The Stovebolt Site Forums The Shop Area Engine Shop harmonic balancer interchange

Will a 216 balancer (using the wide belt) fit and function properly on a 61 261? Need the wide belt on the 261 to accomodate old pump relocation

ryanz,

Wait from someone who has used a 216 balancer on a 261, but I think that any 216/235/261 balancer will work on any of those engines.

Correct.

I have customers that have been running 216 balancers on 235's and 261's for years with no problems.

Fit? Yes.
Better than none at all? Yes.
"Function properly?" No. The primary design features of a damper are:
1. crank layout: OK (both L6, 4 mains)
2. operating RPM: OK (very similar)
3. crank stiffness: the 216 crank is stiffer than the others due to stroke length, which moves its harmonic orders upscale. Each period of harmonic torsional vibration will occur at a somewhat higher RPM in the 216, at which the rubber etc. tuning parts are not accurately "focused".
Is the difference significant? I don't know, but don't operate it continuously at an RPM that makes the steering wheel, pedals, shifter etc. buzz.

panic: So the difference is in the Rubber compound? Harder for higher vibrations and softer for low frequency shaking? If that is so then there would be approximately 3 and maybe four different variations? 1, 216. 2, early 235, 3, late 235(maybe) and 4, 261? Is there a part number difference that matches the thinking? You have answered my question about the "damping" function and thanks for that. Balanced crank shaft has both mass and rotational considerations. Damping has only harmonic issues as I understand. I get stuff wrong all the time. So If I an wrong let me know.

In modern days, they use different durometer rubber, that's how racing companies compensate for the difference in the harmonic frequencies in their balancers for different needs. Back in the old days, GM and others just made the balancers wider and larger OD. Just follow the evolution of the SBC from the 265 to the 400, as the engines progressively got larger in cubic inch, so did the balancers.

What were the differences (besides pulley groove sizes) in 216/235-early/235-later/261 balancers?

X2 - what the rubber is made of (how much sulfur etc.), what vulcanizing temperature, and how much it's compressed to fit the space all play a part.
For the same rubber volume, a band 1/4" wide and 1" in diameter will be much softer (less resistance to movement) than a band 1" wide and 1/4" diameter.
I've heard (and believe) that a too-soft rubber insert can be stiffened somewhat by driving wire brads through front to back in a regular pattern (like 6, 1 every 60° etc.) - it works on suspension bushings.
The reverse (too stiff) can be done by drilled holes in the same axis. This also accelerates rubber deterioration.
I don't think either method will help an old damper with the rubber decayed by ozone, oil vapors, heat cycles etc.

Again: the dangerous stuff is where:
1. it's coming apart - eventually, it will come off and rip out your hoses, then go through your radiator
2. the pulley mis-aligns and ruins your fan and pump drive
3. you run it too long at the same RPM which causes "finger tingle"

Tim, here is a list I compiled from the parts books. LINK

That is excellent information/facts, Dave. Too bad it does not show post-1955 261s. However, the later 235 and all 261 crankshafts were most likely similar in weight (maybe even being the same crankshafts after around 1957/58?).

Have you ever had a problem putting a 216 balancer on a late 55 or later 235? You have probably worked on more of these engines than most people here.

I have twice used a a 54/55-1st 235 balancer on a 1959/60 261. No problems so far, but I have only run one of them about 15,000 (most miles at 60+ mph). Those balancers' weight difference would be about 5%.

The weight difference between a 216 and a later 235 is about 24%. That might be significant.

The funny thing about GM parts books is they seldom admit to making the 261 for most years.

I have been using 216 balancers on 235's and 261's for close to 20 years with no problems.

All years of 261's use the 1954-62 235 crank. (actually the 1953 Power Glide crank also).

Part numbers do tell a confusing tale. Some changes would include the pulley width, or if there are 2 grooves. So not as clear as I would like. Panic makes a good observation: if it buzzes it ain't right. Also his observation about material brake down. Good warning to heed. So...use the best you can find and watch for any "buzzing" would be as good as it gets? Wish I could sit down with one of the Engineers for a beer or 4.