49 ford 302 swap headers have thick flanges, 1/2" Exhaust on 2 and 3 leaking even with new gasket. Put layout fluid on flange and bastard filed the header flange...machinist level shows a high spot on the flange between cylinder 2 and 1. How flat should I work this thing to? Is there some sort of rule of thumb? No way it is flexing and the leaky black marks on the head match the low spots after layout fluid and filing. Appreciate all the knowledge here and I am working it very slow and carefully. Am I shooting for .010? .030? FYI these headers have been on for years close as I can tell it has always leaked. Car is new to me. I am aware that flatter is better but I'm about 1200 strokes in and as it gets flatter the progress gets slower Thank you all.
You could try copper gaskets as they will conform to minor irregularities and not blow out like conventional header gaskets. Spendy but you get what you pay for.
When I've had leaking header flanges, I have used two gaskets, tightened up well, and retightened while warm with good success.
Thank you and I have heard this as well. I got a pair of the remflex gaskets which are popular in the 5.0 community. I may just bolt it up but I hate to leave the flanges with a high spot. I may be overthinking it....
I stopped using gaskets many years ago. I was turned on to a Chrysler product that is R.T.V. style but just plain unreal. I've been using on the race motors with Aluminum heads with never an issue. If you've ever had exhaust leaks between Steel and Aluminum you know that Aluminum always looses and that can be big $$$$. I will get you a part number for it tomorrow. I have actually removed all the bolts holding the headers on the motor and fired it up hoping to just have them pop off. Didn't happen, I still had to use a putty knife and drive it in to cut through it. That stuff it Tough!
Take the header to a machine shop and have it run on there belt sander that they do manifolds on, that will true it up!
Go get TWO sets of stock type gaskets. ( type with perforated metal on one side and gasket on the other.) Take 2 and put them together, gasket to the inside, and metal out. Done this for years. Has always worked. More gasket for crush, and the metal to the outside helps contain the gasket material. Plus a lot cheaper than some of the aftermarket stuff. Loaded a picture of the gasket type.
It wasn't headers, but I once flattened the gasket face of some FE Ford cast iron exhaust manifolds with my hand held belt sander. I was careful to not sand too much and it worked very well, I got them nice and flat and it was a lot faster than using a file.
Flat is flat..! The flange should most obviously match its mating part...the cylinder head. So...the flange needs to be as flat as possible since the cylinder head is most probably within just a coupla thousands of flat. A heavy duty work bench (support), blocks of wood (reaction mass), and a big hammer (persuader) should to the trick. Just like doing body work..! Mike
You can spend a fair amount of time and money trying to cheat. Only to end up at the machine shop anyways. A 1/2” flange has plenty of material to work with. Take it in and be done with it.
These are some 3/8” thick chevy headers that had non-stop leakage issues. Customer tried several of the solutions mentioned in this thread. I ended up first welding the port opening and shaping it to the actual port shape, then running the Bridgeport over them. He now uses no gaskets, and has no leaks.
I have used the Copper but a bigger fan of the Mopar product. That part number is 82300234 MS- GF44D. And as said many times surface the flange for the best shot at success.
Lots of good comments here, we have an excellent local machine shop and had I known how long filing would take I would have definitely removed it and had it machined as mentioned, this is great advice. Pistnbroke thank you for that part number as well I appreciate you!
When I worked as a mechanic for a local dairy back in the '70's the head mechanic used to "surface" straight 6 exhaust manifolds by rubbing them face down on the cement floor of the shop in a circular motion. Called it the "dairy" surface grinder. Don't know if it would work in your situation but worth a try.
RTV is your friend . 100% silicone . Apply a bead to the head and a bead to the header . Allow them to skin over and form a beaded gasket . You’ll be amazed at how well it seals up your leak for ever
Horizontal Belt sander. Works much better for contouring and flattening all sorts of things. I can't begin to guess how many times I have used this sander, but its in the thousands. They cost more than the the smaller vertical belt sanders, but the flat table and gravity make it much more usable. Its also long enough to flatten header flanges, just do it slowly to keep the flange reasonably cool. Put the machinist money toward one of these and then you have it for a thousand other things later on. One of my best tools! I added the wheels and handle so I could move it easily. It was an old HF dolly.
I would cut the flange in 3 places so each port is separate from each other. That should give you a better chance of them sealing up.
I bought a surplus supply of old belt sander belts of all sizes really really cheap. I cut them and clamp them down to my bench. this allows me to rub manifolds back and forth on the belt. I have done this for years, they look like they have been machined and I never had one come back with a leak. no buying a machine or dropping off ,waiting picking up and paying for a machine shop.....it is a work out tho.
That’s cool! Gives me an idea of something I’d been thinking about. What’s the motor speed on the machine?
I've used " Percy's" header gaskets they are called "dead soft" alumininm. Not sure if they are still around. I agree with machineing the surface being a great fix as well and will probably go that way I future projects
Its 3450 and spec sheet says belt speed is 3900. To those of us who like to do a lot of fabricating, this machine is a joy to have. Lay steel plates down on the flat surface and make nice straight flat edges quickly, or rotate the part against the belt and make nice radiused corners that look machined. Radiusing edges is a snap. I don't know how many times I have inadvertantly filed a finger nail while flattening a small lug or bolt. Put a rod or bolt in a drill and turn the drill on while the sander is running and you can taper a starting thread or beautifully make a round end on a shaft. I have a plastic coffee jug mounted on the wall nearby for quick cooling. There are other brands available but you don't see many used ones being sold.......people who have them tend to keep them.
I have done that many times! I have even added weight , for balance and quicker cutting and pulled them with a rope. Sometimes it was a two man job. Mainly just to get a clean surface for the sealer to stick to. But it also show low and high spots real quick! Bones
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