350 4 speed flywheel question
Thread Starter
Pro
Joined: Sep 2002
Posts: 541
Likes: 5
From: Epping NH
350 4 speed flywheel question
Yesterday, we pulled my NOM 350 along with the M-21 trans (original)for a rebuild, and my mechanic brought up several questions.
First, since the engine is non-original, I suspect that the flywheel is non-original to the car also. He seems to feel it is heavier than what should be in there, maybe a truck flywheel, and suggested that I consider something lighter. Since it is pitted, I had planned on having the flywheel resurfaced. Now I am wondering if I should just replace it, and if so, with what. Can anyone who has done this suggest a replacement? The car is a weekend warrior and is not driven very hard.
Also, while we are at it we are going to replace the original oil pressure line. I have purchased a new line from one of the supporting vendors, howver, my mechanic wants to use a brass line. I have heard of problems with copper lines cracking, but am not sure about brass. Any thoughts? Thanks.
Mark
First, since the engine is non-original, I suspect that the flywheel is non-original to the car also. He seems to feel it is heavier than what should be in there, maybe a truck flywheel, and suggested that I consider something lighter. Since it is pitted, I had planned on having the flywheel resurfaced. Now I am wondering if I should just replace it, and if so, with what. Can anyone who has done this suggest a replacement? The car is a weekend warrior and is not driven very hard.
Also, while we are at it we are going to replace the original oil pressure line. I have purchased a new line from one of the supporting vendors, howver, my mechanic wants to use a brass line. I have heard of problems with copper lines cracking, but am not sure about brass. Any thoughts? Thanks.
Mark
Team Owner
Joined: Feb 2005
Posts: 32,519
Likes: 1
From: central America
St. Jude Donor '08-'09
No idea on the oil line...
Here's my opinion with flywheels...there are both benefits and pitfalls to lighter flywheels. A heavy flywheel is good for a car that spends time on highways or pulling (trucks) as they keep the rpm longer aka they take longer to spin up and longer to lose revs
A lighter flywheel will spin up quicker, but will also lose rpms quicker...so if you decrease your speed by downshifting alot, a lightened flywheel will be less effective at accomplishing this. It has to do with rotational inertia of the flywheel based on mass (ahhh, highschool physics again).
If you like a car that spins up fast, and you like to shift, then by all means get a lighter flywheel.
trw
Here's my opinion with flywheels...there are both benefits and pitfalls to lighter flywheels. A heavy flywheel is good for a car that spends time on highways or pulling (trucks) as they keep the rpm longer aka they take longer to spin up and longer to lose revs
A lighter flywheel will spin up quicker, but will also lose rpms quicker...so if you decrease your speed by downshifting alot, a lightened flywheel will be less effective at accomplishing this. It has to do with rotational inertia of the flywheel based on mass (ahhh, highschool physics again).
If you like a car that spins up fast, and you like to shift, then by all means get a lighter flywheel.
trw
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Keep the plastic oil line. If you want to upgrade go to a braided line. The copper and brass will eventually fatigue and crack. I know plastic can do the same but the plastic is better at vibration fatigue.
On the flywheel replace it. If I were going to do it over I would put in a lightweight wheel. I'm pretty sure mine is a 30 pound wheel. I'd like a 12 to 15 pound wheel. Heavy car go with a heavy wheel.
On the flywheel replace it. If I were going to do it over I would put in a lightweight wheel. I'm pretty sure mine is a 30 pound wheel. I'd like a 12 to 15 pound wheel. Heavy car go with a heavy wheel.
Team Owner
Joined: Jul 2004
Posts: 40,380
Likes: 789
From: Redondo Beach, California
It looks like the GM part number for the lightweight flywheel (for engines made after 1986) is 14088646. This is a 12 3/4 inch 16 pound nodular iron flywheel. It's for 10 inch clutches. It has 153 starter ring teeth. It's for cranks with the one-piece crank seal and 3 inch crank flange bolt diameter; the one piece crank seal appeared in Chevy engines after 1986.
It looks like the lightweight flywheel for engines made before 1986 is 14085720. This also is a 12 3/4 inch flywheel, it weighs 15 pounds and has 153 starter ring gear teeth. The crank flange bolt diameter is 3.58 inches. It's for 10.4 inch clutches.
I bought the14088646 for my ZZ4. I think if I had it to do again, I'd buy a 10105832. It's a 14 inch flywheel and allows a clutch up to 11 inches in diameter. It's the one-piece crank flywheel. I assume it's standard weight which is something like 35 pounds (I think).
It looks like the lightweight flywheel for engines made before 1986 is 14085720. This also is a 12 3/4 inch flywheel, it weighs 15 pounds and has 153 starter ring gear teeth. The crank flange bolt diameter is 3.58 inches. It's for 10.4 inch clutches.
I bought the14088646 for my ZZ4. I think if I had it to do again, I'd buy a 10105832. It's a 14 inch flywheel and allows a clutch up to 11 inches in diameter. It's the one-piece crank flywheel. I assume it's standard weight which is something like 35 pounds (I think).
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
I'm not real big on iron flywheels. I know they have been used for millions of miles but if they start to get heat cracks they are more prone to coming apart. I like the steel ones or aluminum with steel inserts. If you are not going to rev it above 6K rpm the nodular iron would probably work. I know it is rare but when the ylet go thay can cut a car in half.
