I have been contemplating buiding an engine with forged internals to get this nagging fear out of ny head whenever I am running the car hard that it is going to blow. So I have been following some of the recent builds and some questions have come up specially with phunk's head gasket issue.

There have been comments about the torque on the studs and maybe the need to retorque. First which studs are we talking about main or head? I understand the possibility of them losing their holding torque but why? You don't have to go in and retorque the studs on your new engine when you buy a new car, I know it was not originally FI but my 300ZX TT was and has not had the studs retorqued in 15 years and 97K miles.

Is this possibilty a parts issue as in studs used or is it a build procedure that differs? Should the engine be allow to sit and then retorqued before final install?

Not knowledgable in engine builds so just throwing some questions out there.

 

ARP are the studs.....main and head. The studs themselves are usually installed finger tight and then there is a nut that goes on the top....different from the stocker that has the bolt and nut attached as one piece like in most factory motors. With the use of the ARP lube and the engine having to go through a few heat cycles I can see how the studs and nuts might back off a little and lose a few ft/lbs.

 

It just seems like there would be a way to make sure they do not back out, if that is the case why don't they make aftermarket studs like the stock ones if they keep torque.

Or design it with a cotter pin to keep them from backing out, I don't know something where this would nto be a concern, you should be able to build the engine and not worry about it.

 

The cotter pin would keep the nut from backing out off the stud but not the stud itself. They can only be installed finger tight...any tighter and you risk cracking or putting too much stress on the block itself. With the factory bolts they don't bottom out when they are torqued down with the cylinder head....the ARP studs do so you can't tighten them into the block. Really there is no way from keeping the stud from backing out slightly.

 

Hmmm, thanks for info, just doesn't seem like a sophisticated way to build the engine and make sure it stays together, all that money riding on 500 bucks worth of studs.

What is the reason for the ARP studs? I assume strength? If so is it for tensile or shear?

 

With the ARP's it is tensile.....less stretch under load and designed for a better head gasket seal and more even cylinder head clamping under boost.

 

Threads are like springs. They push against each other and stay tight via friction.

After heating up and cooling many times, the friction or spring tension changes....mostly weakens.

Steel threads against Aluminum threads is worse cause the metals expand and contract differently.

By re-torquing the bolts or threaded rods, you maintain the engineered clamping force demanded or specified by the engineering of the engine.

After you change your headgaskets a couple of times, cause they failed, you learn to appreciate this requirement.

 

So if you retorque them what keeps them from losening again, does this become a regular thing you will have to do.

I am just asking so much becuase in jet engines we have bolts that go thorugh extreme temparatures and material expansions and last for many flying hours and years.

 

By measuring torque you are actually indirectly measuring the "tension". A typical torque recording can have as much as a 25% error rate against the desired tension. A better measurement of tension can be determined by ultrasonic measuring devices, not torque wrenches.

Re-torquing assumes that the metals involved have stabilized relative to their tension characteristics.

Why don't auto or aircraft engines require re-torquing? Because the engine was designed to allow for the deviation of the tension that is characteristic of the fasteners.

(I paid my way through college as a toolmaker. Now I'm and Accountant)

 

I think once the engine oil has a chance to flush out the ARP lube from the nut/stud at the top it should increase the frictional retention of the parts....hopefully.

 

Exactly, and actually we do retorque on aircraft engines as part of the build process, usually the parts are torqued and then retorqued later before the next higher assembly build, this gives the parts a chance to conform to their applied torque and then the retorque should hold as the parts should not settle/stretch/move more.

 

What exactly has to be done to retorque? Do you have to take the motor apart in order to get this done? Assuming you don't know how to do this yourself, how much would a shop charge to do this job? I am currently building my bottom end and would like to avoid blowing a head gasket.

 

I think you have to take the engine out once it has been installed, I have no clue.

Maybe part of the build should be, it mighth be, to retorque them prior to install of the engine in the car if this is possible, again no clue if possible.

 

If this is the case, that would suck ****! That would be at least another $1400 job.

 

You are very wise to ask these questions.

The head bolts can be accessed under the Rocker Covers.

I would strongly suggest that you get a SHOP MANUAL and read about it so no shop will take advantage of you. I downloaded my manual from the internet but I can't remember where. You can purchase the CD on eBay.

I do not know what a shop would charge you to do this.

It makes sense that if you are going to operate an engine at much higher pressures and temperatures than it was designed for, that you insure that everything is tight.

Pulling the engine is not required.
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Any guestimates of how many hours it would take to retorque and get the job done?

 

It might be easier done than you think.

Gus (Westpak) offered a good point. Re-torquing could take place before the final installation. I honestly do not know.

Depending on the fastener, whether it is a stock head bolt or aftermarket stud and nut, the manufacturer will supply you with very specific instructions as to the proper procedure. Sometimes it is as simple as torquing the fastener in incremental steps to higher and higher settings.
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[QUOTE=westpak]I have been contemplating buiding an engine with forged internals to get this nagging fear out of ny head whenever I am running the car hard that it is going to blow. So I have been following some of the recent builds and some questions have come up specially with phunk's head gasket issue.

QUOTE]


ask charles about the head gasket issue...i don't think it exists...meaning i don't think it was the issue at all

 

This seems kinda of weird. You would assume they would get loose after the motor has been operating for some period of time.

 

If I remeber correctly the head bolts are hidden underneath the cams. So....the cams would have to come out but the engine would not....still alot of work.