Weight of Flywheel - Heavier with weaker engine???

[60Impala4Dad]

I posted this as a reply on the full size car forum, but then realized that maybe it should be over here in the 348-409 engine forum.....
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Showing my knowledge on this topic, or little knowledge I should say... other than higher price, why is a lightweight flywheel sometimes a bad choice? Does the need for heavier rotating mass on engines that are less than high performance make much of a difference when launching from a stop? I am building a mild 348 (.030 over, 9.5:1, .458 lift cam, ported and polished -379 heads with 2.06/1.74 valves). The rear end ratio is 3.08. Running a Muncie M20 wide ratio with 2.52 first gear. I have a choice between 25LB and 30LB flywheels from Autozone at basically the same price. What do you guys think?

[Boat]

Rotating mass is stored energy. A heavier flywheel may smooth out the motor, but will take longer to spin up... I found an aluminum flywheel with steel teeth...maybe 10 lbs.

Used is good :brow

[raymar58454]

I posted this as a reply on the full size car forum, but then realized that maybe it should be over here in the 348-409 engine forum.....
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Showing my knowledge on this topic, or little knowledge I should say... other than higher price, why is a lightweight flywheel sometimes a bad choice? Does the need for heavier rotating mass on engines that are less than high performance make much of a difference when launching from a stop? I am building a mild 348 (.030 over, 9.5:1, .458 lift cam, ported and polished -379 heads with 2.06/1.74 valves). The rear end ratio is 3.08. Running a Muncie M20 wide ratio with 2.52 first gear. I have a choice between 25LB and 30LB flywheels from Autozone at basically the same price. What do you guys think?

If you are going to "launch" at high rpm heavier is better, if off idle lighter is better. Pretty sure there are pro's and con's to this JMO. Hope that 3:08 is a good one.

Ray

[yellow wagon]

that 3.08 is going to take a beating back there...what size tire are you running?:dunno

[boxerdog]

My experience has been that light flywheels can be a PITA with a snappy engine combo and a tall gear, like a 2.20 low 4spd and a 3.08, or something like that...they may sound neat but they aren't fun. If the car is geared correctly for its purpose, a 25-30 lb wheel should be fine. If it is drag only with a good launch gear combo, a lighter wheel is a better option. In your case, I'd use the 30 lb wheel probably to keep everything smooth.

JMO

[60Impala4Dad]

Running 27" Coker radials. Going with the 3.08 because it is the posi that was in the car originally and I really don't want to change out to a different rear axle assembly like a GM 12 bolt, etc. This car is in the final stages of a somewhat stock body-off restoration other than the 4spd, power disc brakes up front, and some internal work done to the motor as I mentioned above. I guess I am not concerned about it launching for repeated 1/4 mile runs, but I do want the car to be a kick-*** fun ride when we dump the clutch at a red light and slam second during the burnout.:beerbang:clap:clap:clap:clap

[CDNpontiac409guy]

HHHMMM.... If you "dump the clutch" with a set of 3.08's and 27" tires out back...
we/re gonna be gathering drive-line parts off the pavement:eek: ( IE, driveshafts, transmission parts, clutch discs:doh )

You need a touck more gear. Even a 3.36

I agree, with the limited cubic inch, and power of the engine, you need a 25-30 pound flywheel.

[yellow wagon]

I agree with all thats been said. I had a hard time picking a gear for my combo as well. If you just plan on driving the car around town and having some fun from time to time, why not go with a 3.55 or even a 3.73 gear? Shoot, even 4.11s! :clap

[boxerdog]

There was another recent thread related to this same issue...it's amazing how long-legged 4 spd cars are with a tall gear. I'd do 3.73s and a 30# wheel unless you see serious 80mph plus freeway miles in the picture.

I used to be a 4-speed guy too, but as I get older I like sticks and autos with a deeper 1st gear to get at least a 9.0:1 overall in 1st, more if possible. Plus around here, you need to loaf at 80+ on the freeway.

So 5/6 speeds and 700r4s get more attractive!

[yellow wagon]

that 2.52 first with a 3.73 rear gear should = FUN! :brow

[DonSSDD]

My old drag car neighbor had a 32 duece coupe with a 4 cylinder motor in it, his wife raced it back in the 50's. It would chirp the tires into second, because he put a heavy flywheel in it.

He later put a V8 in it, 6 carbs, and a caddy 4 speed. His wife drove it that way too.

Don

[60Impala4Dad]

Okay okay okay. I think I am getting it now, and first off I want to thank everyone for sharing their experience to help me along. :clap

This car will be driven to car shows, enjoyed on any day with nice weather, and mostly driven with an occasional lead foot to feel the torque. I also want it to be able to lay rubber with enthusiasm. Thanks to the recommendations on this forum, the 3.08 gears will be swapped out with a set of 3.73's during the overhaul on the rear (bearings, seals, brakes). The flywheel will be a 30 pounder.

There is some history that I need to preserve: My dad had a '60 chevy convertible when he married my mom (way back). He had to sell it after that and all through my childhood I heard stories about this car. He didn't have any pictures of it, but over the years I heard enough about it that I know every option and every bit about the car right down to the spinner hubcaps and dual antennas. Well, I have been secretly restoring a '60 chevy convertible for him and hope to have it ready to present to him late this summer! I was lucky enough to find an original red 348 powerglide car with a posi rear and power steering, just like his. He pulled the PG in his back in the 60's for a 4spd, and that is what I am doing for him (along with modern disk brakes up front and a dual master cylinder). I am doing my best to make the car look exactly like his. The nice part is that in doing so I get to restore the car to stock since it was already red, etc and in the process only add a few minor/reversible changes. I am saving all of the original parts like front drum brake hardware, Power Glide transmission, automatic column, 3.08 ring and pinion to make it possible to bring the whole car back to stock one day if anyone wants to (I am somewhat of a purist). The engine work is hidden inside, and the 3.73's will be hidden as well. The work that I am doing to the engine is to give it that extra snot that he said his had when he says that he and his buddies "did work to the motor and nothing around could touch it back then".:brow
Anyway, I appreciate all of you helping out. I'll post pics when its done, or closer to completion. I can't wait for the day when I show it to him, hand him the keys and tell him that he got his car back.

Doc

[Ronnie Russell]

Doc, Your dad has no idea what you are up to ??? What a shock he is in for. Bet he cries like a baby. I know I would. You are quite a son. We will need pictures of the event . Very special indeed. :clap:clap:clap

[jim_ss409]

That's a great story Doc.:beerbang
You'll have to keep us informed about the progress.

[yellow wagon]

WOW! Cool story!!! Good luck with the project and keep us updated on how its going :clap

[boxerdog]

That's quite an accomplishment...I wish some of my old stories ended like that!

Good luck and good job.

Dave

[rstreet]

Great story.. Could you have someone film the event when you open the garage door and show him and fire it up. Of course we would appreciate his first launch!!
robert

[60Impala4Dad]

Thanks everyone. I have been working on this car since June of last year. I had to replace the floor BEFORE it was available as one piece from Cars, Inc, so I had to butt weld all of the pans in one at a time and fabricate the trans tunnel pieces. All braces were replaced, the inner and outer rockers are new, I replaced the trunk floor, lower rear quarters, and I had to fabricate the pieces that go from the trunk floor to the lower rear quarters. I pulled the body off and now have it on a rotisserie ready to go to the media blaster next week and I dropped the front clip pieces off today. The doors are pretty solid but I did cut windows out of the lower rear corners on the front fenders so that the blaster can clean out around the inner braces (easy repair and good insurance since there was a rust pocket in there).
My parents live about 8 hours away so they rarely visit and when they do I know well in advance. I hide the car and all of its parts in an enclosed car trailer that I bought for when my parents are coming, and I told them that my friend is going through a divorce and hiding the trailer at my house. ;)
The story is being followed by Still Runnin magazine and will be published when the car is done. I have been uploading pics to them every couple of months so they can get the article ready. It will be great to show him the write-up with the car too.
Man I ramble. Thanks again everyone. You guys are a great resource!!!!:bow

Doc

[raymar58454]

Doc, I'm sorry to inform you that I am your real dad and you should be building a 58 convert for me not a 60.:rofl:rofl oh yeah cashmiere blue not red!

Ray