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Cylinder head studs

My 1928 M2 Rugby had when bought, six bolts fixing the cylinder head.

All manuals I have seen, included the one shown in technical page, show studs and nuts instead of bolts. Is that the original configuration for a W5 Continental engine for a 1928 M2 Rugby?

The bolts I have are not all of the same size, two of them are of larger diameter. The manual shown in the technical page for a 1929 four cylinder, show 13 larger and two smaller studs/nuts in position 7 and 8.

A parts list of a 1927 model indicate 13 studs/nuts 7/16 x 3 5/16 and two studs 1/4 - 20 2 7/8.

Can somebody help me putting some light on this issue?

Thanks in advance and Happy new year.


Do You own a car built by Durant? Yes

Re: Cylinder head studs

Ricardo: I checked out one of my manuals for your answer. In the 1928 Star Model "M" repair parts book from Durant Motorts of Canada Ltd. under cylinder head it list

part# 20686 as cylinder head stud 7/16" - 20x3 5/8"
S.A.E. qty. 15

& part# 24058 as cylinder head stud nut 7/16" - 20
S.A.E. qty. 15
Hope this information will help answer yor question

Re: Cylinder head studs

I had the same problem with bolts verses studs.
Original are studs but the threads tend to shear of after a while so when someone wanted to do some work to the head they just changed the studs to bolts.
Unfortenatlly not everyone realizes that the studs are threaded with a taper so that they seal since they did not have thread sealant and they go right into the waterjacket of the block.
So unless you rethread the block for streight threads the bolts will only go in so far and may not torque the head properly and leak water into the cylinders.
It can damadge the head and blow the head gasket.
You can still buy new studs.

Where Are You From? vancouverdurantstarcarconnection.ca

Re: Cylinder head studs

Thank you very much Steve and Franz for your information.



Do You own a car built by Durant? Yes

Re: Cylinder head studs

Franz: You say the studs are available? Is that something I can go down to Napa and get? Will these new studs work OK with a higher compression ratio?

I'm wanting to raise my compression ratio to 7 or 8 to 1 and I'm concerned that the old studs won't hold up.

Any thoughts - ideas?

Where Are You From? home1.gte.net/res02rxl/index.html

Do You own a car built by Durant? 1929 Model 40

Re: Cylinder head studs

Curtis your standard NAPA studs will work if you get the correct one for heads but your gasket may fail when you raise the compression. You are also putting and additionsl strain on the rod bearings. It will not be the studs that fail but other items.

Re: Cylinder head studs

Me again Ricardo, Sorry I posted the wrong model in my first reply. Here is the corrected details taken from Repair Parts List manual for Durant Four (star series) Model M-2 effective March 1928

Under the cylinder head listing it states

part#20686 as stud 7/16" - 20x3-5/16" U.S.S. qty 13
and hex nut 7/16" - 20 S.A.E. qty 13

Re: Cylinder head studs


Thank you very much for your help. I have been investigating more this issue and I agree with you that in my block there will fit better the 3 5/16 studs and that there should be 13 of the same length, but the remaining two that also fix the upper cooling water tube that goes to the radiator, should be longer, and fot those two 1/4" longer will fit better.
Lower end of the studs should be 14 threads/inch to fit my block and upper end 20 as you say.
About the same issue, do you know if flat washers where used or the nuts where pressing directly over the cylinder head?

Best regards


Do You own a car built by Durant? Yes

Re: Cylinder head studs

Ricardo: There is no mention of flat washers being used for this purpose, whereas they are mentioned in conjunction with other applications in this manual.

Re: Cylinder head studs

Be careful when screwing studs or capscrews into blind holes. Any oil or grease at the bottom of the hole will create a hydraulic pressure, when you screw it in. If you have a thin piece, it might blow through it. I've seen this happen on a Ford tractor, and all the rear end oil leaked out overnight.

I'm not aware of "tapered thread" studs. They are straight threads with a slightly larger pitch diameter so that they fit in the threaded hole with a Class 5 interference fit. They should not be screwed in so far that they contact the imperfect threads at the bottom of the hole or so that the imperfect threads on the stud drive into the top of the threaded hole. If the threaded hole is worn too large for a tight fit, you might want to use some of the thread sealer that "wicks" in after the stud is in place.

Generally you use a "hardened" steel washer when the material under it is "soft". Especially the softer aluminums. For a cast iron cylinder head, it's possible the iron is harder than the ordinary hardware store washer. This kind of washer could be worse than no washer. A hard one couldn't hurt, if it will lie flat on the boss.

Hard washers not only protect the softer metal, but they help keep the bolt tight by not letting it sink in. It also makes torquing more consistent.

Studs have this effect also. If you use the same nut and the same oil or grease and the same torque, you'll get pretty much the same tightness. If you are screwing a cap screw into a threaded hole, the torque will vary with how deep it threads in, so you lose a little control over tightness.

I've got W5 heads that have spot-machined head bosses and others that appear to be planed off. Not sure of the story there. Also, early 28 Model A Fords had spot-faced bosses on the front cover. Later they left them as-cast, because it didn't make any difference and saved cost.

Do You own a car built by Durant? yes

Re: Cylinder head studs

Lot of knowledge and warnings in the answers. Thank you very very muchh.


Do You own a car built by Durant? Yes


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