can i re-torque stock head bolts
 

so my head gasket is in excellent condition (engine only has 51,000 mi) and i was wondering if i could just go in and tighten the head bolts down to 75ft/lbs instead of leaving at 58ft/lbs or whatever toyota had it at stock. i want to know if this is ok to do because if it is ill do that and not have to worry about getting a new hg before im actually wanting to rebuild it.

any help is fantastic

There are two negative factors to retorquing after so long... I'm going off memory here so forgive me if either isn't completely accurate. The first is that the jackets may have hardened and could be compromised; I don't think this is very likely. And the other is that now that the bolts have sat in place for so long you're not going to get an accurate torque value for each and may not get them uniformly tightened or you may not even be able to tighten them due to artificially high readings from seizing.

Now, with that out of the way, I think you're fine to do it. Just crack each bolt loose in the correct order by 1/4 of a turn and tighten them in order in multiple passes.

Do keep in mind that it is possible that whoever did the HG last did use a higher torque level... don't go higher just because...

ok and i have never built a 7mgte only honda b16's so is there a specific bolt pattern thati should follow when tightening them and visa versa for loosening??

Yes, there is an order and it is critical.

Here's the service manual's complete section on the head and related work: http://www.cygnusx1.net/Supra/Librar...ection=EM&P=32
Pay attention to all torque values.

The third image down shows the order for removing/loosening the bolts. Use the opposite order for tightening.

oh and is there any risk of the head bolts sheering off because theyre kinda old?

oh and thanx

I would be flat out amazed if that happened. Worst thing I've ever seen is people stripping the sockets out from not ensuring the driver was in all the way. The stock head bolts are VERY robust.

thank you so so much for your help. youve always helped me quite a bit.
and would you mind replying to my thread about removing the fenders front lip and bumper? if you search fender removal it should be right at the top

oh thanks again for all your help

If I had much to offer on the fender removal I'd gladly offer it up. I'll think it over and post back anything that I can think of which isn't obvious.



Would you mind please posting MKIII specific threads in the MKIII section? Some of the folks there may have worked on the fender more recently than I, for example and they may be more likely to see your post there.
Thanks.

you can reuse your head bolts as long as there not pitted

to retorque your head back each bolt off about a quarter of

a turn before you retension it, make sure you drop the coolant first

you will find an engine drain bung at the back of the block behind the

turbo,

i had a head gasket start to leak on my old NA motor about 1500 Ks

from home, retorqued it out the back of a servo & ended up putting

about another 50K on it while i built the turbo engine

ps dont use your tension wrench to back bolts off !

Stretch is the primary concern (the TSRM has details on measuring the bolts to determine if they're healthy). Sure, if they're pitted, cracked, flaking, etc. you don't want to reuse them. You can't check either without pulling them and compromising the HG so it's a moot point in this discussion.

A re-torque usually won't last long if the HG has already started leaking... the longer it leaks the more the gasket material is subject to erosion. Catching it before it happens is key.

i believe it hasnt began to leak yet because compression is still great. and by completely pulling the head bolts i risk comprimising the head gasket?? because i want to replace the eventually but if it isnt necessary then i wont

If you have have the head off, replace the gaskets and do not re-use the head bolts. They are most likely torque-to-yield and will have stretched the first time installed and torqued to spec. Buy new ones and save yourself the pain of a blown HG when the bolts fail to properly keep the head mated to the block and lift under heavily acceleration (or boost if you have a turbo).

They aren't TTY... I do agree with replacing 20+ year old bolts for peace of mind though.

try finding a nut and a piece of steel tube to fit an old head bolt
put the nut in the vice, the tube on the bolt and install finger tight
now take a stretch gauge and measure the length of the bolt, write
this down, torque to a given setting and measure,
keep repeating this process and see if u get even the slightest
difference, ive done this little experiment and found none
i used to use ARP head studs on all modified 7M's but now i see them
as a waste of money on all but the most highly strung engines
about the last 20 7M's ive built have had std head bolts only 2 ive
replaced them & none have had head problems
one of my engines gets cained at 22 psi every day with nothing more
than metal head gasket stock {second hand} bolts & proper head & block preperation

Edited for clarity: I wasn't saying that stretch was likely (actually, I pointed out that the TSRM even provides the measurements to make sure they're fine)... I just didn't think pitting was any more likely. I should have simply said as much. I've only ever had 5 apart that far though. Now you've got me curious, how many pitted head bolts have you pulled from 7M's?

ive only come across a couple of pitted head bolts on 7m's usually they
come with a badly coroded head & most often i'll throw the lot out &
start with at least a good head or another engine for rebuilding

Tanks for clarifying. I figure it would take a lot damage to the HG, block or head for the bolts to pit.

Re-Torquing the head bolts
 

Im about to give this retorquing of the headbolts a try on my 7MGE and i had a couple of questions for CRE and/or Steves 86 Supra

The order for tightening...... The link Cre gave has an order for removing the bolts and then further along it has a different order for putting them in, im presuming that i use the order for putting them in to tighten them up? The one that starts in the centre of the block and works out?

Also, Steves 86 supra, you mention a drain bung in the block on the turbo motor? I presume my non turbo motor will have the same bung? I presume the risk here is that if you dont drop the coolant there is potential for the coolant to bypass the gasket and get into the engine during the retorquing process? At the moment im just getting a little pressurised gas into the cooling system but no water back into the engine and def no water and oil mixing. Ill have a look and see if i can find the bung.

Think thats about it, all i need now is a torque wrench!

Use them both... the removal order for loosening them a quarter to half turn and then the tightening pattern (which is the opposite) to torque it down.

Yes, the coolant drain plug in the block is in the same place. ;)

Retorquing head bolts.
 

I have retorqued the head bolts now but was it worth the trouble??????????????
So far im not sure?!?! Im not sure how much better it is but it definately hasnt made it any worse.
I was able to drive the car today for about an hour with the aircon on (rather than the heater!) and the temp only moved up by 1 notch when i was in traffic and sat at a set of lights for 2 changes.
I wonder if just flushing the system and putting the 50:50 mix of coolant and deionised water wouldve had the same effect without the several hours spent on the tools!

The drain plug to drop the water out of the block was a bitch to get to and was VERY tight! I couldnt see it behind the heatshields.
After it was refillled with coolant/water, i ran it for ages with the car parked so the rad was up high and the heater on flat out. Also removed the thermostat to help but still had bubbles. Not as many as before but still a fairly constant stream. I torqued it up to 75 ft/lb's with a wrench that was recently calibrated, im wondering if i shouldve gone a few more ft/lb's as ive seen a few posts where people say to go to 80ft/lb's.
The process had definately not been done on this motor before though as after cracking each one off a quarter of a turn, my first run with the torque wrench set at 55ft/lb's saw then tightened a fraction tighter than where they were when i started. Then 2 more runs at 65 and 75.
As i say ill give it a few days to settle and a few more attempts to burp the system and ill make some enquiries about getting the HG done properly.

A retorque isn't going to fix any problems... If you've already got problems it is a band-aid at best. If you've got no problems and it works, you'll never know.

Do know that with a retorque there is always the possibility of making a problem worse or of creating a problem where there wasn't one. You can compromise the head gasket by retorquing... generally this is caused by backing off the bolts too far or from the metal jackets in the head gasket having gotten brittle and now cracking opening pathways for erosion.

Well it seems i may have been a bit premature in announcing that retorquing the headbolts didnt work for me.... Have done 300+k's in the car since often in heavy traffic without any movement from the heater guage or the need to put the heating on.

I did pop in to see Paden at Unique automotive in villawood as i was concerned the HG did need doing but by the time i got there it seemed most of the air was out of the system. He suggested that the way i put the coolant in wouldve created a huge airlock in the heater matrix and that is what i think was causing the airbubbles under the rad cap. Air bubbles seem to have stopped now.

So all is looking good.