Guys, after getting all of my newly re-machined parts back from the machine shop I noticed that I’m missing all of the washers for the connecting rod bolts/ nuts (part# C386). This, for a '51 XK120. Can someone tell me of a McMaster-Carr substitute (or even something from the hardware store?) that I can use instead? Seems silly to place an order to one of the other vendors just for these. Also, will using something different effect the weight/ balance in any significant way? This won’t be a race car. Thanks.
There are no washers used on con rod bolts. Certainly not in my experience.
Thanks for the quick reply Paul. Okay, I won’t put any on – and logically I don’t see a need for them in this application – but out of curiosity, why does my Jag standard parts catalog call for them? Again, part number C386 and illustrated as item/ plate number 60 in the Plate A exploded parts diagram. Leaving them out won’t throw off the balance? Thanks.
It’s possible that back then, they may have been called for: I’ll wait for others to chime in, and see if it’s OK to go sans.
However, I worked on many engines, and only one that ever had washers was my John Deere 1.5 hp hit’r miss.
Quite different performance envelope!
And no: given the crank is balanced sans bobweights, and ostensibly the washers were all essentially the same weight, leaving them out–again, if allowed–won’t change the big end weight enough to worry about.
My machinist echoed Paul’s comments about the lack of washers so, that’s enough for me to continue my build without 'em.
The C.386 washers were used on the earlier pushrod engines, along with C.358 slotted nuts on aluminum connecting rods. The usual practice is to use a steel flat washer so the nut won’t cut into the aluminum.
When they went to steel rods and C.2361 nuts, they seem to have continued using the washers for awhile. They are listed as such in the Mark V and XK120 SPCs.
Then apparently decided they were not needed. They are not listed in the Mark VII, 2.4 Mk1 and XK140 spare parts books. A 140 engine I have here, never disassembled before it came to me, did not have any washers.
Washers as a carryover from when they were using aluminum rod caps. That makes sense. Did any of the very earliest XK engines have aluminum rods/ rod caps? Just curious.
Ah: that makes sense.
No, there is no record of aluminum rods being used in XK engines, even the prototypes, that we know about.
Steel rods were used in Mark V 3.5 pushrod engines from about mid 1950, the same C.2448 rod as for XK120.
I would think that any washers (lock or plain) used under bolts with the torque levels seen in rods, mains and heads would need to be hardened. Mild steel washers would crush, and continue to do so in action. The fact that these have a part number, as opposed to a description of size and configuration, indicates they are special. I don’t see why you would need washers unless the steel used in the early rods was deficient.
No, these washers do not seem to be any special hardness, such as tool steel, they are pretty ordinary. I suspect that the reason they have a C. number is that they were specified to a certain thickness .055" and OD .658" so that the engine assemblers would not use the standard 3/8" flat washer FW.106/T which was .072" thick and 3/4" OD.
The slotted nut part no. was changed because the old ones C.358 were BSF thread and the new ones C.2361 were ANF thread.