Who Made this Rod?

[frnkeore]

Can anyone ID this 6.490, FE rod? It has a serrated cap joint, Allen bolts, lightened H beam and doweled rod bearings?

It looks like it might be a high end rod,out of the 70's? Carrillo?

[Stangman]

Maybe an old Mickey Thompson rod?

[WConley]

In my opinion, Allen head screws do not belong anywhere near a connecting rod.  You won't even find those on a lawnmower!!  You can't get anywhere near the torque / clamp load needed for heavy use. 

Makes me scratch my head about what these were intended for.  The rest of the rod looks pretty stout, but the fasteners 

[frnkeore]

Allen (SHCS) are 13% stronger than grade 8 bolts.

[jayb]

Frank, you should replace those bolts if you use the rods.  Allen head capscrews are known for fracturing at the bottom of the hex; in fact they are illegal via NHRA rules for attaching a transmission bellhousing to an engine.  I doubt that this is ever checked, but the rule is there for a reason...

[WConley]

Allen (SHCS) are 13% stronger than grade 8 bolts.

Frank - That's not correct.  The "strength" is in the material, not the bolt head shape.  I can buy Allen head socket cap screws made out out of Nylon.  Jay is right about the cracking issue, plus the internal hex drive / thin walls cannot handle the drive torque needed for good clamp load in a high performance application.  The bearing area under the screw head is also too small to support much clamp load.

You'll never see these six-point socket cap screws in any critical machinery application where they are required to maintain a high clamp load.  That's why I'm really puzzled by those rods...

[TomP]

I have a new old stock set of Mickey Thompson aluminum FE rods from 1965 and they use Allen heads like that.

[Tunnelwedge]

Frank, you should replace those bolts if you use the rods.  Allen head capscrews are known for fracturing at the bottom of the hex; in fact they are illegal via NHRA rules for attaching a transmission bellhousing to an engine.  I doubt that this is ever checked, but the rule is there for a reason...

I think it was a SOHC powered car that crashed after it pulled the bellhousing off.
I vaguely remember a story about that.
And if you buy a new SFI Quicktime bellhousing it comes with cap screws.
You would think it would come with proper bolts being expensive and SFI certified.

[frnkeore]

I'm a machinist and have used Socket Head Cap Screws (Allen bolts) for 50+ years. In my world there are only black oxide coated, steel bolts. For anything else I would add SS or Nylon and know that they are weak. Flat head and button head are also made to a different spec and are weaker and not in consideration.

If you look at the chart on bolt strength, there is only one spec for all SHCS, both min proof and min tensile strength. Both higher than grade 8 bolts. So, when any SHCS is manufactured, it has to meet those requirements, same as grade 8 bolts.

That is what I was going by and have always thought of them as quality fasteners and I would not hesitate using them as head bolts but, as rod bolts I'll be diligent if, I were to buy these. The reason I like them, is because of their design and I can see a strength advantage in the serrations,over dowels but, the offseting thing, is their age and unknown history. I suppose I could Xray and mag them.

I can remember that even using grade 8 bolts for bell housing bolts wasn't recommended, in the '60's and '70's because of their low elongation percentage.

[WConley]

Forgive me Jay, but I need to flex a bit.  This has turned into a pretty nerdy argument, but I don't want people reading this thread to come away with dangerous information.

Yes a standard inch-series steel socket head cap screw has roughly 20% higher tensile strength than a typical grade 8 bolt.  A big reason for that is so the head doesn't explode when you try to torque it.  (The internal hex drive wants to split the bolt head.)   You can't use anywhere near that strength to generate clamp load in the joint.  The small head limits the maximum clamp load too. 

Take that same 20% higher tensile steel and put a proper external Torx or 12-point head on the screw, or even a standard external 6 point hex head.  Then put it on a dynamic fastener "Junker" test machine.  The results will blow away the original Allen cap screw. 

I have a few qualifications too:

- Masters Degree in Mechanical Engineering - Machine Dynamics.
- Passed the Professional Engineer License Exam (which was full of questions about fasteners).
- Cylinder Head Systems Engineer at Ford.  A BIG part of my job was high performance fasteners.  No, you will never find an Allen socket head cap screw holding down a modern automotive cylinder head.
- 35 years experience in machinery design.
- Oh yeah, I'm a very experienced machinist too.  A big part of my current business is building prototypes of my designs using manual mills and lathes, as well as my Haas CNC mill.

[blykins]

Those rods would be an easy pass for me.  They look like a steel version of an aluminum rod design, with serrated mating surfaces and a doweled big end.  A lot of these rod manufacturers have proprietary ways of serrating them.  What happens when they need resized? 

I'd rather have a light set of Molnars...

[frnkeore]

All good points.

[cjshaker]

All good points.

Wait? What, what.....what just happened here?
Did Frank just agree with Bill and Brent?
Where am I? What has happened to this place? 

I get the serrated cap concept, but don't like the idea on a steel rod. Just like the 'cracked caps' they use on today's engines, they are a one and done deal. For an aluminum rod, they make good sense.

[frnkeore]

I hate to disappoint anyone

But, the serrated joint is stronger radially and on a new rod, I would go for it or if I could measure the big end and it be in tolerance but, they're not in hand. Though I could make a cutter to machine the serrations, to resize the cap, it would be way to much time involved to do that and machine the rod to resize it.

Regarding, " The small head limits the maximum clamp load too." It's my recollection that the underside bearing area is the same on hex head and socket head bolts but, I will check that out today.

Don't give up on me, Doug  

[galaxiex]

Oh Noooo's !

I installed the cast aluminum oil pan on my FE with socket head cap screws!

Now the pan is gonna fall off at the most inopportune time!