Anyone Tried 1/2" Head Bolts??

[BlownV6]

Ok another question for the masses. Unlike all of my SBC & BBC buddies , In 20+ years of fooling with these stage 2 blocks I have never had an issue , nor have I ever seen an issue with the head bolt threads stripping/pulling on one of these blocks. That being said , my engine machinist and I are of the opinion that these blocks are cast of some seriously stout material. Reason being I have tore a lot of stuff up over the years but the block material itself has always show amazing toughness. SBC & BBC blocks absolutly will not survive as well given similar conditions.

So I would assume that the threads in the block are up for a serious task!!

Anyone else had any issues with stage 2 block head bolt treads?? Do folks have problems with stock blocks?? Mike

BTW Thanks to all for some good info IMHO

 

[Alky V6]

Look at post #23 :biggrin:.

Doh! Sorry. This threads getting long.

 

[Alky V6]

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.

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.




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.



Maybe I covered that above. If not; let me know.




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.




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’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.

When I mentioned math wiz, it was with the utmost respect, and it wasn't pointed at any one individual. Thank you for the explanation. Well done.

 

[Turbo6Smackdown]

I have a simpleton question for you guys. It'll help me better understand the dynamics you're working with here.
If you go to an exotic metal stud, and it's stronger than the block material, wouldn't that be just like trying to find a grade 8 steel bolt, to screw into a piece of aluminum? If you need to torque something that strong, aren't you going to just pull the stud right out of the block? These blocks aren't that strong.
And lastly, (of course we try to stay away from this but, it doesn't always happen that way) if you're going to get a little detonation, wouldn't you want it to go out the headgasket? Because I heard that if you seal it up too much, it'll just travel downward instead, making for a way more expensive repair. How far off am I?

 

[BlownV6]

I have a simpleton question for you guys. It'll help me better understand the dynamics you're working with here.
If you go to an exotic metal stud, and it's stronger than the block material, wouldn't that be just like trying to find a grade 8 steel bolt, to screw into a piece of aluminum? If you need to torque something that strong, aren't you going to just pull the stud right out of the block? These blocks aren't that strong.
And lastly, (of course we try to stay away from this but, it doesn't always happen that way) if you're going to get a little detonation, wouldn't you want it to go out the headgasket? Because I heard that if you seal it up too much, it'll just travel downward instead, making for a way more expensive repair. How far off am I?

Ok I will step out on a small branch here with a sort of explanation/answer. First you are basically coorect!! But to make more power you have to start pushing various parts and components to their limit. You probably are aware that your not going to make 1200hp with stock crank , rods , pistons ,head bolts ,head gaskets etc. as they cannot withstand the forces that would be be applied to them. Over the years thousands have pushed the boundrys of what the existing parts will stand. MOST will call this a good or bad tuneup!! But it really means that its a safe tuneup staying well with the limits of the parts involved or it exceeded it. I am simply convinced that the parts Ive been using have meet there limits and now I need to find stronger head fasteners. If this works it WILL transfer more stress to other parts and eventually find the next weakest link.
Here is where the beating can begin!! Controlled detonation is all around us.
A diesel engine is controlled detonation , but uses parts that will survive a long life of it. A top fuel car at some point in the run does not need spark plugs or a magneto because it begins to detonate. But again the parts used are designed to survive this for a short period of time. OK now Ive opened up a can of worms!! Gentle beatings please!! Mike

 

[Alky V6]

That's a very fine art that's very hard to accomplish with methanol. A lot of experience is required. Experience which usually means a lot of broken parts piled up in the backyard. But, if you have the will and the means, then I say go for it.

Trying to control detonation will definitely require a method of pulling out timing when the detonation begins, not to mention the hard part of figuring out when that timing retard needs to occur. Flame speed increases DRAMATICALLY! You've already stated that you're odd fire with no way of adjusting timing during the run. I wish you all the luck.

Every tuning parameter, including weather changes, and the relationship between all those tuning parameters becomes ultra critical if that is the tuneup that you're shooting for. Keep extremely good records, including weather conditions. Weather changes while you sit in the staging lanes can change the required tuneup. If you watch top fuel, that is what the crew chief is doing before the car stages. Making a last moment tuning decision.

 

[BlownV6]

Let me clairify that by saying that Im not looking for detonation and would like to avoid it all cost. But the facts are that it happens!! If you have good parts they can survive , if your walking the tight rope they will fail. Thats most likely where I am at this point, any detonation at all and the head gaskets give way , SO thats the piece Im trying to improve at this time!!
Thanks Mike

 

[Alky V6]

You had my heart ticking there. All I could see was your bank account counting down the way the national debt is counting upwards.

Using the term controlled detonation is a little misleading. There is no human being that controls detonation. Detonation decides on its own whether you will have a good day at the track, or not.

 

[BlownV6]

My point is at this level of boost/power detonation can occur. If it occurs do you have the parts to keep it from blowing up. Mike

 

[TurboTR]

Ok a gentle correction Not to get off topic, or that it really matters here. I do have significant experience with diesel engine combustion and controls and emissions research and am compelled to state- diesel combustion is not detonation. Repeat, not detonation.

Diesel begins to burn (ie combust normally) as soon as the fuel being sprayed into the chamber full of hot air (above the self ignition temperature of the fuel) dissipates far enough in among all the hot air in the chamber to get lean enough areas to begin to burn. And a large area of the spreading fuel front begins to do so initially.

So in the diesel an entire chamber full of very hot air is there just waiting for fuel to begin combusting; for the spark engine, a tiny spark point source is all that starts the burn going. Huge difference in what initiates the combustion and more importantly here, how much begins to burn initially.

After the flame starts the combustion is basically the same- a normal burning of the air fuel mix until the fuel is all consumed. It is not spontaneously "exploding" in uncontrolled manner, as in detonation.

It sounds like it detonates in many diesel engines at idle for example because the rapid pressure rise from the diesel combustion does "hammer" the parts more than a spark ignition. Since so much more fuel begins to burn initially, diesel pressure rise in the cylinder is initially much faster than spark ignition.

It is this rapid pressure rise that causes the audible hammering sound, the clattering.

The diesel parts are generally much beefier to handle this rapid pressure rise "hammering". The rapid pressure rise is similar to what also occurs from detonation, but again, this is not because of detonation.

A few things to note that help here; you could get the same audible hammmering in a gasoline engine if you had say, 50 spark plugs in the chamber all going off at once instead of just one. So now instead of a tiny spark kernel evolving steadily into a fireball, we get a big fireball intially. Then the pressure rise would also be very rapid, just like a diesel, but again it would not be from detonation. Hope that make sense about the rapid pressure rise..

And 2), you can make the diesel audible hammering sound go away entirely by using a relatively new techique called pilot injection. Suddenly, your diesel is as quiet at idle as a gasoline engine. VW, M-B, some domestic trucks with common rail injection systems, all can vouch for this.

All pilot injection does is spread the heat release rate out some by injecting a tiny "pilot" portion of the main fuel pulse a bit early. Thus the overall heat release rate is spread out some, softening the pressure curve rise, and the audible hammering stops. But note that it is still 100% diesel combustion. This should prove to even the most die hard skeptic that diesel is not detonation.

We worked with a major euro OEM on pilot injection at SwRI in the mid/late 90's. We always had real time cylinder pressure monitor gear in place (with analog scopes) on the dyno test engines and could simutaneously watch the pressure curve change and hear the results in real time as we tweaked the fueling parameters. The difference is dramatic- Clatter-clatter-clatter at idle becomes dead silence. Is that thing still running? Very instructive to be able to do this, as one can imagine.

Ok, apologies for the detour here, back to the real thread. A very good thread too, again thanks Mike for feeding those of us starving for some serious tech Flame me privately please to help keep this great thread going in its intended direction.

TurboTR

 

[Alky V6]

Mike. What piston pins and rods are you running?

 

[Just a Six??]

Great thread! This may sound ignorant & I apologize but if you want to see what will break next then why not just tack weld the heads on? Very primitive but will find the next weakest link!
Good Luck with your project & again very informative for us!

 

[BlownV6]

Ok a gentle correction Not to get off topic, or that it really matters here. I do have significant experience with diesel engine combustion and controls and emissions research and am compelled to state- diesel combustion is not detonation. Repeat, not detonation.

Diesel begins to burn (ie combust normally) as soon as the fuel being sprayed into the chamber full of hot air (above the self ignition temperature of the fuel) dissipates far enough in among all the hot air in the chamber to get lean enough areas to begin to burn. And a large area of the spreading fuel front begins to do so initially.

So in the diesel an entire chamber full of very hot air is there just waiting for fuel to begin combusting; for the spark engine, a tiny spark point source is all that starts the burn going. Huge difference in what initiates the combustion and more importantly here, how much begins to burn initially.

After the flame starts the combustion is basically the same- a normal burning of the air fuel mix until the fuel is all consumed. It is not spontaneously "exploding" in uncontrolled manner, as in detonation.

It sounds like it detonates in many diesel engines at idle for example because the rapid pressure rise from the diesel combustion does "hammer" the parts more than a spark ignition. Since so much more fuel begins to burn initially, diesel pressure rise in the cylinder is initially much faster than spark ignition.

It is this rapid pressure rise that causes the audible hammering sound, the clattering.

The diesel parts are generally much beefier to handle this rapid pressure rise "hammering". The rapid pressure rise is similar to what also occurs from detonation, but again, this is not because of detonation.

A few things to note that help here; you could get the same audible hammmering in a gasoline engine if you had say, 50 spark plugs in the chamber all going off at once instead of just one. So now instead of a tiny spark kernel evolving steadily into a fireball, we get a big fireball intially. Then the pressure rise would also be very rapid, just like a diesel, but again it would not be from detonation. Hope that make sense about the rapid pressure rise..

And 2), you can make the diesel audible hammering sound go away entirely by using a relatively new techique called pilot injection. Suddenly, your diesel is as quiet at idle as a gasoline engine. VW, M-B, some domestic trucks with common rail injection systems, all can vouch for this.

All pilot injection does is spread the heat release rate out some by injecting a tiny "pilot" portion of the main fuel pulse a bit early. Thus the overall heat release rate is spread out some, softening the pressure curve rise, and the audible hammering stops. But note that it is still 100% diesel combustion. This should prove to even the most die hard skeptic that diesel is not detonation.

We worked with a major euro OEM on pilot injection at SwRI in the mid/late 90's. We always had real time cylinder pressure monitor gear in place (with analog scopes) on the dyno test engines and could simutaneously watch the pressure curve change and hear the results in real time as we tweaked the fueling parameters. The difference is dramatic- Clatter-clatter-clatter at idle becomes dead silence. Is that thing still running? Very instructive to be able to do this, as one can imagine.

Ok, apologies for the detour here, back to the real thread. A very good thread too, again thanks Mike for feeding those of us starving for some serious tech Flame me privately please to help keep this great thread going in its intended direction.

TurboTR

Many thanks for that explanation as I learned a bit and also enjoyed reading it over and over. But in layman terms I still it as close to the same as detonation , only we call it diesel combustion. I would not argue with you that you are correct and I am wrong , but I point out the following similarities.

Diesel combustion requires - oxygen , fuel , compression and heat !!

Detonation requires same - oxygen , fuel , compression and heat!!

Take away any one element from either one , and you have neither one!!

Thats the way I see it!! Mike

 

[BlownV6]

Mike. What piston pins and rods are you running?

I use JE extreme duty pistons with .990 x .180 straight wall pins

This engine has crower 6.250 custom titanium A-beam rods (dont ask)

I have 2 other short blocks I need to get to assembling that have 3.500 stroke and MASSIVE did I say Massive sets of 6.450 MGP aluminum rods.
If this head bolt thing works then I will be getting after it with the alumnium rod combination next. Mike

 

[BlownV6]

Great thread! This may sound ignorant & I apologize but if you want to see what will break next then why not just tack weld the heads on? Very primitive but will find the next weakest link!
Good Luck with your project & again very informative for us!

LOL!! No you didnt say that!! Surely you didnt!! Mike

 

[TurboTR]

But what does the spark also do to start combustion- it raises the local air temperature to (well above) the self ignition temperature of the air fuel mix. So the nearby mix begins to combust and it evolves outward from there in an ~ orderly manner (assuming no detonation Hot air, sounds like the very same mechanism to what initiates normal diesel combustion too, 'cept for a vey different source used to heat a relatively tiny area of the air to > the ignition temperature. The diesel just heats the whole volume of air using lots of compression rather than a spark.

Anyway sure, we can agree to disagree, no problem. It's not that important for most of us anyway.

Hmm, tack welding the heads on- maybe that's a potential new optional "feature" of using the aluminum block

Sometimes a high strength high, temp adhesive on a plain CU gasket sounds like a good idea to try too Something like Durabond 954 maybe? Wonder if it would hold the deck areas down between the clamp bolts..

TurboTR

 

[Turbo6Smackdown]

Then what are those head clamps rjc offers? Is that for more clamping force? And tack welding....hmmmmm Not actually a horrible idea lol. There's got to be a better way to secure heads.

 

[BlownV6]

I have a simpleton question for you guys. It'll help me better understand the dynamics you're working with here.
If you go to an exotic metal stud, and it's stronger than the block material, wouldn't that be just like trying to find a grade 8 steel bolt, to screw into a piece of aluminum? If you need to torque something that strong, aren't you going to just pull the stud right out of the block? These blocks aren't that strong.

And lastly, (of course we try to stay away from this but, it doesn't always happen that way) if you're going to get a little detonation, wouldn't you want it to go out the headgasket? Because I heard that if you seal it up too much, it'll just travel downward instead, making for a way more expensive repair. How far off am I?

Ok let me at least give you some examples , as I dont have the answers. Millions of factory produced passenger car engines use a cast iron block with aluminum heads or visa versa , pro-mod , alcohol dragster or funny car , top fuel engines use all aluminum blocks and heads with large exotic studs. Why? Because as it has evolved , that is what it takes to keep them clamped up. So there are a few examples of exotic studs pulling on weaker block material without pulling the threads out of the block.


OK once again I will just give you an example to think about in this contex. I believe that a factory stock TR or GN comes with a knock sensor , doesnt it? Why would you need a knock sensor if anytime you have detonation it going to blow out the head gaskets?? The gaskets would be the guage!! Fact is that detonation is a vary common occurance and the guage is your warning that detonation is happening so BACK OFF!! So in the case of a stock engine the factory parts are designed strong enough that they will withstand some detonation without any failures. As you begin to make modifications to the combination to make more power the factory parts are pushed futher closer to their limits. So the more power you start to make the less detonation can be tolerated by the factory parts before a failure , which normally is a head gasket. So when making more and more power , at some point you pass the safe zone of the factory parts so you either start upgrading to better parts or you have failures. Usually a failure forces a fix(upgrade).

Hope that helps you to understand things "AS I SEE THEM " Mike

 

[BlownV6]

Then what are those head clamps rjc offers? Is that for more clamping force? And tack welding....hmmmmm Not actually a horrible idea lol. There's got to be a better way to secure heads.

I believe that the RJC clamps basically provide more claming power on the head , basically the same as a stage 2 bock with 6 extra head studs per head does. Tac welding the heads would only help with the outside edges and do very little to help clamp the area between the cylinders , which is where I am having the problem. Mike

 

[dr_frankenstein]

Yupp..... Mike your a Genius.

I think its funny how many turbo guys get there panties in a bunch over the blower.

I guess there jealous of your power!

LMAO! blowers to the front please.

:biggrin:A.j.