jeepguy1948
Well-known member
Has anybody tried the Burtz flywheel on a Model A motor with a stock crank? I’m really much more interested in hearing from someone who has actually done it than guesses and assumptions as to what it would do.
Burtz Flywheel
- Thread starter jeepguy1948
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townsedan29
Member
I have stock fly wheel turned down to 33 lbs I believe the burts are 30 lbs mine works great with stock motor just bought a burts for my pickup expect the same results
BRENT in 10-uh-C
Well-known member
I do not have any first-hand experience with the Burtz flywheel, so I am not going to be of much help to you there, however if you don't mind me asking, what is your concerns about buying a Burtz ...or what are your thoughts when comparing the Burtz flywheel to either a Stipe or a modified (i.e.: lightened) factory O.E. flywheel??
jeepguy1948
Well-known member
Full disclosure; I already bought one I just haven’t installed it yet. My concerns are simply that possibly 30 Lbs. is too light? I know that a typical “lightened flywheel is about 40 Lbs. I understand the benefits of a lighter flywheel I was just wondering how much lightening is too much. The one thing that I do not want to do is anything that is going to increase vibration.
BRENT in 10-uh-C
Well-known member
You'll be fine.
jeepguy1948
Well-known member
Thanks B
nkaminar
Well-known member
Jeep Guy,
Do you have a Model A engine in your Jeep?
There are torsional vibrations at play in the Model A crankshaft and Flywheel. There is node point along the length of the crankshaft. This the point where all the torsional vibrations cancel out so that there is no vibration felt at that point. The dynamics has to do with the flexibility of the crankshaft and what the weights of the pistons and rods are and of course the weight of the flywheel, including the pressure plate and clutch disk. The torsional vibrations are always there but increase when the natural frequency of the system is reached. With the original 65 pound flywheel the node point is right at the flywheel so you never feel the torsional vibrations. With a lighter flywheel the node point moves forward so now the flywheel is experiencing torsional vibrations. The Burtz crankshaft is stiffer and heavier than the stock crankshaft and I am not sure how that effects the torsional vibrations. I suspect the torsional twisting is reduced and the node point moves further forward, but I don't know for sure.
Bottom line: With the lighter flywheel, whether Burtz or another one, you will feel torsional vibration but not so much to cause concern. You can reduce the torsional twisting by installing a dampening pulley on the front. This is a good idea whether you have a stock flywheel or not because the torsional twisting can limit the life of your crankshaft and bearings.
Do you have a Model A engine in your Jeep?
There are torsional vibrations at play in the Model A crankshaft and Flywheel. There is node point along the length of the crankshaft. This the point where all the torsional vibrations cancel out so that there is no vibration felt at that point. The dynamics has to do with the flexibility of the crankshaft and what the weights of the pistons and rods are and of course the weight of the flywheel, including the pressure plate and clutch disk. The torsional vibrations are always there but increase when the natural frequency of the system is reached. With the original 65 pound flywheel the node point is right at the flywheel so you never feel the torsional vibrations. With a lighter flywheel the node point moves forward so now the flywheel is experiencing torsional vibrations. The Burtz crankshaft is stiffer and heavier than the stock crankshaft and I am not sure how that effects the torsional vibrations. I suspect the torsional twisting is reduced and the node point moves further forward, but I don't know for sure.
Bottom line: With the lighter flywheel, whether Burtz or another one, you will feel torsional vibration but not so much to cause concern. You can reduce the torsional twisting by installing a dampening pulley on the front. This is a good idea whether you have a stock flywheel or not because the torsional twisting can limit the life of your crankshaft and bearings.
Terry Burtz Calif
Senior Member
A stock flywheel will work on the new engine because all interfaces for attaching parts are identical to an original Model A engine.
The new engine has a much stiffer (and heavier) crankshaft than an original Model A crankshaft.
When an original 63-pound flywheel is used on the new engine, the engine will be less responsive because it will take longer to accelerate and take longer to decelerate.
jeepguy1948
Well-known member
Nkaminar, suggestion on what/where dampener
Synchro909
Well-known member
nkaminar
Well-known member
Sorry for the late response. I have been away on a road trip. Synchro answered the question anyway. Murray has two version, one for modern lip seals and one for the original style rope seal. I recommend the rope seal. The pulley is larger so it make it harder to remove/install the fan belt.
J and M Machine
Senior Member
Flywheel weight being lighter or heavier is not going to increase vibration.
We would recommend taking your flywheel and pressure plate to a machine shop and having it balanced as a unit.
There's no way that to indiscriminate pieces will be in perfect balance.
often is the case when we balance all types of flywheel assemblies not jut Model A. They are all off and off alot.
One example shown was off 76 grams which equals 76 pounds @4000 rpm before correcting it.
Balancing engine is twofold, makes engine run better and last longer.
http://www.jandm-machine.com/balancing.html
Attachments
jeepguy1948
Well-known member
Good advice J & M, unfortunately it could be a trick finding a competent shop these days. But I’ll look around.
nkaminar
Well-known member
Dynamic balancing is very important, as J and M said. The machines that are used sense unbalance in two positions. A flywheel assembly can be balance statically so that it will not fall towards a heavy side when held on low friction bearings, but it could have a dynamic couple so that when rotated it will tend to wobble and add stress and vibration.
The bob weights are 100% of the weight of the rods at the big end and a percentage of the weights of the small end of the rod, piston pin, piston, and rings, usually about 70%. 100% of the weight at the small end, including pin, pistons, and rings, is not used because these weights are only felt at TDC and BDC and not at the approximate 90 degree positions, where only the weight at the big end of the rod is felt. A crankshaft should be dynamic balanced using the bob weights. It is also important the the rods, pins, pistons, and rings are all the same weights (within tolerance) and that the big end of all the rods and the small end of all the rods weigh the same within tolerance.
All this dynamic balancing does not mean that the crankshaft will not experience torsional vibrations. These are caused by the pulses generated by the pistons, etc. generated at each cylinder during rotation. These torsional vibrations can be severe and cause a crank to break, especially on Model T's that have a very skinny crankshaft. The dynamic dampener at the front of the crankshaft dampens out a lot of the torsional vibrations. Even though you do not feel these torsional vibrations with a stock flywheel, they are still there.
The bob weights are 100% of the weight of the rods at the big end and a percentage of the weights of the small end of the rod, piston pin, piston, and rings, usually about 70%. 100% of the weight at the small end, including pin, pistons, and rings, is not used because these weights are only felt at TDC and BDC and not at the approximate 90 degree positions, where only the weight at the big end of the rod is felt. A crankshaft should be dynamic balanced using the bob weights. It is also important the the rods, pins, pistons, and rings are all the same weights (within tolerance) and that the big end of all the rods and the small end of all the rods weigh the same within tolerance.
All this dynamic balancing does not mean that the crankshaft will not experience torsional vibrations. These are caused by the pulses generated by the pistons, etc. generated at each cylinder during rotation. These torsional vibrations can be severe and cause a crank to break, especially on Model T's that have a very skinny crankshaft. The dynamic dampener at the front of the crankshaft dampens out a lot of the torsional vibrations. Even though you do not feel these torsional vibrations with a stock flywheel, they are still there.
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jeepguy1948
Well-known member
I am just north of Seattle Washington
J Franklin
Well-known member
I think a model A engine will always have vibration, My engine was balanced during rebuild to less than a gram, and the flywheel/PP (standard weight) was balanced by Edelbrock. I still have some vibration. I know all 4 cal engines develope vibration so I just enjoy what I have and know I did the best to lengthen its life.