Looking for a harmonic balancer for a 53-54 235, and i found one on ebay but seller has it listed for 41-54 and has a part # 3701930 its nos and you can see the numbers on the box, anyone know if that number is right???? or someone have one they would like to part with.
Dave Belt width I am open for suggestions,the only parts I have so far are a fresh rebuilt 62 235 long block and your water pump plate. This is all new to me,[last hobby was big hp roadracing 2 wheelers ],I would like to run a 12 volt alt and have replacement parts [ belts,pumps,hoses ] available at the auto parts store if possable.
Belt width is personal preference. Your 38 would have a 5/8" belt and some people like to keep a stock look. The pulley off your generator will fit on a alternator if you go that route. You can go 3/8" or 5/8" belt, you just need to collect matching parts.
The pulley diameter for the 1955-62 pass and truck pulleys are 6 3/4". The difference in the two is, the pass is designed for a 3/8" belt and the truck is designed for a 1/2" belt. By using a truck balancer with a 3/8" belt, the belt runs deeper in the groove, in effect reducing the pulley diameter to the correct diameter.
The damper is designed to work with a specific crankshaft, of which the relevant factors include stroke length, number of main bearings, journal sizes and length. The 216 and 235 aren't very far apart (3.75" vs. 3.9375"), but it's enough for them to vibrate at different frequencies. The 292 damper is even farther away from either of these.
All this damper talk is good,except for the 60 year old part....235 Damper function relies on a heavy piece of steel and a thin disc of elastic material.That elastic material was engineered long ago to tune to a particular frequency.Think it still functions as designed ???? I doubt it.
different harmonics . . . different crankshafts . . . different rods/pistons . . . ???
Then, how can the 235 and 261 harmonic balancers (41-55 3701930 and 53-55 3704338 and 55-57 3729417 and etc) for the same years work for 235 and 261 truck engines?
Go ahead and do what many of us have been doing for many years - use whatever harmonic balancer works with your combination of pulleys. If I was interested in worrying about something, I'd worry about the different diameters affecting cooling (but I don't, because it does not seem to do so).
I know balancers have always been a hot topic, but I wish a GM engineer could tell me why some 283s do not have any balancer at all, just a hub and flange to bolt the pulley on, and some have any number of sizes of balancers, from the factory.
an inline 6-cylinder crankshaft is almost perfectly balanced to begin with due to the 120-degree separation of the rod journals. When we spun an inline 6-cyl. crankshaft up on the balance machine, it was the only one that could be run up to speed without bob weights. A V-8 crankshaft would try to jump off the supports if it was spun at more than a snail's pace without accurately-calculated bob weights attached. Ditto for V-6 or 4 cylinder cranks. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Harmonic balancers are not really about balance but "absorbing" the twisting harmonics of a crankshaft.The longer the crank,the worse it can be. Some 4 cylinder engine have no dampers.Dave mentions the early Chevy V-8's with no actual damper.I guess the theory is the short forged crank and somewhat lightweight parts didn't need one.Or GM cheaped out........... Denny,on a 235 type damper the only place you can see the rubber is two small holes.Have you drilled out the rivets to separate the pieces to have a look? I did out of boredom and it's a very thin disc of rubber like material.It looked ok but who knows if the material has the same properties engineers designed into it after a million cycles and 60 years. In simple terms,I am simple,lol,the rubber separates the hub on the crank to the heavy interia piece.The harmonics are turned into heat from the "wiggling" action allowed by the rubber. The roadway isn't littered with broken 235 cranks so perhaps it's not a big issue for the way these engines are used.
I wonder how many of the self-appointed "experts" who comment on some of these subjects have any practical hands-on experience working with the items they claim to have so much knowledge about? I'm a little more prone to listen to someone who has weight-matched and spin-balanced a couple of hundred rotating assemblies, than someone who has good internet search skills and little or no real-life experience to back up his claims.
A dollar bill weighs approximately one gram. The standard tolerance for weight-matching round track racing engine parts is usually 1/10 gram. Once all the parts are matched for weight, then we calculate a percentage of rotating VS reciprocating weight, and build up bob weights to simulate the piston/rod assemblies. Once they're attached to the rod journals, then the process of making the crankshaft vibration-free can begin by adding or removing weight at the proper position on the counterweights. When I can stand a nickel on edge on the balance machine with the crank turning full speed, it's pretty close to right. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Whether or not the harmonic balancer enters into the dynamic-balance equation depends on the particular engine. Chevy V-8's can be either internally or externally-balanced. 265 through 350 engines are all internally-balanced, and have harmonic balancers that neither add nor subtract from the overall dynamic equation as long as they don't vibrate when spun. 400 cubic inch smallblock engines have a weighted flywheel and harmonic balancer which must be attached to the crankshaft during the balancing operation. Ditto for Ford 302's, which use external balancing. Some John Deere Diesel tractors use gear-driven timed balance shafts to offset harmonics in the rotating assembly that can and will break crankshafts if they're timed incorrectly. Chrysler 2.5 liter 4-cylinders use a chain-driven balance shaft for the same reason. Chrysler 440 engines can be either internally or externally-balanced, depending on connecting rod design. Using a 305 Chevy crankshaft in a 350 causes vibration problems, even though they're dimensionally identical.
Anything attached to the crankshaft must either be dynamically balanced, or add a calculated amount of shake to the assembly. Offsetting torsional harmonics gets added into the mix after the assembly is able to spin vibration-free. That ability to dampen out harmonics is very RPM-dependent, and there will be nodes above and below the normal operating range where the harmonics can't be controlled effectively. That's where balancer technology gets out of the realm of the average engine builder. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Fast truck, I think your common-sense answer is spot-on.
Denny, please keep posting your opinions and observations. Many of us are much more interested in the stovebolt engines than we are in reading about racing engines. Also, you have strongly held opinions but you do not call people names (unless you know them or unless you are clearly joking).
My experiences with engines is sadly limited to stovebolt sixes. Also sadly (perhaps), I was trained by dirt-track race-car mechanics who walked me through three 216/235/261 rebuilds (not enough to even call me a novice). They showed-me and explained to me all the reconditioning they were doing on the heads/blocks (four of them each worked at different car-engine machine shops). I am very interested in learning from people who have experience and who also have an interest in civilly sharing/discussing their experiences.
