Exhaust manifold help, 78 FJ 40 (1 Viewer)

[Chestcutter]

Chasing both exhaust and intake manifold leaks I pulled the manifolds and disassembled. One exhaust horn separated easily - and was clearly the source of one of the leaks at the ring joint. The other exhaust leaks were at the manifold to head gasket (below) and a big leak at the flapper valve bushings.

I am planning to tap and plug the flapper shaft holes and install a block off plate.

Which may be partly because the lower bolts were wrong size / stripped, however the head surface of the exhaust manifold is rough after cleaning up with a Roloc bristle disk. The manifold (s) appear true with a straight- edge and look to have been milled prior.

Also the one horn i was able to remove (the leaky joint) is very pitted and the central portion the bore is rough.

Questions for the experts:

1. Should the face of the exhaust manifold be machined smooth or is it likely to seal with proper torque if true, maybe with a Remflex?

2. Is the horn joint with this much pitting likely to seal with some smoothing with fine sandpaper and new rings / springs or is this a lost cause? Seems like manifolds in decent shape are near impossible to find now.

I've searched a lot of threads but have not seen advice / pics specific to managing this degree of pitting.

Thanks!

 

[65swb45]

I personally have never seen a manifold with ring joint problems bad enough to abandon.

Machining the face of the manifold, even when not strictly or necessarily required, will increase the time until you need to address the manifold again.

Hth

www.marksoffroad.net

 

[Chestcutter]

Thank you Mark. Good to know this is likely to work as I know these manifolds are becoming scarce.

Will see what the new rings, springs, high temp sealant, and coppercoat on the manifold to head gasket will achieve together with fixing my stripped / spinning manifold to head bolts.

 

[greenbeasty]

I have an extra I believe if you end up trashing yours.

 

[Chestcutter]

I have an extra I believe if you end up trashing yours.

Thanks much. Fingers crossed I can salvage this one, but much appreciated.

 

[SteveH]

@Chestcutter - over 30 years of Land Cruiser fiddling, I have found the factory torque spec for the 2F manifolds to be too low. My bolts were chronically backing out, causing leaks. I finally put threadlocker on them (!) and reefed them down (to probably 75 lb-ft) and haven't had chronic leaks and loosening problems since. I realize that rust is your threadlocker in Ohio....

I still check the bolts once every couple years to be sure they haven't stepped out for a beer, as it were. It takes 5 minutes to find and tighten the bolts (with a handful of socket extensions and some creativity) so it's worth doing on occasion. I have used Fel Pro gaskets for the last 20 years, as they are a lot cheaper than OEM and seem to work just as well.

 

[65swb45]

I prefer to just change all the bolts over to studs. No more chance of crossthreading the holes, and they don’t seem to loosen up nearly as much as bolts.

 

[Chestcutter]

I finally put threadlocker on them (!) and reefed them down (to probably 75 lb-ft) and haven't had chronic leaks and loosening problems since. I realize that rust is your threadlocker in Ohio....

Rust is definitely our primary threadlocker, though I will definitely be using something a little more predictable. Thanks Steve - appreciate it!

I prefer to just change all the bolts over to studs.

I'm geared up for that as well. Seems like it will make it much easier to hang the gasket and manifold. Mark any thoughts on the torque specs? Seems like it should be easier with new studs.

 

[SteveH]

My FJ40 came with some studs - just not all. As long as you have a few studs, you can at least hang the manifold without busting a spleen holding it in place to get the bolts started. I think the factory torque spec is something like 35 lb-ft, and I go about double that.

If you think about the manifold pair and metallurgy, and the fact that it's 30-odd inches long, made of dissimilar metals and gets very hot and cold, you can see why you need to keep the bolts tight and check them often. Just part of FJ40/2F ownership. Just think of yourself as Scotty, keeping the warp drives at maximum output.

 

[KY Longhunter]

What size studs would those be?

I prefer to just change all the bolts over to studs. No more chance of crossthreading the holes, and they don’t seem to loosen up nearly as much as bolts.

 

[65swb45]

What size studs would those be?

F engines used 10mm studs. 2F use 12mm studs. And there is that one oddball, 1974 60051 head that was drilled for 12mm studs even though the manifolds were still being machined for 10s. They required a special stepped stud.

 

[Mark Jennings]

F engines used 10mm studs. 2F use 12mm studs. And there is that one oddball, 1974 60051 head that was drilled for 12mm studs even though the manifolds were still being machined for 10s. They required a special stepped stud.

And brass nuts....don’t forget the brass manifold nuts....that’s what keeps the nuts from rusting to the studs.

 

[EWheeler]

I personally have never seen a manifold with ring joint problems bad enough to abandon.

Machining the face of the manifold, even when not strictly or necessarily required, will increase the time until you need to address the manifold again.

Hth

www.marksoffroad.net

Who in SoCal do you recommend for facing 2F manifolds? Someone local to you that you use often and can whip them out? Can you share costs for facing? I have a 2F intake and 3FE exhaust manifolds that are off right now.

 

[65swb45]

Evan

I don’t have anyone. The last shop I used closed a few years ago. My current shop is only useful for cylinder head rebuilds.

BTW, I just finished your carb this morning. It will go out Monday.

 

[island45]

I recently bought a used horizontal woodworking belt sander that uses a 6" by about 6' belt with a nice flat platen for 300 bucks. In years past I flattened my F and 2F manifolds on my 8" wide jointer tables with stick on sandpaper discs, chuffing the assembly back and forth, like for hours,,,.... One day I stopped by a cylinder head shop on tnhe mainland and they were surfacing a head on a moving belt with the head held by hand.... I had thought that was done by High tech magic, bridgeport/.cnc whatever..,.,,,, Well now with my chinese horizontal belt sander I can surface manifolds easily. BTW, I have never used this machine on wood. My current 2f runs and idles like a Swiss watch.

 

[Chestcutter]

I recently bought a used horizontal woodworking belt sander that uses a 6" by about 6' belt with a nice flat platen for 300 bucks

I had one of these years ago for ornamental ironwork projects. Was great for finishing table surfaces for glass, etc. I never really checked the table for flatness with a straightedge - that would be my only worry with some of these chinese made tools that the tolerances aren't so great. I had a bandsaw frame that was so twisted the blade wouldn't track at all.

Good to have another solution though. Local machine shop would not even try to tackle the 2F manifold with the horns. In the end I went with cleaning up the existing, thread refresh and studs, and a remflex gasket.

Details here: Manifold link So far so good for about 300 miles. I plan to retorque and do a smoke test soon.

@island45 That sounds like an impressive one lung engine! I have a 2 HP Hercules I'm rebuilding. Hopefully that will be more straightforward than the 2F manifold

 

[Chestcutter]

And brass nuts....don’t forget the brass manifold nuts....that’s what keeps the nuts from rusting to the studs.

I don't think I have seen these Mark. I got some from SOR for about $45 shipping and some from Toyota parts and they look identical - I assume zinc coated steel?

 

[Mark Jennings]

I don't think I have seen these Mark. I got some from SOR for about $45 shipping and some from Toyota parts and they look identical - I assume zinc coated steel?

So when I was young....hahahaha....I worked at a VW dealership, e.g. 40 hp was still a new thing, and when we did valve jobs/mufflers, we used brass nuts on the exhaust studs....so the next mechanic doing the job....and there always was (is) the next guy....could get it apart without breaking the studs.

My 68 Land Cruiser that I bought in 1994, one of the first fixes was replacing a cracked exhaust manifold....and the installed nuts were brass...I assumed they were factory.....they’ve been on there forever. And I have never had issues with the studs breaking.

Head to NAPA or True value and use brass on those high rust components, think of the next guy....

 

[Chestcutter]

think of the next guy....

The experience will definitely make me think of the next guy! I don't want to be the PO everyone complains about on MUD!

 

[65swb45]

I have a bin box of brass nuts I have pulled off of manifolds over the decades. All are 10mm/F engine. I have never seen a 12mm nut on a 2F.