Rod bolt torque

I bought these bolts, and nuts from SNG.
They are labeled as OE for a 140 , but they can’t be as they are non split pin. They have a sort of chamfer under the head which will need cleaning up.
What sort of torque is suggested for this type?
Thanks Jim

The chamfer is required, a feature I had to add when I bought my ARP parts, so though yours are not strictly OE, they DO appear to be designed for the Jag rods. Torque will probably be in the 40-50 range, but you need to ask SNG or the manufacturer as to torque and lube. ALL quality, 3/8" rod bolts carry a quite-high torque spec. Don’t know what you mean by “cleaning up”.

That is impossible to recommend without knowing the allowable tensile stress of the steel they used.

I will ask them, I just hoped someone had been there before as I suspect getting an answer won’t be easy. The chamfer looks like it has been put on by hand, on some it is is good and on others too thin or lopsided.

If you aren’t happy with the quality of the chamfer then I would send them back and source ones with better quality control.

You can see the typical variation in torque recommendation due to the allowable tensile stress in this chart from the ARP website.

Jim the recognised replacement bolts are from ARP if you need to replace. initially the ARP bolts did not have the chamfer and caused some issues. That has now been fixed and when i bought a set recently (from chesman engineering) they are a perfect fit. although they are no cheap!

Let us not forget, the stock rods bolts, with modern nuts, are completely adequate for all but the highest horsepower apps.

The champfer or radius under the head is intended to relieve a potential stress concentration. You would want to be sure there is a corresponding champfer or radius in the hole in the top side of the rod.

Are we talking about the chamfer around the bottom circumference at the edge of the head or the forged/rolled chamfer between the bolt shank and the head? You could slightly modify the former with relative impunity, but no way no how should the underhead radius at the shank be molested, by anyone.

This is the one I am talking about. The left one not too bad, the middle a bit tapered the right only the corner taken off.

That “wedge” (chamfer, to me, is more associated with the small radius between the bolt head and the shank) is not a worrisome mod.

Though the use of the term is correct, I was confused by it, years ago, in a thread that became contentious: I then realized that we all were talking past one another.

That wedge is needed to ensure that the bottom face of the bolt is in good, solid contact with the rod, itself. The bolt should not be torqued a bit sideways by that part of the bolt head interfering with the rod bolt notch.

I would trial fit each bolt to each rod bolt hole to ensure that fit.

This is the one I am talking about. The left one not too bad, the middle a bit tapered the right only the corner taken off.

1 Like

Just even them up: that notch isn’t for strength, but to keep the bolt from rotating in the hole.

The one on the left is the way I modified my bolts and is all you will need as far as clearance…you can slip a length of thin-wall brass tubing over the bolt shank-to-head interface to protect the shank as you Dremel(or file) the proper relief/chamfer into the bolt heads…as you say…“cleaning them up”. Of course, always test-fit(mock-up) all assemblies before final assembly.

1 Like

I would say you can grind away at the bottom edge without much risk. The knuckle radius between the head and shank is a stress concentration zone. You touch that at your peril.

To my eye, the lack of apparent heat treating would lead me to be skeptical of the ARP attribution.

Photo I took some years ago of Jaguar rod bolts on hand at the time.

“A” is the one Mike and I were afraid you wanted to “clean up”. Do not; its an important feature, intended to relieve a stress concentration there.
Be sure the hole in the rod also has a radius, and does not make a point contact there.
“B” looks to me like poor quality control if they are not all the same.

1 Like

Mine look like your XJ6 and are 1/2" socket and as SNG describe them as OE I suspect that is what they are, so maybe OE Jaguar but not OE XK140 .
I have emailed them for more details.

I spoke to SNG . The bolts are XJ6 . The bolts are OE for that car .
The torque is 35.7 to 37.5 lbs
They say their info make no reference to lube , so a dry fit