Head bolt stretch, numbers, tensile spec

[Excalibur]

I discovered two of my '61 pan head bolts look like they've been stretched. After checking my new STD head bolt threads I found two bolts wouldn't screw in nicely. After chasing the bolt thread I can see a few threads have been torn up. This is at a point where I'd expect any stretch to occur.(near the shank)
The bolt numbers are 1038 CP which I read are OEM for the era.
What are suitable replacements? Are high tensile bolts from bolt supply shops suitable? STD head spec says 50 - 55ft lb.
The pic below also shows a Shovelhead bolt which might do at a pinch if I use the original washers.

DSCF4847_zpsgrkcdn0o.jpg

DSCF4845_zpssyn6pe9r.jpg

[58flh]

excaliber---I wouldnt worry about it,personaly As long as it cant bottom out on anything Then your good to go!-55lbs.is not all that much.If you feel different /you can get one anyplace or buy all new colony kit ones./The bolts will take that stress without issue!--I would worry more about A cyl. thats .090 over & not round at the bottom because it was not tourque-Plated while machined!.Yhe bolts fine!---Respectfully---Richie

[Excalibur]

Thanks for thoughts

I'd checked for bottoming out especially reading that the bolt at the intake port can break through. All my bolts had enough clearance as they were so I didn't really need to shorten the one at the intake as advised. The insert threads themselves did need cleaning up though. It was as though the makers tap was tapered so the last couple of threads were shallow. (Same thing with the rocker cover threads which cleaned up with the equivalent 3/16W).
Interesting thought on the stretched bolts. I'd feel better about replacing them though as they have yielded at some stage. Getting a Colony set isn't going to work for me as that would take 10 -14 days. I don't think the bolts were anything special as far as I can tell. Bolts with the same number code are found on various other areas on the bikes. So I believe high tensile bolts from a bolt supplier is an option.
I don't like to make assumptions and you just never know what the brains trust can tell you.

BTW, I'm up to getting the guides reamed/honed and cutting seats.. That's todays job to drop the heads at a machine shop.

[Excalibur]

I found Pan and Shovel had the same part number for the bolts so there must have been some superseding in the 70's.
My local Harley guy had 2 NOS on the shelf! The packet was showing sign of age but the plating was mint.
The threads are roll-formed so probably stronger than the cut-thread originals.

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[Bosheff]

There were 2 different head bolts used on shovels. Your pic shows a -77 pt. number on the package, but if memory serves me correctly, it was either 78 or 79 when they changed. At any rate, one version of the headbolt is in fact longer than the other, and will bottom out before proper clamping force is achieved. One of the headbolts had the washer built into the bolt, while the other version had a seperate flat washer that was used with it. Late 78 cylinders were different than earlier units, so I'm guessing this is why the headbolts changed....bosheff

[Excalibur]

Thanks for the thoughts, most interesting.

Yes, of course, there was a change around '78 when the factory began gearing up to increase the bore size to make 80 cubes

To add some more detail my parts book is printed in 1977. Exploded diagrams of Pan and Shovel show washers on both. Basic part numbers are the same but with the Pan having 2 additional/optional part numbers. To add a mystery, my '83 Shovel has the identical bolts to the NOS, indeed the additional bolt in my first post is from the '83. That bike has been in parts since I first acquired it some years ago but I've always believed it doesn't have washers. I'll find out if ever it gets put back together..

[bigbox]

Part number: 16814-48' colony part number:8221-20

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