Some one far wiser than I may have that answer: @Roger_Payne? @ptelivuo? @Dick_Maury?
Are all six of them stamped N2? By any chance are the left side of the timing cover and block also stamped N2? Or the main bearing caps?
Your second pic is the normal stamp.
I was prepared to say, ānope, never seen thatā, But, then I thought I would actually look.
The rod on the left is of indeterminate heritage (painted black???) stamped HO
middle rod, probably from a XK150 3.4L, stamped XQ
right rod, S3XJ6 4.2L stamped XD
The black rod and the XK150 are stamped on the opposite side of the cylinder number stamp, the XJ6 on the same side. Like yours, the stampings are on both the rod and the cap (stamped twice)
Is there anything Dick doesnāt know about Jags? Iāve been trying for almost 20 years and he hasnāt failed once!
v/r
Pat
J. P. (Pat) Harmon, DCDR-16
I looked at both of the complete sets of rods I have on hand. Here is how they are marked:
(In retrospect, I think the rod I identified as XK150 is most likely from a 1964 3.4L MK2)
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Hmmmā¦ tolerance references to put some cap on some rod, out of a basket, for initial machining??
I got nuthinā.
Two letters, a letter and a number, two numbersā¦???
Only thing that is consistent is the if there is a letter and a number, the letter comes first.
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The other 5 rods have an alph-numeric soup of numbers and letters, all matching. The 'ā2ā shown in both places on rod #2 is just a coincidence.
Iām thinking these mixed-soup marks were made as the rods and caps were first machined. If stamped at random it would be hard to make a mistake and it would be unnecessary to follow a pattern or series. The side marks in sequence are obviously marked as they were mated to the block.
Hmmmmmm. Got meā¦ hope one of our eminence gris listers chimes in.
I love a good mystery!
I checked 7 of my old MG T-Series rods and sure enough, the alpha-numeric marks are on each of those too, seemingly at random and not connected to their placement in the engine, unless of course they built 16 cylinder engines.
I this case rod and cap #1 (tics) is marked K16.
Must have been a foundry matching mark. No other reason for it.
Iāll have to check the single Rover rod Iāve got, to see if this pattern persists.
One lung engine? Cool. Did it run the A/C?
Hehe: it was the one that had a spun bearing in it, when Margaretās engine lost the oil pump. Those I had reconditioned.
The piston had gotten chipped when the broken upper chain guide got flipped into its skirt.
I got another piston/rod out of a spare engine, had the other piston weight-matched to the other 3, then put the other rod out in the boot (āparts departmentā) of one of my parts cars.
Itāll be awhile before I get out there!
Itās out in one of the boots of my spare cars, so itāll be awhile before I get out to it.
From the XK140 engine with the split skirt pistons:
ZX
SJ
P3
RD
V7
I& (yes an ampersand, clear as a bell)
From a Mark V engine:
A222
C131
D228
D221
F271
The Mark V rods are not stamped with a hammer, they used an electric stylus scratch pen.
Remember these rods were matched for weight within 2 drams in sets of six, assembled with caps, nuts and bolts.
I am inclined to suspect this marking was to match caps with rods before they were assigned to a specific engine, and were then later stamped with their cylinder numbers.
See the 1961 factory tour video at about 10:35
As far as pistons are concerned, the arrow towards the front must be followed as those have offset pins. If you look at the side view you can see the pin is a couple of millimeters closer to the inlet (thrust) side) than the exhaust.
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Unless you are racing in a pure stock class, when flipping them improves the angularity of the connecting rod during the combustion impulse, producing a fraction more torque at the expense of a little noise from skirt slap.
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Yup. Hereās an interesting case:
I have a set of 96 mm Arias offset-dome 4.2 pistons. Two off them have central domes (#2&5) two have the domes offset one way (1&6) and two the other way (3&4). So how come there are only two part numbers for all six?
Because the pins are central so you just flip the offset ones around.
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I have Arias pistons in the 3.4. Symmetrical, but the intake & exhaust valve reliefs are different sizes, so they have a definite orientation. Rods are 0.400" longer than stock, so the pin is moved up. Big ends are sized for small block Chevrolet sized Clevite 77 bearings. Rods are Crower.
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Nice setup.
My 3.4 is bored/linerd to 3.8 like Momo did for Cunningham to make the first 3.8s. An authentic look for a long-nose whose blocks didnāt say 3.8 on the side
Itās otherwise a ācookingā bottom end running standard early rods and 3.8 E offset pistons, albeit dry sumped. Wish Iād even had a set of S3 XJ rods handy but Iām not going above 5500 and see how the block behaves. No point going too radical on the top end as it canāt use a straight port head, so just cams an 1.875ās in a flowed B head.
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