Repeated head gasket failure

lpfan

Registered User
I am looking at a 1994 sc automatic with 120,000 before the odo broke anyway it just had the headgaskets replaced 2 months ago and then a few days ago the went out again what could be causing this .
I suspect crappy workmanship by the shop maybe not getting the head checked or whatnot but any suggestions would be appreciated ... thanks
 
Heads may be screwed AND the torque to yield bolts may have been torqued down improperly.

I had a sim issue with a 91. Heads were checked, new TTY bolts used. Gaskets went again in a month. I even used the special dial indicator to do it correctly (so I thought).

ARP studs, stock felpro gaskets, nice surface on heads you should be ok


Now if you have a fuel related issue or major detonation...That can be another thing
 
no the women said it was just the head gaskets i plan on ordering the arps and stuff if the shop doesnt cover it under warranty
 
I am looking at a 1994 sc automatic with 120,000 before the odo broke anyway it just had the headgaskets replaced 2 months ago and then a few days ago the went out again what could be causing this .
I suspect crappy workmanship by the shop maybe not getting the head checked or whatnot but any suggestions would be appreciated ... thanks

If the motor got very hot from the earlier HG failure, the deck of the block may be warped and need resurfacing, but it's more likely a sloppy repair job that caused the 2nd failure.

David
 
hi ever-one, its been awhile

regardless of who covers what...buy the ARPS before they/you start the job

you might give the ARPS a try, plus a resurface on the heads while your there


cheers
 
I don't believe in 'tty'

I have successfully re-used tty bolts many times, no HG failures yet...
One of the motors is a 20 psi pump gas DD. Just ate its 2nd tranny:rolleyes:
As long as the bolts in question hold about 90'lb on the wrench they are good to go... IOW if you set the wrench to 90 and it keeps turning/doesn't click, throw that bolt away...
'Torquing to yield' holds an assumption that every bolt is going to put an even amount of pressure on the head when turned 'x' after torquing to 'y'.
I don't think that's a good idea.
 
I have successfully re-used tty bolts many times, no HG failures yet...
One of the motors is a 20 psi pump gas DD. Just ate its 2nd tranny:rolleyes:
As long as the bolts in question hold about 90'lb on the wrench they are good to go... IOW if you set the wrench to 90 and it keeps turning/doesn't click, throw that bolt away...
'Torquing to yield' holds an assumption that every bolt is going to put an even amount of pressure on the head when turned 'x' after torquing to 'y'.
I don't think that's a good idea.

Sounds like a great idea!! Who needs ARP?
 
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hi ever-one, its been awhile

regardless of who covers what...buy the ARPS before they/you start the job

you might give the ARPS a try, plus a resurface on the heads while your there


cheers

What he says..
Wile you have it apart check for signs of other issues and use quality gaskets
 
I have successfully re-used tty bolts many times, no HG failures yet...
One of the motors is a 20 psi pump gas DD. Just ate its 2nd tranny:rolleyes:
As long as the bolts in question hold about 90'lb on the wrench they are good to go... IOW if you set the wrench to 90 and it keeps turning/doesn't click, throw that bolt away...
'Torquing to yield' holds an assumption that every bolt is going to put an even amount of pressure on the head when turned 'x' after torquing to 'y'.
I don't think that's a good idea.

Do you even understand what TTY is? That final degrees of rotation after the torque value takes the bolts past the elastic stage to where they stretch out and get longer, then in to the plastic stage to where it can no longer go back to the original length, which is called the yeild point, in which the next point is the shear point where they actually break. Once a bolt goes in to the plastic stage they lose a tremendous amount of the original strength and should be replaced.
 
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omfg, never re-use tty bolts. they are 1 time use bolts for a reason. that reason is older then anyone that thinks its ok to use them. if there is a warning or fact that is older then you are, then abide by it.

anytime the head gaskets blow always get the heads resurfaced. the block might be ok if not over heated but the heads are somewhat weak aluminum and will warp easily.

when choosing head gaskets get ml gaskets or use copper spray with normal gaskets.

most all engines when replacing head gaskets you want to re-torque them after about 200 miles. thats not a real option on these engines unless you dont mind taking everything back out. before putting the final yield on the heads bolts recheck the torques up to 6 times. they will go down as the gasket settles.

arp studs are king, not really needed if your not going to big but no matter what they work better then bolts providing up to 20% more clamping force.

dont get rough on it for atleast the first 1500 miles after re-installing the heads. give it that time for the gaskets to seal up good. the first few times you run it make it short trips not allowing the engine to get hot.

the heads are something that no one wants to go back and redo, take your time, go slow, make sure everything is done by the book.

just my advice, take from what everyone says and formulate your own route of action.
 
Do you even understand what TTY is? That final degrees of rotation after the torque value takes the bolts past the elastic stage to where they stretch out and get longer, then in to the plastic stage to where it can no longer go back to the original length, which is called the yeild point, in which the next point is the shear point where they actually break. Once a bolt goes in to the plastic stage they lose a tremendous amount of the original strength and should be replaced.

I have argued at great length about this with engineers.
It is pointless, because both methods are correct, from a physics standpoint.
Either the fastener will hold the value, or it will not hold the value.
when a tty bolt does not hold 90'lb, then its going to:"stretch out and get longer" no matter how much it is turned.
If it holds 90, it will hold 90.
I am only stating that they can be re-used with success.
:)
"The last step is to turn the bolt a 1/4 turn from the last torque reading (65 ft/lbs for an 11mm headbolt) set your torque wrench to 100 ft/lbs and do your 1/4 turn. If the bolt is good you should have no problem getting that reading before you hit the 1/4 mark, if a bolt is bad it won't come up to the 100 ft/lb mark. Just replace that one and continue on to the rest of the bolts.. I mention this little test of mine because I know most FWD Mopar racers have a bucket of bolts lying around from engines that have been striped, so spares 9 times out of 10 usually aren't a problem..."
 
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no offense but i would never reuse them i think it is a foolish shortcut i will be going the arp route if this shop doesnt repair it i am time pressed and will not be able to get the arp studs before the shop gets it fixed if they will honor the repair if not i will post their contact info to stay away from
 
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tty is a bad joke, while they work to some degree, for myself i hate the idea of a throw-away bolt, unless it is damaged

when i did mine i replaced all the top-end bolts with high grade bolts
plus the arps for the heads

while i dont mind working on my other cars, they just dont have all the clutter this thing has, its just to much of a hassle to tear this one down to the heads

do yourself or the shop a solid...and do the arps and with a resurface on the heads

maybe a good temp gauge as well...the first sign that its on its way to over-heat get it off the road

if ordered - the arps - are a day or 2 out..

get the ones for the 2.8 chevy

they worked out great on my 90



i guess if your just going to get rid of the car after the fix


cheers
 
I have argued at great length about this with engineers.
It is pointless, because both methods are correct, from a physics standpoint.
Either the fastener will hold the value, or it will not hold the value.
when a tty bolt does not hold 90'lb, then its going to:"stretch out and get longer" no matter how much it is turned.
If it holds 90, it will hold 90.
I am only stating that they can be re-used with success.
:)

Yes it may hold 90 lbs, if that bolt was still in the elastic stage and not taken to the yeild point when tightened the first time. The head bolts are put right on the edge of the elastic/plastic stage so whe would you take the chance. This is plain simple metalurgy and mechanics.
 
I have argued at great length about this with engineers.
It is pointless, because both methods are correct, from a physics standpoint.
Either the fastener will hold the value, or it will not hold the value.
when a tty bolt does not hold 90'lb, then its going to:"stretch out and get longer" no matter how much it is turned.
If it holds 90, it will hold 90.
I am only stating that they can be re-used with success.
:)

90ft/lbs is not 90ft/lbs when "torquing" TTY bolts..Or really any bolt for that matter. A majority of what we read as torque is caused by friction but we also need to worry about things such as stretch on any fastener.

This is one of the reasons stretch gagues are reccomended for installing critical fasteners where one can be used. Such as rod bolts. Reusing a TTY bolt will result in uneven pressures being exerted on your head period. Just because it reads 90...Doesnt mean anything really, especially when reusing bolts.

Anyways..This isnt my forte,...But a good article to read is

http://www.enginebuildermag.com/Article/2343/threaded_fasteners_torquetoyield_and_torquetoangle.aspx

He explaisn it rather well in laymans terms and claims it isnt his forte either...But a good read
 
Good article Damon...the part about the 9/16" bolt potentially having less clamping force than the 7/16" bolt was especially enlightning.

David
 
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