What is everyones opinion on the stock composite head gasket and retorqueing the stock head bolts? I figured that toyota made the supras with the torque specs at 58 ft. lbs which is the lowest i've seen in my life for heads to be torqued at. Personally i've read forum after forum about torqueing the head bolts to 75-80 lbs on a composite gasket but in my opinion that would squash the gasket way past the normal squish rate. The head bolts i feel aren't a problem because metalurgy test that i've read showed that they were as strong as the 2jz's head bolts. I feel that most supras went over 100.000 miles with the factory torque specs at 58 ft. lbs. I will give the benefit of the doubt and say more like 68 ft lbs seems sufficient to hold the gasket better and not exceed the squish tolerances. Any opinions on this well debated subject? :nono:
7mgte head gasket torqueing using oem composite gasket and stock head bolts
- Thread starter alien4real
- Start date
On one of Toyota's head gasket recall that I did when working there, we used a composite gasket and much more than 85 lb feet. It was the 4 Runner 3V-E. I think that was the engine code. Anyway, it got 33 lb/ft, the 1/4 turn and 1/4 turn. The 1/4 is done with a breaker bar, because it takes a lot of grunt to make it that tight. You won't hurt the composit gasket. And at the same time, you don't want to over do it for the sake of the head. The common amount of 70-80, such as the 72 listed above is just fine.
alien4real;1590694 said:
In my opinion if you wanting to stay stock, pull the head and that 20year old HG, goto toyota order a new one.
Install it properly, and torque it down to 70-80lbs, ARP's would be a good idea also.
Theres plent of guys who have done what i just listed and exceeded 350-400hp for a long time and
if you just plan on staying stock then it will probably out live you.
&& there is no squish tolerence lol, if you go too far you will only hurt the head not the gasket.
Heavy D;1590896 said:
The correct answer is to torque to ARP specs - the ones on the sheet that come with the hardware
Alien - you are correct that the stock head bolts are quite strong from a metallurgy perspective. The problem is not with HG "squish", instead a over torque can put the bolt in the elastic region for the head bolt steel - especially when the engine gets hot. The difference in thermal expansion between the steel block and the aluminum head can easy do this if excessive torque is applied - ARP limits torque to 75 ft/lbs for their head bolts for this exact reason. The recommendation for 70-75 ft/lbs of torque is safe for stock head bolts.
Studs are less susceptible due to the reduced torsional stress on the steel shaft compared to bolts - ARP studs are not limited to the same 75 ft/lbs (this does not mean that you can over torque tho). In both cases, it is a wise idea to properly preload the bolts/studs - you do this by torquing in steps to the correct spec, in the TSRM installation pattern. Followed by loosing the hardware a half turn or so and torque back to spec - ARP recommends 5 of these cycles (#5 is the final torque) for proper installation. This "burnishes" the hardware threads and insures a very accurate final torque.
Is there a risk of compromising the composite gasket in doing this? Tq all to say 60 ftlbs? back all of them off 1/2 turn in the loosening sequence? then re peat the tightening sequence to 60 fltbs? Or do them one bolt at a time (tq, loosen, tq loosen etc..) I try to be as direct as possible for things I'm not familiar with.
Do them one at a time in sequence - ARP spec for their hardware - 70-75 ft/lbs for stock bolts.
There is no chance of harming a composite HG doing this.
There is no chance of harming a composite HG doing this.
jdub;1591305 said:
As I understand it, you go through the initial torque sequence in three passes - 58,68,90. Follow that by 1/4 turn back in the torque sequnce then retorque -one at a time. Then repeat this process 5 times?
Thats how I understood it..
Correct me if I am wrong
Sam
^ dont go to the final tq until the 5th burnishing. Thats why i posted 60ft lbs, then step it up to 70-75 on the 5th cycle of that bolt. And for any body reading this, the tq values are hypothetical. Just trying to grasp the process fully
Here's what ARP has to say on this subject:
http://www.arp-bolts.com/Tech/TechInstall.html (click on "Using a Torque Wrench" link on the left.
My interpretation of "final torque" is the last pass at the spec torque for the bolt...i.e. I torque to 5 ft/lbs below spec for each of the 1st 4 passes, back off 1/2 turn for each bolt/stud individually and re-tighten (each counts as a "pass"). I then set spec torque on the last pass. This is technique - doing what Grim is doing is not wrong....I simply prefer to get closer to the spec torque to insure the min torque deviation between bolts for the last pass.
http://www.arp-bolts.com/Tech/TechInstall.html (click on "Using a Torque Wrench" link on the left.
My interpretation of "final torque" is the last pass at the spec torque for the bolt...i.e. I torque to 5 ft/lbs below spec for each of the 1st 4 passes, back off 1/2 turn for each bolt/stud individually and re-tighten (each counts as a "pass"). I then set spec torque on the last pass. This is technique - doing what Grim is doing is not wrong....I simply prefer to get closer to the spec torque to insure the min torque deviation between bolts for the last pass.
^ i'm not into re inventing things at this stage in my life. seeing as how its worked for you I'll go with the 5 ftlbs below final value. I know we are beating the details to pieces here but it helps weekend warriors like me sleep easy at night!