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Old 08-26-2021, 01:06 PM   #1
philcobill
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Question Are These Head Studs Long Enough?

This is a photo of a nut on top of a head stud on the aluminum cylinder head I am trying mount on my 1929 Special Coupe's engine block. A gasket is in place and there is a washer under the nut. The stud is hand tightened into the block. The nut was tightened with a regular wrench and not torqued. I imagine that even if it is torqued the nut will not tighten much more. I tried backing off the stud to give more height above the surface of the head. However the studs were loose in the block when backed out to make a difference. My question is what should I do?
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Old 08-26-2021, 01:25 PM   #2
1931 flamingo
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Default Re: head studs not long enough

Is the stud the correct length?? What if you don't bottom it out in the hole??


I believe there are two different stud lengths.
Paul in CT
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Old 08-26-2021, 01:29 PM   #3
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Default Re: head studs not long enough

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Originally Posted by 1931 flamingo View Post
Is the stud the correct length?? What if you don't bottom it out in the hole??


I believe there are two different stud lengths.
Paul in CT

I got the studs from an online Model A parts supplier. There were 11 regular studs, two for the coolant neck, and one for the ignition cable.


Bill
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Old 08-26-2021, 01:31 PM   #4
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Default Re: head studs not long enough

No washer needed! Get correct length studs!
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Old 08-26-2021, 01:33 PM   #5
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Default Re: head studs not long enough

https://www.fordbarn.com/forum/showt...+head+studs%3F

This explains why no washers on head studs.
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Old 08-26-2021, 01:35 PM   #6
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Default Re: head studs not long enough

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Originally Posted by Gary WA View Post
No washer needed! Get correct length studs!
Gary,



When are these used?


https://www.macsautoparts.com/model-...8-28375-1.html


Bill
Walworth, NY
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Old 08-26-2021, 01:38 PM   #7
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Default Re: head studs not long enough

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Originally Posted by philcobill View Post
Gary,



When are these used?


https://www.macsautoparts.com/model-...8-28375-1.html


Bill
Walworth, NY
Never to my knowledge!!Model A's for over 50yrs never used washers on head!
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Old 08-26-2021, 01:39 PM   #8
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Question Re: head studs not long enough

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Originally Posted by Mike Peters View Post
https://www.fordbarn.com/forum/showt...+head+studs%3F

This explains why no washers on head studs.

I think this is referring to standard stock cast iron heads, and to lock washers. These are not lock washers and the head is a high compression aluminum.


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Old 08-26-2021, 01:40 PM   #9
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Default Re: head studs not long enough

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Originally Posted by philcobill View Post
Gary,



When are these used?


https://www.macsautoparts.com/model-...8-28375-1.html


Bill
Walworth, NY
Never to my knowledge!!Model A's for over 50yrs. I never used washers on head!
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Old 08-26-2021, 01:46 PM   #10
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Lightbulb Re: head studs not long enough

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Never to my knowledge!!Model A's for over 50yrs never used washers on head!

Yes, it is true that they are never used on standard stock heads, but I imagine that high compression heads, especially those made of aluminum are a different beast.


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Old 08-26-2021, 01:47 PM   #11
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Default Re: head studs not long enough

Measure the length of the stud bore in the head. That's the distance from the machined surface of the head to the stud boss on top of the head. All the stud bores should be 2-7/32". That's the stock head bore length and that's the length the studs you bought are designed for. Check your stud bore length and then come back and we'll know how bad the problem is.

It's not uncommon for vintage aftermarket heads to be a lot taller than the stock head. If yours is more than about 1/4" taller than stock, I think you're gonna need to source new studs from a place like ARP. The strength of a steel-to-steel joint increases as the length of thread engagement increases, up to one nominal diameter (e.g., for a 7/16"-14 stud, 7/16" depth of tapping or about six full turns). Beyond that there is no appreciable increase in strength. The threaded depth on the block is about 3/4", so you can back the stud out 1/4" without losing any strength in the final bolted joint.
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Old 08-26-2021, 02:18 PM   #12
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Thumbs up Re: head studs not long enough

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Originally Posted by alexiskai View Post
Measure the length of the stud bore in the head. That's the distance from the machined surface of the head to the stud boss on top of the head. All the stud bores should be 2-7/32". That's the stock head bore length and that's the length the studs you bought are designed for. Check your stud bore length and then come back and we'll know how bad the problem is.

It's not uncommon for vintage aftermarket heads to be a lot taller than the stock head. If yours is more than about 1/4" taller than stock, I think you're gonna need to source new studs from a place like ARP. The strength of a steel-to-steel joint increases as the length of thread engagement increases, up to one nominal diameter (e.g., for a 7/16"-14 stud, 7/16" depth of tapping or about six full turns). Beyond that there is no appreciable increase in strength. The threaded depth on the block is about 3/4", so you can back the stud out 1/4" without losing any strength in the final bolted joint.
I will check the height of the head out. Should I be concerned about loose studs if I back them out?
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Old 08-26-2021, 02:27 PM   #13
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Default Re: Are These Head Studs Long Enough?

return them to the vendor and buy the correct ones!
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Old 08-26-2021, 03:29 PM   #14
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Default Re: Are These Head Studs Long Enough?

Considering your vendor and the fact that lock washers (IM0) are about as useful as grease on a pole I would take the above advice and get some studs that will grip about 5-7 threads or more - not bottoming out. With the nuts snugged before the gasket starts to crush you should have about 1 full thread showing regardless of which head you have - no washers. If the studs wiggle by hand before touching bottom you may need heli-coils. ARP studs are about the best and you can get and at any length.

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Old 08-26-2021, 03:33 PM   #15
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Default Re: head studs not long enough

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Originally Posted by philcobill View Post
I will check the height of the head out. Should I be concerned about loose studs if I back them out?
Hard to tell without being there and seeing how "loose" they are. Wobbly studs can be caused by the threads in the block being worn down, or by the studs using a Class 2 thread fit instead of a Class 3, but I think the regular vendors all sell studs that fit closely.

I forgot to mention, the height of the washers will need to be added to the stud bore height.

If you need ARP studs, I think the P/N you want will be AP3.750-1SB for all the studs except the water outlet studs. Not sure what length those would be, but it's possible the stock studs would work for those because no washer is needed on those two.
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Old 08-26-2021, 04:01 PM   #16
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Exclamation Re: head studs not long enough

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Originally Posted by alexiskai View Post
Measure the length of the stud bore in the head. That's the distance from the machined surface of the head to the stud boss on top of the head. All the stud bores should be 2-7/32". That's the stock head bore length and that's the length the studs you bought are designed for. Check your stud bore length and then come back and we'll know how bad the problem is.

It's not uncommon for vintage aftermarket heads to be a lot taller than the stock head. If yours is more than about 1/4" taller than stock, I think you're gonna need to source new studs from a place like ARP. The strength of a steel-to-steel joint increases as the length of thread engagement increases, up to one nominal diameter (e.g., for a 7/16"-14 stud, 7/16" depth of tapping or about six full turns). Beyond that there is no appreciable increase in strength. The threaded depth on the block is about 3/4", so you can back the stud out 1/4" without losing any strength in the final bolted joint.

The bore hole through the head and taking the washer into consideration is about 2-3/8 " " or about 5/32 " longer than you stated above for a standard stock head. I will double check the measurements for all of the bore holes, but it is clear that they are longer than standard.


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Old 08-26-2021, 04:14 PM   #17
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Default Re: Are These Head Studs Long Enough?

Standard Model A stud on the bottom, ARP AP3.750-1SB on the top. Sounds like that would give you the extra length you need. Probably looking at ~$60 for a full set.
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Old 08-26-2021, 06:00 PM   #18
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Default Re: Are These Head Studs Long Enough?

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Originally Posted by alexiskai View Post
Standard Model A stud on the bottom, ARP AP3.750-1SB on the top. Sounds like that would give you the extra length you need. Probably looking at ~$60 for a full set.

I just ordered a set. It looks like the studs I ordered are 1/4 " longer than the stock model A studs.


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Old 08-26-2021, 06:12 PM   #19
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Default Re: Are These Head Studs Long Enough?

Almost any stud can be ordered from McMaster Carr. As others have stated, you will need longer studs with thicker heads. You may also need a longer connecting shaft for the distributor.

The aluminum heads will cave in near the stud to form a concave surface where the nut rides. The thin washer supplied with the heads are not strong enough to prevent this. A substantial washer is needed to spread out the load. I have seen this happen on my car when installing an aluminum head.
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Old 08-26-2021, 07:10 PM   #20
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Exclamation Re: Are These Head Studs Long Enough?

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Originally Posted by nkaminar View Post
Almost any stud can be ordered from McMaster Carr. As others have stated, you will need longer studs with thicker heads. You may also need a longer connecting shaft for the distributor.

The aluminum heads will cave in near the stud to form a concave surface where the nut rides. The thin washer supplied with the heads are not strong enough to prevent this. A substantial washer is needed to spread out the load. I have seen this happen on my car when installing an aluminum head.

The studs which are 1/4 longer than the standard stock ones have been ordered. I will be sure to try them out before applying sealant and tightening the nuts down.


This is not a "new" head, it was on the car when we had it shipped out this spring. The distributor fit fine, so I imagine it will be okay.

I ordered some hardened steel, not stainless washers. Hopefully, they will be okay. The head nuts had no washers when I started.

Bill

Last edited by philcobill; 08-26-2021 at 07:34 PM.
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