head bolts

[djm16]

I am doing the head gasket on my P3 again. The 70 yo head bolts are looking a little fragile. Several of them have been exposed directly to coolant and are quite corroded. I imagine that they are also work hardened and brittle. It also seemed to take a painful amount of rotation at the bolt head to break the head bolt torque.

I think I also figured out at least one reason why the head gasket blew. I don't think that I tightened up the three head studs to full torque when I last assembled it. Mea culpa.

My question: Assuming I can buy generic BSF tensile bolts locally, is there a good reason that the bolts have a waist? And does it matter if the new ones do not?

[djm16]

While I am on this thread, I want to pass on my experience with yet another bit of screw up with this engine. It had been "rebuilt" by a PO. I have noticed that when the engine gets hot / and under load, the rocker space fills up with oil. I can tell this by the sudden loss of power and massive smoke screen that occurs when a pint of oil is dumped through the breather into the air filter. When the engine is running with the rocker cover off, the reason is obvious, oil is absolutely pissing out of the inlet rockers.

"Must be worn." I thought, but no. When I disassembled the rocker shaft, I found there were new bushes in the rockers and a new rocker shaft. There was some wear on each, but it was less than a thou each. what I did find was first that the rocker bushes were reamed to at least 4 thou greater than the rocker shaft dia. Much worse still, the rocker shaft had the rocker lubricating holes in the wrong place. They were 100 degrees out. So the load bearing parts of the shaft were getting no lubrication, and oil was pissing out of the widening gap between shaft and bushing. And this was a new shaft.

At least the rocker shaft was made out of a hard steel. When I tried to drill new locating holes (to move the lubricating holes around) even my centreing drill (usually good for drilling welds) just bounced off and blunted. A quick google search revealed that an ordinary, cheap masonry bit would do the job! Indeed it does, although I have to sharpen the carbide tip on a grindin wheel first.

[enigmas]

Waisted bolts are stronger due to the manner in which they are manufactured by virtue of maintaining the grain structure through the thread as opposed to die cut bolts.
en.m.wikipedia.org/wiki/Threaded_rod

Socket head cap screws are also some of the most high quality fasteners available.
I use these in many applications that are under severe loads/stress (eg. Brake & Steering systems)
www.hobson.com.au/page/unbrako/socket-head-cap-screw-unbrako.php

Here is a well known company (ARP) that manufacture high quality 'engine Stud Kits' for professional/serious engine builders/racers. Definitely not cheap but high quality. They may have something suitable in tbeir vast inventory.
arp-bolts.com/kits/product.php?PL=34

[Sam Bee]

I fitted ARP studs on my P6B and have a set waiting for my P5B. Would recommend, if you can find some to fit, as in future all you have to do is undo the nuts so no chance of bolts shearing and am told have less stress problems.

[enigmas]

Sam...did you fit them on the the 'mains', cyl head or both?

[djm16]

Interesting article in Wiki about types of threaded rod.

There are at least two different types of waist. There is the apparent waist that appears when a thread is rolled rather than cut, throwing up metal into ridges (threads). However head bolts in the P3 are narrowed down further for 3/4 of their length, and it is this latter waist that I was referring to.

OK, so I will go take some pictures.

[djm16]

I know, I still have not taken pictures. I have however ordered a set of head bolts and studs from John Craddock at the quite reasonable price of $250 inc postage. I also sourced a spare pair of head gaskets from Australia for another $240. I never had a reply from Meteor Spares. Anyone know if they are still in business?

Meanwhile I cleaned up the head and block surfaces with 600 grit W&D lubricated with Plus Gas. Yes, I was concerned too not to get abrasive slurry in the bores and oil ways.

[Sam Bee]

Enigmas, just for the heads on the P6 as I did not need to touch the lower end. But if I had to I would contemplate studs for the bearing caps.

[djm16]

The P3 head is back on with its new bolts! The majority are 60 y old NOS and came in original packaging together with a layer of heavy grease / wax. The 4 medium length bolts were newly manufactured to a pretty high standard, lathe turned and threaded, and well black finished.





This time I made sure to torque down the 3 studs that pass though the rocker shaft mounts. I think I had not torqued them last time, forgetting that they go through the head and into the block.

On its inaugural run, the motor sounded lovely, and I used the car to take wife and dog to the vet (it was the dog needing treatment). It was a hot day (36) and getting hotter. Guess what, the ba#$ar& wouldn't start. My much vaunted Pertronix electronic points replacement had failed, and I needed a tow truck to get home. Wife and dog were very patient, despite having to stand outside in the shade for a hour. The tow truck owner, a very understanding imigrant from Gloucester, has his own vintage vehicles, he also was fine with the dog in my arms in the cab.

Naturally the original points are now back in. Not a roadside job!