BHG repair ??

[BoostJunkie]

I'm gonna pull the head sunday and get it mill and all that good stuff. I am gonna us the Cometic metal head gasket and ARP studs. First, can the ARP studs be reused or just get new ones? Second, what torque should I go with? Several people have said 72ftlb and some have said 100ftlb. I saw the one thread on here about goin up to 100ftlb but I thought that might be a bit much. The 72ftlb sounded more reasonable.

Any other tips on doin this to prolong the life of the "almighty" 7M.

Oh yeah, when I got the car the previous owner said it had 3500 miles on a rebuilt motor but now the headgasket has decided to quit. I have had the car for about two months.

 

[CyFi6]

You can reuse the studs but for the best torque precision you should get some ARP moly lube for the threads. If you are planning to use the MHG im assuming you are pulling the engine apart to get the block deck surfaced right?

 

[jdub]

ARP studs can be reused...in fact, they are better once "seasoned". ARP spec for studs using moly for lube is 80 ft/lbs...that is what you should use, not the "I heard" specs

If you are going to use a Cometic MHG, both the block and head decks have to meet a 50 RA smoothness spec.

 

[BoostJunkie]

Now with the block, do I just need to make sure it is smooth? Or does it need to be checked to make sure it is flat. A friend of mine (who is a mechanic) said the block should still be flat, just make sure it is smooth and doesnt have any grooves in it. I figure I should ask around here about that bein the fact that the 7M seems to be as fragile as glass.

 

[jdub]

The 7M is not fragile...it is however, very intolerant of even minor errors in it's assembly.

The block/head decks need to be both smooth and flat. If not, the MHG will not seal.

 

[BoostJunkie]

Well alrighty then, fun fun fun!!!

 

[Dr Chill]

I torqued my arp's to 9O .... Not a problem with that at all .... & yes they were used arp's ,

 

[jdub]

I torqued my arp's to 9O .... Not a problem with that at all .... & yes they were used arp's ,

And, you over torqued them
You need to do some reading on the ARP tech site before you start recommending an over torque like you know what you're talking about. Frankly, it's not very smart.

 

[Supracentral]

I torqued my arp's to 9O .... Not a problem with that at all .... & yes they were used arp's ,

Very fucking bad idea.

http://scitation.aip.org/getabs/ser...00128000003000379000001&idtype=cvips&gifs=yes

While this study is specifically about pressurized cylinders, it shows what happens to fasteners (your "used arps") when you over stress them. There is a reduction in fastener tension which translates into a partial—yet permanent—loss of the clamping load and a potential source for fatigue failure.

In other words, that's a damned foolish thing to do, and implying that someone else should go ahead and follow your lead is irresponsible.

http://www.arp-bolts.com/Tech/Tech.html is a good place to start. There's lots of other information out there where you can learn how/why these fasteners work so well, and how improper installation can cause you a world of hurt.

Sorry for the detour everyone, but misinformation is one of my pet peeves...

Back on topic.

 

[Dr Chill]

And, you over torqued them
You need to do some reading on the ARP tech site before you start recommending an over torque like you know what you're talking about. Frankly, it's not very smart.

I did not recomend anything , I was just stating that I torqued them a bit more than recomended , thats all .... With the 4 inch extention on the torque wrench the actual torque was most likely near 8O to 85 .

 

[jdub]

I did not recomend anything , I was just stating that I torqued them a bit more than recomended , thats all .... With the 4 inch extention on the torque wrench the actual torque was most likely near 8O to 85 .

Sure sounded like a recommendation to me...nice tap dance. Funny, since ARP specifically recommends NOT to exceed spec torque...the reason, read the link SC posted.

Another myth BTW...an extension does not affect torque values at the fastener.
You're batting a 1000 so far sport

 

[Dr Chill]

Im not trying to flame this thread , but where in my post does it say do that ?
I just stating what I did , thats all .

 

[jdub]

Im not trying to flame this thread , but where in my post does it say do that ?
I just stating what I did , thats all .

And, we are pointing out you fu*ked up by over torquing your studs...that's all

Back on topic.

 

[Dr Chill]

And, we are pointing out you fu*ked up by over torquing your studs...that's all

Back on topic.

I can accept that ,

I just got done reading about over torqueing ,
I may not ever over torque again , I have to do are build soon too
The only bolts Ive ever over torqued were head bolts ... Because the factory specs are truely .....Fail....
You guys here always have helped me out & Im greatful for the advise .
thanks

 

[Supracentral]

It's cool. For fasteners like ARP, just follow the spec ARP provides with the bolts. Pay special attention to the diffferences between using moly lube and regular lube, it really does make that much of a difference. The factory spec for the factory bolts, yes, it's incorrect. But when using ARP, just follow the spec they provide.

 

[Dr Chill]

It's cool. For fasteners like ARP, just follow the spec ARP provides with the bolts. Pay special attention to the diffferences between using moly lube and regular lube, it really does make that much of a difference. The factory spec for the factory bolts, yes, it's incorrect. But when using ARP, just follow the spec they provide.

Will do ,
So with all this being said , what is the best specs to go by ?

I have 2 builds coming up sometime this year . My bro's car has a knock
& mine started last week .

 

[Supracentral]

Will do ,
So with all this being said , what is the best specs to go by ?

I have 2 builds coming up sometime this year . My bro's car has a knock
& mine started last week .

For all "factory" fasteners, just follow the TSRM. Other than the original stock headbolt spec, the rest is dead on. For fasteners like ARP, use the moly lube and the spec provided by ARP for the fasteners when used with moly lube.

 

[jdub]

You shouldn't take stock head bolts over 70-75 ft/lbs. Spec for ARP studs are 80 ft/lbs w/ moly. ARP head bolts are limited to 75 ft/lbs w/ moly on an aluminum head.

 

[got_boosted]

I just put some ARP studs into my 2JZ after replacing the headgasket. I followed the instructions and torqued them to 80ft-lbs with moly lube.

However I do have some Q's.

1. Do I need to do a 500 mile retorque like I've heard so many times? The instructions basically said torque them and leave them alone.

2. Just out of curiosity, do you torque used studs/bolts to the same spec as new ones?

Thanks,
Collin

 

[Supracentral]

1. Do I need to do a 500 mile retorque like I've heard so many times? The instructions basically said torque them and leave them alone.

I exclusively use studs with moly lube. I have never retorqued. Any properly installed fastener should not need a retorque.

2. Just out of curiosity, do you torque used studs/bolts to the same spec as new ones?

Never reuse factory head bolts. ARP's can be safely reused, and torqued to the same spec as they were when new. I rarely reuse them anyway. For the low cost of the ARP stud sets, to me it's worth the extra insurance to just use new ones on every build. I also don't reuse MHG's.

Here's something directly from ARP about installations however:

Friction is an extremely challenging problem because it is so variable and difficult to control. The best way to avoid the pitfalls of friction is by using the stretch method. This way preload is controlled and independent of friction. Each time the bolt is torqued and loosened, the friction factor gets smaller. Eventually the friction levels out and becomes constant for all following repetitions. Therefore, when installing a new bolt where the stretch method cannot be used, the bolt should be tightened and loosened several times before final torque. The number of cycles depends on the lubricant. For ARP recommended lubes, five loosening and tightening cycles is sufficient.

Many people skip this critical step and pay for it later.

As an aside, if you ever decide to retorque factory bolts (for example a car that still has it's original headgasket), it's important to do so with a cold engine. Whether or not this is a good idea is a completely separate discussion. Some people have had good results, others disasters.