Flywheel weight options

Well, this is for my DJ project.

Motor is the original Chevy 153. Tranny will be a T-5 out of an S-10. Pretty close to a bolt up. I'm nearing the point where I need to commit to a flywheel, bellhousing and clutch kit and I'm looking for some general input on flywheel weights.

The 153 is not a long stroke motor like the F-head. It's over square, as I recall 3.875x3.43 on bore and stroke. Motor was just rebuilt with a few mods including a different cam and should put out around 95HP, more if I should decide on a FI system.

Chevy 153/2.5L
T-5 first gear is 4.03:1
3.73 Dana 44 with Trak lok
235-75-15 tires
vehicle will probably weigh in at around 2100#, maybe less

Driving will be some stop-n-go, some road trips and some off-pavement. It would be nice to take off from a stop in second gear as first is the steep 4.03 to 1. I want the engine to be smooth and able to carry me up and over the hills without endlessly down shifting. The ability to idle over off pavement obstacles would be good.

There are advantages and disadvantages to heavy and light flywheel set ups. I am leaning to the 168 tooth flywheel I have, along with an 11" clutch. I'm concerned that this will be a bit too much rotating mass for the engine. The 168 tooth weighs 28#. I don't want acceleration to suffer too much, but too light of a flywheel is not a good idea on a 4 banger either. I could go with a 153 tooth and a 10.5" clutch. The 168 tooth flywheel is only drilled for 11" clutch.

Because this is a hybrid of sorts, mixing early and later Chev stuff, some of my options are limited, primarily in the clutch disc. The easiest and cheapest set up is with a clutch kit featuring an 11" disc- out of an Astro van of all things.

Any thoughts?

 

10.4" clutch is overkill for a 153 engine.
I would suggest the 9-1/4" Auburn clutch.
It transmits 216 ft lbs or torque.
That should be plenty sufficient for the 151 foot pound of torque that the 153 engine has available.

This clutch became an option for CJ's in 1960 and later it became the standard for F-134.
You can use the stock 9-1/4" Auburn cover plate and get a 9-1/4" Borg Beck disk with 1-1/8" diameter splines.

 

Thanks Ken,

This is a DJ with an all chevy engine/gearbox set up- no jeep parts or design involved. The input shaft is 1" diameter and 14 spline- different from earlier chevys. Stock discs are either 9 1/8" or 11". Summit/Advance Adaptors have a 10.4" disc as well.

I debated whether to put this question up as there are some odd variables to it that probably aren't going to apply to any other build on this forum. Questions like this are more common on a jalopy forum like the HAMB, but there is a lot of experience and common sense on this forum and someone may have some insight into my question.

The bigger clutch is overkill for the vehicle, true. An 11" disc is more suited to at least inline or V6 power and torque. The original clutch for the S10 I pulled the T-5 out of is a 9 1/8" disc, so 11" is big. I could put in a smaller disc in the 11" pressure plate.

I do want some weight for the 4 cylinder. It's common to have a heavier flywheel with a smaller engine in order to smooth out the motor, especially in an older design like the 153 with no counter-rotating shafts, etc. V8s are inherently smooth and don't require the averaging out qualities of a large rotating mass. It's just a question if the combination I have in mind is too much. It will have a hydraulic clutch and a diaphragm style pressure plate, so the pedal pressure should be manageable.

I guess I could try it and change it out if necessary to a lighter set up.

(I will be putting the 9 1/4" Auburn clutch in the M38A1 this winter at the same time I go through the gear boxes. It wouldn't surprise me that the clutch in there is original)

 

I'm going to be a dissenter here and say go with the larger flywheel and clutch. You will need to make sure the bellhousing will accept the larger components as many won't. I have a bellhousing from an Astro Van that had a T-5 sitting in the garage and the one I have will accept the 168 tooth flywheel and 11" clutch. Many S-10 bellhousings would not.
The reason I feel the larger flywheel would be an advantage is for the very reason you mention, the mass. It smoothes out the engine pulses making for a smoother idle and also makes for easier starts in stop and go traffic without having to slip the clutch as much. It will reduce how quick the engine will rev however. If you think about it, this is one of the reasons the heavy flywheel was used on Dauntless equipped CJ's.
we put a 153 from a Chevy 2 in Dad's '43 GPW and it had the 168 tooth flywheel with a 12" clutch and it was a pleasure to drive, even for a scrawny 14-15 year old and that was with mechanical rod and lever clutch linkage adapted from the original with through the floor pedals.


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Just to add to this, one reason they used smaller bellhousings, flywheels, and clutches in S-10's etc. was to reduce the size of the tunnel in the cab floorboards to allow for more foot room etc, in the cab. The bean counters and engineers were banking on most people not hauling heavy loads with the smaller vehicles so the smaller components were deemed sufficient.



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Couldn't agree with nickmil more on this. I have a NP542 5-speed, with a flywheel out of a school bus, behind my 153. The clutch disc is larger than the Powerglide flex plate. It runs quite well and has no problem revving up, also with a 3.73 gear and 235-75R-15's. My first gear is 7.24 and it will take off from an idle in first or reverse. It does smooth out the four cylinder very well. I would suggest the largest flywheel and pressure plate that will fit in your bellhousing. The clutch disc size can be smaller with an increased unit loading without a high pedal effort.

 

The larger mass clutch assembly is supposed to make it easier off road, also.

 

During my research on flywheel weight, I came across an article from one of the online 4x4 magazines, I think, where a guy with a Wrangler added a weight on to his flywheel. I think it bolted on, not sure. But it was an extra 9 pounds. The idea was to have the added mass for pulling Moab-type inclines. He was able to do things after the mod that he couldn't do before. This was a 4 cylinder rig. Perhaps this was an additional reason the Dauntless V6 had a heavy flywheel- to sort of try to duplicate the low end pulling and climbing abilities that the F-head had naturally (that is, in addition to what nickmil was saying about smoothing out the V6).

 

Thanks for the replies. Hearing about the personal experiences on this was what I was looking for.

I have 2 bellhousings- both can accommodate the 168 tooth flywheel. The aluminum one was the preferred, but it doesn't snug up on the centering pins on the bell. Seems it got wallowed out somehow- might have been because it was part of a set up on a 3/4 or 1 ton truck and saw heavy use. I won't take the chance of using it. The other bell is the old style cast iron chevy truck bell with the mounting ears for bolting down to a crossmember (I won't be using them though) It has the open bottom to it and the 3 holes for mounting the starter. It fits up snugly on the bell and I'll use it.

The clutch kit I'll get is for a late 80s Astrovan- 11". It has the proper spline count and diameter in the hub. Going this route is also the cheapest as there will be no need for sourcing another bell, flywheel, fork etc. I'll only have to get the kit and a starter motor ($40 for the starter and $130 for the kit; well, there is an adaptor plate too between bell and trans which means no alteration to the input shaft).

MrGJ- glad to hear the acceleration didn't get hurt too much. Whatever possessed you to put in a tranny like the 542? That is a real truck transmission! I got my T-5 out of the picknpull for 80 bucks. Came from an S10 with 105K miles. should work behind a 95hp engine for awhile.

 

My reason for suggesting 9-1/4 Auburn was threefold.
1) It's plenty strong for I-4/153 Chevy.
2) Less pedal pressure required than a larger clutch.
3) It's using Jeep parts

I failed to see your running a T-5, so the suggested input diameter and spline count is a different concern.
I was thinking you could simply use a heavier or thicker flywheel if engine lugging is desired.
That way you have no need for extra mass provided by large diameter clutch cover.

 

Tri County Gear out here in Pomona had their inertia ring featured in Peterson's off road I believe, a few years back. Exactly what you described.

 

Good catch- it was Tri-County's inertia ring.

What's interesting about this build is realizing that just because something came from the factory doesn't mean it is the most appropriate. An example would be what nickmil said- the bellhousing on the S10s may have been nothing more than the bean counters' idea for saving some money. Who knows how many of those trucks were junked early simply because the clutch went out prematurely. Heck- Willys and Kaiser were infamous this way (IMHO) considering how many quite simple things they could have done at minimal expense (bigger clutch, full floating axles, 11" brakes, Saginaw steering, etc) which all existed back in the day.

But I guess they have to find the middle ground...

Ken- yeah I think the disconnect was that this is a chevy set up but just happens to be in a jeep. I would rather doubt the F134 flywheel would bolt to the chevy crank, though who knows. The 9 1/4" auburn would be sufficient, but so long as the driveability is not affected, the 11" is fine and it fits the flywheel I have. If I were to go with the 9 1/8" disc from an S10, I would have to get another flywheel and probably another bellhousing. At any rate, the Astrovan 11" clutch kit should work in the end. And last forever.

In the case of my DJ build, the larger clutch and flywheel should give me the combination of smooth idle, good take off from stops in 2nd gear and overall better driveability both on and off road.

Thanks for all the input!

 

Flywheel weight? "Heavy versus light or even lighter"?.......No question a 4 Cylinder with long
duration's between cylinder Ignition firing and it's inherent low horsepower at Low RPM's can benefit from the heavy flywheel both on and off the road. Off Road at low RPM's it will carry the motor through without stalling in many cases........On pavement just after letting the clutch out the added weight induced "Inertia" helps to move the vehicle away from a stop.......but from that point on there is a price to pay asking the little motor to accelerate the additional flywheel weight. That in it's simplest form is just pure physics.

Willys , back in the day when it introduced the Buick Odd-Fire V6 to its line in late 1965 found it necessary to do something to the Buick motor to mask it's Odd Fire rough running pulse. The Odd Fire V6 had a similar problem as the 4 Cylinder mentioned above which is to much time in crankshaft degree rotation between Ignition firing @ low RPM's..........hence the need to have "Inertia" in some form carry it through.

With the advent of lower "Crawl ratio's" the heavy flywheel in my opinion may be more of a liability rather than an asset in some combinations other than those mentioned above and here is why:
The heavy Flywheel cannot add Torque per se as the engine does when it creates Horsepower. The heavy flywheel can only add "Inertia" as it spins and is then loaded. The application of the load to the spinning mass uses that Inertia to increase momentarily Torque. After that kinetic energy is absorbed only the original Torque of the engine is left available. At that moment , the extra mass of a heavy flywheel becomes a liability as the motor tries to
re-accelerate it.

I think any under powered engine or one that suffers from high altitude tuning and or one that perhaps does not have a low enough crawl ratio my benefit from the Heavy Flywheel.......on the reverse side if you have a low crawl ratio.....and even fired V6 or V8 and Fuel injection I think the extra weight at the crankshaft is just not necessary.

These are my opinions only and welcome anyone's else's...........

 

Tarry99 is right but you have to take into account the intended use of the vehicle. I run a 231 evenfire with the car light flywheel (30lbs or so). In sand, mud, and normal street driving the light flywheel shines. In heavy low speed trail running, rock crawling, or stop and go traffic there are times I wish I had the heavier flywheel. This is with a mildly warmed up 231 Buick V-6 set up for torque primarily.
Take a look at the use you plan on and build accordingly.
With your use I still think the larger, heavier flywheel and clutch assembly would be a good choice. But remember, advice is free, you get what you pay for .


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30# or so and it's still considered "light"? My 168 tooth is 28# and I thought that would be as heavy as I'd want to go.

 

For the Buick engines that is light for a stock flywheel. The 225 Jeep flywheel is seriously heavy, at least 60+ lbs.
I had an aluminum flywheel behind a sbc in a stock car that was less then 15 lbs. if it makes you feel better .


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As I was researching all this, I saw that Jegs/Summit type outfits sell new flywheels for $78 shipping included. I know nothing about the quality. The 168 tooth they sell was 28#- same as the older chevy nodular I have on hand and the 153 tooth they sell was only 16# (that's a steel flywheel).

60+ pounds is definitely heavy.

I once dumped a 198 cid V6 (out of a 63 Buick) in a flatfender. I don't recall the flywheel being all that heavy, but I was a kid at the time and would never have noticed how heavy that flywheel was.

 

Jeep did not use the Buick 225 flywheel.
Jeep Dauntless 225 flywheels weigh in right about 48 pounds.
That weight does not include anything else besides the flywheel.
I suppose Jeep wanted greater inertia to smooth the idle and also increase the Jeeps lugging ability.

The 225 puts out 1.5 times the torque as the 153 engine.
My math indicates that a 32 pound flywheel will provide an equivilant torque to flywheel weight ratio.
So the 28 pound flywheel and a normal size clutch ( 9-1/4 or 9-1/2") is probably about right for the 153 engine.

 

I'm too long out of school to intelligently discuss math... but is the implication here that flywheels are- at least partially- tailored to torque output? 153 tooth/16# flywheels are routinely placed behind Chevy V8s and they certainly have more torque than the 153.

I think the Dauntless 225 is perhaps such a different motor that comparing it to others might be tricky. I have never had a jeep with one though as I mentioned a couple posts back, I did have a Buick 198. That was a lot of years ago and though I don't recall much about it, I don't remember it being very smooth idling. Weren't the 225s semi-notorious for being inherently unbalanced and therefore needing the big flywheel?

 

I merely came up with a torque to flywheel weight ratio comparison.

The oddfire 225 and the I-4/153 are certainly different engines.
The 153 has less need to smooth out the firing impulses.

I'm mainly saying that a 32 pound fly on the 153 would yeild a similar inertia equivilant as the 48 pound fly on the 225.
Personally I think a little under 32 pounds would likely be ideal for the 153 engine in slow RPM situations.