Main bearing cap bolts vs. studs

[Fingolfin]

Good afternoon all,
This is my first engine rebuild, so bear with me for some silly questions over the next few weeks.

Here's the first one. The block, crankshaft, head, etc. have had their machine-shop work completed and it's time for reassembly to begin. The engine (1275 out of a Midget) came with bolts to hold on the main bearing caps. The main cap fastener kit I ordered, from ARP and for A-series spec, uses studs and nuts. The threads and diameters are all the same.

Now, my question: is there any reason I can't use the studs?

[oliver90owner]

I would say it is unusual for studs to have the same thread. Usually studs are used so that the same clamping force can be applied at a lower torque value. So the coarse thread is not needing to be screwed into a cast iron thread to achieve the clamping force required. I cannot recall an engine with studded mains, mind. Perhaps I will recall one after posting this! Perhaps required if there is an additional support required across the standard caps?

[Fingolfin]

Mini Mania (an American supplier, and not where I got my stud kit) says this about the kit I bought: "this system was used on the Cooper S bottom end, and this stud and nut kit does the same for 1300 & A-Plus blocks." It's ARP part number 206-5401. I can confirm that the studs do screw into the block.

Seeing the "1300" is probably why I bought it, since people often say that as shorthand for 1275.

[oliver90owner]

Well, it would not be a lot of use if they did not screw into the block!

My point was that the studs usually have different threads on each end for an application such as this. Manifold studs, and such like, often have the same thread these days, but in years gone by, they were made with fine threads for brass nuts, so they could be undone more easily at a later date. Simple proper engineeering, not modern bodgineering. Most, or all, of my tractors have studded head fixings. Coarse thread in the block and a fine thread for the nut. All about clamping force, really.

[philthehill]

http://www.morrismania.com/invdetail.cf ... tCarType=3

There is absolutely no reason why you cannot use the studs and special nuts instead of the bolts.
Make sure that you use the ARP stud lubricant and tighten to the ARP torque specification.

The main bearing caps are held in place by the locating dowels and not the bolts/studs.
The bolts/studs are there to secure the main bearing caps to the block.

http://www.moss-europe.co.uk/shop-by-mo ... 275cc.html

Phil

[BLOWNMM]

Fin
As Phil said there is no reason not to use ARP studs rather than bolts with the correct ARP lubricant - in fact ARP claim it is better to use studs rather than bolts for head and main bearings. For reasons refer to pages 38 and 45 in the ARP 2014 catalogue and page 49 for installation tips.
Bob
http://pdf.arpcatalog.com/ARPCatalog.pdf

[bmcecosse]

The bolts are pefectly satisfactory - I would return the studs etc for a refund.

[les]

The beauty of studs is they are not removed like bolts so the block threads are protected. A small point as neither are removed that often but in engineering terms better.

[philthehill]

Whilst I agree that the bolts are perfectly satisfactory for general use - but if you have a preference to improve the build quality of an engine ARP studs are much better.
Not withstanding any comments / recommendations by ARP -
Firstly you know that the threads of the stud have gone fully home and there is no need to disturb the stud again after initial fitting even if the main bearing caps have to removed in the future for examination / replacement.
I personally use a little Loctite Stud lock on the stud thread were they screw into the block.
The ARP nut is of a much better quality than the head of the bolt and you can see that the nut has fully engaged with the stud.
The ARP stud is of much better quality than the bolt shank.
So all round if you can afford to replace the bolts with ARP studs / nuts I would do so.
In my own case with the 4 point secured centre main bearing cap ARP studs and nuts are used.
I also use ARP big end bolts, ARP head studs and ARP flywheel securing bolts.
When using ARP main bearing studs - if they are done up as per the ARP instructions you alleviate the need for main bearing locking tabs.
You cannot get better.
Les - you beat me too it and yes a very valid point.
Phil

[BLOWNMM]

Hi all
It really amazes me that people can profess to have superior knowledge than that of ARP who have spent many hours and years to perfect fastner technology. Even though OEM bolts would be OK why not go for the best in a newly built motor when the additional cost is a very small percentage of the build cost and should provide much more confidence.
Bob

[Fingolfin]

I couldn't think of a reason not to use the studs - but I want this engine to be assembled as correctly as possible, so when in doubt, I ask! Thanks all. I will use the studs (especially since I got a very good deal on them!). I did get the little packet of lubricant with the studs.

Another question: will using Loctite interfere with the lubricant, or vice-versa?

[amgrave]

Loctite on the end in the block lub on the part of the thread you put the nut on

[philthehill]

The Loctite stud lock will not interfere with or effect the ARP lubricant.
The stud lock is only applied to those stud threads which screw into the block - only a smear is required for each stud.
Wipe the excess off when the stud is fully tightened home and before fitting the main bearing cap.
The ARP lubricant should only be applied to the nut threads - again only a smear is required.
The ARP lubricant should not be applied to the whole of the stud.
Phil

[Fingolfin]

Aaaahhhh. Told you this was my first time.

[philthehill]

We all had a first time