. It looks like this one on ebay:


That outer ring is what I'm inclined to remove, take it down to the OD step that the ring gear fits on. Will mean re-balancing since the balancing cut in mine, like that one and about the same size & location, will totally go away in the process.

I'm going to try the existing R&P ratio and see how it works out, but I have considered going to a ~3.5 R&P. I was living with a 4.03 X 3.73 so this new to me trans is a move in the right direction anyway.

_________________
Thom

Cross-threaded is tighter than Lock-tite

My engine guy looked at the flywheel and thought that it could have that ring removed until he saw the balancing cut in the ring. Removing it would remove that cut so he set it up on the balancer and it is not neutral balanced. argh. Good thing I marked the orientation before removing it.

Using the late 90's 2.2L S-10 clutch disc (9.25" OD, 1-1/8" x 26T) did require opening up the counter-bore around the flywheel bolts to ~5" to clear the disc's hub & springs. I think that I took it to 5.03" That was a spooky set-up....

So back to my original question, what weight flywheel is used for sports car type driving/racing? IS aluminum where I'll need to go to get this weight?

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Thom

Cross-threaded is tighter than Lock-tite

I would leave it. 20 lbs is not very heavy from an RPM perspective. if you want lighter, get aluminum.

Lou

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Home of Slant6-powered fun machines since 1988

Where my head is at is in thinking that a 10%-15% reduction in Moment of Inertia (MOI) would be about right. I don't know that, it's a wet thumb in the wind guess. Which is why I'm curious what road racer's and auto-X'ers are using. If they're close to stock then I'll leave the f/w alone.

I'm also thinking that going to a diaphragm PP would be a weight/MOI reduction, but have yet to confirm that there is one that will bolt in place of the 9.25" Borg & Beck currently in the car.

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Thom

Cross-threaded is tighter than Lock-tite

FWIW, I used the aluminum flywheel and a stock clutch assembly on my 170 (68 engine in a 65 Val).
I didn't weigh the setup, but it revs like an F1 car!

OK, maybe not, but it sure seems like it by comparison to the stock wheel.
My engine is pretty close to stock but it feels very lively.
I highly recommend using the lightest you can get.

_________________
O==\=/==O

"A mechanic is Somebody."
- Jim Preston

OK, if you have the $$, then go aluminum. I have one in my 64 Dart 225 and it does rev a bit more easily (by ear/seat of pants) with the alum vs. the stock 20lb wheel.

Lou

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Home of Slant6-powered fun machines since 1988

Its a trade off, like most things. Heavier will idle smoother, drive better, but will wrap up a bit more slowly. If you value a smooth idle, and drivability, stay with a heavier flywheel. My slant got considerably smoother when I went from a stock cast iron flywheel to a toque converter, which has even more dampening effect that the stock flywheel. I guess I am getting to be an old poop, but I like the smoother, better driving set up better.

Sam

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Having driven the standard slant six truck flywheel in my car and the stock slant six version back to back I can comment better:

Idle will matter on your build, tuning, as well as having the assembly fully balanced and the flywheel being a big chunk of iron won't damp the harmonics as well as the torque convertor as the flywheel doesn't have fluid running through it soak some of the vibration up.

Shifts will be a little quicker with the lighter flywheel...that being said changing your crankshaft weight will negate that (I got quicker shifts/rpm recovery out of using a cast crank engine with the heavier truck flywheel than the forged crank engine with the stock flywheel...so that 15 lbs of crank weight negated the increase in flywheel weight when power driving or racing). Note that if you have a heavy vehicle (1970's+), the heavy flywheel will give you better launch

Hopefully I'll have some feed back soon enough on what things are like with the most flywheel we can install (truck 11") in the same car as the above experiments.

2 cents,

-D.Idiot

This is the car in question:


build:
ntsqd's Valiant

I'm more likely to do a track day with the car than to drag race it, and more likely to Auto-X with it once in a great while than I am to drag race it. Drag racing is pretty much extremely unlikely. Spent enough time on a S/C -> TAD pit crew to learn that drag racing isn't my thing. For the few times that I'll Auto-X it a hard launch isn't worth biasing towards. However my plan is to drive it as a DD, so an uber-light flywheel isn't a great idea. I drove an Elva Mk VIIs like the below pic with a 2.0L, 200HP BMW 4cyl in it. Had an aluminum flywheel and an Alcon 5.5" twin disc clutch in it. No desire to replicate that!



No intention of straying from the 170, the small displacement and in particular the shorter stroke appeals to me. Guess that I'm weird that way... Correct me if I'm wrong, but I don't think there were any cast 170 cranks, so that option isn't available.

This engine is supposed to be stock rebuilt (sourced by the PO's PO, so nothing is known about it) and by my way of thinking it should idle dead smooth. It's not that I highly value that, it's that the lack of a smooth idle is telling me that something is wrong with this engine. I'm not looking for the flywheel to solve this problem. I'm looking for a more responsive engine and this is one of the avenues that I'm exploring.

I think that what I'll do for the 170 short block that I got from pishta when I have it rebuilt is to order the McLeod steel 'wheel and then look it over & weigh it. If it has the same "inertia ring" and isn't much different in weight from the one in the car now I'll cut it off and try it. Can always turn a steel plate into a ring and add it back if I don't like it.

Thank you all!

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Thom

Cross-threaded is tighter than Lock-tite

Too bad you're not closer - I'd let you drive mine before you count it out.

It's nice on the street, since the rotating assembly, flywheel, and clutch still have plenty of inertia, and you and I haven't gone far beyond the factory tractor tuning.

It's not a rev-n-slip like that little BMW probably was. I bet that 200hp was all way up in the attic!

How much did your Elva weigh, and did it handle like it looks it would?

_________________
O==\=/==O

"A mechanic is Somebody."
- Jim Preston

Oh, and my car has an 833OD and a 3.55sg 7 1/4, FWIW.

_________________
O==\=/==O

"A mechanic is Somebody."
- Jim Preston

Yeah, starting from a dead stop was a "whack the throttle and let the oil-can clutch out on the engine's deccel and then try to catch it with the throttle before it stalls while not spinning the tires too badly" kind of trick. I call it an "oil-can" clutch because it was very digital, on or off with no in between.

The Elva was a customer's, I just worked on it. Had to drive it to make sure that our first time in setting up a Hewland transaxle was correct before taking the car up to Sears Point for a vintage race. 5th gear needed just at 100 MPH to viable. This was CA 192 btwn Craven's Ln and the polo fields near Carpenteria, CA about 15 years ago now. Wet, ready to race it weighed about 1200-1250 lbs. Top of the roll bar is less than waist high. 192 would have been a good road to really flog it on to learn just how good it handled, but being a customer's car we just needed to know the it went into and out of each gear like it was supposed to. Most of the speed was on a long, downhill straight where I had plenty of warning if a farmer was about to back his tractor out into the road.

There's a Weber tuning guru in the LA area with an O-Scope, a 3 gas analyzer, and a chassis dyno all on a trailer. When he was done with tuning the car it made 198 HP at 7800 RPM and the tires were slipping on the rollers with no way to load them harder, so it likely actually made more HP than recorded. That was before Steve Jennings' shop freshed it up. The owner/driver reported that the freshened engine was significantly more powerful on the track. My boss and I both suspected that it was more an "area under the curve" improvement rather than a peak HP improvement, but the car never went back on the dyno during it's stay with us, so no idea.

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Thom

Cross-threaded is tighter than Lock-tite

Very cool.

_________________
O==\=/==O

"A mechanic is Somebody."
- Jim Preston