Big Head Studs....

[Thom]

This is all probably a "how long is a piece of string?" consideration, as the elephant in the room is the bore spacing. Btw, has anyone ever tried to install auxiliary/smaller studs somewhere about halfway between main head studs, at some hypothetical place where they would not interfere with coolant flow in the block and the valvetrain? That would be some interesting project for someone with engine spares and free time.

[chris white]

You know, physics is such a bitch. Let’s get the stiffest head studs known to man and torque them up to a bizzilion ft lbs with a mls head gasket that doesn’t compress…..all on an alusil block that expands with heat. Sounds like something will eventually deform and not have a flat mating surface anymore…..hell with physics, bigger must be better right?

[Cyberpunky]

You know, physics is such a bitch. Let’s get the stiffest head studs known to man and torque them up to a bizzilion ft lbs with a mls head gasket that doesn’t compress…..all on an alusil block that expands with heat. Sounds like something will eventually deform and not have a flat mating surface anymore…..hell with physics, bigger must be better right?

pretty sure he intends to use the vulcan cut ring HG not MLS. I plan to use same HG with raceware studs torqued to about 90lbs but curious what you suggest?
Sorry but not sure what to take away from your comment as it sounds like you are saying it is all futile, because physics?

[Thom]

I think Chris is saying that the head and block need room to expand as they warm up and putting in between a steel HG torqued to hell may cause issues.

[chris white]

It’s frustrating to only have 4 studs per cylinder, putting too much pressure on the mounting points in the head will eventually flex the head and create high and low pressure spots at the head/block interface. The problem is too many variables. If you just change the head studs to stiffer (by material or size or both) you can figure out the correct torque. There is pressure sensing material you can sandwich in between the head and block and torque it and it will show the pressure distribution……when cold. Now you add in thermal expansion and it gets a little fuzzy. Traditional head gasket have a little flex that can deal with expansion cycles but MLS and ring gaskets do not - making exact torque much more critical. Too many times I hear people thinking that very high torque is better. Truly flat surfaces with the correct torque is the right answer - and the torque spec changes with every different combination of parts.

[RUG8RB8]

I truly think this is a no brainer, stick with the HMR hardware, it has the same specs as the ARP. I have both too, and will use the HMR on 3 motors. I have custom 5-Layer Cometic for each motor. There is zero chance of head lift with the “Proprietary” torque used on this setup. As Chris has mentioned, there is no more safety net, wrong tune, detonation, etc and Kaboom. However, if you want to run high boost on massive engine, This Is The Way! I Have Spoken!

[gruhsy]

Have a read
Enjoy
Supports what Chris knows

[Biggles]

Just to say that I use 9/16 head studs that were purpose made but have to torque to a min 128 lb to get a bit of stretch ( worked out by my engineer ) . Gets a bit tense with an old block .
On the flip side Turbo Tim was well over 30psi on his engine with OE head studs with out issue .

[michaelmount123]

Those that consider larger head studs need to know there's a 944 head stud that's close to a main girdle stud at the bottom of their respective threaded holes. I've seen two 944 blocks with cracked main webbing due to threaded and stressed holes being so close to one another. This issue is exacerbated with larger head studs. Frankly, I don't recall which studs are at issue, but someone please look at the main studs at the 4th main bearing, and the head studs between cylinders 3 and 4.

I never saw a need for a closed deck block, but I'd certainly be interested in cylinder distortion it may cause at the top of the stroke. I'd surely want to finish the bores after a plate is installed. I'd then heat the block with hot oil or boiling water around the cylinders to see what cylinder distortion the additional "support" may cause. Again, no personal experience, but something to consider. The 2.7/3L blocks have the best support for the cylinders, and the 2.5L blocks can be filled to improve their cylinder support.

Are the Honda guys still welding or pressing in deck supports or did they determine it was causing more problems? Patrick's engine, I believe, had a closed deck and big head studs. It failed in a big way very quickly.

MM

[RUG8RB8]

The way it should be done if you are going to do it! Michael highlighted just some of lengths taken to do things properly. On a plane, can’t go into details, but precision like this is rare and expensive. Cylinders are parallel to 0.0001”, all machining done at temp, custom one off boring plate torqued to proprietary torque during machining, everything B&B to crazy numbers that I don’t prefer to share.