headstuds stick out too far
 

Hi guys, first of all, humble apologies for being a low-level contributor on the board- my knowledge simply pales in comparison the the average Pelican, and I've always been of the school that says it's better to remain silent and let people think you're an idiot than to open your mouth and prove it unequivocally!

Here's my issue:
I've begun re-assembling my '76 2.7 that I had Dan Hall's in Portland install case savers into. Wayne's book says to install the head studs to a depth of 135mm from the machined flat surrounding the stud threads. Unfortunately, my studs all bottom out at right around 137mm from the cylinder spigot face.

Here's my question:
What now? Can I get away with simply using an extra washer under each barrel nut to take up that slack? Is this normal? Are case savers blind or are they an open cylinder and that's just the depth of my stud holes? (each one measures around 26.8mm deep)

I'm on a tight budget and I'm not building a highly-stressed race car, so I figured I could just re-use my old steel head studs (which are in nearly perfect shape)

Thank you in advance for your thoughts...

Did they actually bottom out in the case or just the casesaver? The inserts get tight when you reach the bottom but you just crank it past and set them at the correct depth. The case hole should go a bit deeper than the saver and I bet it does otherwise it would be hard to bottom tap it.

The last 2 or 3mm's on mine where tight. I used the snapon collet to install them, I don't think the double nut trick would work to hold the stud.

Thank you tons for the replies guys!

Craig, I think the stud bottomed out in the case- I put as much torque on it as I felt comfortable with. It's kind of hard to tell, but I think the hole ends right after the insert: http://www.curtfranklincreative.com/...case_saver.jpg

4sd, I don't have the collet tool, but I used a barrel nut and a bolt of appropriate size- there's no way this baby will slip because it acts just like a cap nut, but it's easy to take off the stud without fear of damage once you're done. Here's my tool, just in case someone else can use the idea:
http://www.curtfranklincreative.com/...stall_tool.jpg

I did go back and try tightening the stud a little more. It did go in just a wee bit, but it felt like the insert was moving further into the case rather than the stud moving further into the insert, so I decided to pull the stud out and do some more double-checking- and the case-saver started backing out of the case...
http://www.curtfranklincreative.com/...acking_out.jpg
I'm positive I didn't strip the case saver out of the case, but now I'm concerned that even if I screw it all back in to where it meets mild resistance, that maybe this case saver won't hold? I thought that once in, case savers were supposed to be nearly impossible to remove? BTW, since I was trying to test fit this stuff, I have not used the Locktite 271 on these threads yet...

I wouldn't be afraid to just screw that case saver back in with some red locktite. The bottom studs are the ones that pull so if that stud is a top one there is even less to worry about. There are nuts you can use instead of the barrell nuts that will work even with the studs too high. Others (who are more knowledgable) can tell you where to get them. I suspect that ARP studs use such nuts. I would rather not use extra washers as you would be intoducing a new variable in the clamping system. Extra washers might allow the nuts to back off easier.

-Andy

Thanks Andy- I used the same logic to come to the same conclusion, and having someone concur goes a long ways towards making me feel a little better about my choice! I went ahead and gingerly tightened each stud down to about 139mm and figured that I might be able to find some solid 5mm thick stainless steel spacers to replace the stock washers, but I do like your idea better- I'll do a search on that topic and post what I discover (unless a simple search turns up a lot more solutions to this problem than I initially found)... I think Henry's head stud sets use a similar star-shaped nut (if my budget wasn't so skinny, I would have gone that way from the start)

Curt

Raceware makes a nut that will work. They're sold here for $170 a set. Those case savers need red loctite. You can also measure the depth of the hole to see if you are bottoming out.

Excellent, thanks for the tip!

I did manage to get the red loctite on every stud except for the one that started pulling the case saver out... per Andy's suggestion, I went ahead and put some loctite onto that case saver before threading it back in last night. I'm not sure how long it takes for that to fully set up, but I would think that by tonight it should be strong enough to back that last stud out and re-apply the loctite to the stud itself.

I had also measured the depth of the hole (26.8mm to the very bottom on average), and the holes aren't deep enough to even get the studs another 4mm in. It all seems very odd to me- like Porsche didn't drill the holes deep enough to meet the spec in the first place.

Possibly the wrong case saver's were used. On one of your photos it looks like the case saver has a closed bottom. All the ones I've seen are hollow and about 25 - 30 mm long. The hole in the case before the saver is installed is about 36 - 37mm deep. I'm only getting this data from the last few 7R case's I've had done at Competition Engineering and Ollie's.

That would explain a lot here... I had wondered about the case savers themselves (see the third paragraph in my original post asking about whether case savers were cylindrical or blind).

Virtually all of the threads are engaged, so will I be getting the full "strength value" from the case savers that they installed? Or do I need to send the cases back and have different case savers installed? Are these shorter case savers likely to just pull out? Is there enough benefit to be gained to make the extra effort, time and money worth while? (they installed the case savers over a year ago and I've finally gotten the time to assemble it only recently)

The shop I went to was recommended by a fellow pelican who was happy with their work (and of course, their pricing), so I figured they knew what they were doing. I still need to have the heads gone through- I guess I'll be using a different shop for that work (Rothsport is only 25 minutes from my house). This process is becoming a little discouraging...

Curt

Curt, If you are only 25 min. from Jeff's, take the case over to him and see what he thinks.

This is the timecert to the left in the picture with the original cutting and installing tools. The flat guide is for do it yourself VW man.
Bruce

http://forums.pelicanparts.com/uploa...1280258190.jpg

Hey Bruce, It's nice to see the profile of the Timecert in the documentation shown in your photo- it looks like my machine shop did indeed use the case-saver product (my inserts did not have the shoulder that the Timecerts seem to have), even if it's not the case saver product normally used for this application.

Mark, I appreciate the advice- I think I'll go ahead and take the case to Jeff & Steve and see what they think- I'll drop off my heads at the same time (having Rothsport do my heads is my gift to myself to celebrate my 50th birthday!)

Curt

You know you have to insert all 24 on a mag case because the top ones pull too
Bruce

Thanks for the double-check Bruce - not doing all 24 is a mistake I could easily have made, but luckily, didn't.

Hopefully what has been done already will be just fine- it's bound to be stronger than the original was in spite of not using the longer inserts, especially in light of the fact that I already have the 11-blade alternator fan, and I have a back-dated exhaust system to replace the original thermal reactors... living in the mild Pacific Northwest will no doubt help too...

Curt

okay- I just chatted with Jeff at Rothsport- with my relatively mild engine, it sounds like I should be okay with my head studs as long as I can get the spacing figured out (ideally a single spacer, but it sounds like multiple washers might also work- as Bruce had suggested to me earlier)

Heads will go for rebuilding either tomorrow or Monday depending on when I can get the cam towers off and clean 'em up a bit... ... thank you guys for your input- I'm feeling a lot better about this situation!

Curt

I'd use flange nuts.

You can get them with the required 10mm thread, and a 17mm socket wrench size. That way, as long as the thread on your studs is still below the level of the stock washer (or a bit more would be better), you can screw these nuts on without pushing an Allen tool out of its barrel nut socket. With a socket, especially a deep well one, you won't have issues tightening it up. And you won't be stacking washers.

Plus these nuts let a bit more air flow than a barrel nut would.

I bought a bag of them from Maryland Metric some while back - they had a minimum order, but the overall cost was still modest. I couldn't see paying the small fortune Raceware wanted for their version of this nut. But maybe someone sells these in lots of 24?

I don't think Henry's nuts would work. Part of his system is to use a finer thread on the nut end of the stud for better torque control - which is what Porsche did at some point (3.0?) with the case through bolts.

Thanks for the suggestion Walt, I'd really prefer to not stack washers, and it seems to me that the more threads engaged, the better. I think that while my heads are being done, I'll search the local area for those nuts first, since I know very little about how to spec nuts... I may be able to take a through-bolt cap nut with me and say "I want 24 of these, but not capped". Jeff Gamroth suggested that I have a machine shop make a new set of 6mm thick washers to make up the difference, but if I could find the appropriate nuts, it'd likely be a cheaper and better solution- then I would just use the stock washers.

I know our host sells flange nuts for this application too, so that might be a smart way for me to go.

Curt

Curt

On reflection, I realized that the flange nuts for 10mm stud application have 15mm wrench size heads. 17mm is the normal 10mm nut size, and you'd have issues getting a 17mm socket down there. But none with a 15. If PP sells them, problem solved.

I think the grade of nut (assuming you purchase from a reputable seller) is not important. 8.8 ought to be plenty good. It is the 120 or so mm long stud between fastenerswhose stretch and yield strength that is at issue, is it not?

For what it is worth, I don't think the stock barrel nuts are made of any special steel. I can drill through them crosswise without too much fuss, and a chisel and punch put a decent dent in them.

This is good, because if your stud sticks up too high, and you tighten the barrel nut down pretty tight and then have the Allen pushed out, you have the dickens of a time getting the barrel nut back off. Distorting its tippy-top helps give more Allen grip surface, which is nice given that it is down that deep dark hole.

I don't think a 12.9 nut would be this soft, but I might be wrong about that.

In any case, Maryland Metric's on-line catalog did not give the usual 8.8/12.9 strengths for its nuts.

Thanks Walt- I'll go see if I can find a set of 8.8-grade flange nuts to fit on a 10mm x 1.0 with 15mm flats (I'm just guessing about the thread pitch- which I'd definitely want to verify)... what you're describing sounds very much like a set of cylinder base nuts for a Yamaha YZ250... I might even have a few of those laying around to use as an example piece (assuming it fits)... funny- those nuts on my bikes never rusted regardless of the sloppy wet conditions I rode (but then I suppose they weren't subjected to the heat that the barrel nuts have to endure either)

I wonder why Porsche chose to use the barrel nuts instead of the flange nuts in the first place? Maybe they got a volume discount for also buying them for that row of barrel nuts on the cam tower? For their aerodynamic qualities in a high-heat area? because a cylindrical nut just looks better in the holes?

Curt

Stock head stud threads are M10x1.5

Why barrel nuts and not flange nuts?
 

The barrels seem like the 1964 solution to not having enough room for a 17mm socket of standard OD.

Witness the three barrel nuts on each cam carrier, where the semi-circular relief is tight.

So perhaps reduced head flange nuts were not available in 1964 or earlier when the engineers for the 911 gained their knowledge of such details? Or it wasn't clear at that time that they were as strong? Or something.

I started wrenching on a motor scooter in maybe 1953 or 4, but I didn't start contemplating strengths of materials and similar engineer-like things until the late 1980s when I read Carroll Smith's Nuts and Bolts book. So I have no clue as to when flange nuts came into play in any mechanical field.

I do know that some fastener parts, which Smith declared to be worthless, are in use to this day. For instance, split washers. Smith ridicules the notion that these will a) if the fastener elongates under load, keep the clamping force which the original stretch gave, or b) did their cut endges into the nut or bolt head on one side, and the clamped piece on the other side, so as to provide mechanical resistance to loosening of the fastener beyond that provided by the clamping force.

Of course, he didn't think Schnorr washers were useful either.

So maybe engineers, like the rest of us, focus on what hasn't worked, or what they think can be made to work better, and forget about optimizing anything else. Like the barrel nuts: if everything is right, they certainly work. Only with the ever increasing HP/liter has anyone thought that the reduced impeding of cylinder head air flow of a barrel nut compared with a flange nut was worth thinking about. And maybe that is negligible anyway?

Ah, thanks for the correction Walt- that'll make things much faster and easier to either find locally or add it to my "hurry up and order it from PP" list.

Whatever the reason was for barrel nuts, I guess Porsche did the best anyone could have done in 1964- certainly better than I would have done at that time!

Speaking of Schnorr washers, what do you think of the idea of using those under the head nuts in stead of the stock flat washers (assuming I can find some with the correct dimensions)? Or is that overkill and the main reason for re-torquing the heads has more to do with the "gasket thingies" settling in?

What about this washer? Its a little large for the OD but you can turn them down to 21mm so they fit, they are about 2mm thicker than the originals.

McMaster-Carr

I like having extra options! Thanks Craig!

Curt

Another option (albeit more expensive than just new nuts) is Supertec headstuds.
they also have an open-ended nut.
Good quality stuff.
With Supertec studs you don't need to worry about how much stud is sticking out of the case. 135, 137, 145, all good, screw in and fasten.