I will shortly be building a log-style header with 1 3/4 pipes as the runners and 3.5" pipes as the log. My only question is that the way i am planning to make mine involves the pipe to come straight out of the engine for a foot or so before starting to make a gradual swoop downwards and to the rear. How do you sneak the pipe from #4 around the firewall? do you cut the firewall and weld in a cup for the exhaust to fit in? bend the pipe initially so that it goes around? Thanks for any help!
In a perfect world you want all 4 runners to be the same length. Note I said "perfect world"!!! If you are going for every last available horsepower these things matter. On other cars aesthetics are more important
Bend #4 so it goes around, and then for "looks" bend #1 to match, and come straight out with #2 and #3.
It really also depends on whether you want it to look era correct or not. I have seen one or two exceptions, but "tuned exhaust" and other sort of plumbing with pipes going this way and that for either matching the back-pressure for maximum horsepower or the best sound wasn't very commonly done till after WWII. It was done a fair amount in the '30s, so a lot of photos from then can be found.
In the '10s and '20s, exhaust was often run straight out if the firewall position allowed. If the firewall was in the way, sometimes only number four was bent. Numbers one and four were sometimes bent toward each other for aesthetics reasons. Sometimes pipes went straight out. Sometimes they angled. They may have angled up, down, or back. A lot depends upon your body and whether you want to keep the pipe away from a passenger or yourself or not. Exhaust was also sometimes run down and back, or even straight out with no manifold.
My first speedster.
The gray race car I used to have.
Both of these had number four bend forward to combine with number three. Both of these were driven a lot and never had troubles from the exhaust. The big pipe often went clear to the front of the engine outside the hood. Many people think that looks better (I may be one of them). Sometimes the big pipe was tapered, sometimes not. Many options here.
In the '10s and '20s, speedster and race car's non-stock exhaust systems were usually very simply made. Therefore easy to make now.
Drive carefully, and enjoy, W2
Here is a period correct header but spaghetti headers would be more effective. The small pipes going into the big one reduce back pressure but the spaghetti type actually super charges the exhaust with each one pulling the next one,
You might want to look at this as an option:
You'll have to make your own intake or buy a downdraft manifold for a Model A. Stock A or T intakes won't fit with this header.
Thanks for the picture frank. Did you bend #4 around the firewall as well? I know the modern style headers would be better but i want to stay period correct and outside the frame rail it just looks cooler... and ANYTHING would be better over the original right? I tour with mostly stock Ts in the touring, runabout, and closed car selection so im not really worried about anyone leaving me. Im putting in a 3:1 and the car has domed pistons already from the previous owner. I need to swap the valves out however. I have the original 2 peice. Any suggestions on that front are welcome as well.
Lots of answers:
Number 4 just comes straight out horizontally for six inches as do all of the other three. Then they all have a six inch radius. Then they all go straight down for 10 inches. Number four passes about one inch from the fire wall and the others move forward equal to the spacing of the exhaust ports on the block.
Then the pipes are placed in a jig positioning them at a 30 degree angle. Make a 1/2 inch block of steel and drill two holes matching the exhaust ports on the engine block. Relieve the block to let the pipes slip into it.
The three and a half inch tail pipe is then marked off to let the pipes intersect. Simply draft out an orthographic drawing of the intersection of the 30 degree pipes intersecting with the 3 1/2 pipe and cut the holes letting the pipes slip into the larger out pipe. Then plot a flat plan drawing from your orthographic sheet metal development drawing so that you will construct the ellipse to lay over the big pipe and cut away so that the small header pipes can slip in to it. This will position the system outside of the frame rails for all to see. Angels are very important and we all know that unrelated intersecting lines offend the viewer.
They do not have to be at 30 degrees but THEY MUST BE ALL BE AT EXACTLY THE SAME ANGLE !
If you do not have drafting skills go to the library and check out a book on sheet metal development. You will need a compass and a degree wheel.
The big pipe can't be bent so you take pieces of 90 degree elbows of that size pipe and use just enough to re-aim the pipe over the rear axle and suspension. Another simple technique is to cut a "fish mouth" V-slot in the big pipe and bend the pipe so they just touch and weld the pipe back together. Now the pipe is starting to turn. Continue and cut in different positions in order to re-aim the pipe to where you want it to go. Remember to avoid offensive angles that are displeasing to the eye. ;~)
3 to one gears are a bit tall unless you also have an under drive and don't forget the accessory brakes. If you have a two speed system, you will have your foot on the low pedal much of the time because high gear will allow not much less than 30 miles an hour. Stay with stock gearing unless you have an under drive.
I learned the pipe intersection drafting techniques in my seventh grade drafting class back in 1944.
thanks for the great information! i cant see the exhaust hangers on your car. How many did you use? what style are they? where did you mount them? Also, any suggestions on valves?
early small Chevy V8 valves but I don't have part numbers, ask on the site specifically which ones to use. Also put in hard seats while you are at it.
My tail pipe is fastened by a bolt welded to an arced saddle welded to the pipe and a bracket attached from the fire wall. That holds it against the frame. The pipe is so stiff that it only requires a half round saddle bolted to the rear of the frame so as to capture the pipe. We have lined it with an 1/8 inch piece of heat proof fabric so it doesn't squeak or rattle from engine vibrations and when the frame twists.
At 1600 RPM I doubt that much can be gained by building a real modern race type header.
If you are going all out for power than it is another story.
Im just going for a good running speedster that looks great!
Aaron we turned the Chris Egsgaard BBR RAJO engine 4600 rpm a couple of weeks ago with its Meyer and Drake pre Offenhouser steel billet crank. And, my number 22 turns 3300 with its T crank.
More model T speedsters back in the day ran near stock engines than did OHV. Near stock engines also tend to be more reliable that hotter engines. Build one that looks good from twenty feet and is fun to drive. Then enjoy it. With overdrives, three of the five speedsters I have had and driven had been clocked at 70mph or better. I don't know what the gray car could do, but I had it near 80 once and it was not full throttle. Its engine block was an original highly modified block with huge valves, but nothing much else to brag about.
They are a lot of fun! But be safe.
Drive carefully, and enjoy, W2