The way it was explained to me...stock head bolts vs ARP head studs:

stock head bolts have more elasticity, they will actually flex and rebound

arp head studs will undergo plastic deformation..and remain deformed (they stretch and do not rebound-so when it happens one time, that's all folks )

As far as your question about swapping out head studs...it can be done with the motor in the car, but would be MUCH easier with pulling the motor...

the stronger head stud idea...yes, you could torque them down slightly more...for really extreme power, you are going to want to use larger diameter studs, not just because you can apply a greater amount of torque, but also the larger diameter will provider better clamping force over a larger surface area...so even torquing a 14mm stud to 77ft lbs is better than a standard arp stud to 77ft lbs
The best combo is a 12 or 14mm studs torqued down to 105ft lbs!!! (with use of time certs of course)

 

OverZ, the OEM head gaskets I have in front of me show quite a bit of movement across most of the cylinder bore, rather than just the bridges between them. Maybe 350zDCalb can chime in on the condition of his, as I know he just took his engine apart as well.

I am am still unclear if the cylinders are actually moving, or if the lack of adequate clamping force is causing the combustion gases to break the head gasket.

 

yes, movement looked pretty consistent. i was looking at the inner most ring going around the cylinders, and i was only missing this compound on the bridges. weird thing about it is though, i was missing more of it on the head side of the gasket than the block side. i had what appeared to be back and forth marks around the outside of the end cylinders. i need to get a microscope and look closer, but this was consistent on both head gaskets, and the marks were on the block side, not the head side.
have an easy fix for this too, lol

 

I looked at my head gaskets again today, there was unifrom wear; no ryme or reason as to any pattern, each cylinder portion of the head gasket had wear and material missing, there wasn't an area that had more wear than others...

-TODD

 

What it probably comes down to, is that upgraded studs will take people to 650-700whp, and sleeves will be required beyond that. Darton sleeves with standard ARP studs didnt start blowing gaskets until 750whp+.

 

as it is sounding to me with what todd saw on his gaskets and what i saw on mine, is that it is the head flexing between the head bolts. my fix takes care of one of these axises. either way, i feel the upgraded head studs is a good idea, but i don't think they are as much of a problem as originally thought. but anyone going 575rwhp or more, should definately go with the upgraded head studs, 1/2" or L-19.
my head gaskets showed a pretty uniform pattern that was not hard to read. there is also 3 dimpled rings that go around each cylinder. my main concern was the first ring sealing the cylinder. luckily with the block fix junk i put in there, it left alot of markings making my gaskets alot easier to read. still a microscope or magnifying glass will be needed for me to confirm exactly where or if i was getting movement on the cylinder tops.

 

That's what I had been hoping to hear. It was making me sick to think that I paid all that extra cash for the sleeves if they wouldn't atleast help avoid the head lift issue some.

I just got my SVRT 3 inch exhaust and w/g dump/relocation kit and electric water pump and thermostatic controller. Car should be done real soon, break in, then tune. Just waiting on my ATS triple disc clutch and flywheel, which has been held up in customs now for like a week (or atleast that's what I'm being told).

Just want to avoid the headlift issue this summer, cuz I'm thinking that since I got the sleeves I'll be punching this out to the 3.8 next winter and, if needed, can add the 1/2 studs then. Also, been thinking about looking into a half tub for the rear wheels. I wonder if (if half tubbed) we could fit a 335 out back.

 

awesome yancy, gotta post pics and vid when your all done!!

 

subscribing

 

subscribing for hope

 

didn't have time fri to locate the parts needed for this. will get it figured tomorrow and let everyone know by tomorrow night. i'm starting to think this should be stickied. this is something that can effect everyone that is f/i.

 

i wanted to add that since replacing my head gaskets last week i have put about 250 miles on the car so far, and once getting all the air out of the motor, i have not lost a drop yet. again, before the swap, i could only make it about 100 miles before all my water was gone, even driving like a grandma and never making it out of vacuum.
i am a pretty darn quick wrench and the swap still took me about 20 hours non-stop. i didn't even remove the exhaust manifolds or turbos or anything. i was able to lift the head and support it about 2-3" off the block and clean underneath it.
now the reason i am sharing this is to say that atleast in my situation, the heads or block were not seriously warped, creating the compromised seal of the head gasket. i got into the throttle pretty hard this weekend without loosing a drop of water, where before i would have been out of water literally a couple minutes later.
now for those of you contimplating having just your head gaskets swapped. take into account the time it takes and the labor prices. this was more of a test for me, as you should have the head and block decks atleast checked for straight. but the stock gaskets are cheap at about $30-$35 each.

 

a 14mm stud is insane, these aren't top fuel cars. if a 1/2" stud isn't can't lock the head down, you're problem lies elsewhere. a 1/2" stud can take well over 2000hp.

stock head bolts will not strech and reform. and you will not be streching 1/2" arp studs without massive detonation, enough so that you'd split the block in half first.

 

here is a pic showing the comparison of the stock, stock size arp, and then the 1/2" stud we are using from arp.

left to right-1/2" arp, stock size arp (ya it is missing the threads), stock head bolt



the 1/2" is now available through me at $250 a set. along with purchase will come the install instructions for the VQ35. machining costs will be around $300. again this is the same bolt i used and process for reaching over 170lbs torque (last known figure) and still managed to get another 1/4-1/2 turn on the nut, which could put the block thread test strength up around 200lbs torque. unfortunately i didn't have anything to read higher and my arms couldn't turn the torque wrench more, so we never even found the failure point. all we know is it is well past whatever can be tossed at it.

 

searching the country right now for the correct parts needed to complete and package the other fix i have found. should know by the end of day which way i need to go to package this in an easy diy kit.

 

Any news you can share ?

 

man i wish. i was hoping to get this sorted today, but i have gone through 2 of the biggest bolt suppliers in my town and searched about 40 pages on the net today, and nobody makes what i need. really costly to have made also. i think i have found a way to make it work from a product i can adapt. but would need to get it here from texas first.
my main concern is to keep this a relatively cheap mod, and at the same time very effective. i know those are words most of us are not used to in the f/i 350Z forum my cost target is $75, hahhaa. yes, there wasn't supposed to be more zeros in that, only $75 big ones! until i can install this for people to see, it will be pretty much worthless to try and explain. but i definately know now, it won't be easy at all to copy this trick!!

i will be posting another thread about it once it is sorted out. i feel everyone should be familiar with this mod and everyone, built motor or not, will benefit from it. heck, this can be done in the car with regular hand tools in a couple hours, even if your slow!! if you can put an intake on, you can do this.

 

You got me now !!!! I thought it was going to be something to do with the head gaskets . I couldnt amagine what it could be to help with the head lifting problem . And only take a couple hours .

 

lol. it is out of the box thinking my friend. this is why it would be hard to explain without pics. trust me, it is a solid solution. just so happens the fix is easily accessible.

 

Royce so..not sure if you meant to agree with me or you were saying that the stock head studs do not deform..this is not my opinion , this is fact:

the stock head bolts are designed to be able to flex and reform a bit..Talk with some of the engineers at ARP and they will explain how the arp studs differ from stock, in that they do not rebound ..this is not an issue if you are running moderate power, but when pushing these motors to say, 550 and beyond, a larger diameter stud (or stronger stud) will help clamp the head with greater force...

12mm should suffice for high power, but I am using 14mm in my motor..I'm sure this is overkill, but that is the way I roll .

also, your claim of how a 12mm stud can take over 2000hp..this is a generalization you can't make regarding all motors...the head stud pattern differs from motor to motor...the vq head utilizes 8 studs holding it to the block...the location of the studs isn't as beneficial in overall clamping force as say some american motors (that may have 3 studs surrounding each cylinder). The larger the stud, the more surface area that it will cover (and clamp)- the greater it will uniformly hold the head... we are limited at how large we can go with the head studs, because we begin to run out of material in the block to surround the stud Even at 14mm, there is plenty of "meat" holding the stud in place

We will offer a 12mm head stud upgrade, with use of time certs (these will allow the larger stud to clamp into a larger surface area--reducing any chance of stripping out of the aluminum block (again, probably overkill for torquing to 95-100ft lbs..but also an extra safety measure to prevent pulling your motor out later than sooner )

-TODD