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By Don Warren - 4 Years Ago
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I had my 312 recently rebuilt. At 2000 rpm you can feel a distinctive engine resonance through the steering wheel. This occurs while driving as well as standing still in neutral I'm wondering if the harmonic balancer has gone south. has anybody else experienced this?
Thanks, Don
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By Cliff - 4 Years Ago
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Did you have the engine balanced?
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By Don Warren - 4 Years Ago
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Crank was balanced, pistons and rods were weighed and equalized
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By Cliff - 4 Years Ago
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A good balance should include all rotating parts. flywheel or flex plate, crank, rods (with bearings) pistons (with rings, pins and keepers) and the damper, if it's a stick then add the clutch cover.
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By Ted - 4 Years Ago
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Was the crankshaft dynamically balanced to match the current weights of the pistons and rods? The answer above was not quite clear on this. And then there’s the matter of the flywheel. Automatic or standard? If a standard, was the pressure plate and clutch disk balanced along with the flywheel?
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By Ted - 4 Years Ago
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If you feel comfortable that this is not a rotating assembly balancing issue, then I’ll suggest performing a cranking compression check on the engine and insure that all the cylinders are running within 10% of each based on the lowest to the highest readings. You don’t mention if this is a points or a breakerless ignition. If breaker points, then a worn distributor can create some varying timing issues between the cylinders. More detail on what your engine combination looks like would help.
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By Ted - 4 Years Ago
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Was the harmonic damper balanced along with the rest of your rotating assembly?
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By Hoosier Hurricane - 4 Years Ago
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Have you run it to 2000 rpm with the fan belt off? Could be the fan blade out of balance or bent.
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By darrell - 4 Years Ago
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my son had a 5.4 in his truck that always had a tremble.it was the fan.i had never heard of this before.
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By Tedster - 4 Years Ago
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That's a really good point, something to check for sure.
Seems like it would be obvious visually though, with bent blade(s) or something like that? These older solid steel fans give me the willies, I've heard just enough stories about them letting go that I went and bought a new manufacture replacement. Particularly working around them and spooling up the RPMs.
I did re-discover what I already knew or had forgotten, the fan cannot be removed or replaced without first moving the radiator out of the way. The fan bolts are too long. At least on the trucks. So my brand new radiator fan is waiting.
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By KULTULZ - 4 Years Ago
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These older solid steel fans give me the willies, I've heard just enough stories about them letting go that I went and bought a new manufacture replacement.
Are you describing an aftermarket flex fan or an OEM blade (blades attached to fan hub w/ rivets) that was generally used with a fan clutch (much later usage than period being discussed here)?
The only way a solid blade/hub would come apart is if there was a stress crack in the assembly.
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By Tedster - 4 Years Ago
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Just those plain jane solid steel fans used on myriad cars and trucks for decades. What happens is a fan blade lets go, maybe due to corrosion. It probably doesn't happen very often, but they can do tremendous damage or serious injury when they do. "Stress cracks" or other defects may not necessarily be visible to any casual or even not so casual inspection.
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By KULTULZ - 4 Years Ago
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Please describe how a full metal fan comes apart.
The blades (if not solid stamped) are either riveted and/or welded together at the hub and either the rivets have to come loose, the actual hub mounting fails or a stress crack (hidden or visible) causes a failure.
Never seen an actual solid steel stamped blade come apart. Seen plenty of later design with flex blades come loose.
FAN BLADE - 3 BLADE STAMPED -
FAN BLADE - 4 BLADE WELDED -
FAN BLADE - REPLACEMENT TYPE ( BIRD VENDORS) - Blades Rivet to Hub
This was later FORD ASSEMBLY also (It is this one you can't stand to either side of with engine running).
Please don't take this as personal because I don't want to be directed to your bag of tricks ... 
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By Tedster - 4 Years Ago
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I sincerely hope you get to feeling better soon or, whatever personal issues might loom. See also: Passive Aggressive. Jeeze Louise. We're all here for ya ...
Anyhoo for whatever reason, 60 or 70+ year old steel fan blades just fail now and then. We don't need an FAA level investigation to know this. Beware old fan blades, particularly when performing tune ups. This was my only point.
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By KULTULZ - 4 Years Ago
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I sincerely hope you get to feeling better soon or, whatever personal issues might loom. See also: Passive Aggressive. Jeeze Louise. We're all here for ya ...
Anyhoo for whatever reason, 60 or 70+ year old steel fan blades just fail now and then. We don't need an FAA level investigation to know this. Beware old fan blades, particularly when performing tune ups. This was my only point.
Oh, I am feeling much better not having heard YOUR BAG of TRICKS being suggested for my evening feeding.
You made a general statement and I just wanted to know when you saw an early fan blade come apart. No big deal, take your pack off and stand easy. Smoke 'em if you got 'em. Reach down and pull that sucked in MARVIN out of your posterior.
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By dbird - 4 Years Ago
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Fans can and do come apart, though rarely. Many years ago, I was riding with a friend in his new 396 when there was a sharp noise followed by a large vibration. The upward dent in his hood was the first clue, but one of the blades had separated from the rest of the fan. We limped back to town which pretty much destroyed the water pump. The dealer replaced the water pump under warranty, but not the fan and certainly didn't fix the hood.
Anyway, that's my fan story.
Don
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By KULTULZ - 4 Years Ago
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... one of the blades had separated from the rest of the fan ...
What style fan was it? Did a riveted blade become separated or did a solid fan fracture?
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By paul2748 - 4 Years Ago
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Ford had a big ? problem with the 3 blade fans in the 55 Tbirds coming apart. The fix was an added reinforcement plate
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By KULTULZ - 4 Years Ago
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Ford had a big ? problem with the 3 blade fans in the 55 Tbirds coming apart. The fix was an added reinforcement plate
Do you have any tech reference to the above statement? FORD replaced the 3-blade with a 4-blade in the service history. There has to be a SERVICE LETTER reference somewhere.
Is anyone here a member of CTCI? They seem to have much info but you have to be a member ($$$) to access it.
https://www.ctci.org/earlybird-technical-article-index/?selected_category_id=87
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