MTFCA Forum

As I explore superior carburation and breathing for the intake side of my speedster, I'm aware the downstream flow should get attention as well.

I have one of the header plates as a base for fabricated exhaust. This seems like a lot of work, so I'm also thinking about the accessory dual exhaust manifold the vendors carry.

1. What have users done downstream of the manifold for piping, muffler(s) and so on?

2. I've emailed this question to Langs, but do any forum members know if the manifold is just one big chamber inside, or is there internal passages to pair up cylinders for more effective scavenging (I assume it would be cyls 1 & 3 thru one port and cyls 2 & 4 through the other).

My speedster has a fair bit of stuff and a couple footrests on the passenger side, so an external header might be more complicated than on some cars.

As always, thanks in advance!

Consider that the firing order is 1.2.4.3.
So I think that 1&4 are on one pipe and 2&3 are on the other. I actually have a new one sitting in the garage, but I’m in the house now.

Right. 1-2-4-3. Of course. Duh.

From the looks of it, they are likely paired 1-4 and 2-3.

If you think of it tomorrow when you’re at the shop, please confirm. Thanks Les.

From a Donnie Brown Speedster discussion http://www.mtfca.com/discus/messages/82 ... 1530408436 --
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Also another from Seth of NC http://www.mtfca.com/discus/messages/41 ... 1409115883

Because Duncan and Fraser lowered and set the steering column sideways on my wide body roadster, there was enough clearance to allow me to use the dual exhaust manifold on my RHD car. However, to simplify getting the pipe to the rear past the pedals and the starter switch on the floor, I siamesed the two pipes from the manifold into one larger one before sending the pipe to the rear. It gives a nice throb to the note rather than a real noise, as befits this elderly gent's image!

Allan from down under.

Thanks for the riplies and input. Frank's photos from Donnie's speedster build were definitely helpful.

Allan, did you run that one larger pipe back and through a muffler or leave it au naturale?

Chris, I make model T mufflers, with the correct Canadian pressed steel ends and deflector. The muffler looks like a T model one, but has a larger input pipe and outlet opening. I can't vouch for it's level of performance, but I do like the note!

Allan from down under.

I have one of these manifolds on my '23 touring. I had a local muffler shop fabricate a 2:1 reduction to a larger pipe and muffler. I also have a Stromberg OF, .280 cam, high volume intake, and Z head on the car. I lost low end torque but also have a Ruckstall. I topped it out on a Montana tour at 58 mph while passing an Amtrac passenger train and decided that's the last time I'd do that with stock steering, suspension, and 2 wheel brakes.

Noel,

Was the exhaust the only change when you noticed the loss of low end torque? Or was the loss potentially related to a combination of changes. No criticism, just curious. I try to limit the number of changes at one time to help sort out what causes the change. Of course I don't always follow that but I try. Probably just me.

I think I lost a little low end torque with the high volume intake but the biggest loss was with the exhaust change. However, once I get a few RPM, I walk up hills I used to downshift for and can pass other T's struggling up long grades. However, now that we have a few tours under our belt, we're more likely to just stay in line and enjoy the view.

Noel, your upgrades are exactly what I have on my roadster, with one exception. I run an E Timer, and I love it! On a recent tour I did have an intermittent skip under power when cold. I think I have a spark plug breaking down a bit.
I forgot, my Ruckstell has a 3.25:ratio gearset.

Allan from down under.