how to re-torque the stock 7MGTE head bolts?

[doobs]

Ey all,

Recently I picked up an MZ20 soarer, it has done 90,000ks. I want to re-torque the head bolts as I have no idea whether they have been correctly torqued before. My question is, how should I do this? I know I can’t just grab the torque wrench and tighten them, I have to do it in a certain pattern (I have the full engine manual here), and tighten them progressively.

I have been reading this thread:
http://forums.toymods.org.au/index.p...art=0#msg_7828

But there is alot of conflict, can someone please tell me how I should re-torque the head properly.

Thanx

[love ke70]

dont you basically just start with the middle one and work out in a spiral type shape...like all alloy heads
my 2c

[CLG]

Using the toquing sequence suitable for your head, crack the bolt loose, then retorque to the desired force. You always crack the bolt loose to remove the extra force needed to overcome the current torque through the bolt - which results in incorrect torques. you'll typically find the bolt will move another 20 degrees or so - you can check this by marking the untorqued bolt, retorqing, and then checking where the mark now sits.

[chris davey]

Can you reuse the head bolts on a 7m? I was told that I couldn't reuse the head bolts for my 1jz.

[love ke70]

its always recommended that you use new bolts
thanx for the info on cracking the bolts first clint..didnt knwo that (Y)

[myne]

I'd be removing each bolt, greasing it and then torquing it.
It's the only real way to get the torque correct.

[doobs]

Thanx forf the replys, +1 for all, but I have a few more questions..

Is it highly recommended that I get new head bolts? If it will be worth it, I will definetly get some new ones, what are they worth?

How great is the chance that I will damage the HG when I re-torque the bolts? Should the engine be able to take some abuse with a stock HG thats torqued correctly?

Also when compression testing the 7m, what should be the cylinder pressure be?

Thanx

[urantia]

Well some guy (reg reiemer?) did a test on the stock 7m head bolts and they were good for 75ft-pounds (or thereabouts), so if your 7m is still going with stock torque 54ft-lbs or whatever it is, then i'd say your right to just torque them up.

I personally whent to 68ft-lbs and rechecked every 6 months, well 3 years later they never loosened and i never got a BHG.

I got about 155-160PSI on all cylinders, and the motor is good, doesn't burn a drop of oil and feels like its claimed 230HP, just something for you to guage against for your motor.

[RyleyMA61]

i got aftermarket head bolts and they seemed to have worked a treat. you gotta remember the bolts are probably 20 years old, so new ones would probably be a bit better..

good luck!

[oliveoyl]

What's the latest advice on this guys?

[Daddio]

Stock head bolts are not TTY (Torque to Yield) by design however they can stretch. The recommended procedure is to measure them for stretch before re-use. In reality, they are rarely stretched, even when torqued to 70ft/lb. Given that measuring requires removal, I'd be replacing with ARP (or similar) bolts or a stud kit..Personally, I didnt bother measuring and replaced with ARP studs (I used: Cometic MLS head gasket, ARP studs torqued in 3 stages to 85ft/lb..ran 22psi without issue)

[oliveoyl]

Can I remove and replace in situ? Ie without removing the head? The car is currently in good condition with 20000kms on the rebuild.

[JustenGT8]

What's the latest advice on this guys?

Learn to weld alloy to steel....it's the only way to be sure

[oliveoyl]

Learn to weld alloy to steel....it's the only way to be sure

Lol - shove off you

Arps it is, one at a time, what's the worst that can happen? :-)

[trdee]

bhg..... so basically it can't be any worse than it already is