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PostPosted: Mon Feb 10, 2020 1:21 pm 
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Car Model*: 1968 Dodge van
Hello 225 guys, i'm inquiring about a 1985 225 S/6 Is the pulley harmonic balancing bolt just there to hold the a tool to press the pulley onto the crank ?? or is it a fixed bolt to hold pulley to the crank ? I am missing this bolt. If anyone has a lead on where i can obtain one? Please let me know, Thanks.


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PostPosted: Mon Feb 10, 2020 3:27 pm 
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It holds the damper on somewhat. Some Slants have them, some don't. It really should not be used to pull the damper on either.

IIRC, it is 3/4 fine thread by 2" long.

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PostPosted: Mon Feb 10, 2020 6:04 pm 
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Quote:
It holds the damper on somewhat


Doesn't, not even a little bit. The damper is an interference fit on the crank snout. Always has been, from the first Slant-6 built in 1959 to the last one built in Mexico in the early 1990s.

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PostPosted: Mon Feb 10, 2020 9:49 pm 
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However, in deference to the "caution" (read legal paranoia) of some sanctioning bodies and some techs it's not out of line to sport one when having your car teched at the strip.

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PostPosted: Wed Feb 12, 2020 4:14 am 
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SlantSixDan wrote:
Quote:
It holds the damper on somewhat


Doesn't, not even a little bit. The damper is an interference fit on the crank snout. Always has been, from the first Slant-6 built in 1959 to the last one built in Mexico in the early 1990s.


Taking this a step further, the effectiveness of the damper to do its intended job requires the interference fit. The damper needs to "think" it is an integral part of the crank in order to deal with the harmful harmonics, and an interference fit achieves that. If the bolt is actively holding the damper in place, something has gone amiss. I see no harm in using one in light of the above.


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PostPosted: Wed Feb 12, 2020 5:18 am 
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It's interesting that the Slant is the only Mopar engine (of the good years anyway) that didn't use a bolt. One must draw certain inferences from that.

I've read of some Hellcats, and Ram V-10 trucks, which had premature engine failures due to the damper bolt not being tightened and coming loose etc.

Here's my at-a-glance opinion....the damper dampens engine harmonics, and those same harmonics can overcome the press fit and cause the damper to loosen. So, the bolt tension serves to stop that from happening.

Let's not forget, too, that the average damper is also doing double duty in that it is driving several HP worth of belted loads. That can be a lot to ask of a press fit, especially a press fit that has to be loose enough to be installed and removed without heat or special tools.


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PostPosted: Wed Feb 12, 2020 8:34 am 
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Plenty of late-model engines (Honda, for instance) rely on the bolt and key for the damper.
Remove the bolt and you can pull it off by hand.

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PostPosted: Wed Feb 12, 2020 10:33 am 
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Is it really ssafe to compare modern day super computer FEA, etc designed engines with a 60 year old brute force motor designed with pen, paper, and a slide rule?


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PostPosted: Wed Feb 12, 2020 5:11 pm 
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It's just food for thought since the subject is being discussed.
There's more than one way to accomplish the task, no matter whose name is on the engine.
For another example, Chrysler went to keyless press-fit dampers and really long bolts for their 4 and 6 cylinder engines.

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PostPosted: Wed Feb 12, 2020 5:21 pm 
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GregCon wrote:
Here's my at-a-glance opinion....the damper dampens engine harmonics, and those same harmonics can overcome the press fit and cause the damper to loosen. So, the bolt tension serves to stop that from happening.


Cool story, bro, but they built a gazillion Slant-6 engines without such a bolt, and this what you imagine happened exactly never on any of them. Harmonics do not overcome an interference fit. That's not a thing.

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PostPosted: Wed Feb 12, 2020 6:05 pm 
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I think the inference I mention above is the Slant has lower harmonics, and other damper-related needs, than most engines. My guess? It's thanks to its mega-heavy crank and low RPM lifestyle. It's a very under-stressed engine with lots of mass.

We all know the story...Chrysler wouldn't have spent 25 cents per car for a damper bolt on all those 340's, 440's, 426 Hemi's, and 273's if they weren't needed. Same for all the 5.7L and 8.0L and 6.2L engines they build in modern times.


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PostPosted: Wed Feb 12, 2020 6:36 pm 
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I'll be interested to learn if ever there arises a cogent explanation of why an imagined phenomenon that doesn't happen, or the use of a bolt on engines that aren't Slant-6s, should make anyone want to use a bolt in a Slant-6 engine.

This is really simple: A bolt is not needed there, but it also won't hurt anything, so if you want a bolt there so you can easily turn the engine with a wrench (or because you'll sleep better at night), put a bolt there.

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PostPosted: Wed Feb 12, 2020 9:39 pm 
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Make it a cap screw. :lol:

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PostPosted: Thu Feb 13, 2020 5:45 am 
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Turbo Slant 6

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The real blessing in all of this is that Chrysler did provide a nice threaded hole in the snout, so if a bolt is desired it can easily be used. There's not a day goes by I don't set aside a moment to be thankful for that. That, and the complete absence of Carrottop from all major TV and media outlets.


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PostPosted: Thu Feb 13, 2020 5:51 am 
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Turbo Slant 6

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Do you see what I see...? lol


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