Cometic MHG reusable??

[BJ91T]

Hello , well as some of you know by now my brand new motor is doing some things that need fixing. It has a cometic 2.0mm MHG (1,77mm) on it and has less than 300 miles on this rebuild, however i plan to have my stock rods resized and stress relived so naturally the head will need to come off. I am not sure if the cometic can be reused like the hks etc..... I have arp studs on this motor @100ft lbs.


Thanks In Advance
BJ

 

[JustAnotherVictim]

Did you use moly lube or oil on the studs?
The cometic is reusable is it isn't marked up. So inspect it carefully for imperfections.

 

[BJ91T]

moly lube

 

[JustAnotherVictim]

That torque is way too high for moly.
Should be 75 or 80 depending on what your arp spec sheet said.

 

[BJ91T]

thats due to tourqe wrench failure (it was reading wrong) when i checked them with a good wrench they were at 100 i had the bad wrench set to 85

 

[BJ91T]

so i assume when i redo this i should use oil not moly lube?

keep in mind this thing has reallllly low miles on it

 

[JustAnotherVictim]

Ahhh I see.
Look over your head for cracks while you have it off.
If you want to be real through have it checked. Hopefully nothing happened.

The moly lube is fine just use the good wrench at what your spec sheet recommended.

 

[BJ91T]

ok since the gasket was at 100 if i redoit to say 90 or lower wont it not seal as well due to the crush from 100???

 

[JustAnotherVictim]

If it's cleaned up and sealant is applied on all three layers I believe it's supposed to be fine. I'll wait for someone else to chime in on that though.

From what I recall you shouldn't have any problems with it because the mhg don't really "crush" so to speak.

 

[BJ91T]

ok thanks JAV for the help

 

[jdub]

JAV is correct...80 ft/lbs is the spec for ARP studs using moly. The MHG will seal fine at that torque, even used.

Make sure you clean ALL the old Viton sealer...paint thinner or Acetone works well. Once clean, apply a coat of copper sealer to the MHG and let dry for 10 min or so...you only have to coat both exterior sides of the MHG. Carefully lay it on the block and install the head.

 

[TurboWarrior]

FYI to anyone considering a cometic gasket. Make sure you use a spray on sealant or whatever the forum recommends. I used a cometic gasket on my build and it leaks. Torqued to 88ft/lbs. Complete engine rebuild i did everything right. Oil passage leaks into the coolant compression seems ok. Im using an HKS this time.

Retorqued it after i noticed it was leaking to 95ft/lbs. It leaks less. But it still leaks.

 

[starscream5000]

You've most likely stretched the ARP studs too much to be safe anymore. Best be using new ones this time.

 

[TurboWarrior]

aw jeeze really? should i look at them visually before buying another set? Or just buy a new set reguardless?

 

[starscream5000]

I was referring to the OP with his torque of 100 ft/lbs with moly. That's 20 ft/lbs higher than the recommended figure. What's the cusion between the recomended value and the stress point? 25%?

Yours is right there with his though...

Research what the torque point is on the ARP's to where they will no longer be reliable and should be discarded.

 

[TurboWarrior]

I think you are right. ARP site says

"81ft/lbs torque based on 75% of strength"

ill make a call on that when i see them im running low on money. Really, I can't afford to be doing this twice. But then again i really can't afford to do it 3 times heh

 

[starscream5000]

That's 101.25 ft/lbs max rating with no give, not accounting for expansion of head and block when heated. The 81 ft/lbs is the old rating too IIRC, it's 80 now, so yep, 100 ft/lbs is the max. If I were the both of you, I'd get new ARP studs if both of those torque values are on ARP moly lube.

 

[TurboWarrior]

You're right its cutting it very close. Moly was used. Looks like ill be getting another set.

In these high torque ranges do you think the head may be deformed after only a summer of use? Is another machining nessecary?

I know too many questions

 

[starscream5000]

The only true way to tell is to take the head to a machinist and have it checked for warpage.

 

[Idealsupra]

FYI to anyone considering a cometic gasket. Make sure you use a spray on sealant or whatever the forum recommends. I used a cometic gasket on my build and it leaks. Torqued to 88ft/lbs. Complete engine rebuild i did everything right. Oil passage leaks into the coolant compression seems ok. Im using an HKS this time.

Retorqued it after i noticed it was leaking to 95ft/lbs. It leaks less. But it still leaks.

ummmm NO.