TR2/3/3A Cylinder head stud methodology

Cylinder head stud methodology, I have all ten head studs out and I am looking to install the head. I could put all ten studs in and try and drop the head down, or I could just put in a couple. The ones that go deep into the block would seem the most probable because of the need to feel them go in correctly. Then there is what happened to Keith’s engine when it looks like the studs might have been over tightened and the additional toque wrenching caused too much tightening and the block cracked. At least that is what Mad Max thought might have happened, and I consider him an expert. Anyways just looking for opinions and suggestions on how and when to install the head studs on a tr3.

I install prior to putting on the head. I also like to put a little high temp silicone sealant around the threads, you could consider it a lubricant for installation, but I have seen TR3/4 leak around the studs. I then wipe up any excess around the base of the studs prior to installing the head. You do not need to tighten the studs into the block much. Just barely beyond hand tight is my practice.

Jerry

The studs go finger tight into the block, preferably using an anti-seize compound on the threads. I would install them first, but there is no reason I can think of you couldn't install them after the head.

These studs are dry...I.e. not exposed to coolant. So sealant is not necessary...but then, it shouldn't hurt anything using that for anti-seize.

I had my torque wrench calibrated after the problem with the block and it came back with 1 percent error. I don't think that was the problem. The only thing I might add to the ideas above would be to install 4 studs in a square pattern to set the head gasket then install the rest of the studs. Sometimes the holes in the gasket aren't perfect. I did use ARP studs the second time.

We had a run of blocks with stripped threads and broken head bolts on the TR-register forum and did so research into this.

If you check the torque specs for UNC and UNF bolts a few intersting things will show up.

1. the torque for UNC is a good bit less than UNF,which is awkward on a mixed stud
2. there is a big difference in recommended torque between lubricated and dry bolts
3. a torque of 110 ft.lbs would want a Grade 8 UNC bolt

A TR block will not be a strong as a Grade 8 bolt and there will be some fatigue cracks by now.
So be careful and don't pull too hard on a lubed bolt.

Alan that's very interesting about the torque readings. I used the recommended lube on my ARP studs on both the course and fine threads. I torqued them down to the books 100lb recommendation. I've heard that lubes and sealants on threads may change the torque readings. Can you be a bit more specific on the findings? Do you build your engines with dry or lubed bolts?

I used ARP studs and nuts, and used their recommendations that came with the studs. Basically it says "Torque values are based on 75% of the fasteners yield strength. Use the manufacturers torque sequence but do not use the manufacturers torque specs. Torque the nuts to 90 ft.lbs. with ARP moly assembly lubricant (or ARP thread sealer) or torque to 130 ft.lbs. with 30 wt motor oil". That's the difference that friction makes, even with oil.

That's right off the sheet they sent with the studs. I used their lube and torqued to 90 ft.lbs.

Edit: I can scan that sheet if anyone's interested. It has some other goodies mentioned also.

Just a minor point, but when the factory data says 100-105 ft lb, the range is to allow for the precision of your torque wrench. In other words, they really mean 102.5 ftlb, plus or minus 2.5%

Also, the TR4 workshop manual specifies to install the studs before the head gasket (although I have no idea why). That's what I normally do as well. The TR2/3 manual doesn't really say, but shows several photos of the studs in place while working inside the engine (checking ring gaps and so on), plus of course using the studs to clamp the liners in place while installing pistons.

A professional mechanical engineer (who also worked on Jaguar engines in his spare time) once told me that studs should always be lightly torqued into their blind holes. Something about compressing the stud to spread out the load on the threads; I didn't really understand that part. But it seems to work for me.

Things like block castings tend to be a polycrystalline mess. So on a micro level there are hard, soft, ductile...etc. spots in the matrix. As the tap moves into a blind hole (or any hole) the swarf will carry these sometimes superhard materials (carbides, harder than the cutting tools alloy) along the cutting boundary before being hopefully expelled. The result being that finger tight really won't result in all internal and external threads making contact and more uniformly distributing the torque from the start. I suppose it would be an interesting experiment to test an old cracked block with some grade 8's to see where they let go, both dry and lubed.

The finger tight recommendation comes from Carrol Smith's "Engineer to Win". It's a very worthwile book all about bolts, studs, torques and how to do them right.