RV8 ARP studs

[minorv8]

I found an interesting thing with ARP studs. I have two sets of mains and cylinder head studs. My own sets are old but unused, still in box. The other sets are bought about a year ago. Both mains stud sets have the same part number, the same applies to the cylinder head studs.

The older sets have info sheet that quote 70 lb ft for cylinder head studs (65 lb ft for aluminium heads) and 90 lb ft for mains.

The newer sets quote 80 lb ft for cylinder heads and whopping 110 lb ft for mains.

Now, for comparison 4,6 litre factory manual quotes 72 Nm for bolts 1-8 and 92 Nm for bolts 9-10. If i would fit the newer set into a 4,6 and follow the ARP spec to the letter the bolts 1-8 would have twice the torque setting. Sounds insane !

Ideas ?

[DEVONMAN]

But the 4.6 uses stretch bolts?

[SuperV8]

How do the threads compare?
The thread on the ARP nuts to the thread in the Rover block/rods?

[garrycol]

The OEM help bolts are stretch bolts so no torque as such is given.

As far as the ARP head studs are concerned if the ones the OP has had for a while they are most likely for the 215 Buick, the 3.5 and 3.9 Rover engines - ARP now make different studs for the 4.0 and 4.6 engines - I understand these have more thread contact with the block.

Garry

[stevieturbo]

And just because you can tighten something up to xxx...doesnt mean you have to.

What size of fastener is it they're using for 110lbft ?

That's into 1/2" territory

[minorv8]

Yes, 1/2" studs for mains.

I have an old ARP catalogue from 2005. It quotes different torque values for studs, fine and course threads for each bolts size. ARP catalogue from 2011 only has one torque setting per bolt size (roughly the highest value from the 2005 spec).

I did some testing with 4,6 bottom end. With factory mains bolts / torque setting the crank rotates very nice. I replaced the bolts with ARP studs and torqued the nuts in three steps to 100 Nm. The crank still rotated pretty nice. At 110 Nm the crank sits solid in the block. This particular block starts to distort at this setting and still the torque is far from the ARP specified 110 lb ft. OK, ARP states the the block may need line honing/boring but maybe common sense and more sensible torque value can be used.

The ARP settings are general even if the hardware is for specific engine. I am not sure if one even can use 110 lb ft in a Rover block It would be interesting to try that and measure how much the bearing bore distorts. Or if the thead gets pulled. Unfortunately I don´t have any damaged block to use as a guinea pig.

As for cylinder head studs, I have used 215 studs for 4,6 engine with tin gaskets simply because at that time there were no 4,6 specific sets available. I used factory torque setting for the ARP studs and have had zero failures.

[stevieturbo]

When I DIY'd some 1/2" head studs into my old 3.9 block I wound them up to around 110-120lbft.

They never gave any issues for me. Really cant say I did a great job of drilling and tapping the holes though LOL
Doing it manually ended up with a lot of the studs at an angle, and large hammers/wood were needed to get the heads on.

Although when I did take it apart some time later it came apart ok. So I wouldnt reccommend DIY'ing drilling/tapping studs without some sort of vertical guide tooling lol

[minorv8]

I have converted a number of Mini blocks from 9 studs to 11 studs with same results. Would it be possible to have vertical threads if you tried to put them at a slight angle 😊

[unstable load]

Would it be possible to have vertical threads if you tried to put them at a slight angle 😊

Probably, but one would need to accurately determine the full amount of offset and the angle of drift that would occur prior to setting off on the drilling and tapping.