AllanWorms

Well-Known Member

• Mar 8, 2022

• #1

Argh. Imperial doesn't fit my brain.

1997 Disco 1 3.9 V8:

Are the studs in the cast exhaust manifold outlet, to the Y pipe, Metric or Imperial?
Searching suggests they are 5/16" UNF. My nuts [] are fairly poked, but look more like the UNC tap I have.

Are they in fact metric? I want to buy one new stud and 6 new brass nuts on the way home ... I only have the nuts and one broken, mangled stud to go on... and they studs are still in the car at home and I finished the job last night in the dark!

Thanks

 

AllanWorms

Well-Known Member

• Mar 8, 2022

• #2

Ooof... Somehow those pictures are giant

 

Stanleysteamer

Well-Known Member

Full Member

• Mar 9, 2022

• #3

If you have a caliper or a micrometer you can measure the diameter and it doesn't take a genius to count the threads per inch, even if you haven't got a whole inch to measure, the maths ain't difficult.
The threads look pretty coarse to me.
So measure, count and post it and someone will tell you what you need to know.

 

AllanWorms

Well-Known Member

• Mar 9, 2022

• #4

Thanks...

Yeah... I had to go home to measure them... turns out they're M8x 1.25!... yet several suppliers say they're UNF and have the same part number. I guess either will work... with enough force the thread and diameter aren't too different

Still... got it together and it doesn't sound like it has a rod knock anymore

 

discool

Well-Known Member

• Mar 9, 2022

• #5

AllanWorms said:

Thanks...

Yeah... I had to go home to measure them... turns out they're M8x 1.25!... yet several suppliers say they're UNF and have the same part number. I guess either will work... with enough force the thread and diameter aren't too different

Still... got it together and it doesn't sound like it has a rod knock anymore

Click to expand...

That’s correct, M8 if the Y pipe has “cats” and 5/16 UNF if the pipe doesn’t.
So find a supplier that knows the product and can read a parts catalogue, part numbers are different for both of course with the M8 nut being ESR2033

 

AllanWorms

Well-Known Member

• Mar 9, 2022

• #6

discool said:

M8 if the Y pipe has “cats”

Click to expand...

Good Grief... So only cat models have metric there? Which is weird considering cat/catless models were sold at the same times, for different markets

Miine doesn't have cats now, but clearly used to - It's Jap spec anyway.

Thanks for the info!

 

discool

Well-Known Member

• Mar 10, 2022

• #7

AllanWorms said:

Good Grief... So only cat models have metric there? Which is weird considering cat/catless models were sold at the same times, for different markets

Miine doesn't have cats now, but clearly used to - It's Jap spec anyway.

Thanks for the info!

Click to expand...

All UK spec 3.9 models had cats as standard when they left the factory, thats 1993~94 onward to the 1998MY.

The early 3.5 RR didn’t have cats until the 3.9 was introduced and fitted with cats, rumours back then was that the 3.9 was introduced to compensate for the perceived power lost due to cats, I did see much of that, as they overtook me a few times on steep hills