Pre-war (up to 1942) 322 ci Flathead Intake Manifold Rebuild

[39LaSalleDriver]

Please gentlemen, focus....I've got a problem I'm trying to remedy and I'd rather not see this get sidetracked with penetrating oil silliness. If you want to discuss such things, by all means please start your own thread. I promise I will find it as interesting as anyone. But this is about rebuilding a manifold for a flathead V8 engine.




That being said I now find that someone, at some point has drilled a hole into the center port area of my exhaust manifold where the alignment stud fits. Looks like they were drilling another stud hole for some reason and then punched another straight on through original spot to the outside. Guess I'll dab some of the Pyro Putty in there to seal it off unless someone can give me a good reason it should be there.

[Cadman-iac]

So if I'm reading this correctly,  there is supposed to be a hole there,  but they elongated it by trying to drill out something else?
If the hole is not supposed to be there, can you tap threads into it and install a plug perhaps as a temporary fix, until you can get another one, or do you want to repair this one as it's in good condition.
I thought I could see some flaking of the metal on the inside of the port. I don't know if that's what it actually is,  or if it really matters much. Just an observation.

If the hole is supposed to be there but is only enlarged by the previous repair attempt, can it be welded closed and redrilled to the proper size and position?
Of course to weld it, it would have to be blasted clean of all rust and flaking metal before the attempt is made.
I'm sure it's not a common part anymore, if it ever was. I wish you luck on your repair. That's a great car.

Rick

[39LaSalleDriver]

If you look at the first picture, the dark gray area is where a factory hole was bored. It is there to align on a stud mounted to the block. It looks to me like someone drilled a hole all the way through the center of that for who knows what reason, then shifted over slightly and started to drill another hole for the stud to fit into (the rusted area), but quit about 1/4" into it. I can think of no reason for it, and honestly, it would be covered by the gasket and so forth. It probably wouldn't hurt anything to leave it alone, but since I've already got some Pyro Putty coming, I might as well just fill it in with that and let it be.

[Cadman-iac]

Gotcha, I misunderstood. I thought that it was perhaps one for a mounting bolt.
Is it possible that your manifold is slightly warped and would not sit properly on the short alignment stub/pin, therefore necessitating the need to move the hole?
Since it's not actually being held onto the engine by something going through it at that point, your putty idea seems like a reasonable approach.
Does the manifold expand and contract enough with the heating and cooling that it might need this larger hole to accommodate this? Just a thought.

Rick

PS: I recall that some of the 6 cylinder engines that GM made for Chevrolet and GMC used mounting points between the intake and exhaust ports and just alignment pins on the ends that would allow for the expansion and contractions.

[LaSalle5019]

I had already been shopping for new manifolds on Ebay and even found a pretty nice looking set. Unfortunately, they are the wrong ones as mine has the choke stove arrangement on the drivers side.

Jon,
I had the same issue and just drilled and tapped the bosses on the driver's side exhaust manifold and switched sides for the heat riser so it ended up on the driver's side. On the exhaust manifold alignment pin hole, that would be easy enough to fill in with braze and re-drill. Not sure pyro putty would hold up.  The block side of an exhaust port runs a lot cooler than the manifold itself.  I'm really not sure how critical that pin is and whether it is used for alignment or actually holds the manifold from shifting.

As for your snapped off bolt.  What I would do is soak the area with the penetrant of choice, then take a 1/2" nut, place it over the 3/8" broken bolt and MIG weld down through the center of the nut onto that broken bolt.  Then put a wrench on it while still hot and the broken bolt will probably come right out. All you need is one of the cheap portable 110v welders. If you don't own one, hopefully a neighbor or friend does.

What you are seeing is oxidation erosion over the years vs a bevel.  I had some of the same and it was still evident on the passenger side crossover point even after the mill work (zoom in on my picture a little).  The reason I milled my intake manifold was to get that eroded crossover port cleaned up well to provide the gasket enough compression to seal against the block port, which should be fine even with that narrower margin.  A little pyro putty on the eroded area would help.

Scott

[39LaSalleDriver]

Is it possible that your manifold is slightly warped and would not sit properly on the short alignment stub/pin, therefore necessitating the need to move the hole?

PS: I recall that some of the 6 cylinder engines that GM made for Chevrolet and GMC used mounting points between the intake and exhaust ports and just alignment pins on the ends that would allow for the expansion and contractions.

It's a possibility I've thought of. I'm going to do a dry fit tomorrow and see if it lines up okay. I know the stud itself hasn't been redrilled/repositioned.

Jon,
I had the same issue and just drilled and tapped the bosses on the driver's side exhaust manifold and switched sides for the heat riser so it ended up on the driver's side. On the exhaust manifold alignment pin hole, that would be easy enough to fill in with braze and re-drill. Not sure pyro putty would hold up.  The block side of an exhaust port runs a lot cooler than the manifold itself.  I'm really not sure how critical that pin is and whether it is used for alignment or actually holds the manifold from shifting.

Mounting the choke stove cover on the drivers side isn't a big deal. The problem is that everything I find has a big rectangular bolster along the passenger side for what I presume to be a Stromburg arrangement fits. From about every picture I can find, pretty much every 39 LaSalle running a Carter carb doesn't have that bolster on the passenger side. So that's kind of a deal breaker for me unless somebody can demonstrate to me that 39 LaSalles with a Carter carb sometimes left the factory with that bolster on the passenger side. I would be thrilled with that. There is a fantastic set on Ebay right now and the price is right, but it has that bolster on the passenger side. 

As for your snapped off bolt.  What I would do is soak the area with the penetrant of choice, then take a 1/2" nut, place it over the 3/8" broken bolt and MIG weld down through the center of the nut onto that broken bolt.  Then put a wrench on it while still hot and the broken bolt will probably come right out. All you need is one of the cheap portable 110v welders. If you don't own one, hopefully a neighbor or friend does.

Unfortunately I don't.  It was on my agenda to buy one of those small, portable acetylene kits this spring. Growing up, dad insisted I learn to arc and acetylene weld, as well as blacksmith to some degree. I was probably the only kid in the county to have his own anvil and forge by the age of 10  I consider the acetylene to be the most useful system for my general purposes of working on the car. But, I got laid off with this virus business back in March and haven't had a regular income since. Sooooo....that got back burnered. I'm probably just going to drill and re-tap or chase it. I've had pretty good luck with that before. Even had to do it for the heater line outlet on my left head. I note that it is on a tab or wing that extends out, so it's not like boring directly into the block or anything.

What you are seeing is oxidation erosion over the years vs a bevel.  I had some of the same and it was still evident on the passenger side crossover point even after the mill work (zoom in on my picture a little).  The reason I milled my intake manifold was to get that eroded crossover port cleaned up well to provide the gasket enough compression to seal against the block port, which should be fine even with that narrower margin.  A little pyro putty on the eroded area would help.

Gotcha. I guess I'll go ahead and find a machine shop that can mill the faces on the exhaust and intake manifolds tomorrow. By the way, interestingly enough, the four bolts holding down the crossover pipe broke loose just as easy as you please leaving the threads in good shape. I was shocked.

[LaSalle5019]

You could stick weld that nut on too, but drill and tap is fine. If the threads look bad, I would definitely heli-coil one or more.  It is a very easy process.  I had one thread that was a bit marginal and it ended up pulling out when I installed the intake manifold in the middle of reassembly  . I had a longer SS bolt on hand and was able to get a nut on the back side - problem solved.

I see the issue you refer to on the exhaust manifold.  Shown is what I thought you might have. Along with the manifolds that I had which, as you can see, have bosses on each side.  I think the bolster design was post 1939.
Scott

[39LaSalleDriver]

I see the issue you refer to on the exhaust manifold.  Shown is what I thought you might have. Along with the manifolds that I had which, as you can see, have bosses on each side.  I think the bolster design was post 1939.
Scott

Nah, I've got the setup shown in the photos below. It is consistent with what I'm seeing in photos of other 39's. Granted, there may be variations, I honestly don't know enough about it, but I'm just playing it safe. I too suspect that those are for later flatheads. Mine work for now, they're just not pretty, but if I find a good set, I'll probably hop on them. I've also got feelers out for those repro choke stove plates that were offered sometime back.

Today I was able to get out there and more or less finish cleaning up the mating surface on the block. I also cleaned most of the crap and crud out of the valley. Makes me sick, when I had it all cleaned up and painted you could have ate off of it. I'll do some more final cleaning when I'm done surfacing it. Also, I was very lucky and was able to drill out that bolt hole. Started off with a 1/8" bit and worked my way up to 5/16" then ran a tap down into it. Feels pretty good and looked to be straight and centered, plus I got quite a bit of rust residue out of it so I'm going to call it a success. If the threads give out when torquing it down I'll probably just do what you did and get a longer bolt, put a nut on it, and call it a day.

I wasn't thinking about today being a holiday, so the machine shops were closed. I'll try to drop my manifolds off tomorrow morning and see if someone can shave them down for me. Hoping I can get them back in a day or two. I was able to get by an Ace Hardware and pick up all new bolts. I'm leaving the studs alone. None of them loosened when I was removing the clamps, so unless I have to pull them, I'm going to clean up the threads and leave them be unless they interfere with my touching up the surfacing. I also cleaned up my carburetor which had some gunk buildup on it too, and also painted the manifold clamps. One other thing, I also stuck some modeling clay up in that mysterious hole that had been drilled in my exhaust manifold and dry fitted it to the block. The stud fit perfectly into the factory hole, so there's no warping and I still have no idea why someone would just randomly start drilling into it. Maybe a machinist at the the factory wasn't paying attention?

I expect my Pyro Putty to arrive tomorrow so I'll be able to get started on that. Hopefully my gaskets will arrive too, and with any luck, I might be able to get it all put back together by the weekend.

[39LaSalleDriver]

This morning I was able to finish getting everything put back together, and WOW! It sounds like a whole different engine. Gone is the tik-tik-tik that I always felt was oil starvation to the lifters it's had since I got it three years ago, gone is the roaring sound from under the hood, gone are the gas fumes, and gone is the stuttering it started last week when I figured out something needed to be done. It was a pricey and painful experience (neighbors probably learned some new words ), but I think worth every penny and effort. I have no doubt this situation was brewing since the day I brought it home and finally the dam broke a couple of weeks ago.

I hate to be overly optimistic, but I wouldn't be surprised if I use less gas and oil now. Ultimately, I really hope it might stabilize some of the overheating issues I have been fighting for a long while.

[LaSalle5019]

Excellent. Glad it all came together.
Scott