Thanks Robin. So since a British ton is 2240 lbs, a grade S bolt would have a tensile strength in the range of 112,000-134,400 lbs, pretty much equivalent to SAE Gr5.
So just for interest, what grade is an original main cap bolt?
I’m placing this here only to show how using the wrong bolts can get you in trouble. '54 140.
Obviously the PO had difficulties and dove in head first to fix the problem. The current owner opened the case and found this. Can you imagine if just one of those bolt heads got loose…
Note: Grade 5. He came so close to getting it right.
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On a positive note, at least the safety wire made it easy to make sure all the bolt heads were accounted for. 
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Yesterday I received a set of ARP rod bolts from one of the usuals (for my 3.4 120)
They don’t even fit into the holes. I tried 2, even a few light taps with a hammer won’t get them even close to seating.
I think they tend to be a pretty heavy fit. ARP probably recommend the use of a press, but I’ve seen engine builders on TV pounding them with a BFH on American V8’s.
Like an old back-yard mechanic I used to know liked to say: “Get 'em tight until they turn easy, then back off a quarter turn”.
Regards,
Ray L.
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IIRC, mine needed a bit more than a light tap too. Probably a few hard hits with a plastic mallet.
So if you do get one in, why not torque it up with its cap and then measure if there’s any gap remaining under the head with a feeler gauge. Before I chamfered my bolts, the head would seat with the sharp corner digging into the radius machined on the rod and a gap under the other side.
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The 3.4 rods have a significant chamfer at the hole.
I tried again and each of the rods shown got 5 or 6 good solid whacks with a 2 pound thunder wrench and stopped moving. Upon removal (more pounding ensued) I see significant galling on the bolt. I don’t rebuild engines with a hammer, I’m sure ARP doesn’t have a fit this tight in mind.
I just measured 3 of Jag’s bolt diameter 1/8" down from the head and 3 of ARP’s bolts. ARP’s bolts are .002" larger than Jag’s.
The ARP tech folks are notoriously vague and inconsistent, and if you tell them what you’re doing, they’ll just repeat the party line…”we don’t make rod bolts for Jags”.
But, perhaps you could ask them what an appropriate interference would be. Don’t forget that later OE Jaguar bolts added a significant knurl under the head, so perhaps they found their fit on earlier rods to be insufficient?
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That’s 0.0012" too much bigger.
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After I towed my rust bucket home from Youngstown on a two wheel dolly, I went to drain the rear end. It was bone dry and bolt head fell out. Every bolt head had snapped off the LSD unit. Surprisingly, after rebuilding it it had only a couple thou runout IIRC
Thanks for the info - something to consider. XKS Unlimited doesn’t say who makes the main brg cap bolts they sell. I’m curious what their dimensions are. They should be awfully good bolts for $25 each.
Mine all appear to be in excellent condition, so I guess I’ll just reuse them.
That’s my understanding, too. I’ve never seen any in their catalog.
I dug through a bin of at least 30 main cap bolts, all of them marked the same way: BEES 55 T 65, so 134,200 psi to 158,600 psi.
Were your stock bolts knurled a bit below the head? (Too lazy to go pull one and check for myself!) The later XJ6 bolts were knurled, so interference fit. I’m certain if I dig enough I can find a fit spec for the ARP bolts.
Some of this is getting outright scary. You can buy O.E. rod bolts and nuts from the usuals - why wouldn’t you. One of the purposes for a specific torque figure used in tightening the nuts is to stretch the bolt shank enough to get it into the elastic range in stretch. That’s what keeps the nut on without the need of cotter pins etc. If you don’t know the quality of the steel in the bolt you don’t know the torque value unless you use a stretch gauge. Buying O.E. bolts eliminates these issues. ARP manufactures bolts for use in the main bearing caps, but don’t sell them as Jaguar parts. You just need to look up the necessary size in their catalogue. They will tell you what to torque them to - as I recall it’s 90 pd feet using their thread lubricant. But anyway why wouldn’t you use the original bolts and torque figures without the soft steel locks.
One last point - a competent machine shop sizes the rods and the mains using the bolts you supply and torques and lubricants you tell them to use, or what they decide to use from their experience. When you reassemble your engine you use what they use - if you don’t you’ve wasted your money on sizing.
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No. just straight.
…
Easy: Jag-Lovers Overthink(c)…
When I rebuilt Tweety, after 160,000+ miles, more than a few of them in anger, on a track… the stock rod bolts, along with original nuts (which Dad pal-nutted) had… a perfect torque still on them.
However, Tony Lee had NOS MiL-spec rod bolts, on which I stuck Chevy nuts, which I ordered, for less than $30. Perfect fit.
Easy, simple, and proven.
Mitchell,
Maybe an over-abundance of caution on my part, but your comment suggests that you might not have understood the location of the chamfer that Clive was suggesting:
I have marked in pink on the ARP bolt the edge that needs to be removed (carefully, without nicking the shaft). If you don’t do so, on some E-Type rods (can’t comment on the 3.4) the “pink” edge will pick up on the radius on the rod, and prevent the bolt head from seating. If I misunderstood your comment, and you already understood this, my apologies. Either way, I hope it will prevent someone from repeating the experience that at least one person has in the past with disastrous results.
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Thanks Drew, that’s exactly what I was trying to describe and that is the exact area that I filled off the ARP bolts.
And just to remove any doubt, here is a drawing I prepared at the time showing how the ARP bolts do not seat properly in the Jaguar rod. I didn’t discover this by myself, in fact I may never had noticed it except that I was visiting fellow lister Peter Conway in his machine shop and he pointed it out, so we delved further.
I think ARP nuts and bolts are beautifully made and finished but if they aren’t right for the intended purpose…well, good luck.
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