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Connecting Rod Bolts


Matt Wilson

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Do you guys normally re-use the connecting rod bolts when you are rebuilding your flatheads?  I'm rebuilding my 265 (actually converting a 251 to a 265) and I suspect it will be tough to find replacement bolts.  The 265 uses a rather odd, unique-looking bolt that has a nub sticking off the side of the head, and this nub fits into a recess in the rod, to keep it from rotating when torquing up the nut.  The 251 and 230 rods and bolts are different from this, and not interchangeable.  I doubt anyone like ARP makes anything that.  My 265 bolts generally look ok, but some of them are scraped up along the shanks, where they pressed into the rods, and some have other bits of damage.  I tried cleaning up all of that by blending it out with a fine file, but I'd rather find new (or NOS) ones if I could.

Is it your normal practice to re-use them?  Do you bother cleaning up damage?  Do you normally see damage like I'm describing?

Thanks,

Matt

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Matt, welcome to the best Mopar forum around, these guys know their stuff..........dunno if this helps, I went & checked the service manual I have for the Oz Chrysler Royal,......they used the 250 cube engine and there is no mention of the rod bolts except to use them.......lol.........no specific inspection, measurement or anything else that I can find.....it does list torque specs for the con rod nuts at 45-50 ft lbs..........maybe try Andy Bernbaums for any NOS stuff or other similar places.........maybe contact an engine builder that does other older/vintage style engines and see what they say...........regards, Andy Douglas    

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   If you do take a file to the rod bolts, make sure that you file along the length of the bolt, and not across it. The file marks can cause stress cracks in high-stressed components, and if you’re going to have such, it’s better to have them length-wise rather than cross-wise. This is based on what I was told way-too-many years ago by a race-engine builder, who had a habit of reusing components. I’ll now admit to doing that, too. I drove a sling-shot dragster (back then, I was the skinny one, and was the only one who could fit into the car), and in between rounds, I’d pull all of the pushrods, put them on the pavement in the pits, and stomp on them to get them straight again. Ahhhh, now those were the days.

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Thanks, guys.  Regarding the advice to run the file lengthwise along the bolt, I agree with that.  In fact, repairs are part of what I do for a living, except on aircraft parts, so I understand exactly what you're getting at.

 

Thanks!

 

Edited by Matt Wilson
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Matt,

   You’re more than welcome. Good luck with your project. On a personal note—I’ve reused fasteners on engines, even an all-out top-fuel dragster GMC 6-71 supercharged hemi engine, with no failures to report. Luck??? I don’t know, but I’ll take luck when other factors fail. Further, I doubt you’ll ever wind a flat-head 6-cylinder engine as tight as I did the dragster motor (said to be over 10k rpm, but I can’t attest to that, since everything happened in just under 10 seconds, and 180+ mph (after all, it was 1969, and 1970), and there was no time to look at a tach, even if the car had one (and it didn’t . . .). Best regards . . . .

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On ‎5‎/‎17‎/‎2017 at 7:08 PM, DrDoctor said:

Matt,

   You’re more than welcome. Good luck with your project. On a personal note—I’ve reused fasteners on engines, even an all-out top-fuel dragster GMC 6-71 supercharged hemi engine, with no failures to report. Luck??? I don’t know, but I’ll take luck when other factors fail. Further, I doubt you’ll ever wind a flat-head 6-cylinder engine as tight as I did the dragster motor (said to be over 10k rpm, but I can’t attest to that, since everything happened in just under 10 seconds, and 180+ mph (after all, it was 1969, and 1970), and there was no time to look at a tach, even if the car had one (and it didn’t . . .). Best regards . . . .

You're probably right.  I don't intend to operate at sustained rpm's of more than 2800 - 3000, which I realize a lot of people would say is too high for this engine, but knowing that folks like George Asche and others have routinely gone MUCH higher than that, my operation should be ok.  And WOW, 10,000 rpm!  I knew more modern motors (compared to the flatheads) could rev, but not sure I knew they would go that much.

Thanks for the well wishes.

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A Flathead revving to 10,000 .....:D

I'd get at least 2 blocks away and fast!

I've once had my slightly built 218 to 5200 and that was scary...

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18 hours ago, Don Coatney said:

Only one file should be used to clean up threads and that is as pictured. This file is designed specifically for this job and everyone should have one in there tool box.

https://www.mcmaster.com/#thread-repair-files/=17ovyxr

 

thread file.png

 

 

12 hours ago, bones44 said:

A file or rethreading die.

TR5618B.jpg

Thanks, guys.  Yep, I've got one or two of the ones Don showed, and some thread dies, which I had to use on one of the bolts.  Most of the damage to several bolts was to the shanks, just underneath the heads.  It appears to have come from scraping against the bolt holes in the rods, since the bolts and rods have an interference fit with each other.  Portions of metal were pushed up against the underside of the head.  I carefully filed away the raised material, using a couple of fine files, trying not to get into the radius under the head, as that is a typical weak spot in bolts.  I spoke to my machinist about this, and he said it's pretty common to do that with rod bolts, so I don't feel as uncomfortable with them as I did before, but it would still be nice to find some better ones.  However, I don't think they are to be found, as they are about like hen's teeth, apparently.

 

12 hours ago, Dodgeb4ya said:

A Flathead revving to 10,000 .....:D

I'd get at least 2 blocks away and fast!

I've once had my slightly built 218 to 5200 and that was scary...

5200 rpm is pretty impressive, especially for the 218 with its offset rods.  I'm going to try to avoid that with my 265.

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I did that 5200 RPM watching my Dixco tach back in 1968 in high school racing a 53 chev... beat him of course.HA Ha..

Never beat any flathead  engine that hard since. Think I just needed to do it hear it once.

I have a 265 in my truck and with that 4-3/4" stroke...... I would never beat on one of those either!

I like my stuff to last forever.

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Hey Matt,

Welcome to the forum. As a retired helicopter mech, I share your concern with re-using hardware. But, not to marginalize safety, When a bolt breaks on a car engine it won't fall 10,000 feet or more from the sky. Plus the fact that the hardware your using was made at a time when American's took pride in the work and made good quality parts. If it really is a concern, or a questionable damage area, hook up with an NDI buddy and have him check it out for you.

Best of luck on your rebuild.

Joe 

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  • 4 weeks later...
On ‎5‎/‎21‎/‎2017 at 11:24 AM, soth122003 said:

Hey Matt,

Welcome to the forum. As a retired helicopter mech, I share your concern with re-using hardware. But, not to marginalize safety, When a bolt breaks on a car engine it won't fall 10,000 feet or more from the sky. Plus the fact that the hardware your using was made at a time when American's took pride in the work and made good quality parts. If it really is a concern, or a questionable damage area, hook up with an NDI buddy and have him check it out for you.

Best of luck on your rebuild.

Joe 

Hey Joe, I just realized I never replied to your post.  I actually work at a helicopter company as an engineer, so we have some common background (aside from enjoying these old cars).

Edited by Matt Wilson
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Well, I'm still searching for rod bolts that are in better condition than mine.  As mentioned previously, several of them are beat up.  One in particular has damage that is more than I am comfortable with.

So I'd like to ask you guys if you, or someone you know, might have a spare 265 rod bolt, or a few of them, that you'd be willing to part with.  I'd like to at least find ONE to replace the worst-looking of the bunch that I have.

You can see what they look like in the attached photos.  This type of bolt is flat on top of the head, and the head has a little bump sticking off the side, where it fits into a recess in the rod, which keeps it from rotating when tightening or loosening the nut - essentially a key.  The photos show one of the better-looking ones.

Any help would be appreciated.  These bolts are unique to the 265, and I've exhausted a lot of resources, and found that these bolts are just not to be had.

 

Thanks,

Matt

265 Connecting Rod Bolt _1.jpg

265 Connecting Rod Bolt _2.jpg

Edited by Matt Wilson
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1 hour ago, Don Coatney said:

When I assembled my 251 I had one bad rod bolt. I called George Asche and he sent me one.

Thanks, Don.  Yeah, I called George a few weeks ago and I got the impression that he might have some bolts, but he didn't seem too keen on parting with any of them.  He didn't say "no," but he seemed hesitant.  If I make it clear that I only want one, maybe he would be willing.  I will probably call him back.  I think the 251 bolts are much more common.

Edited by Matt Wilson
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