I guess this is what happens when I don’t keep up. Not that I feel myself to be the authority on threads and studs; but several of you have been polite enough to tolerate me; and I feel that I should answer some of the questions.
So.....you are saying that pistons, rods, other parts will fail before the 1/2" studs? not quite sure....(am a machinsit by training, but looking for a job....
)
I believe that the new 1/2” studs will survive most anything thrown at them. As the 7/16” studs were not catastrophically failing; I don’t see that the 1/2" studs will have any problem surviving.
Chris:
Probably not as much Stage II experience as you. As I was the one that bought your heads and valve train; you should know. Have I miss something?
I’d have to rank my Stage II experience below production Buick; and even that below Donovan 417, Big Block Mopar, Small Block Ford, Italian OHC engines and various Japanese motorcycles; and of course the obligatory SBC’s. One thing they have taught me is that the bolts don’t seem to care what engine they are in.
Do you have any experience in Destructive and Non-Destructive Failure Testing of Fasteners in Compressional, Extentional, and Shear Loading? I do; but it never seems to be enough.
Joe
Joe, That question was intended for others but I felt the sting. I certainly have no engineering degree and have no experience with any sort of testing except life and racing(which at this level is nothing but a test!!)
You seem to have some engineering behind you so I would like to ask you a question!! In my little Hillbilly mind the question of weather I weakened the deck of the block by drilling it for 1/2" studs is still a good one that I would like to discuss. The reason I made this an open book project was Im sick and tired of seeing people bail out of the v6 world and go to SBC or BBC mainly because they cant see the potential of this v6. I would venture to say that most of those defectors had no idea what they were about to spend ,and were disappointed with the results.(meaning there are very few defectors who have gone nearly as fast as Fiscus , Gomes or Lyons have with v6's).
Ok , About the deck strength issue!! If you look at the deck of a stock block or the center 2 rows of a stage block they are relatively the same , with a triangler shaped deck surface being supported by the cylinder wall on 2 sides and the exterior (side of block)on the third side. Putting a 7/16" bolt hole in say the center would put the thread ?? closes to those supporting walls. Drilling that hole to 1/2" actually shortens the distance to the supporting wall and in my mind would actually strengthen that deck surface because the pull of the threads is closer to the supporting structure!! The pull of the bolt is at the thread and now the thread is closer to the structure that supports it!!
In my mind thats the way I see this!!
Example: 2 wagons loaded with 60,000# of material were parked centered up on a 30' bridge. First wagon has a 20' wheel base(7/16" thread) so its weight is 5' from each support. Second wagon has a 26' wheel base (1/2" threads)so its weight is 2' from each support. Which wagon is putting the most load on the bridge span(deck surface)?? From nearly 60 years of lifes experiences I say the bridge is subject to less load(less flex) with the bigger wheel base. Im all open to any and all opinions on this!! Thanks Mike
The comment about Destructive and Non-Destructive Failure Testing of Fasteners in Compressional, Extentional, and Shear Loading vs. Stage II experience was directed at Chris; who had just sold me a set of heads and valve train. I’m not sure Chris thought much of my plans for them; but he sold them to me anyway.
No engineering degree here either. I did help with some testing done for threaded fasteners; and ran many of the tests. I was surprised at what failed; and why. Things didn’t always fail like I figured they would; but they always failed at the weak link.
Did you weaken the deck by drilling? Yes. How much? I don’t know. The deck is weak by design. Most of the 4.1 production, and a lot of the 3.8 production and Stage blocks crack parallel to the cylinder at the head bolt holes. This condition is worse on blocks that have been bored. I would think removing material for larger bolts would do the same thing.
I see your point about moving closer to the long wall of the cylinder; but you’re also removing mass that supports the stud.
Example of two wagons; both would put 60,000 pounds plus the weight of the trailer on the bridge supports. You might have less flex in the bridge with the longer trailer; but the force is the same. Imagine the structure turned upside down; with the bridge deck glued to the supports. If the glue can hang over 5 feet on each side; you’ve got more retention power on the deck than you would if the glue can only hang over 2 feet on each side.
As far as the 1/2" vs. 7/16” studs; I’m sure it will be application specific. The problem is; 7/16” bolt holes in Production and Stage blocks fail. It may not be from the head retention; but they still fail.
And; I don’t know where you’re from Mike; but I doubt that you’ve got the Hillbilly market cornered.
I was wondering myself about that statement. It made the question marks fly around in my head. I too look forward to a better explanation as to why drilling the holes larger would weaken the deck as it relates to this particular situation.
I think I do understand the attempted point about the amount of thread material available after going from a threaded 7/16 to 1/2 hole though. What is the proper drill size for tapping a 1/2" hole that will give the proper amount of thread engagement in cast iron?
Maybe I covered that above. If not; let me know.
7/16' OD is .4375 so you can figure that the outer tips of the tapped holes were around that. The drill size used for the 1/2" tap is 27/64" = .4219. so the tip points of the 7/16 tap were .0156 bigger than the drill requirement for the 1/2" tap so an estimate would be that say 10% of the hole was .0156 bigger than the sugessted drill size. I dont see that as much of a loss.
He is also correct about the fact that I went from 14 threads per inch to 13 threads per inch and that was a huge concern of mine a while back!! I checked into 14 pitch 1/2" taps and I could get them made , but when I talked to ARP about it, they checked into it. You may be able to imagine the cost of the machine that rolls precision threads on these bolts/studs and the cost of custom making a die (just for me) to do this. ARP checked with some of there top engine builder customers and it was hands down agreed that there was no problem with going from 7/16 x 14 to 1/2 x 13 in a block. I said OK but still had a question in my mind so I took a piece of aluminum and set it up on my mill and drilled and tapped a 7/16 hole , then redrilled and tapped that out to 1/2" x 13. I looked over the treads I just tapped and ran a stud in it. To my amazement the treads looked pretty good and felt very good!! Then I wondered what the treads in the block actually looked like , so I inspected those with my magnifing glass and installed a 7/16 stud. Much to my supprise the treads in the block did not look as good as the ones that I just tapped and the stud had much more play than the piece I tapped. So from that moment on I was convinced that it would work!! Mike
I would agree. If that percentage were lost off the tips of the threads of the stud, I would be worried.
Have you calculated the total thread engagement? Taking the diameters of the two different studs into consideration, not just the TPI?
I didn’t think about thread contact. There’s probably a lot in here that will defy calculation; but here goes.
At 6 threads for each:
7/16 inch stud; 0.205977 Square Inches.
1/2 inch stud; 0.255065 Square Inches.
At 5.5 threads; the 1/2 inch stud drops to 0.23381 Square Inches.
At 5 threads; the 1/2 inch stud drops to 0.212554 Square Inches.
I don’t know how much engagement you can get; but if you get a full 6 on each; the 1/2 stud will have about 24% more thread contact (at 5/8’s stud to block pitch contact). 5.5 threads; and you get about 14% more. Only 5 threads; and you only get about 3% more. But; at 5 threads of contact; you have probably also reduced your clamping potential by 10% of what you could get at the full 6 thread engagement.
I know the L19 studs aren’t supposed to stretch; but the cast iron block probably still will. I don’t know how to figure that. 6 threads is the old 98% standard; and probably works here best it can.
As for your work; I have no doubt that your hand cut 1/2 inch threads are better than the long used factory cut 7/16 threads. Again; I don’t really know how this will come into play; good or bad.
Not totally sure what the question is, but I have no way to calulate anything having to do with thread engagement between two different thread sizes!! Maybe someone eles can chime in. The deck surface on the center 2 rows is approx .750 thick and the studs have threads that are .800 long. so considering that there is a fairly healthy chamfer at the deck which actually sinks the stud slightly , the studs will actually be completely engaged in any threads in the block. Hope that helps. Mike
What I mean is, if you were to stretch one thread from your 7/16" stud into a straight line and measure it (circumference of one thread), and compare that to the same with the 1/2" stud, and then multiply by the number of threads that are making contact, I'd bet you're netting more actual thread surface contact with the 1/2" stud regardless of the difference in the pitch between the two sizes.
I think I got this covered; but there’s still some unknown.
You’d have to know the tensile strength of both the stud and the block to get a real number for number of threads needed to engage. It could be that you have plenty of strength in the block to hold the stud at full load.
I kinda like the fact that the aluminum is hugging the stud. That would certainly control any walking of the head if it were prone to do that. My studs fit like that on a couple of the holes through the heads. The ones that were sleeved during the intake port work. It's easier to screw those two studs out of the block and head before trying to pull the head off.
Maybe a math wiz among us will do the thread engagement math for us. I'm really interested in how much more engagement contact you're getting.
I’m not sure about the “hugging” potential of the studs. All bets are probably off as soon as the engine starts. There are going to be a lot of forces that can’t easily be measured when things start heating up; and there will be some position change regardless of how the studs rub on the heads.
My goal here wasn’t to be the math wiz. Maybe I deserved that.
