Torque for new manifold studs? Sealant or not on gaskets? (6 Viewers)

[sunrk]

Took my 1hz's old Genie headers off yesterday - they have a fair number of weld cracks and pinholes due to rust/age/vibration/etc. all of which couldn't be seen without removing them. To be honest, they are pretty ugly and one of the weld cracks was 1/2 way around at a join where three cylinder pipes merge together.

Only 11 studs were present - one has been broken off for a long time as this pic shows:

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That's the bottom stud position for #4 cylinder. Looks like someone in the past tried to get a broken stud out and broke off a bit of the head casting rendering it useless. Argh. Good thing the motor will be replaced hopefully this year.

Anyway I'm fitting 11 new genuine studs and nuts along with two genuine, manifold gaskets with new Pacemaker headers replacing the now-scrapped Genie's.

I can't track down two pieces of information:

- when fitting new studs to the head what torque do the studs need to be snugged up to in the head? So far I've hand tightened them with a torx E8 socket them snugged them a little more with a small ratchet handle.

- Do I need to use any sort of sealant with the new genuine manifold gaskets? I've given the surfaces on the head a really good clean with a paint scraper, brake cleaner, some sanding blocks, etc. just to make it as good as I can for an original head on a 635 k km motor.

I'm using copper grease on the studs where they go into the head based on lots of recommendations to not use anything else.

Thanks, Craig.

 

[scottryana]

That looks pretty crusty my man, I don't know how you are going to get a good seal with a surface like that and only 1 stud. Try your best to get that surface clean and as flat as possible. I normally wouldn't recommend it, but I would think you might have to use some type of permatex high temp sealant to get it to work?

 

[inkpot]

That looks pretty crusty my man, I don't know how you are going to get a good seal with a surface like that and only 1 stud. Try your best to get that surface clean and as flat as possible. I normally wouldn't recommend it, but I would think you might have to use some type of permatex high temp sealant to get it to work?

I’m thinkin that factory cast manifolds would be the best bet to allow minimum blowby without repairing that broken stud.

 

[inkpot]

I would torque the new studs into the head at just a little more than finger tight. When the nuts are torqued, that will also draw the onboard end of the stud up to torque.

 

[sunrk]

Yeah I know it's not pretty. That pic was before I cleaned the area up. Can't do much with the head in situ and I'm not in a position to take the head off the block or fit a new head. So some sealant then - I can get something like CRC Maniseal and there are some permatex and other products that might work.

I've VHT flameproof coated the new headers in the meantime. And as for the new studs, just a bit more than finger tights sounds about right to me unless there's someone who knows what the factory spec is for their torque (very light presumably).

 

[bigredmachine]

a bit more than finger tights sounds about right to me unless there's someone who knows what the factory spec is for their torque (very light presumably)

personally I haven't ever noticed a torque spec for studs, just tighten them snug and when you tighten the nut down that will also help to tighten the stud

 

[Malleus]

x2. Studs do not have a torque spec. Bottom them and tighten the nut on them to the proper spec (which is given).
I do not have a diesel engine manual, but I can't imagine the exhaust manifold torque spec is different from the gasoline (petrol) model:

 

[sunrk]

thanks yeah the spec for the manifold nuts is showing as 30 ft lb in a few books. Definitely seems there's no spec on the studs themselves. I guess it's much better to have them come out rather than break off (which seems to have happened with a previous owner of my 80 - that engine is the orignal one so been in the vehicle since 1992!).

 

[Malleus]

That's not why they don't have a torque spec. The nut puts tension on the stud by clamping the part (in this case, the exhaust manifold). The stud cannot come out if the nut is properly tightened. There is no torque spec on any stud on any Toyota. This is an industry standard.

 

[gummycarbs]

It's probably more important to clean the threads on the block than to hit a specific torque value.

 

[sunrk]

Located my 1hz/1hdt FSM and it specifies 29 ft-lb as the torque spec for exhaust manifold nuts. As already mentioned there's no mention of anything for the studs. So I just took them out again (I'd snugged um a bit beyond finger with an E8 socket) and re-screwed them by fingers only. I've half-fitted the new header sections and the nuts are going on without a drama apart from trickiness of accessing the bottom ones for cyl 5 and 6.

 

[SHREDwagon]

Located my 1hz/1hdt FSM and it specifies 29 ft-lb as the torque spec for exhaust manifold nuts.

Hey Man - Just past finger tight is proper for installing manifold studs into block. I usually measure projection after - just to confirm they're seated correctly. Good idea to apply high temp never seize (copper) to all studs if you want to avoid breaking anymore next time around. Same with all turbo (if you have one) and exhaust bolts.

For the sheared stud: if you can't drill and tap - drill and Heli-Coil.

 

[sunrk]

This is the new Pacemaker manifolds halves mounted to the motor.

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They're painted with VHT flameproof grey over the top of sanded back factory 'pacemaker blue' factory coating so I'll be curious to see how the two coating layers cure together once the motor is running again.

I've been dealing with some other aspects of removal of the old Genie headers (which have cracks and pinholes in various places) since it's stuff that normally never gets touched like fixing up the damaged heatplate directly behind the exhaust pipework in front of the drivers (RHD !) footwell and damage to coatings on body behind that. It's previous owner damage I've known about the whole time but haven't had inspiration to sort out until now.

This is said heatplate:

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It's fasteners were easy to remove - M6 bolt through top hole and M6 nut on fixed stud through bottom hole.

Trying to get a new plate out of Toyota but it's really hard with stuff like this to work out the correct p/n with Toyodiy, etc.