Goin' w/ studs for the head on a 606 - PeachParts Mercedes-Benz Forum

96E300D · #1 11-01-2005, 04:58 PM

After going through the threads on blown head gaskets, it seems to me that one way to circumvent another head gasket replacement is to replace the bolts with studs. After calling ARP bolts, they wanted to know the hole depth, thread depth, counter bore and column height. If anyone can verify what I've come up with for the first three that'd be great. Hole depth=40mm, thread depth=25mm and counter bore=9mm. The head's at the machine shop, so I'll have to wait on column height till tomorrow. The only issue I see in terms of assembly is the oil cooler line that "pulled out", so I may have to pull the oil filter canister to get that back in.
Matt

Hit Man X · #2 11-01-2005, 05:18 PM

Any clue what they plan to charge for custom studs? Are you going with stock diameter or larger (more clamping force)?

96E300D · #3 11-01-2005, 05:45 PM

As soon as I get the dimensions from the head I'll know what the cost of the studs will be. I'll be keeping it simple in terms of staying with the original 10mm/1.5 threads.
Matt

Hit Man X · #4 11-01-2005, 05:47 PM

Excellent. If these aren't super spendy, I'll probably do them on the 603 when I swap heads (along with a copper gasket).

Do keep us posted!

TimFreeh · #5 11-01-2005, 08:38 PM

Is a stud stronger than a bolt? If so why?

Nate · #6 11-01-2005, 08:46 PM

I think the reason they're used is so that when take the heads off, you dont wear the holes in the irreplaceable block, but in the replaceable studs

~Nate

boneheaddoctor · #7 11-01-2005, 09:27 PM

Quote:

Originally Posted by TimFreeh

Is a stud stronger than a bolt? If so why?

Head bolts are typically torque to yield (stretch)

Studs you torque to spec....(they don't stretch)

Red Pike · #8 11-01-2005, 09:48 PM

Any torquing will result in some stretch. I would suggest getting these studs with an interference fit--very close tolerance, harder to put in but won't back out as you remove the nuts...

You want the interference fit on the block side only, obviously.

boneheaddoctor · #9 11-01-2005, 09:51 PM

Quote:

Originally Posted by Red Pike

Any torquing will result in some stretch. I would suggest getting these studs with an interference fit--very close tolerance, harder to put in but won't back out as you remove the nuts...

You want the interference fit on the block side only, obviously.

True but the stretch doesn't become a major factor in determining when its tourqued correctly.

Red Pike · #10 11-01-2005, 10:03 PM

The engines I usually work on have studs holding on the cylinder heads. These are waisted studs, and are torqued on, preferably, using hydraulic jacks threaded onto the studs above the nuts--and about 600 bar hydraulic pressure is used to stretch the studs. Then the nuts are snugged up by hand and with a short (6 inch) "tolly bar." This is done simultaneously to all 4 or 6 studs, depending on the engine. Alternatively, the nuts can be tightened by bringing them all down even and snug by hand, and then using a large wrench and a 16 pound fine precision adjustment instrument (sledgehammer) to move each nut an additional two flats (120 degrees) to achieve the proper torque.

Oh, these engines have one head per cylinder, and each cylinder (bore 840-900 mm, stroke 1.5-2 m) puts out 3,000 to 5,000 hp. I have an injector tip on my desk, as a pencil holder, which is attached to the injector body by 12 cap screws, each torqued to 90 n-m.

t walgamuth · #11 11-01-2005, 11:05 PM

that studs are used where an engine is anticipated to be torn down a lot. they cost more and therefore arent used on normal low cost production car engines.

like race cars, marine diesels, etc. ( maybe 603s are a good candidate too)

tom w

TimFreeh · #12 11-02-2005, 07:41 AM

Quote:

Originally Posted by boneheaddoctor

True but the stretch doesn't become a major factor in determining when its tourqued correctly.

I don't think this is correct - as I understand it stretch bolts are actually tightned until they deform to a specified standard. The amount of deformation is not measured directly but the tightening procedures are supposed to ensure than the bolt does actually deform a little bit on the final torque appplication. This is supposed to give the bolts better holding power than non stretch bolts. I can tell you that I've tightend lots of head bolts of both stretch and non stretch varities and the amount of torque you have to apply to the stretch bolts is at least an order of magnitude higher than the non stretch bolts. It's pretty easy for me to believe that the stretch bolts are being deformed when I'm done tightening them - and my arm/shoulder is plenty sore the next morning.

It's still not clear to me that studs are stronger or provide more clamping power than the factory MB stretch bolts.

t walgamuth · #13 11-02-2005, 08:06 AM

that stretch bolts pull any stronger. the reason for them is that the method provides a more accurate amount of pull on the head than using standard torque values. standard torque values will be affected by lubrication on the threads dirt etc. the stretch bolts are forced into their plastic mode. there is only so much plastic mode available to work with before you run out and the bolt begins to fail or gets too long to use without bottoming out. hence the measuring methods to determine if they can be reused.

i dont think that studs will provide any more pull either, but will not degrade as much in multiple removals etc.

they also are more common with aluminmum blocks, i think, where degradation of the threads in the block are a serious consideration. (remember how the little bolts in the thermostat housing like to bring out material with them? imagine how you would feel if this happened to your, say, ferrari? or porsche?) both of those aluminum block engines have studs instead of bolts.

now when you use studs you probably can use one of the lock tite products or similar. when you glue them in i suspect the holding power might go up some, but not a lot. i would guess less than 5%. this is pure speculation on my part. but in buildings you can instert steel rods into concrete with types of epoxy and they will hold tremendous amounts of weight in pure tension.

the threads on a bolt are designed to develop the full strength of the steel in the shank. in fact if you measure the contact area of the threads on a bolt you will find that it matches the area in the shank of the bolt. i learned this from my non college educated father. so unless you make more thread area available in the block to avail more holding power, then use stronger bolts i dont see studs developing much more pull. this could be done by drilling out the threads and re threading larger. is there enough block area there to support larger threads? maybe, but not for sure. this is why drag racers and the like blow engines up. they go ahead and drill things out and such and take the risk in the search for more power. do you want to take chances ike this in your street car? probably not. blowing up on the dragstrip is one thing, blowing up on the highway on the way to grandmas with the whole family in the car is another thing!

bottom line: i suspect that studs wont help much in the case of 603s. probably not enough to justify the cost. what does the supplier say about them? and i would call the mfgr of them and talk to the engineer on staff. i have found that engineers will give me the straight poop on products even when it may mean a loss to his company. as opposed to sales staff who simply need to sell the product.

tom w

boneheaddoctor · #14 11-02-2005, 08:13 AM

They do work better (studs) but the question is in this application would you really know?

A corelation is this....true its a gasser but its a gasser that routinely sees 300K miles of abuse in many cases...

Honda...THe tuner crowd takes these 1.6 liter engines , puts forged pistons and stronger connecting rods...cometic head gaskets (think Copper) ARP studs adn some people pull 25 lbs boost on racing fuel with no head walk or gasket failure...You can't to that with stock torque to yeild head bolts...BUt then we are talking 400-800 HP out of a 1.6 liter 4 cylinder that had 80-160 hp stock....

t walgamuth · #15 11-02-2005, 08:28 AM

they glue the studs in?
and how long do these rice burning grenades last?

tom w