3-Piece Exhaust Manifold Question

[emtee]

Hey all,

I tried searching for an answer on this, but can't find much to go on.

I've removed the intake/exhaust manifolds from a '77 FJ40, and it looks like they need to be machined (more than 2mm out of plane). I haven't separated the intake from the exhaust...what I'm reading indicates they should be bolted together for that procedure. (I'm open to advice on this point, too.)

My questions are:

1: How do I separate the end pieces? One side spins (sort-of) freely; the other is frozen. Looks like I can still get replacement seals/springs, but am I asking for trouble trying to separate/clean these up?

2: How is a machine shop going to immobilize these end pieces to get them square with the rest of the assembly?

3: Extreme long shot, but if anybody knows of a good machinist in the Albany, OR area, I'm all ears!

(pic courtesy of SOR)

 

[Nomis]

This should help you:

https://forum.ih8mud.com/40-55-series-tech/75788-manifold-spring.html

I had a local NAPA machine shop plane mine - cost me around $70 IIRC.

 

[emtee]

Nomis,

Good info; thanks! Just what I needed! I may have to take a mallet to the frozen end for some gentle persuasion.

I asked the local NAPA here about machining and all three guys behind the counter shook their heads in unison. My quest for a good machine shop continues...

 

[Nomis]

I asked the local NAPA here about machining and all three guys behind the counter shook their heads in unison.

They don't want to do it because it tears up the belt sander - shreds the belt. The various ears and protrusions on the manifold dig into the belt and tear it up. Or, they may not want to do it in case they damage it in the process - they don't want to be held liable for the cost of a new manifold combo.

 

[island45]

I've done lots of them right here, including the 3 pc exhaust type... I have a long bed jointer in my cabinet shop, but any flat surface will do... We use adhesive backed sanding discs on our palm sanders, and i stick a row of them down on the bed of the jointer.. maybe 6 or 7 long. I just start sliding the combination manifolds back and forth. It is very obvious where it is cutting by the fresh metal.. When it is all fresh metal showing, you're good to go. Sounds kinda hillbilly, but really, it's the same thing....

 

[justindaley]

I recently picked up a manifold from a wrecking yard which has the two outer branches soldered to the middle. I presume this is to keep it in line to enable it to be faced consistently.
It kind of defeats the object of having a split manifold, but you at least have the option to split the manifold after it has been faced.
I have found this to be a fairly common approach from the relevant threads that I have seen.
Hope this helps.
Does anybody know if you can get the first section of exhaust pipe including the flange for this 3 piece manifold?
I'm converting back to standard after having warped headers and obviously the previous exhaust has to be replaced.

Regards

Justin

 

[emtee]

Island,

How do you keep the 'free-wheeling' end pieces immobilized during that procedure? I'm no machinist, so any information in this area is welcome...

I finally got the frozen endpiece off of the exhaust manifold and have the old rings/springs removed. One side is in pretty decent shape, but the one I had to PB and heat to get loose is pretty rust-pocked.

My next question: If I take this to a machinist to get cleaned up, it'll basically be reboring at least one end of the main manifold. Do I need to find an overbore set of rings/springs (assuming there are such things...)? How compressed do the new rings need to be to get a good seal?

I'd hate to spend a lot of money cleaning up the head face on the manifolds only to discover I've got massive leaks on the ends when it all goes back together...

Here are pics of what I've got; this is the good side:

 

[emtee]

And here's the ugly side:

 

[Poser]

They don't want to do it because it tears up the belt sander - shreds the belt. The various ears and protrusions on the manifold dig into the belt and tear it up. Or, they may not want to do it in case they damage it in the process - they don't want to be held liable for the cost of a new manifold combo.

Or it could be, that the specific NAPA he went to does not offer machine shop services.


Further, the machine shops that I have used in the past use a cylinder head facing machine and not a belt sander to resurface an intake and manifold assembly, and the individual end pieces are clamped securely to the table while installed in the manifold.

 

[Poser]

There is a lot of life left in that manifold.


Clean out the ring grooves, take a piece of 120-grit emery cloth to the inner bores, install new sealing rings and call it good.

 

[matt.mcinnes]

I have one if you need one. Working hear riser too.

 

[island45]

When I did mine, the ends were pretty well frozen on, which was perfect for my purposes... I later heated and soaked them to get it apart. I think the brazing sounds like a good plan. They're currently on my seldom used rusty pig in the back 40 and I've been thinking of stealing them for my current project. They have sealed well for 15 years/40,000 miles, So I guess my method works. If I could drive down the block to a machine shop, I might have done that... but everything here has to be shipped off and wait til its done, then shipped back, and it was my dd and I needed it the next day for work, so I've had to be creative, not to mention cheap.....

 

[emtee]

Poser,

Thanks, will give the emery cloth a shot. If I can find a piece of doweling that's about 2 1/4" diameter, the cloth should snug right up against the bore and I'll (hopefully) get a pretty concentric face...

Another question on the manifold face: the intake looks pretty good with a straightedge laid across it; it's the exhaust ports that have backed away, leaving the problem gaps. Is there any reason I couldn't widen up the bolt holes at the heat riser connection and move the exhaust manifold forward 1mm or so to minimize the amount of material that needs to be shaved off the intake? Or am I asking for trouble there?

Matt: Thanks for the offer; if things go horribly wrong with this repair, I may take you up on the offer. I was amazed to find that the riser on this one functions, too!

Island: If both of my endpieces had been frozen, I would've been golden for refacing the head surface and then breaking them loose to refurbish the rings/bores, but one end still worked, dagnabbit! I'll be interested to see how they clamp this thing down to plane it; never seen it done before. I've got a line on a local shop that's supposed to do good work on older rigs...

Justin: The downpipe on my rig is in pretty good shape; if Matt's willing to separate the assembly he has pictured...?

Thanks for all the help, guys! Learn something (or two) every day. I'll post up pics of the finished repair once I get there...

 

[island45]

If I remember correctly, back when I did my pig manifolds the heat riser had always annoyed me with it's leakage around the shaft. I decided this was the time to address it, so I called toyota dealer about replacement shaft and bushings. They were 75.00 and he said they were stainless and that's why. I remember how amazed I was to undo the screws from the shaft to remove the flap. They were perfect and came right out. Talk about an extreme environment, and this 2f had 150,000 on it! I didnt buy the shaft, instead I ran a bolt through with a copper gasket, both sides and snugged it up. Nice and Quiet.... until 2 years passed, and the mild steel bolt dropped out in two pieces,corroded down to the size of a hair in the middle. Old shaft/flap went back in where it remains...Thats a really good stainless assembly to hold up like that. These are a very high quality vehicle for sure.

 

[emtee]

Island,

Is it just the valve/flap that retains that assembly in place? I'm considering installing a stainless steel blank (to protect the intake) to replace the factory "scoop" style insulator in there now and replacing the valve assembly w/ a stainless steel bolt. (The stock assembly could be reinstalled at a later date if wanted/needed).

This valve rotates freely with a minor amount of slop; I imagine there's some leakage at that location, but it's probably the least of my worries at this point.

 

[justindaley]

I have a heat riser manifold that I picked up for free, but it was similar on both sides to the scabby side of your manifold. I had written it off as scrap, but it's still in the shed.
The next manifold that I got is designed to have a blanking plate instead of the heat riser, but since it was separated from the intake when I got it, the blanking plate was not included. I was going to fit the heatriser plate instead, but probably should make a solid plate to protect the intake. I live in the tropics, so cold starting is never an issue for me.
If I make a plate, it sounds like it should be stainless then?
Would a mild steel plate just corrode in short shrift?

Justin

 

[justindaley]

Matt

Would that jet hot coating that you have used, fill in the imperfections on a scabby manifold?

 

[handcannon]

emtee

I'm not sure that NAPA in Albany has machining available. But, go across Santiam to Carquest. They have an in-house machine shop. I had them do my older one piece manifold set last year. You might also check out Virgil Hanson out on Commercial Way. I just recently had him help me I.D. a Chevy I-6 block using casting numbers. He has been around Albany for years and was very helpful to me. My impression of him is "old school". He also had some old Ford flathead motor parts in there when I was in there.

 

[island45]

I think any plate or bolt from mild steel will go the way my bolt did. Though it was 15 years ago, I still remember talking to someone about protecting the aluminum intake from the heat. I can't remember what I made, but I did get a new stainless plate from toyota with the 2 gaskets because the old one was cracked in a few places and leaking. I hate manifold leaks, a real pet peeve with me.

 

[matt.mcinnes]

Matt

Would that jet hot coating that you have used, fill in the imperfections on a scabby manifold?

No the coating is actually very thin.