XK con rod for push rod engine

Hello Gents, I hope you are well and to any Australians out there, I hope you have toilet paper. I am looking into using a 3 1/2 crank in a 2 1/2 litre engine and when looking at a selection of XK conrods today, I noticed there were some detail variations in the rods. All the rods I looked at have the small end oiling channel , but the beams vary where they meet the big end. Is there a particular part number that would be best suited to my needs please, as I am not certain whether these rods are 3.4, 3.8 or other. On a slightly different tack, would a MKV 3 1/2 litre have alloy or steel rods, or is this dependant on build date?
Thanks again gentlemen, I am hoping someone can assist with this. Cheers.

with best regards,

Anthony.

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Hi from the USA.
I was not aware that a 3-1/2 crank could be used in a 2-1/2 engine.
Ed would know about such things. Is he still with us?
The 3-1/2 L Mark V had 3 different rods according to the Spare Parts Catalogue. The engine numbers for each are listed there.
Early cars had alloy aluminum rods C1049 with an oil tube on one side to supply the piston wrist pins.
Mid-range cars had alloy aluminum rods C2844 drilled through the center for oil supply.
Late cars had steel rods, the same part number C2448 as XK120 and Mark VII.
The part numbers of each type are cast into the side.
It is very important to use the correct bearing shells for each type, so the oil hole matches and that the oil supply is not blocked.
If you are selecting steel rods, be sure to get 6 all matching part numbers, and of the same weight, and I recall the tolerance was within about 2 grams.

He chose to suspend from JL: he still answers questions through his email.

Hello Anthony.
The rods with the slimmer profile at the big end are most likely MK5 or 120 / MK7,
if you have a set then way to go, if not then a set with matching numbers, as
previously mentioned.
3 1/2 crank in a 2 1/2 block not a prob , BUT which block 36 / 7 or 38 on.?
Whats the project?
Peter B

Yes, both engine sizes had dural and steel rods at various times. If you are fitting a 3.5 crank into a 2.5 block you will need special pistons to let you use the 3.5 rods with their larger diameter gudgeon pins and you will need a special crown height because of the longer stroke.

Peter

Hello, thanks Rob for responding to my query. I have spoken with Ed, he suggested finding the lightest matched set, as was my intention, but I wasn’t certain which p/nos would be best suited, as the keeper of the rods has many with various p/nos in 3 boxes.
So, I suppose C.2448 would be the best choice, if I can find a complete set. Cheers.

with best regards,

Anthony.

Hello Paul, thanks for your response. I have spoken with Ed today.

with best regards,

Anthony.

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Hello Peter and thank you for your response. I believe there is a company here in Adelaide who will make the pistons once the dimensions have been calculated. Cheers.

with best regards,

Anthony.

Hi Anthony,
I went down this path (XK rods) in my 3.5 pushrod several years ago.
In addition, my main bearings were changed to 350 Chev…

Have a look at the build sheet from Crankshaft Rebuilders as there may be other info in here that may be applicable. (She pulls like a train now :grinning: )

Jag Engine Rebuilt Summary Pages 1-3 - No Pricing.pdf (1.1 MB)

The Chevy 350 job sheet is very interesting. Thanks for posting.

Peter

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