Wanted-qty 1 conrod for 4.2 - 937 grams

I need one conrod as one of my 6 is undersize by almost 100 grams!
Average of the 5 good ones is 937 grams (inc end cap, bolts and nuts)
Does anyone (in UK) have one hanging around?

Cheap set on ebay now…https://www.ebay.co.uk/itm/Jaguar-XK-engine-conneccting-rods-con-rods-X-6/153799086859?hash=item23cf23d30b:g:104AAOSwUGFeIOc0

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[quote=“MGCJAG, post:2, topic:386839”]
Cheap set on ebay now

Top shout thank you! They do look odd (not of the same set), but I hope there is one of the correct weight required.
Thanks again

I submitted an offer and got them for £100. Worth the gamble that between the 12 rods, I have 6 within tolerance. Fingers crossed!

Nice one…result…Steve

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Received the 6 conrods today. There is still a discrepancy of weight:
3 @ 846g
1 @ 828g
1 @ 836g
1 @ 847g

I am closer than with my originals, but still have a 19g spread. Better than the 100g!

Can anything be achieved to improve the weight distribution and are they too far out of tolerance to use?

Maybe they don’t do it with XK engine rods but I thought part of a engine rebuild, especially if the engine is being “balanced and blueprinted” included machining a bit of metal off of the ends of the rods to balance them and make all of them weigh the same.

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Can you find 20g to remove on the other 5?

Philip your machine shop will (should be) able to balance these, by removing weight from the bottom of the cap. I’ve been through this - with rods that were more out of balance than these. They were used in a mild power 4.2l racing engine I did 25 years ago and ran until a couple of years ago. I ran it on the track the first year and autocrossed with it for the balance of the years. Regularly ran it to 6000 rpm with stock Hepolite pistons. Give them all 12 rods, to balance 6.


As I recall, connecting rod balance was pretty much a standard process in an engine rebuild. As Paul mentioned, grid off 2o to match to the lightest one.


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My con rods with caps/bearings/bolts/nuts were 813 g to 809 g. (1965 4.2) Not so much luck w/ new Jahns (cast) pistons. They were 15 g out lightest to heaviest. Replaced them w/ A&E. They were only 3 g out lightest to heaviest. Getting good parts for these cars is getting harder & harder. As this becomes more & more difficult, next best step is to find a quality machine shop and/or rebuilder. Good luck.

Don’t do that! Conrods need to be balanced at both ends. That means you lay each one horizontally with one end on the scale and the other end on a platform the same height as the scale, thereby weighing one end of the conrod. Weigh both ends of all conrods and remove weight from the ends that need to be lightened to equalize the set.

I’ll also add that one much lighter than the others makes me nervous. Unless there’s an obvious reason, I’d worry there’s a casting void hidden in the metal somewhere.

Sorry…not familiar with that abbreviation

Company brand of pistons and conrods