Manifold machining

Terry - yes that is exactly what happen to my exhaust/intake.

RockHillWill - I sure would of been happy if my machinist had come up with your great idea. Only question I do have with your way is "I wonder if it would have worked on a Auto-Lite heater exhaust?

This guy that had done the work for me sure has done some great work for me in the past but not on this project.
 
I second that, the surface must be true. I made a jig to hold the manifold which makes milling a whiz; using a fly cutter leaves a course surface to grab the gasket.
 

Attachments

  • IMG_00000214.jpg
    IMG_00000214.jpg
    55.8 KB · Views: 237
Everybody wants to over engineer the Model A. This car was built as an improvement over the T but still be simple enough for people who had no mechanical aptitude to keep it running for decades. I use a 6" belt sander from Harbour Freightto resurface manifolds and have never had a customer complain or even mention he had a problem, no matter how small, when installing. The first several I had done were done on a 16" automotive sander and worked fine.
 
CA Victoria said:
I second that, the surface must be true. I made a jig to hold the manifold which makes milling a whiz; using a fly cutter leaves a course surface to grab the gasket.
Click to expand...


I like you HORIZONTAL mill :eek::D

Bob
 

Attachments

  • IMG_00000214.jpg
    IMG_00000214.jpg
    6.1 KB · Views: 581
Again, just as information:

The issue that I had with both of the first two attempts at surfacing on a sanding surface(a 6" belt sander and a 24" round sander) was that the manifolds were not held 90 degrees to the carburetor mounting surface.

If you do not run engine pans this might be a small issue, but if you are interested in helping to cool your motor or are having the car judged, this has resulted in the front section of the muffler not fitting in the 'notch' at the rear of the engine pan.

If the manifold flange is about 2" wide and the distance from the intake/exhaust is 12" (both estimates), then the difference of the error in grinding will be a factor of 6 at the engine pan opening. So a .030" difference at the manifold will be 3/16" at the engine pan. You can 'rotate' the muffler extension to adjust for this error, but it will minimize the contact area at the flanged connection between the manifold and the muffler and make an exhaust leak easier to occur.

It was clear that the sanding operators also contributed to the problem as in each case, the edges had a rounded section, generally at the top, and while the surfaces looked flat, they were each out more than .010" when measured at each end. No problem when installing, but one of them started leaking after about 400 miles.


Again, just a thought.
 
Last edited:
James Rogers said:
Everybody wants to over engineer the Model A. This car was built as an improvement over the T but still be simple enough for people who had no mechanical aptitude to keep it running for decades. I use a 6" belt sander from Harbour Freightto resurface manifolds and have never had a customer complain or even mention he had a problem, no matter how small, when installing. The first several I had done were done on a 16" automotive sander and worked fine.
Click to expand...

Thanks James for this info. I agree with what you say about over engineering. I've been using a file but I have or had a longer belt sander that I sometimes used when I was building my house. I think that using a belt sander will be much easier than using a file.
 
One Tool and Die shop I worked in (Many years ago!) we used to ocassionally sharpen our blanking dies by holding them to the a 6" sanding belt. After one or two times on the sander, we would have to clean them up on a surface grinder. The sander is a quick fix. Not a good and proper answer. It is not over engineering to make two surfaces, intended to be flat and seal to be just that, flat enough to seal. The surface behind the belt is usually worn concave, especially at the rest, and incapable of producing a flat surface. And as Cape Codder and others have said, it must be 90 deg. to the carb mounting surface.
Terry
 
Last edited:
Few have the skill of Mr rodgers to freehand the resurfacing. I am stubborn and will continue trying to master this skill, but I have limited funds and besides it is fun to try to get better at this. Sofar with 5, or 6 done by hand with a file and then with 80 grit on a piece of slate I continue to learn what not to do. Rockhill Will is correct that getting off verticle screws things up. Bottom line is recognizing that the surfaces of the manifolds need to make good contact with the block. A good machine shop is definitely the first choice although freight to North carolina could be factored in.
Bob
 
Its also best to use a cutter in the mill that is wider than the manifold. If you chose not to do it that way you will have step in the work. This happens because metal is elastic and will move some with the pressure of milling. Plus the cutter will give some also. Depending on the dept of cut.
 
Most home shops probably don't have a vertical milling machine. Wills info is good but doesn't apply to the common man with a home shop that is doing his own repairs. The best way would be a new manifold in many cases. Most if not all manifolds will be warped to some degree from heat and over tightening. Some manifolds will only be off just a small amount, This is the manifolds that I try and save. I check my work with a metal straight edge and know what will work. If the manifolds are so badly warped that a little filing or sanding will effect carburetor alignment, I don't figure that anything will save them and I give them to my son in law for junk iron. I do run engine pans on our roadster and sedan.
 
After you reinstall them you need to re-torque them after a heat cycle. It took 10 times to get mine tight. If you don't you will blow the gasket
 
Buy a new exhaust manifold and new intake manifold and bolt together and check the alinement with a good straight edge and go from there,,, yes they will still need tweeking ......at least they should be straight and not rusted metal......I will think it will run a couple hundred, but this is a vital part of running gear.... Snyders or Brattons.... Good Luck, John
 
Since this thread is about manifold maching, how many of us will pick up a couple of HP by boring out an A intake. This is one of the cheapest and quickest ways to get a good feeling when you step on the gas. I'm sure with a Stipe cam and mod B carburetor, the effect is even greater. However it will be noticeable with a stock A engine. We're back to having a Bridgeport or another vertical milling machine. The part that's drilled out is the intake (Carburetor) part of the manifold. I use a 1.250 drill that cuts oversize (1.260 perhaps, Depends who's sharpened it) Drill the full length of the port. But the iron is getting thin so be sure to use an alignment plug and clamp the manifold Tightly to the angle plate. You don't want the drill coming through the sides. Center the carb. port with the alignment plug replace the plug with the drill and start drilling. When you're done take it off and polish it somewhat with a small (1") flap wheel. Polish any intrusive casting imperfections where ever you can and Voila!. You just got yourself 1-2 HP.
With the Head, I machined a cleanup cut , just a skim with a flycutter maybe .010 off the top, water outlet surface. It's flat, no low spots or pits. Set the tool to overreach the sides of the outlet and one or two cuts will do it. Next is a little harder. I used two .437 (7/16) drill blanks in the forward head bolt holes to locate the head as I held to the table with a very large C clamp. Let me clarify, The head was clamped to the back of the table, upright, and it was resting on the the two pins (drill blanks) . This gave me a good access to the surface where the water pump is attached as this is the surface I wanted to machine. Once I had the head setup, I had to swing the Cross arm around to get at the head. That being done, I took a skim cut of the water pump face. Again, I set the tool wider than the surface to be cut. .010 should do it in most cases. Then I did something else. I set the tool inboard, just maybe 1/8" larger than the water pump bore, I picked up the the new surface with the tool centered on the water pump bore an raised the head about .003 on the gasket face. So now the head has a concentric ring where the gasket seals. This provides a better seal for a water pump.
Terry
 
So, the general consensus is, if I belt sand it and get off by maybe a degree it will render the manifolds useless?
 
I just picked up my Exhaust Manifold today, I had it Surfaced. Should I still use the Gland Rings, I have the one piece Gasket. They milled off 20 thousands, to true it up.

The head in the background, I had Magna Fluxed , hot tanked, bead blasted, and surfaced, 15 thou. to clean it up, for another Engine.
 

Attachments

  • 100_3673.jpg
    100_3673.jpg
    68.3 KB · Views: 95
  • A9440-7410-xl.jpg
    A9440-7410-xl.jpg
    71 KB · Views: 42
  • A9433F-7429-xl.jpg
    A9433F-7429-xl.jpg
    18.5 KB · Views: 35
Jazzjr said:
I just picked up my Exhaust Manifold today, I had it Surfaced. Should I still use the Gland Rings, I have the one piece Gasket. They milled off 20 thousands, to true it up.

The head in the background, I had Magna Fluxed , hot tanked, bead blasted, and surfaced, 15 thou. to clean it up, for another Engine.
Click to expand...

If your manifold holes all line up, yes, use the gland rings.
 
Put the 4 gland rings in and push the manifold to the block without any gasket and see how much clearance you have for the gasket. If the rings don't pinch before the gasket is compressed, then you're good to go.

You can grind the rings thinner if you need to.
 
James Rogers said:
Everybody wants to over engineer the Model A. This car was built as an improvement over the T but still be simple enough for people who had no mechanical aptitude to keep it running for decades. I use a 6" belt sander from Harbour Freightto resurface manifolds and have never had a customer complain or even mention he had a problem, no matter how small, when installing. The first several I had done were done on a 16" automotive sander and worked fine.
Click to expand...

I did the same thing a few years ago and it has worked fine. I've been afraid to mention it before thinking I was just lucky. Glad to hear that you do it as well. :)
 
You must log in or register to reply here.
Back
Top