I have run into a few problems. I keep busting head bolts. I have busted 4 so far. I dont get it. I bought all new ones. I have never seen anything like this in my life. I can get them torqued to 45 ft pound and then trying to go for 50 the bolts twist in two. The service manual clearly states 54 foot pounds. I have tried three different torque wrenches. They are not breaking in the same holes everytime. I ordered a stud kit and will go that route. I will keep everyone posted.

 

I can tear this motor down in about 2 and a half hours. lol

 

Snappin at 50 lbs? We are stuck with garbage. My old VW was 63 plus a half turn. when I built The block I upgraded to ARP headstuds.

 

That is strange in deed... i've torn the 4G94 down many times and actually never had head bolt/rod bolt problems. In fact i actually set the head bolts to 65ft lbs when i retorque them about a week after doing the initial torque. I've heard mitsu went to some lesser grade bolts in 03 so maybe this is the result... check with the dealer for an updated torque spec... they may have lowered it do to this fact. It's better that you are going to studs though... leaves a better future open as far as boosting goes. Nice write up by the way keep it going... many need this kind of info!

 

I did a Google search on "torque to yield" and found the following....

TORQUE - TO - YIELD

CYLINDER HEAD BOLTS

Bolt Performance

Under the application of load, all bolts exhibit four main phases; the elastic phase, the plastic phase, the yield point and the shear point. In the elastic phase a bolt will stretch under tension but return to its original length when the load is removed. As we continue to apply load the bolt reaches the plastic phase from which it can no longer recover to its original length and is now permanently stretched, The point that separates the elastic phase from the plastic phase is called the yield point of the bolt. Finally, if we continue to apply load the shear point is reached and the bolt material wastes and breaks.

Torque to yield head bolts

Torque to yield (TTY) bolts, also commonly referred to as angle torque or stretch bolts, are used in many of today's modern engines predominantly for cylinder head bolts but also main bearing and big end caps.

Compared to conventional type bolts, TTY bolts offer the engine manufacturer a number of advantages including greater flexibility of design, reductions in component costs, more accurate assembly and reliability of seal. Engines designed utilising TTY head bolts require fewer head bolts to achieve the desired clamping loads then those using conventional bolts. With fewer bolts the engine manufacturer has more flexibility in cylinder head and block design as well as reducing the cost of the engine.

Whilst TTY bolts are attractive to the engine manufacturer, there are disadvantages to the engine repairer. For the most of us it would be unthinkable to replace a conventional head bolt unless the bolt was damaged, i.e. stripped threads, the bolt head was rounded off, the shank was severely corroded or pitted.

Conventional head bolts simply just did not wear out. Torque to yield head bolts however, by the very nature of their design, do wear out and should NEVER be reused.

Installing Cylinder Head Bolts (General Information)

When installing cylinder head bolts (and any bolt that has to be tightened to a specified torque), the thread of the bolt and under the head of the bolt should be oiled before assembly. This will give 2 - 3 times the loading over a dry assembly. Where head bolts penetrate into the water jacket, coat the threads with a non hardening sealant.

Installing TTY Bolts

TTY head bolts are also tightened in a series of stages and in sequence, however they are not tightened to a predetermined torque, they are tightened through a series of specified angles. This data is provided by the engine manufacturer and should always be adhered to. While the first step in the tightening process is normally stated as a torque figure it is done so only to provide a uniform baseline from which the true load is then applied. This is commonly referred to as a pre-load or snug torque. A typical tightening specification would look as follows:

uniformly tighten in sequence in several passes to 78Nm

tighten in sequence 90°

tighten in sequence a further 90°

This procedure ensures that friction does not cause an uneven bolt loading and that the correct high tension is achieved every time during assembly. It is essential that a quality wrench with an accurate angle gauge be used to achieve the correct angles of turn of the tightening process.

Unlike a conventional bolt, TTY bolts are tightened beyond their elastic range past their yield point from which the bolt material can recover to its original length, and into the plastic phase of the bolt material. The bolt is permanently stretched and for this reason should not be reused. The reliability of these bolts once stretched is greatly reduced. If they are reused, they are permanently stretched further a second or third time. It is also for this reason why you should never retorque a torque to yield bolt.

Some engine manufactures provide a measurement within which a head bolt may be reused, however the age and history of the bolt is not taken into account. The bolt may well be within specification to pass a simple measurement test but the bolt could be very close to its shear point. Only one failed bolt can result in serious combustion leakage. The cost of a new set of TTY bolts is well justified when compared to the cost of having to repair an engine for the second time because of insufficient clamping load due to bolt fatigue.

This information was supplied by Gasmiser, suppliers of Gasmiser Head Bolts.

 

i have found that there are many mistakes in the service manual, so maybe its not suppose to be 54ft-lb? just a suggestion.

 

yea things are weird liek that, ask mitsu about it when i completely replaced my head it was an 02 head, but i have an 03, so the guys put in the original 03 crank sensor, but it would turn over, they just pulled it out and put on the 02 sensor worked fine, weird, and now theres a crank sensor warning now all the time, i will NEVER get rid of my CEL lol

 

That was very interesting Dale. I should of added this before but when the piston exploded it made hundreds off small pieces. I posted some pics of them before. I also wanted to note that if you are doing this piston swap like I did without removing the engine check the intake very carefully there were alot of piston fragments that were stuck up in there. DOnt want to bend a valve right off the bat! I will get my stud kit Tuesday. SHould be alot stronger. It also should be easy to get the correct torque reading. Dale would the torque specs be different with the stud kit, Since there wont be any give in the bolt?

 

I'm not a mechanic. I just wanted to post some info about current technology with headbolts because I thought it might apply to your situation. I would expect the new kit to have very specific instructions and if it didn't I'd contact the company and ask.

 

with studs, you want to make sure the hole is EXTRA clean, then, cleaner than that. Screw the stud all the way in, then back it out a half to 3/4 of a turn. (you don't want the stud bottomed out) then put the head on, thread on the nuts, and torque them down in sequence in 20lb incriments. Just use the stock final torque spec, or a little more. 60lbs sounds good. Remember to let it sit overnight, then check the torque again the next morning.

 

THe service manual says to set the initial torgue at 20lb increments to 54lbs. Then looses and tighten to 20lbs put a paint mark and tighten in 1/4 turn increments to 90 to 100 degrees. That spec was for factory bolts. Will the procedure work for the aftermarket studs. Since the factory bolts flex and the stus do not.

 

i would assume that they would be the same specs because they should be the same size/length etc, you might just want to bump it up to 60, i think that would be fine, plus boe said he retorqued it to 65

 

agent, two questions since I'm doing the same thing right now (bleah). 1. Any tips on removing the oil pan? Did you have to rest the tranny on a stand or was it ok on its own? And 2. What stud kit (I'm assuming you ordered an ARP kit of some sort) are you going to be using? I'd like to do that too while I've got the engine torn down.

Right now I've just drained oil and removed the valve cover, vacuum hoses, and injector wires. Throughout this week I intend to take off the oil pan, head, crank and remove the pistons and connecting rods.

 

The oil pan comes off in two parts. THe bottom them the top. DO not use a screw driver to pry the pan away. The factory sealant is very strong and could tend to be a ***** to get off. Use a piece of wood and a hammer from the side to break it free. You will not have to mess with the trans at all. You may have to remove the sump(two Bolts) to get the right angle, depending if you removed your exhaust completely. I didnt so I did. The stud kit is from ARP. It was kinda pricey buy worth it. After all the trouble I have had with the head bolts, it is just one more thing I wont have to worry about, plus it will allow more boost pressure. Dont forgt to check the intake for piston fragments if your piston exploded like mine did.!

 

I didnt remove anything that didnt have to come off. Like injector wires. I just unbolted the intake- it has two support bolts that have to come off as well. THe intake will just fall back and it is plenty out of the way. I used and air compressor and a stove cleaner to clean out my intake. YOu can tear the whole motot down including removing your pistons. Be if you palan of replacing your bearings to check the paint codes on the sides. Our 4g94 is a balanced motor so you have to replace the bearing accordingly. Mine just happened to be all "black". Do not rotate your crank counter clockwise!!! Also I had a machine shop press my new pistons on. It was only 7 bucks a piece and well worth it! HAve your head checked too. also let the machine shop know that the valve lash springs are very sensitive, dont let them stick somthing up in there to clean them it will ruin the spring and you motor will sound like a deisel. Other than that be sure and do your math correctly when filing your rings. you should be in good shape.