Heisenberg

Goal: A lightweight (22lbs or so) steel flywheel

Will accept: Any flywheel that will work.

Disclaimer: I'm a noob to SBCs, located in the KC area. Please don't hate on me but I've been a life long MOPAR guy and this is my first foray into actually modding a Chevrolet. About a year ago I bought THE car I would have purchased on my 16th birthday (if I had a job that was a bit better paying than what the local movie theater was paying in 1977.)

My 1977 4 speed 'Vette still had the original, stock L-48. It runs fine, but guys, come on? 180 hp??? Really??? Get real! Soooooo, I'm doing a "simple" engine swap. But I'm having a hell of a time finding a correct flywheel.

I'm swapping the original generation 1 SBC engine with a gen 2, roller cam 1990 block, one piece rear main seal, externally balanced 355 ci. engine. It's a used, low miles local machine shop's version of a GM ZZ3 or 4 crate engine (The gen 2 engine I am swapping into the car originally had an automatic with an externally balanced flex-plate behind it.) Unfortunately, I don't know the name of the shop that built the engine. I do HAVE the flexplate and see the offset weight on it. So it's obviously an externally balanced assembly. I test drove the car that the engine was installed in. It ran smooth with no noticeable engine vibrations from idle to 5800 rpm.

On the Corvette's original 1977 L-48 engine, I've been running an 168 tooth 32 pound flywheel with an 11 inch stock-style clutch that is in excellent shape with fewer than 6,000 miles on it. To use this newer engine with my stock clutch and trans, I understand must switch to a newer one piece rear main seal flywheel.

Is it true you can swap a flexplate with a weight on it with a weighted fly wheel and all is good?

In other words, going from an auto trans to a manual trans causes no balance issues and you need not consider rebalancing the assembly - as long as I have a decent conter-weighted flywheel I will be ok?

Were the externally balanced flex plates and flywheels all counter-weighted the same from the factory? I'm trying to avoid tearing the rotating assembly apart, and having the whole deal re-balanced with a flywheel in place of the flex plate. If it's not a possibility that it would be a "bolt on and go" flywheel, could a balance shop extrapolate the weighting on the flex plate and apply an equivalent weighting to the flywheel?

Now back to my #1 goal. I'd like to run a lighter than factory flywheel (not aluminum), but I cannot seem to find a lightweight steel, one piece rear main, externally balanced 168 tooth unit. Do they exist?

Can anyone help me?

MelWff

why do you want a light weight flywheel to start with? Is this car intended for racing only? You mention a 4 speed but don't mention the rear gearing, what gears do you have? The Chevy Performance catalog lists a 17lb flywheel for 1986 and up. 14088646 Have you also looked at Summit Racing and Jegs?

Pop Chevy

I used to see lightweight flywheels on eBay. If you are going light then go with a steel one NOT cast. and consider a scattershield. They also make a balance plate that works pretty well.

redvetracr

I might look around at the Scoggin-Dickey site

Heisenberg

Thanks Mel. I'd guessed that I had probably include WHY I wanted a lighter flywheel. That is, after I had already written the longest first tech-help post in history - so I didn't add to it. Thanks for reading through it. Since you asked. No, the car will not be race only, but will be driven spirited often. Also, each year, I participated a race at a vintage road track in in eastern Kansas.

http://hooniverse.com/2014/10/01/for...arnett-kansas/

I'm 54 years old and have always had a quick, manual transmission car in my stable.
I prefer heal-toe driving and match revs between nearly every shift. I truly enjoy the challenge, precision and sound. I was very lucky to have still had a set of 3.70:1 rear gears that my father had in his Corvette when I was a teen. I installed them in my car last spring, hoping to liven up the L-48... It did, a bit. But a more power is desired - to make the experience more fun and a lighter wheel will help a 350hp engine rev quicker.

I dont want to drop weight too low, but I've seen a lot of 22lb wheels for the Gen 1 SBC. I'd hoped I find similar to that weight for my application.

Summit, Jegs? nope. I'll look in the Chevy performance catalog. Thanks for the tip.

AW IR C3

More information will be needed.

Sometimes people will bolt together an "externally balanced" damper and flex-plate/flywheel and go from there. Other times the machine shop spins the rotating assmb and balances it as closely as they can. If you say this was built at a machine shop it may have been balanced there, in which case I wouldn't go with an off the shelf unit.

Just a reminder, a lighter flywheel is going to accelerate and decelerate the engine rpm quicker than a heavier flywheel, so if you enjoy driving the thing spiritedly it may be to your benefit to have a heavier one so you're not constantly rev matching or lugging the car down.

gkull

I might be stupid, but are any 350 chevy's built externally balanced?

i used a 22 pound billet steel SFI for years really nice I went to an 11.5 pound and I will change back some time. i don't race and i have to slip to go

Ibanez540r

Its an interesting question and probably why this is not getting any solid answers.

The 1pc RMS 350 did have an external weighted flywheel, but a neutral front balancer. So, from what I've read, they are not "external" balanced as say a 400, but they are also not internal like a standard Gen 1 350. Kind of its own confusing beast.

gkull

You would have to balance them as a set don't you think? Damper, crank, and fly or flex. Because you can bolt on a fly wheel in any position and then you would be way off.

I've seen stock flex and fly's having a welded weight, but that is for neutral balancing just that item.

tfi racing

Yep,(I know you are not stupid,I think almost all the popular GMPP (ZZ,604,etc)crate motors are,the 14088646 flywheel is lkely what the OP needs,we have used that one and the neutral balance pre 1986 version on circle track cars for years,just line up the extra dowel hole in the flange,no need to balance them as a unit.It should be easy to find a new take off,many oval racers pull that flywheel off the 604 crate if they a using a multidisc 5.5" unit.

Heisenberg

OP here: Thanks to all for weighing in on this balance issue (pun intended.)
I am SLIGHTLY less confused... Because I plan on reusing my 1977 style clutch, pressure plate and bell housing I'm not interested in exploring a DMF. So here's my plan - at this point. I'm going to purchase a 1p RMS flywheel that is designed as "externally balanced." I will take the wheel and the weighted flexplate (that is original to the engine I intend to install) to a reputable Kansas City balance shop and ask them to check the flywheel's balance and weight positioning relative to the flexplate and modify the flywheel to suit. Then pray is all good when I start and run the engine. I do not intend for this engine to see RPM higher than approx 5800.

Still, I hope to find a mid level weight wheel (20-25lbs) that is for an eternally balanced crank.

BTW, anybody have an opinion on a neutral balanced flywheel used with that offset weight plate for my application?

Luce

While I may have a Cobra and a vette, I'm a MOPAR guy too. This SBC stuff is a little confusing at times. I've had to do a lot of studying.

And I also heel toe all the time, just to practice the art, I even did it in the jeep before giving it to the 17 year old just because I could.

gkull

I can't heel and toe a stock pedal position C-3.

ronarndt

"I can't heel and toe a stock pedal position C-3." Yeah- the pedal position in the C3 is a little difficult. I feel like my knee is up to my chin when I use the clutch. Unlike my RX-7, where the Japanese engineers probably spent months getting the pedal position just right. Which is good, since things happen real fast at 8000 rpm in that car and a missed shift gets you into 5 digit rpm.
RA

Luce

I must admit, I haven't tried the c3 yet

Heisenberg

Heh heh heh, I've owned six RX-7 cars (two first gens and four FC-3s) They're the type car I learned to heal-toe while match revving on deceleration. Damn, those cars are pure driver's cars. Somewhere in there I also had a 1970 340 Duster and two '70 'Cudas. All of them 4 speeds. That Duster was fun as hell, but like the C3, the brake pedal was just too high to do a proficient job.

Yes, in my 'Vette, actual heal toeing the brake and the accelerator is pretty difficult. I have long narrow feet and when I drive it I wear a pair of slip-on "Born" brand shoes that also have a narrow profile and soft uppers - so they contort easily (and my left toe doesn't get stuck between the under dash and that way too high clutch pedal) I actually have to do it "backwards" of the (ahem) "proper" way, with my heal on the brake and toe on the accelerator. It ain't pretty, but it works. I'd like to raise the accelerator peddle about two inches.

Before I bought my 'Vette, I was seriously considering buying a nice RX-7 and doing one of the ubiquitous LS-1 swaps. But, alas, I grew up with the C2 & C3 being the pinnacle of cool, so I figured I had better own one before it's too late.

Ibanez540r

OK, don't take it as 100% factual, but this is what I believe is the difference and explanation between the 1pc and 2 pc RMS cranks and their balance.

I didn't want to mention before because I don't like to provide info that is not confirmed factual. But should help the OP.. (I had looked into the same info a while back when planning a 1pc RMS block build. Still haven't got around to it yet.)

The 2pc cranks have have a small counterweight on the flange that the flywheel is bolted to (many of you can picture it), but it is never drilled or altered. The larger counter weights inside at the main/crank journals are drilled or filled as part of an internal balance. The 1pc crank, due to the 1pc seal housing that occupies the same space, did not have room for the additional counterweight on the flywheel flange. So, the weight was placed onto the flywheel itself to compensate. However, I don't THINK this weight is ever altered or changed, and the crank is in fact balanced the same as an internal 2pc crank. Obviously the flywheel does have to be attached for it's role, but it's weights are not altered as part of the balance.

I think the terminology as "internal" or "external" is what makes it confusing. It technically is internally balanced but is not the same as most think when referencing an internal balance gen 1 SBC. It is labeled as external balance in summit and other advertising, but again it is not an "external" balance as most think like a 400 SBC.

Anyone who has more expierience or can confirm 100%, please comment in.

Heisenberg

Thank you Ibanez, this helps to comfirm what I have begun to conclude myself.

ronarndt

Heisenberg- hope they don't mind Japanese car comments. "I've owned six RX-7 cars (two first gens and four FC-3s)" You have me beat. I had an 86, 87, 90 bought new and still have a 93 where I am second owner. The 90 was a GTUs with the factory handling package. When I bought it new it was one of only 100 made in 1990 so Mazda could compete in IMSA. That car is on the back cover of the book by John Matras, who found out only 100 were made. Best handling car I ever owned. I finally sold it in 2005 to a guy in NH who set all kinds of local records at the local race tracks in New England. My 93 is highly modified. I think the seats are the only thing stock, although I had them re-done with high end tan leather. 0-60 in 4.2 sec (depending on outside temperature) on street tires and 185+ mph at Pocono International Raceway back in 2006. Fun car, but lousy sounding exhaust tone- unlike my 68 BB convert!