Hi guys,

I've got to the stage of putting my sump back on (4.0V8, Thor).

Of the three studs that are supposed to be in the front cover only one stayed in place on removal.The other two came out with the nuts, as they've rusted together.

I 'could' just screw the studs/nut combo back in..... but would rather get new studs. However the LRCat diagram doesn't show the studs on the sump page, or on the front cover page....

I think the nut is NH505041L (5/16 thread) but can't find the studs,

Any idea what the part number might be please?

I suppose I could hacksaw carefully through the two stuck nuts, and tidy up the thread below, but it's a lot of work for two studs.

Thanks

Edit - is it 252513..?

It looks like the nut is correct and the stud looks like it might be except https://parts.jaguarlandroverclassic.com/252513-stud.html?code=L3G03015 says it is for earlier engines. This site shows it to be 5/16 UNC x 1" 3/8". But, one of the differences between the earlier engines and the Thor is that most of the threads changed from Imperial to Metric, so the exhaust manifold bolts on a GEMS, and anything earlier, are 5/16 UNC but on a Thor they are M8.

Hmmm. Thanks Richard. That would be dissapointing on the basis that I've just ordered some 5/16 threaded bar!

If it's M8, it isn't the most common thread - quite coarse, which I assume is because it's going into Alu.

Because my working diary is stuffed I'd hoped to avoid a specific trip to our local fasteners supplier, but I guess I'll have to.

I noticed though that the bolts which hold the front cover on have 11mm heads (or are in fact an imperial size which closely equates to 11mm) so I wonder if the change to metric was a bit piecemeal??

The bolts on the cover on microcat show the 5/16 thread if that's any help. With 5 of one length and 6 of another.

Standard M8 is 1.25 mm pitch.

If its coarser it ought to be 5/16 UNC which is 18 TPI, equivalent to 1.41 mm pitch. If so the nut should be nominal 1/2" A/F.

There is a non-preferred coarser metric 8mm x 1.5 mm pitch floating around. I defy any normal person to tell the difference between that and UNC with components of normal production tolerances. Originally adopted for sensors, banjo unions and similar duties its creeping into a lot of unexpected places. I'd have thought the Rover V8 too old to have that oddity inflicted on it but the Thor rejig was done under BMW ownership and they use some non preferred strangers.

Often wondered how the normal guy in the garage manages without sets of thread gauges, a micrometer or vernier and some sort of reference book. For standard stuff the Zeus book is compact and handy, I have about 5 scattered around but when it comes to potential oddballs like that you need something more comprehensive. My go to is a listing from Andy Pugh that covers pretty much all the common sizes, along with a range of oddities folk dealing with really old stuff may encounter, arranged in size order. Dimensions in both imperial and metric. Mine is 6 A4 pages in Excel spreadsheet format. PM me if you want it. I really need to update it with some of the becoming less oddball things like M8 x 1.5.

Clive

Thanks for the further replies folks.

I can confirm that it is in fact 5/16. I found my thread gauge yesterday and couldn't get any of the similar metric ones to work, so I was more or less convinced, but the 5/16 nuts and threaded rod I'd ordered arrived today, and that's the right thing for my car.

Work can recommence.