Blown MHG?

[supraman323]

I have a metal headgasket (cometic) installed and my compression in cylinders 5 and 6 is at 90 (the others are 160)

Does a metal headgasket "blow" or am I looking at something more serious as a head issue?

Taking it apart now, any experience will help

 

[airhead04]

Did you do the piston rings in the engine?? They may not have sat right n those cylinders if the engine wasnt broken in properly. What was your final torque for the head? (meaning the head bolts)

 

[supraman323]

rings are fine, cooling system has lots of extra pressure, white smoke in exhaust so it is the headgasket

torqued to 82 ft/lb

 

[airhead04]

Well that sucks. How long ago was the headgasket job?

 

[GrimJack]

I've popped a MHG - cometic, too, for that matter. Of course, I've also seen heads popped.

Only way to tell is going to be tear it apart and look.

 

[supraman323]

About a month... I'm not sure what would have caused it, just checked torque and the middle nuts were pretty loose, all others were at around 80 ft/lbs

I was only running 18psi, anyone know what a metal blown head gasket looks like?

How much of the head can I leave assembled as I remove it? I think i'm going to try leaving the exhaust manifold/turbo on, as well as the lower intake, shouldn't be more than 2 hours to find out what it looks like on my own

 

[akito]

I usually leave the lower intake and take off the exhaust/turbo manifold because of weight. If you are capable of removing the head with turbo manifold and turbo then go for it.

 

[airhead04]

Did you retorque the bolts after the heat cycles?

 

[kamikazemkiii]

Was the head and block decked? rivets removed from the mhg?

 

[Koenigturbo]

About a month... I'm not sure what would have caused it, just checked torque and the middle nuts were pretty loose, all others were at around 80 ft/lbs

I was only running 18psi, anyone know what a metal blown head gasket looks like?

How much of the head can I leave assembled as I remove it? I think i'm going to try leaving the exhaust manifold/turbo on, as well as the lower intake, shouldn't be more than 2 hours to find out what it looks like on my own

If the middle bolts were lose and the rest tight, then would that cause the gasket to blow? Or warp the head?

 

[Supracentral]

if the middle bolts were lose and the rest tight, then would that cause it to blow? Or warp the head? With the middle bolts lose, That could be the reason your gasket is blown.

I came here to say that. The long aluminum head on the Supra relies on even loading on ALL of those bolts. If any of them were loose, that's your problem.

 

[supraman323]

rivets were not removed, its a newer cometic so they are not touching the mating surfaces

nuts were retorqued at 200 miles, then 1000 miles

it has been about another 1000miles

How would the middle (4th row from front) nuts get loose?

I'm probably looking at a warped head then? I understand it is all speculation, but it's getting torn apart next Tuesday so I'll know for sure.

 

[Koenigturbo]

[

I'm probably looking at a warped head then? I understand it is all speculation, but it's getting torn apart next Tuesday so I'll know for sure.[/QUOTE]


only one way to find out.

This is a long shot: It may have been just be your loose bolts, that maybe your problem however at this point why chance it.

 

[Kevin]

imo your head's warped due to the loose studs

 

[Koenigturbo]

rings are fine, cooling system has lots of extra pressure, white smoke in exhaust so it is the headgasket

torqued to 82 ft/lb

Just curious: why did you go 82 l.b.s? and how did you arrive at that number? There has been "(research)" or someone arrived to the conclusion that M.H.G. for our cars should be 75 ft. l.b.s.

 

[Kevin]

Just curious: why did you go 82 l.b.s? and how did you arrive at that number? There has been "(research)" or someone arrived to the conclusion that M.H.G. for our cars should be 75 ft. l.b.s.

i thought arp specs should be used? iirc 85ft-lbs for studs?
i started a thread a while ago on this.

 

[SideWinderGX]

An 'exact' number has never been found or claimed by anyone. ARP says 85 ft-lbs IIRC.

It's more important to have the torque value be ENOUGH, than what it actually is. Generally that is about 75 and up. Some people go overboard and torque it to 100 ft-lbs, although I wouldn't personally do it...but they didn't have any problems with it after installed.

 

[Koenigturbo]

i thought arp specs should be used? iirc 85ft-lbs for studs?
i started a thread a while ago on this.

Kevin: I asked this question a while ago, I can't remember what the replies were on the torque spec or how they arrived at 75. I don't believe A.P.R. came up with that number, they just sell the bolts, don't don't give a shit what you torque them to, they have spec on what the bolts will hold up to, but they are not gonna have spec on what to "we" should torque them to, that's kinda up to us. I forgot that he used studs, if thats the case then, 85 is probaly right, altough I wouldn't know, I have the A.P.R. bolts.

 

[SideWinderGX]

ARP sells these studs specifically for our cars, I'm pretty sure they put a little R&D into what the torque value should be

 

[Koenigturbo]

ARP sells these studs specifically for our cars, I'm pretty sure they put a little R&D into what the torque value should be

SIDEWINDER: I guess, I owe you an appology: you are correct. 75 for the bolts and 80 for the nuts.