Hi,
I am collecting parts to start to rebuild my 140,000 mile 5.3 HE. I have been offered a set of NOS con rod assemblies part number JLM12044 which I think are a later alternative part number to the ones fitted in my engine. Do I risk using the existing ones in my engine or swap to the later part number? I cannot find any info on the JLM12044 con rod to decide if it is a better design. What are people’s thoughts?
Andy

 

They are fine. Do they have the big end bolts with them (they should if genuine NOS). The bolts are the most important thing to renew IMO. JCP says that this is a later part number but still a genuine Jaguar V12 5.3 rod. Often as not, just a re-numbering exercise as a result of the Ford takeover in the late 1980s.
Greg

 

What is wrong with your current connecting rods?

 

The engine has had a hard life with most of the oil is on tbe outside.....and was used to hammer arround tbe yard a few times so am not to if it has been over reved perhaps? With thw xhance of swapping tbem out cheaply sounds good but I couldnt find out if the new con rods would be better or worse??

 

Sorry I should have read the post before sending!
The engine has had a hard life with most of the oil being on tbe outside.....and was used to hammer around the yard a few times so am not to if it has been over revved perhaps? With the chance of swapping them out cheaply sounds good but I couldnt find out if the new con rods would be better or worse??

 

I mean the wear on the connecting rods is just in the bearings, unless your current rods are bent there is likely little to zero difference between the two, plus we are talking about forged parts.

 

Ah yep, I understand what you are saying. Unless anything catastrophic happened inside, by replacing the big and small end bearings, and the con rod bolts and nuts I should be good.... being over cautious!
Thanks

 

You should make posts on the condition of the bottom end. I'd love to see some data and pics on wear. Not a lot of high mileage V12s on here but I've always speculated these are 200-250k mile engines

 

OEM conrod bolts are fantastically expensive, you might find it quite a bit cheaper to buy these bargain NOS rods.

 

I have just been through this.

From experience. I would replace the bigend bearings only, if the rod stud threads are ok I would not replace them. If you do replace them then you will need to have the big ends honed.

Mark each rod, pin and piston so they go back with their mate, or you will need to replace everything.

One thing I found was I had one rod out of spec, it was 0.020" short, it was still used but as I replaced pistons with Chevy its mating piston was modified to ensure compression height was correct.

 

Hi Warren, thanks for the advice. What would be the reason for honing the big ends if new bolts were fitted?

 

Yup.


Pretty much standard auto machinist practice. Put on a stands to assure alignment of small to big openings, fix and any bend or twist. If minimal, o'wise do not use. Grind the flats on the big end. Hone to assure they are round, Not egg or oval.


If doubt, magnaflux for unwanted cracks. Use new bolts.


If one or more let's go, it is pure mayhem.


Oh, balance them. a large and small end technique.


Carl.

 

Guys,
The reply’s have been spot on. I now fully understand the honing logic and also the rod balancing..... the re-build should be fun!
Thanks,
Andy

 

Because when you replace the bolts the caps will not be in exactly the same place. If you do not hone the bore then you could spin a bearing.

 

Thanks for the explanation Warren,
Andy.

 

what warrjon said , the new bolts maynot be a perfect fit,for rod to cap alighnment, so recommend honing!

also Jag V12 rods are very robust, i doubt any problems with them, unless catestrophic damage.

ron

 

Hello ,, are you stil looking for a Koenig body kit ? as i shave one complete ,same as the one in your 5 photos, i am new to this site and do not know how to contact you ?, thanks