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!

             

[frnkeore]

I found a couple of 7/16 x 14 bolts. The ones in the rods would be 7/16 x 20 but, I couldn't find a matching pair of those. One grade 8 and the other SHCS, both the same length.

Regarding head bearing area, the G8 is .580, while the SHCS is .640 or 10% more bearing area. The head thickness for the G8 is .290 and the SHCS is only .187 at the bottom of the hex drive area. OA height is .437 so, that won't be as strong. The corner radii, under the head, looks about the same but, less than 1/64 on both. The socket is 3/8" and the corners of the socket are .429 so, the socket, itself won't add much to the head strength above the root of the thread.

[WConley]

A high performance fastener, like a 12-point, will in general have more bearing area than a socket head cap screw.  The hardware store six-point Grade 8 you're comparing to isn't suitable for a critical application.

I don't care about showing people that I'm right.  All I care about is keeping people reading this forum from getting bad information.  In mechanical engineering practice, you will not see socket head cap screws used in critical, high performance joints.  They are inferior to the external Torx or 12-points that are in all of the specialty / racing / military / aerospace applications.  Those are what you want.

[mike7570]

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...

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.

My SFI certified Quicktime FE-C4 bellhousing came with cap screws (just about the only fastener that will fit) I tried to use grade 8 hexbolts but there is not enough clearance for the bolt heads. NHRA list them as illegal for certain certified bellhousing for manual transmissions, for Automatic transmissions the bellhousing bolts are not mentioned. It's probably because a flywheel/clutch explosion creates much more stress on the bellhousing.

[Tunnelwedge]

My SFI certified Quicktime FE-C4 bellhousing came with cap screws (just about the only fastener that will fit) I tried to use grade 8 hexbolts but there is not enough clearance for the bolt heads. NHRA list them as illegal for certain certified bellhousing for manual transmissions, for Automatic transmissions the bellhousing bolts are not mentioned. It's probably because a flywheel/clutch explosion creates much more stress on the bellhousing.

I'm working on a Lakewood that needs bolts.
I have these steel ARP 7/16x14x1.5 with a small shoulder. I need to trim them for length.
That's what I used on the Quicktime.
You can also get some flange head bolts from Holley. They should come in the box with the Quicktime.

https://www.holley.com/products/fasteners_and_hardware/transmission_and_drivetrain/transmission_bolts/parts/RM-172

[Heo]

 

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.

 

[Tunnelwedge]

They are in Mickey's HEMI Galaxie.

https://www.youtube.com/watch?v=xtY7OMT49CE

[Rory428]

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!

             

I certainly hope that you are not comparing the stress of 20 bolts holding a 10 pound oil pan to the block, to the stresses of 2 connecting rod bolts pulling down a piston at high RPM, and keeping the rod anchored  to a reciprocating crankshaft, right?

[MeanGene]

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

I had a NOS set like that in the box that I found at Turlock, and sold to someone- same ones?

[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!

             

I certainly hope that you are not comparing the stress of 20 bolts holding a 10 pound oil pan to the block, to the stresses of 2 connecting rod bolts pulling down a piston at high RPM, and keeping the rod anchored  to a reciprocating crankshaft, right?

It was posted as a joke.....     

[Stangman]

I have an old Mickey Thompson aluminum rod from our 389 Pontiac and it had the serrations that why I said that was a MT rod. The aluminum rod didn’t have those bolts though.

[frnkeore]

I passed on them so, I can't add anything more.

[Joe-JDC]

Wise move.  Headache avoided.   Joe-JDC