blown 944

I have read quite a few older threads regarding head studs. Most had no resolution (pet peeve)

My current engine is having some head lift problems at anything over 21-22psi. The added compression must be creating quite a bit more cylinder pressure than the stock studs can handle. The current setup is stock turbo studs (out of other engine which could handle quite a bit more boost) with cometic MLS.

I have been reading that the DSM guys are having to opt for an expensive stud for their high compression builds.

So...I am wondering, what is the current top dog head stud available? Would a set of new factory studs be an improvement?

The plan at the moment is to have the head o-ringed and use a widefire along with new studs. I just want to get a proven part.

TIA

pole position

Performance Developments in Costa Mesa/ CA used to offer a higher tensile strengh stud Afaik you had to redrill/tap for the larger diameter. CEP. I believe offers similar or the same.

Raceware/ARP I am not sure about if the really are a improvement over a new stock stud.

m73m95

Could the problem be the MLS gasket? I thought there were some known weaknesses with that?

More compression yes, but you've also run much higher boost than 22lbs before, with no issues....

fortysixandtwo

I'm not sure about PD having head studs, but Heritage makes a larger diameter stud, that requires the block to be drilled and re-tapped. Honestly, I think the benefit of this is debatable.

Raceware studs are used on some very high horsepower cars. I know some that are in the 500+rwhp range, that have several race seasons on the same studs.

pole position

I am not questioning the quality of Raceware but myself and others had less than satisfactory results in a 951 engine and again, myself and others went back to new stock. Same with a cometic headgasket, some have success, some don't .

There should be plenty of info in the archives.

333pg333

Why do you think it's debatable?

JET951

It could possibly be that even though you are going to a larger stud which may allow more clamping force to be applied, the problem would then be transferred to the alloy block. The thread in the block ( being alloy) may only permit a certain percentage of extra clamping force before it pulls the threads. Certainly something to think about.
On that subject I do remember Adam talking about drilling the entire block so that it's one length of bolt holding the head and crankshaft girdle. I'm not convinced that this would be a good idea either as drilling the block may cause weaknesses.
Sean

Van

I'm curious... people call it "head stud stretch"... But isn't it also likely that either the aluminum threads in the block are moving and/or the head is warping a little bit due to the high pressures? I guess what I'm asking is, are you certain that the steel studs are the weakest link.

blown 944

Because they have been having the same problem under similar conditions and they have found a solution. I don't just look at what one particular engine does to find my answers,especially since there aren't many high compression high boost 944t engines running around. At least not that I've seen.

Don't get me wrong, I'm sure that the cure can be found within this group. I just read and spoke to a friend about them and thought that there may be something to it.

I am leaning towards the old studs being a problem or the threads in the block (hope not)

blown 944

Thank you, I'll look into them. And thanks for your thought on the factory stud. Obviously, I'll have to make a decision, maybe it'll be best to start with new factory studs and then go to the race ware and if needed then try the larger diameter.

I will be building another engine shortly and I'd like to get this sorted on this one.

blown 944

Mark, I've already had a composite on here with the same results. The difference is that with the cometic I can just turn the boost down and still run it, the composite meant a tow home :-).

mudbuddha

Sid- I am using MLS w/ stock (new) studs and have taken it up to 21 psi with no issues. New studs and of course the preresquisite flat, smooth surfaced head should hold up fine.

blown 944

Thanks for your experience. I think the compression and added head flow may change things a little bit though. I had no problems with the low compression at very high boost. I am flowing the same amount of air at 20 psi with this engine that I was at 25 psi with the last engine measured at the maf. It may end up that I am just limited but I'd like to see if I can solve it.

I did just go and pull the cam tower and re-torqued the nuts and a couple were not at 85# where most were. I went ahead and backed them all off and now I'm going to do a full re-torque after adding some oil to the threads. I doubt this is going to solve anything but it isn't taking too much work either.

DLS

Are you sure it´s head lift and not hot spots in the head?
Maybe you are at the same point were corleone needed to do some special mods to his head?
since i went to e85 and higher compression I've had a lot of trouble with pressurising the coolant.
Now i´m gonna try arp studs and mount o-rings in the block ( before i only run with the groove in the block) and do some more steam vents in the head.
and if that doesn´t work backing of a little on the timing.

blown 944

It is possible, the only mod I have to coolant flow currently is the tapped port in the rear of the head and an additional coolant catch can. I'm not sure how far I'm going to go with this engine...but it is a guinea pig setup so.....

I will be curious of your results.

We have pulled the timing down quite a bit already