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Re: '38 six cyl question
Not too shy to talk
Joined:
2016/10/6 6:59
From Grants Pass Oregon
Posts: 25
I just installed the last piston and am ready to torque the rod bolts.
My "Motor" manual torque specs for the rod bolts indicate sixty ft pounds. That seems high because I had just done a 454 Chevy that also uses 3/8" rod bolts and the torque spec is fifty??? Also, do I really need the cotter pins? No other motor I've ever built needed pins and, I would need to back off tightness to install a cotter pin? Thanks again, Bob

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Posted on: 7/13 13:45:00
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Re: '38 six cyl question
Forum Ambassador
Joined:
2007/3/14 16:01
From New Jersey
Posts: 15678
Good practice is to "dress" the backside of the castellated nut if necessary against some very fine abrasive cloth backed on a flat surface to get an alignment of the cotter pin at the correct torque. Of course clean scrupulously before assembling.

I'm not familiar with your specific engine. If your rods just have plain castellated nuts, then the bolts will have been drilled and you must use cotters or wire. If the bolts aren't drilled for cotters then one of the many types of self-locking fastener was used.

Posted on: 7/13 13:58:58
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Re: '38 six cyl question
Home away from home
Joined:
2007/10/28 7:49
Posts: 2222
Today we have blue Loctite which avoids those problems. Especially on the main bearing studs into old aluminum which can pull out or snap. Yes, the torque on those bolts is pretty darn high, but Packard liked to use superior materials and I never saw one of those bolts snap.

I have tested blue Loctite under very severe conditions and it has never failed. I still have test units rattling around out there in severe service.

Posted on: 7/14 5:53:49
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Re: '38 six cyl question
Home away from home
Joined:
2013/12/21 11:14
From Scottsdale, AZ
Posts: 141
Toymanbob;

I’ve checked several ‘Motor’s Manuals’ and found the six cylinder engine should have 3/8 – 24 rod bolts torqued to 45-46 ftlbs.

The plot thickens a bit for later eight cylinder engines with 7/16 – 28 rod bolts that have a torque specification of 60-65 ftlbs. Those engine used ‘all metal self-locking’ nuts that have a rather high running torque that might explain the higher than expected torque.

I’ll defer to others on the subject of whether the 110 & 120 models used self-locking rod bolt nuts. The industry that I worked in considered self-locking nuts as a ‘one-time’ use item. There is also a precautionary note in the '54 Packard shop manual to reject rod nuts that have lost the self-locking feature.

Dp

Posted on: 7/14 10:14:06
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Re: '38 six cyl question
Forum Ambassador
Joined:
2007/4/20 17:54
From Fresno CA
Posts: 15368
Agree about replacing locknuts if there is any question. McMaster-Carr has the three common non insert all steel types. Castellated takes a cotter key, flex top has a smaller diameter thread in a segmented area which squeeze the bolt threads tightly as the segments are forced open by the bolt diameter and interference has malformed or distorted threads that because of the mismatch with the bolt threads becomes very tight on them. Flex top and interference locknuts are rated for high vibration use.

Posted on: 7/14 10:29:09
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Re: '38 six cyl question
Not too shy to talk
Joined:
2016/10/6 6:59
From Grants Pass Oregon
Posts: 25
Thanks David Packard(Really?) for the correct specs. There is no way I was going to over tighten them, I don't believe Packard made "better bolts". I wonder about the accuracy of "Motor's Manual". How many people overtightened their rod bolts? The photo is from my 1948 Motors. How many other specs are wrong?
And why cotter pins or lock nuts or Locktite anyway. No other motor I've done needed any of that. I did tighten the nuts to 40 and then went tighter to install the pins.
And, one more mystery. The front seal is an interesting piece. On the other photo you can see the spring loaded cup that spins with the crank and pushes a cork ring against the inside of the sheetmetal timing cover. I noticed the wear inside the timing cover on disassembly but only today figured it out. I was tempted to reuse the old cork as it hadn't leaked at all!. The solid brass cam retainer is also a nice piece, the 4 bold main bearing cap, etc. Just about done, Bob

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Posted on: 7/15 18:04:47
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Re: '38 six cyl question
Not too shy to talk
Joined:
2016/10/6 6:59
From Grants Pass Oregon
Posts: 25
Can you see the humor? I have the engine on a stand and tilted so the lifters are at eye level and they are still difficult to adjust. I cut down and ground an old 1/2" wrench and set it in the valley to hold the lifter from turning, another 1/2" wrench to turn the adjusting bolt, a third 1'2" wrench to tighten the lock nut and, the feeler gauge to deal with. And they want me to do it running! Bob

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Posted on: 7/17 17:44:56
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Re: '38 six cyl question
Home away from home
Joined:
2014/7/15 11:30
From Terrebonne, OR
Posts: 1346
Quote:
The plot thickens a bit for later eight cylinder engines with 7/16 – 28 rod bolts that have a torque specification of 60-65 ftlbs. Those engine used ‘all metal self-locking’ nuts that have a rather high running torque that might explain the higher than expected torque.


I had this problem on my 1940 110 when I first rebuilt it in the ‘60 at 16 or 17 years of age. Whenever I got to the prescribed torque, it would suddenly loosen again as that was exactly the point where the bolts stretched! I was using a 1956 Motors Manual and the torque was for the larger 1946 engine bolts. Fortunately I had a spare engine for replacement bolts.

Posted on: 7/19 15:21:04
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