Head Bolt Retorque: An Unbolting Developent…

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Retorquing the head bolts this morning and had done several, none of which moved much at all, when Alas! one on the right side, which holds the horn bracket, was loose and would not torque. Egad, Montressor! So drain the coolant and off comes the head. I have it undone but I’m waiting on my College Student to help lift it.

I did remove the offending stud which was obviously pulling out of the block. I hope I am able to use a thread repair (Helicoil) to get it whipped into shape. This is a good time to replace the cheesy hardware-store head nuts and plated soft washers, and maybe the studs. I am very open to advice about this situation.

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Hi Randy, I prefer Time Serts for the iron block head stud threads.

Were the threads on the stud bad? or the threads in the block?

There are new studs available from Dorman. I’m not sure I have the part number

in my computer, I’ll look.

Greg

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Greg, the stud looked pretty good other than the threads damaged by pulling so I suspect the block rather than the stud is the root cause. The engine in my Car was rebuilt after the PO bought it and the threads is this spot were maybe already marginal and just let go. It wasn’t at all tight when I first put a wrench on it. Every other one was quite tight and barely moved during the retorque.

Timesert: will use this. Thanks!

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Turns out the stud looks good; there was thread sealer or some similar substance in the thread root; cleaned up great with a die.

Ordering a gasket from Olson’s and the Timesert is on the way.

Thanks!

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I think you will like the timesert product/system. locks in place, no metal tang broken off inside the engine.

And the kit is equipped with very good tools..

I’d grab each installed cylinder head stud, and wiggle it at the tip. If you can wiggle the stud in the block, then those threads are also loose, and should be inspected.

I believe that Pierce had a selection of oversize and undersized head studs that were selected for fit in the threaded bores in the cylinder block.. I’ve measured hundreds of the studs, and the threads on the end that goes into the block can vary in OD by as much as .012″. I’ve found my selection of studs quite useful for finding a tight-fitting thread on some blocks that seem to have slightly oversize threads..

Look at each stud, at the upper thread where the head nut is threaded on. Look to see if the threaded section is stretched, and is thinner in the middle of the threaded portion. It will look like an Hour-glass’. You can use a caliper to measure the OD of the threaded portion at the top, middle and last few threads. Any stretched studs will show a smaller diameter in the middle of the threaded section.

This stretching and the corrosponding smaller diameter often lets a head nut slip or strip it’s threads.

Also, you mentioned buying new head nuts and better machine washers. This is a good idea, but take along a head stud and check the new 7/16″-20 nuts before you buy them.. I’ve found some batches of nuts that are oversize and are way too loose on the stud, and would not take the torque needed.

A lot of ‘stuff’ for just the head studs and cylinder head nuts.. Huh?

Here is an image of the Dorman head studs. As you can see they are slightly longer, which can be ground off if you will be annoyed by a stud being slightly longer than it’s neighbor.

Greg Long

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Be sure your new nuts won’t bottom out on the stud, causing a false torque reading and head gasket issues. It’s a common problem with cheap acorn style nuts not to be properly machined deep enough. As Greg said…….inspection, inspection, inspection…….it’s the crazy little details that will jump up and bite you. I have used the timesert often when I had my modern repair garage, probably twenty five times, and never had a problem or failure. Good luck, Ed

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Good ideas, Fellows. I did torque all the other studs anyway, and they all went to torque with minimal movement; additionally each one will ring if tapped on the side with a small wrench. For some reason (age? 90 years…) this one turned loose at some time in the past, since the overhaul circa 2004.

Are the correct head nuts just nuts? I was not planning to use acorn nuts; are they correct? I know the nuts and washers I found on my Car are zinc-plated hardware-store items. I was planning to use hardened washers and nuts, plain or phosphate finish, from a professional source.

You are right about the fits. At work we run into a lot of studs with class 5 fit which were never intended to be removed. You have to be careful when replacing with class 3 so we use gauges.

The Timesert-type repair is what we typically use at work; the bushings are made to order, not commercially available, but they have the strength of the original and we use them in critical applications (i.e. pressure).

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Randy, the eights and twelves used chrome acorn nuts, or studs, I don’t know what the series 80 or 81 cars used off the top of my head………Ed

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For what it’s worth my series 81 in my Fleet Arrow Wagon has chrome acorn nuts. I’ve been trying to find some replacements and have found the modern acorn nuts have a much smaller outside diameter and of course the depth is an issue as mentioned above.

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Photos of restored Cars I have taken show regular nuts. That’s what I am using for now.

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Hi Randy, Series 80 engines used regular nuts, and amazingly they were 5/8″ and installed without washers.

I do the same as you plan: hardened washers and good quality hex nuts. It is very hard to find 5/8″ nuts for 7/16″-20 threads. I usually use 11/16″ nuts. They look ‘right’.

Series 81 introduced the acorn nuts on the engine. Then for 1929, the new straight-8 engine had head bolts that had an odd acorn head..

Greg Long

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Greg, I meant to show you at St. Louis: I found some 5/8 nuts made by ARP which have a washer forged onto one side; they are strong and very nice for this application. My studs were not long enough for a thick washer so this worked great.

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Hi Randy, how accurately did the ARP threads fit the Series 80 head studs? Nice and snug? or loose and sloppy?

Greg Long

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They fit very nicely. I believe based on their appearance that all the studs were replaced when the engine was overhauled so this probably helped.

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